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| Fruit Crop Advisory Team Alert newsletter | |||||||
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| Vol. 23, No. 11, June 17 2008 |
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| In this issue Tree fruit news Keep an eye on downy mildew in grapes Summer leafroller control: Gather the information needed to make a sound management decision Rainfast characteristics of insecticides Sooty blotch and flyspeck disease of apple and pear – The newest addition to Enviro-weather Enhancing return bloom with summer NAA 2008
Small fruit news. Mid-season weed control options for blueberries Irrigating blueberries Grape IPM Twilight meeting Blueberry IPM Twilight meetingOther news Regional reports Weather |
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| Keep an eye on downy mildew in grapes Recent rainy weather is conducive to downy mildew development in grapes. Downy mildew is caused by the oomycete (fungal-like) pathogen Plasmopara viticola and can attack all green parts of the vine, particularly the leaves. Young tissues are particularly susceptible to infection. Downy mildew can seriously damage leaves and clusters of susceptible cultivars. Leaf infections may lead to premature defoliation, which can reduce winter hardiness and sugar accumulation in the fruit in severe cases. Sometimes newly planted vines fall victim to this disease because people think that no sprays are necessary in the first year of establishment – heavy defoliation can set back vine growth and winter survival. The first symptoms may be light green or yellow spots that may have a greasy appearance (oil spots). On older leaves, lesions are smaller and more angular as they are delimited by leaf veins. Infected shoot tips tend to be curled and have a shepherd’s crook appearance. Infected flower and fruit clusters may be covered with a downy white growth and later become necrotic. On leaves, sporulation usually occurs on the underside of the leaf. This is in contrast to powdery mildew, where sporulation mostly occurs on the upper surface. |
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| Biology of the pathogen The pathogen overwinters as thick-walled spores (oospores) in fallen infected leaves on the ground below the vine. As the leaves break down, the oospores are released into the soil where they can survive for a long time. Only oospores at or near the soil surface will germinate in the spring. Oospore germination is favored by moist soils and moderate temperatures (over 50°F), which were common in the past few months. Oospores develop a second spore type (sporangia), which are splashed by rain or carried by wind to young leaf and shoot tissues. Therefore initial infections are often found on the lower parts of the vine, unless the sporangia blow in from other vineyards, in which case lesions may be found in the upper canopy. The optimum temperature for germination of sporangia is 72°F-75ºF. The sporangia release multiple zoospores (swimming spores) which need a film of water to infect the plant tissue. Zoospores infect the plant exclusively through the stomates, so only plant structures with functional stomates are susceptible to infection. Berries become less susceptible as they mature, but the rachis remains susceptible for a long time. Under optimal conditions, the time from germination until penetration is less than 90 minutes. Lesions appear 5-17 days after infection. The fungus will sporulate through the stomates of infected tissues under humid conditions (95-100 percent RH) at night. The optimal temperature for sporulation is 65°F-72ºF. Rain is the principal factor promoting epidemics. Temperature plays a less important role by retarding or accelerating the development of the disease. The most serious epidemics occur when a wet winter is followed by a wet spring and a warm summer with intermittent rainstorms every 8-15 days. Recent research in Europe has indicated that oospores may germinate over a fairly long period of time (from early spring until mid- or even late summer) and secondary cycles of sporangia production may be less important in disease development than previously thought. This may explain why disease prediction models for downy mildew have not worked as well as expected. |
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| Summer leafroller control: Gather the information needed to make a sound management decision A review of the 2008 season, thus far The increased availability of several excellent leafroller control materials in the past several years has resulted in reduced obliquebanded leafroller pressure in Michigan apple orchards. Early season use of Rimon and Proclaim for codling moth control in 2007 provided excellent leafroller control. Many growers have incorporated two additional materials into their 2008 first generation codling moth management program, Altacor and Delegate. Both also provide excellent leafroller control at these early timings. Individuals that have survived these treatments are just beginning to pupate and emerge as adults. It is time to begin to gather the information needed to make sound decisions relative to summer generation obliquebanded leafroller control. Scouting for obliquebanded leafroller should include monitoring adult activity with pheromone traps and sampling for larvae. As larvae mature in late spring their presence is relatively easy to detect. Visual inspections for larvae or signs of their presence can save growers the cost of unnecessary, and often expensive, summertime insecticide applications. In other words, a key piece of information growers need in order to make a good economical decision for summer leafroller control is the extent to which larvae survived the early season treatment. With the excellent control provided by the new compounds registered in recent years, fewer and fewer overwintering larvae are surviving. Monitoring with pheromone traps Moth captures in pheromone traps provide valuable information to the scout and grower, including the establishment of biofix, but are not a reliable indicator of leafroller abundance or potential damage. Obliquebanded leafroller traps have a large active space, potentially catching moths that originate not only from within the trapped orchard, but also from neighboring or more distant orchards, and native habitats. Thus, high moth catches may or may not indicate that the orchard being monitored has a leafroller problem. On the other hand, very low catches of less than five per week strongly hint that obliquebanded leafroller is not a problem. In either case, assessing larval activity is highly recommended to determine if a treatment is warranted. Assessing larval abundance to determine the need for control measures Scouting orchards for surviving obliquebanded leafroller larvae in growing terminals is the best way to judge whether intervention in the summer is likely to be needed. Larvae are green with brown to black head capsules and are about 25 mm long when fully grown. Often, a scout will detect signs of leafroller activity rather than the actual larva. The name leafroller comes from the larva’s habit of rolling leaves to form a shelter. These feeding sites are most often found at the tips of growing shoots. Larvae will use silk webbing to attach two leaves or a leaf and fruit together to form a shelter. The presence of webbing is a good clue that leafrollers are around. Orchards in which less than two percent of the terminals were infested should be monitored in the summer, but controls may not be warranted. Inspect the undersides of leaves within the fruiting canopy, especially where fruit are clustered. Higher levels (less than two percent) of shoot infestation by overwintering larvae are cause for concern and control measures are likely needed to prevent fruit injury. Table 1. Obliquebanded leafroller GDD model and insecticide timings
Timing control measures Degree-day models are essential tools to be used in timing insecticide sprays. Optimal timing for summer sprays varies according to the life stage or stages that are targeted by the product of choice. For conventional insecticides, like organophosphates (OPs), pyrethroids, and carbamates, the first sprays should be targeted between 400 and 450 GDD (base 42°F) after biofix to control hatching larvae before they can damage fruit. Obliquebanded leafrollers are resistant to organophosphates in most apple growing regions of the state, and are generally not the best option for control. The newest options for growers, Proclaim, Delegate and Altacor, require ingestion by larvae, but have shown excellent activity against obliquebanded leafroller. The first sprays should be targeted between 400 and 450 GDD after biofix to control young hatching larvae. Good, thorough coverage is the key to leafroller control with materials requiring ingestion to be effective. If Bt products are used, the latter timing of 450 GDD may be the better choice because they have a short residual, which must be present to control the larvae at the time and location they are actively feeding. If the first application is applied too early, it may take four or more sprays to keep the active ingredient on the foliage throughout the long period of larval activity. Bt's are most effective when applied during warm weather conditions (daily highs in the 70s ). Additionally, they are generally more effective with a lower tank pH. SpinTor has been a very good leafroller management option for a number of years. It primarily acts through ingestion, but also provides some contact efficacy. The latter activity will help kill larvae as they move to the actively growing terminals. SpinTor is also a good choice for leafroller control in cherry blocks where control with organophosphates and pyrethroids is failing to provide adequate protection. Intrepid is another good leafroller material that can be applied both early to target coverage of eggs or later to target older larvae. If Intrepid is used early it should be targeted to cover obliquebanded leafroller egg masses around 350 GDD post-biofix, so that larvae will consume the chemical as they eat their eggshells upon emergence. The later timing of 400-450 GDD protects fruit against damage from older larval instars. Upon application, Intrepid has a long residual effect, but should be reapplied where necessary on a 14-day interval to insure coverage of new terminal growth. The addition of an agricultural adjuvant to Intrepid 2-F is recommended to improve spray deposition. Rimon acts by suppressing development within the egg, as well as larvae that consume it. Hatching of eggs laid by treated adults will also be inhibited. Eggs are particularly susceptible to these products when laid on top of sprayed residue, thus application of sprays should be timed for 100-200 GDD after obliquebanded leafroller biofix. Similarly, Esteem applied at obliquebanded leafroller egg laying timing will also provide some control, though it is more typically used for the overwintering generation. Summer control of other pests It should be noted that treating the summer generation of obliuebanded leafroller with Delegate, Altacor, or Rimon also will provide control of codling moth, Oriental fruit moth and spotted tentiform leafminer. Intrepid applied at the earlier summer obliquebanded leafroller timing would also assist in controlling codling moth and tufted apple budmoth. Esteem will provide control of San Jose scale crawlers and some added control of codling moth. Bt's also will control other leafrollers when applied in the summer for obliquebanded leafroller control. Resistance management As with many of our key apple pests, obliquebanded leafroller has a track record of developing resistance to insecticides. Currently, there are some good options for control of this pest. Practicing good resistance management should help conserve their efficacy. We encourage you to rotate materials with different modes of action (Table 2). For example, if Rimon was the material of choice for control of overwintering larvae, opt for Delegate, Altacor, SpinTor or Intrepid if a summer treatment is warranted. During periods of warm weather, Bt is an excellent option and a good resistance management strategy. Table 2. Chemical class, activity and timing of insecticides used for OBLR control.
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| Rainfast characteristics of insecticides The heavy rainfall events experienced in Michigan over the last several weeks has prompted many questions about the relative “rainfastness” of the insecticides used in fruit production. Very little research has been done on this subject in recent years, leaving growers to depend largely on folk-lore to guide their decisions of whether or not they need to spray after a rain event. In 2006, the Michigan Agriculture Experiment Station provided funds to purchase and install a state-of-the-art rainfall simulation chamber at the MSU Trevor Nichols Research Complex. Precipitation events vary in duration, intensity (water volume per minute), and droplet size. In our first field season (2007), we focused our efforts on calibrating the new equipment to simulate various precipitation patterns relevant to Michigan’s spring production season. We were able to run some initial trials in apples (funded by Michigan Apple Research Committee) that can provide some preliminary insights, although it is important to complete the study before final conclusions are made. In the 2007 apple study, we compared the performance of Azinphosmethyl (GuthionÒ), Phosmet (ImidanÒ), Esfenvalerate (AsanaÒ), Indoxacarb (AvauntTM), Novaluron (RimonÒ), Emamectin Benzoate (ProclaimÒ) and two neonoctinoids, Acetamiprid (AssailTM) and Thiacloprid (CalypsoÒ) on the codling moth. We sprayed all treatments on Red Delicious apple trees using labeled field rates, harvested fruit clusters 24 hours after sprays had dried and simulated half-inch of rain. These fruit clusters were then exposed to codling moth larvae in the laboratory, comparing fruit protection to untreated samples with no simulated rainfall. Parallel fruit samples were analyzed for their surface and sub-surface residue levels by the MSU Pesticide Analytical Laboratory to document the resulting chemical wash-off under the simulated rainfall event. All treatments that were exposed to the half-inch of rain after 24 hours of drying provided good control of codling moth, even though residue losses to wash-off ranged from 10 to 50 percent. This suggests that even with significant residue wash-off, fruit protection is maintained from insecticides in the first few days after a spray. When fruit clusters were collected from the same field treated plots eight days later, some differences in performance became visible. Whereas performance of Calypso, Avaunt. Imidan and Guthion remained relatively equal between the rainfall and no-rain fruit, the activity of Rimon, Assail, Proclaim and Asana on codling moth was reduced from the half-inch of simulated rain. For the conventional insecticides Asana, Imidan and Guthion that have primarily surface residues, the amount of chemical lost from half-inch simulated rainfall ranged from 30 to 50 percent. This suggests that pyrethroid and organophosphate insecticides are similarly susceptible to wash-off from precipitation, but that the OPs’ higher toxicity to codling moth larvae maintained performance, though this may not occur in commercial orchards where OP resistance exists. Assail and Calypso, being neonicotinoids, have systemic movement into plant tissue. The residue data showed that even though losses of surface residues were similar to that of the OPs, the residues that had moved in and below the plant cuticle were protected from wash-off. For Avaunt, Rimon and Proclaim the residue wash-off from fruit was significant, but residues in leaf tissues appeared to be quite resistant to rainfall wash-off. There is much more work to be done in this area of research, including the simulation of more severe rainfall events. We expect to be reporting our findings as they develop over the coming years. |
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| Enhancing return bloom with summer NAA 2008 Some years it is desirable to try to enhance return bloom on apple varieties that tend to be biennial. This is especially important on trees that have a heavy crop load. Most years treatments of summer NAA applied at five, seven and nine weeks after bloom will increase return bloom even on varieties that have heavy crop loads and tend to have poor return bloom. This timing is after any potential thinning from NAA has past. Fruits are often one-inch in diameter and won’t respond to any NAA thinning action. Flower bud initiation has already begun, but can be enhanced by NAA treatments during the next 30 days after the thinning period ends. Summer Ethrel can also enhance return bloom by treatments of 200 ppm made at the same timing of five, seven and nine weeks after bloom. However, summer Ethrel can some years thin 1-inch diameter fruit and summer Ethrel can advance maturity of early maturing varieties. Summer NAA Apply 5 ppm (2 oz/100 of Fruitone N) of NAA starting five weeks after bloom and apply two additional spray treatments at seven and nine weeks after bloom. The rate of NAA applied per acre should be adjusted to tree row volume levels. The applications can be concentrated, but treatments will benefit from increased water amounts. Try not to concentrate water amounts greater that four times. These sprays can be added right to the cover sprays during that time period. Some years these treatments do not perform well, especially during drought years. Varieties that have a moderate to high biennial bearing tendencies should be considered for bloom enhancement sprays (see Table 1). Summer NAA treatments will not cause any adverse affects to the trees or crop. Treatments during extremely hot temperatures (maximum temperatures above 95°F) should be avoided. If surfactant or oil is included with the application, consider reducing the NAA amount by one-third. Follow the guidelines listed in Table 2. Table 1. Apple Variety Biennial Tendency
Table 2. Summer NAA rate use guidelines
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| Mid-season weed control options for blueberries Spring-applied herbicides do not always provide adequate weed control through the harvest season. Summer flushes of annual grasses (crabgrass, fall panicum) or broadleaves such as pigweed often are problems. Some Michigan blueberry areas received large amounts of rain in early June, and this may reduce the effectiveness of preemergent herbicides by leaching materials below the weed seed germination zone. Easily leached herbicides are soluble materials that are held less tightly to soil particles. The leaching potential is hard to predict exactly for all soils, but common blueberry materials might be ranked as follows:
This means that weed control from Sinbar and Velpar is more likely to be reduced by heavy rains than perhaps Solicam. Unfortunately, herbicide options for use in mid-season are limited by label restrictions, primarily pre-harvest intervals. The label restrictions for preemergent materials are:
Aim, Gramoxone, and Rely are burn-down materials. Pre-harvest intervals are listed on the labels for Aim (one day) and Rely (14 days), but the Gramoxone label indicates it should not be applied after growth begins. These herbicides kill treated plant parts, but do not move within the plant. As a result, perennial weeds are usually not killed because the chemical does not move to the roots. Rely may move slightly in plants, because it often provides a slightly better control of some herbaceous perennials, such as dandelion. Aim is relatively inexpensive, but does not control grasses. Rely is much more expensive, but controls broadleaves and grasses. All three herbicides kill green bark and leaves of blueberries, so take care to keep spray off blueberries. Fusilade and Poast are selective grass killers; they have no effect on bloadleaf weeds or blueberries. Poast has a PHI of 30 days, and Fusilade is only for non-bearing plantings. These products would not be effective if applied in the summer because the grasses are too old. Grasses must be treated when they are four to eight inches tall in the spring. If grass is taller, the control is poor. Glyphosate (Roundup) products have a PHI of 14 days, so they can still be applied to most fields. Glyphosate is the most effective postemergent herbicide for blueberries, but also the most hazardous because it is absorbed by green tissues and moves throughout the plant. Perennial weeds are killed because the chemical moves to below-ground plant parts. Translocation is a two-edged sword. Glyphosate applied to blueberry branches moves within the bush, and can kill large canes or whole bushes. The most effective time to treat perennial weeds is late in the summer because absorbed glyphosate tends to move down to the roots. This timing is also most hazardous for blueberries. Use extreme care to avoid contact with blueberry tissues. |
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| Irrigating blueberries Irrigation is vital for maintaining high yields in commercial blueberries in Michigan. Blueberries grow best in moist soils. Many Michigan blueberry plantings are located in areas with a high water table, so the bushes have ready access to water located close to the surface. But blueberries are shallow-rooted and sensitive to drought stress, and most Michigan plantings are on sandy soils that hold very little water. Drought prior to harvest reduces berry size and yield, but drought stress anytime in the summer or fall also reduces bud set for the following year. Severe drought events reduce returns for several years. Most fruit in Michigan is not irrigated, but 70 percent of the Michigan blueberries are irrigated. Irrigation is particularly critical for young plantings. Because roots are shallow (12-inches), more frequent irrigation is needed than for older plants. Good soil moisture levels optimize vegetative growth on young plants by reducing or avoiding moisture stress during the growing season. For established plants, the goal is to optimize fruit production for current and subsequent seasons. Irrigate to prevent moisture stress during the June-July fruit development period, when drought stress will reduce berry size and yields. Drought in August-September reduces bloom during the next year, so avoid stress after harvest when fruit buds are formed. Comparison of irrigation systems options for Michigan blueberries.
Irrigation systems Overhead sprinklers are best where the water supply is adequate and spring frosts are likely. Trickle systems are best if your water supply is limited because they apply water directly in the row with little evaporation. Traveling guns are economical, but may apply excessive water rates and have poor uniformity. The soil water reservoir depends on texture and rooting depth (Table 1). Assume the rooting depth is 12-inches for young plants and 18-inches for older plants or excavate beside bushes to determine exact depths. Sandy soils may hold less than one-inch of available water in the root zone, and half of this can be lost in two warm summer days. Many blueberry fields have slightly elevated areas that dry out quicker than other areas. Hardpan or a shallow water table may limit rooting in other areas of fields. These variable characteristics complicate scheduling. As a rule, irrigate to maintain drought-prone areas of your field. Table 1. Available water in a blueberry root zone as affected by soil texture and rooting depth.
The evapotranspiration rate varies during the year depending on the amount of leaves on the plants and the weather condition, heat and relative humidity. The temperature is the most important factor, increased heat increases ET much more than increasing humidity decreases ET. Estimated blueberry water use in Michigan blueberries in inches
Sprinkler systems The amount of water applied by sprinkler systems is determined by the size of the nozzle and the water pressure at the nozzle. For example a 9/64-inch nozzle at 45 psi will deliver about 0.15 inches an hour. If the system delivers 0.15 inches water per hour, 0.6 inches would be pumped in four hours. However, about 20 to 30 percent of water from overhead sprinklers may be lost to evaporation, so increase the operating time accordingly. Also, irrigation systems are not completely uniform; they apply more water in some areas than others. The uniformity of sprinkler systems can be measured (Ley, 1994b), but are usually only 70 percent uniform. This means that to recharge all areas of the field, 30 percent more water than calculated would need to be applied. In our example, operating time should be increased by 20 percent to account for evaporation losses, plus 30 percent due to non-uniformity. So, increase operating time of four hours by 50 percent to six hours to ensure all areas receive 0.6 inches. Trickle irrigation The application rate for lower volume trickle systems (48-inch spacing, 0.42 gph emitters) is about 0.17 inches per hour. The more common moderate flow systems (24-inches spacing, 0.42 gph emitters) deliver about 0.3 inches per hour. Since evaporation and uniformity are not significant in trickle systems, we do not need to increase the application time. We would need to run the lower volume system twice as long to apply the same amount of water. These systems should be run at least one to two hours every day to replace the water used by the plants. |
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| Grape IPM Twilight Meeting r When: Thursday, June 19, 6:00-8:00PM. Where: Tim Seppala’s Farm, Lawton, Michigan. What: Timely updates for control of diseases, insects, and weeds. This is a free meeting with a light dinner served at 6:00 PM. Spray credits available for attending. Hope to see you there! For more information, contact Paul Jenkins at: jenki132@msu.edu; or 517-432-7751. |
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| Blueberry IPM Twilight Meeting When: Tuesday, June 24, 6:00-8:00 PM. Where: Carini Farms, 15309 Port Sheldon Road, West Olive, Michigan (west of US-31). What: Timely updates for control of pre-harvest diseases, insects, and weeds. This is a free meeting with a light dinner served at 6:00 PM. Spray credits available for attending. Hope to see you there! For more information, contact Paul Jenkins at: jenki132@msu.edu; or 517-432-7751. |
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Regional reports Last week’s weather was generally dry with highs near 80°F, and lows in the 50s and 60s. Scattered storms passed through the region over the weekend. These storms brought rain and hail in some areas. Rainfall totals from these storms was generally light, from a tenth to less than an inch. Soil moisture levels are falling and sandy soils are becoming dry. We expect cool temperatures for the coming week with highs near 70°F and lows near 50°F. Our GDD totals are now about three or four days behind 2007 .
Tree fruit Deer browsing continues to be a problem in many fruit plantings. The warm temperatures increased insect activity. Leaf roller larvae are feeding in some orchards. Young trees should receive sprays to kill potato leafhoppers. Tarnished plant bug feeding damage has been reported in apples and peaches. Rose chafer is out and Japanese beetles are emerging. Obliquebanded leafroller adults were trapped last Monday, indicating the flight of the overwintering generation has started. Aphid numbers are building. We are catching lesser peach tree borer. Trunk sprays or pheromone disruption are recommended for borer control. Apricots are almost two inches in diameter. Peaches are 1 to 1.5 inches in diameter. Growers are hand thinning excess fruit. Oriental fruit moth egg hatch has ended and few shoot strikes have been reported. Pit hardening has not yet begun. Bacterial spot has been reported, but not peach scab or rusty spot (powdery mildew). Green peach aphid populations are climbing. Sweet cherries are coloring and showing red color. Harvest of early varieties such as Cavalier should begin late this week. The cool, dry weather has suppressed brown rot infection. Brown rot requires warm, wet conditions, five to six hours of wetness at 70°F and growers should be prepared to protect against this disease at harvest. The weekend rains were cherry leaf spot infections in some areas. Tart cherries are coloring. Growers should wait until all the fruit are straw-colored before applying ethephon sprays. Recent rains were cherry leaf spot infections in some areas. No cherry leaf spot symptoms have been reported. Bacterial canker symptoms can be found on tart cherry leaves and fruit. Plums are almost an inch in diameter and the pits are hardening. Growers still need to protect against black knot. Plum trees also need to be protected from the peach tree borers. Apples are an inch in diameter. Fruit drop over the several weeks has been heavy and for some varieties the crop is very light. Apple scab leaf symptoms can be found in sprayed orchards. These lesions will release spores during every rain. Growers with active scab should continue to protect against scab infection. Waxy fruit is resistant to scab. Fire blight infections are becoming more common, but they are not severe in most orchards. Trap catch for codling moth remains high. We are now in the treatment window for codling moth and egg hatch is underway throughout the region. Spotted tentiform leafminer will form leaf mines soon. White apple leafhopper is hard to find. European red mites are moving about. San Jose scale adults are flying. Sprays for San Jose scale crawler should be targeted for 300 GDD50 after biofix (June 1), about June 20. Green aphid populations are climbing. Pears are 24 mm in diameter. The crop looks good. Small fruit Blueberries are growing rapidly. Cranberry fruitworm trap numbers are still high, and controls have been applied to many fields. Post bloom fungicide sprays should target anthracnose. More growers are reporting dead blossom clusters caused by phomopsis infections of the flower clusters. Shoestring symptoms are easy to find. In grapes, Concord and Niagara bloom is ending. Wine grapes are blooming. Rose chafer was common is some vineyards. Grape leafhopper can be found in many vineyards. Insecticides to control grape berry moth should be included in the post-bloom spray. Strawberry harvest has begun. Warm temperatures and dry conditions following the rains of June 5-7, have moved the crop rapidly. Fruit size and quality are excellent. Cool conditions should extend the season. Leather rot and sap beetles can be found in some fields. Raspberry and blackberry bloom is ending. Growers should be scouting for Japanese beetles. Raspberry sawfly larvae and leafroller larvae are feeding in some plantings. Raspberry sawfly eats the leaves between the veins, while leaf rollers curl and web the leaves together. Raspberry cane borers are laying eggs, so look for wilting shoot tips and a ring of parallel girdles at the base of the wilting. The eggs are laid between the girdles. Primocanes in fall bearing raspberries are 12 to 18 inches tall. Cranberry bloom has begun. Upcoming meetings The next Monday Fruit Update meeting will be Monday, June 23 at the Fruit Acres Farm in Berrien County. There is a twilight grape IPM meeting Thursday, June 19 at Tim Seppala's farm, southeast of Lawton at 6:00 PM. There is a Blueberry IPM meeting Wednesday, June 24 at Carini Farms in Ottawa County at 6:00 PM. |
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2 -- Southeast Most areas of southeastern Michigan have continued to receive a fair amount of rain, with many areas picking up another inch to 1.50-inch, and a few reports of two to three inches of rain from these slow moving scattered thunderstorms. We have not had any reports of hail in this most recent set of thundershowers. Our season remains about normal in terms of degree day totals as well as tree phenology. We have seen a tremendous growth in all of our fruits as a result of this moisture, with the exception of tart cherries. Southeast Michigan growing degree day totals for March 1 to June 16
Tree fruits Apples have taken on a big swell of growth over the last week. Most apples are in the range of 1.0 to 1.25-inch in diameter. Apple drop from thinning and frost/freeze injury seems to be coming to an end here. I would assess our apple crops as being a good crop overall, however with some varieties being very light, most notably Northern Spy, and other varieties, like Golden Delicious, being generally being too heavy. Codling moth trap catches have remained high over the last week. Overall, as I look at codling moth trap catches this season, we’ve had some very high trap catches. Even in some pheromone disruption blocks that have been disrupted for a good number of years; I am seeing some fairly high trap catch numbers. I think this bears watching throughout the rest of the season. Plum curculio stings are fairly common around the district, and I continue to see a fair amount of recent plum curculio oviposition stings. Oriental fruit moth trap catches are generally down with a few shoot strikes being seen. Obliquebanded leafroller trap catches are fairly high with an average of ten to 20 per trap. I am even finding some fairly good numbers of obliquebanded leafroller adults in codling moth traps. Spotted tentiform leafminer mines are now plainly visible; however their numbers are generally low across the entire region. This concerns me a bit. Potato leafhopper are present in apples and other tree fruits, however their numbers are low to moderate. White apple leafhopper nymphs can be seen occasionally, however their numbers are also fairly low. San Jose scale crawlers are beginning to crawl as of this morning. A number of aphids continue to be seen; however the numbers are low and are under control, these include green apple aphid, rosy apple aphid and woolly apple aphid. I reported last week that apple scab lesions were more prevalent across the district. I continue to find it on both the top and bottom of the leaf, and generally the leaves are a little over a month old. I think that most of this scab came in early May sometime. It’s puzzling why we are seeing so much scab this year around the district, as many growers have done a good job of trying to keep them under control. The apple scab lesions appear to be burned out at most farms, and I think that the story is pretty much history. With the rain event of Saturday night, I caught apple scab spores. One of the two trapping stations had a rain event on Sunday night, and from that station I caught no spores. Based on the time of year and more importantly the fact that we didn’t catch any spores at one of our trapping stations, I am calling an end to primary apple scab season as of Sunday. Fireblight strikes continue to be seen, however the numbers are very low and does not appear to be getting any worse. Pears are about one-inch in diameter. There is a fair amount of pear psylla showing up in suckers. I believe that fruit finish may be an issue this year from frost/freeze injury. We generally have a light crop of pears this season. Peaches have a wide variety of fruit sizes on them, with the largest fruit being 1.25-inches in diameter, and most of the fruit is between 18 mm to 23 mm. It is now pretty evident what fruit is going to remain on the tree at harvest time, and therefore many peach growers are thinning quite aggressively. Tarnished plant bug continues to be seen in fairly high numbers in some peach blocks. Plum curculio is a lingering threat this year in peaches. Potato leafhopper have been seen in peaches as well. Some blocks have moderate numbers of green peach aphids in them. X-disease is starting to be seen at a few farms. Bacterial spot infecting foliage is more evident this week. There are a number of trees that have bacterial canker infection starting to become evident. Sweet cherries are nearing harvest for some of the early maturing varieties; I estimate that we will begin harvest at most farms in about a little under a week. The maturity cycle in sweet cherries has been shortened this year. Most fruit are around 20 mm to 22 mm in size, with some of the larger fruit being 24 mm. On some of these early varieties, it has been amazing to see how much the fruit have colored over the last week. Cherry fruit flies have been caught in traps at two farms in the last two days. It seems as if cherry fruit flies have been flying much earlier the last several seasons, as this is the earliest that I have ever caught cherry fruit fly in sweet cherries. Some signs of plum curculio stinging have been seen in both sweet and tart cherries. There have been some reports of bacterial canker infected spurs in sweets as well. Tart cherries have not sized much over the last several weeks, with most fruit being in the 12 mm to 14 mm size. We are at pit hardening. There continues to be a fair amount of drop in tart cherries. Fruit finish is also poor due to freeze and frost injury. Plums continue to drop quite heavily with most fruit averaging about one-inch in diameter. Plum curculio activity is heavy in several blocks. Small fruits Strawberry harvest is now underway across the entire region. We have a nice crop of strawberries coming along this year at most farms. Strawberry harvest and heat don’t go well together, so growers are welcoming this recent cooler weather. Leather rot is a new problem to report at a few strawberry farms this past week. I have also seen some strawberries grown in southeast Michigan that have signs of anthracnose. It appears to be very localized in areas that have higher moisture levels or where there was a bit more free standing water over the last couple weeks. Potato leafhopper have been seen in fairly light numbers in strawberries. Slugs continue to be a problem at a few farms. Newly planted plants are runnering very well over the last week. Raspberries are nearing the end of bloom and are at fruit set for just about all of our summer bearing varieties. Fall raspberries are about 15-inches to 20-inches in length. Raspberry sawfly feeding injury to foliage has now slowed a bit. There are several farms that had significant amounts of sawfly damage at this time last week. Blueberries are at fruit set to small green fruit across the region. In cutting a good amount of fruit over the last week, there appears to be some brown discoloration from frost/freeze injury that is lingering in the fruit. Where the damage is severe, I expect that fruit to drop prior to harvest, where damage is lighter, I would expect fruit to continue to mature, however not being as large in size as normal. Cranberry fruitworm and cherry fruitworm covers were applied over the last week at most farms. |
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3 -- Grand Rapids Area Degree day accumulations at the Sparta weather station continue to be right at or slightly ahead of average. Most apples are in the 20 to 25 mm stage or bigger. There seems to be quite a heavy fruit drop going on in apples with some blocks nearly completely without fruit. Overall, we might be looking at 50 percent of an apple crop in the Grand Rapids area due to the effects of the freezing temperatures through out this spring. Tree fruit If there was any trauma blight from high winds or isolated hail during the June storms, it will probably start to show up at any time now, so be watching closely for that. There are a few reports of trauma blight showing up. Nectria canker is being seen in Romes. At first, it will look like a fire blight strike, but if you look closely, you won’t see any oozing bacteria, but rather a sunken canker area from the nectria fungus. No new egg laying scars from plum curculio have been found in tree fruits, but there are reports from other areas of the state where they are still active. Continue to monitor for plum curculio closely. Additional newly laid European red mite eggs can be found. New nymphs are expected to be seen soon. Continue to monitor mites closely. For codling moth, a regional biofix has been set for the Grand Rapids area for May 24. We’ve collected 366 degree days base 50 since that biofix, so controls for newly emerging larvae should be maintained for at least another three to four weeks. Peak egg hatch is expected to happen around the middle of next week. Obliquebanded leafroller are starting to fly, but not very regularly so a biofix has not been set for the region yet. A regional biofix for Oriental fruit moth has been set on May 8. We have accumulated 601 degree days base 45 since that biofix, so Oriental fruit moth should be just past peak egg hatch right now. Cover sprays are still very important in stone fruits to prevent shoot damage and fruit damage as well, especially peaches and sweet cherries. Small fruit Blueberries in central Michigan, north from Van Buren, are in the green fruit stage. There were new storms affecting the central region, especially the areas located north of Muskegon. Blueberry fields located in the area of Rothbury, Michigan suffered extensive flooding that may make the application of pest control measures difficult. In Muskegon, Ottawa and Allegan counties there were also flooded fields, but at this time the waters have been drained from almost all affected fields. So far, no damages to plants or crop have been reported. However, it is still too early to evaluated plant injury to the root system of blueberries in flooded fields. Regarding other weather related damages, we are finding that many fields located in Muskegon, Oceana, and Mason counties were severely affected by spring frosts. Affected blueberry fields were in green tips up to 0.25-inch green when the freeze/frost events occurred. This caused damage to all green tissues that were exposed at that time. Two weeks later, affected bushes showed many shoots with plenty of fruit but no leaves (Photo 1). Another effect of late frosts is seen in young plants. There was injury to tender growth that became a port of entry for Phomopsis infections (Photo 2). Growers need to take measures to control these infections in order to prevent further damage. One measure is to prune the infected shoots and apply any of the fungicides recommended in our Michigan Fruit Management Guide. The freeze/frost damage is also observed in some early varieties across the central region, mainly in fields located in low lands (Photo 3 and 4). These fields are showing shoot dieback resulting also from Phomopsis infections. Again, it is advisable that growers observing these symptoms in their fields take samples and send them to the MSU Diagnostic Lab for identification and take the appropriate control measures.
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4 -- West Central A series of storms and rain have occurred over the past week. This area has not seen so much rain in such a short period in time in many years, if ever before. Reportedly, Mason County received anywhere from four to 12 inches of precipitation in 11 hours. Official readings by our Enviro-weather stations were from 0.76-inch in Hart to 4.15 inches in Manistee and Bear Lake. There have been a lot of flooding and related problems including ruptured main pipes, washed out roads, closed roads, etc. There have been a few reports of hail in spots that did not cause major problems. Strong winds in the northern parts of the district did pull some trees out and cause many broken limbs and branches creating entry points for disease invasion. Crop report Our “short” crop is getting smaller. There is a lot of fruit drop in apples, cherries and peaches. West Central Michigan growing degree day totals from March 1, as of Sunday, June15
Stormy conditions created a suitable environment for disease development. Last week there were two apple scab infections for Oceana and Mason counties and three infections in Manistee and Bear Lake. The heavy rain of June 12-13 resulted in a moderate infection period for Manistee County and light infections for Oceana and Mason counties. Scouts are reporting findings of a few lesions in few blocks throughout the district. Fireblight is of major concern, after all of the rain, wind and hail and quite warm temperatures that followed, fireblight symptoms are starting to show up. Canker margins started oozing just before the storm providing plenty of inoculum to be dispersed around and find a home within the tender newly developing leaves, broken shoots, hail-injured leaves, shoots and fruit. Nectria shoot blight symptoms are present in Rome blocks. There were two (Oceana and Mason counties) to three (Manistee County) cherry leaf spot infections this past week. No leaf lesions were found at this time. Bacterial leaf spot and bacterial canker symptoms are spread widely throughout the district. Brown rot symptoms are starting to appear on the frost and freeze injured cherry fruit that has not fallen off and is beginning to crack as the fruit is gaining in size. Cherry leaves with cherry-yellows symptoms are starting to drop profusely. Powdery mildew is becoming more visible in the blocks. Insects have been quite active. Codling moth numbers have gone up significantly. The average catch is from 8.6 moths per trap in Mason County to 20.2 moths per trap in Oceana County. For growers that rely on regional codling moth biofix, the table below shows the growing degree day accumulation since the biofix. Codling moth: GDD accumulation post biofix as of June 16
There are reports of the first rose chafers in the area. Plum curculio is still very active with scouts reporting increased numbers of trap catches and stings on the fruit. Tarnished plant bug is commonly found in blocks throughout the area. Pear psylla instars and adults are present in relatively high numbers. American plum borer numbers are still high. The average number per trap has gone from 3.75 to 8.3 per trap. Greater peach tree borer numbers have gone up from the average of 0.5 to 8 per trap. Lesser peach tree borer numbers have more than doubled since week the before. The average numbers have gone from 34 to 84 per trap. There have been no cherry fruit fly catches yet. |
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5 -- Northwest Growing degree day accumulations at NWMHRS Growth Stages at NWMHRS from June 16 at 5:00 PM Apples are at 16-18 mm. Bartlett pears have 16 mm fruit. Sweet cherries: Hedelfingen and Napoleon have 13 mm fruit. Gold have 12 mm fruit. Tart cherries: Montmorency and Balaton have 13 mm fruit. Apricots have 28 mm fruit. Plums are 15 mm. Grapes have 10-16 inch shoots. Weather The weather continues to surprise us again this week. Despite the meteorologists’ best efforts, we never know what to expect with the current weather conditions. Last week, temperatures were more seasonable as daytime highs were in the mid- to upper 70s, and nighttime temperatures were in the mid-50s to the 60s. Growing degree accumulations are behind where we were at this time last year, and at base 42 and 50, we have accumulated 906 and 490 GDD respectively. We received significant rainfall in the region in the past week. Here at the NWMHRS, we accumulated 0.4 inches of rain on Thursday, June 12, 0.95 inches on June 13 and another 0.12 inches on June 15. The rain continues this Tuesday morning. We also have reports of significant hail in southern Leelanau County on Sunday evening. In fact, from May 30 to June 17, a 19-day period, we have had only five days without some recorded precipitation. Overall, we have had good moisture this season, which is much needed after droughty summer conditions in the past three seasons. Crop report The final verdict on the cherry crop report is still out as much of the region is experiencing June drop. Sweet cherry orchards with what initially appeared as a healthy crop have dropped a lot of fruit in the past week. The surprisingly sizable June drop may be attributed to poor pollination, freeze/frost damage, or to the past years’ droughty conditions. Additionally, many sweet cherry orchards do not appear to be as healthy as we would expect with all the good moisture; we have observed tattered foliage, yellowish leaves, and symptoms of bacterial canker. Tart cherries continue to size, and the crop is estimated at 60 million pounds in northwest Michigan. Gibberellic acid has been applied in cherries during the warm weather last week. Growers have been thinning apples in locations not impacted by the freeze damage. Windy and rainy conditions have presented tremendous difficulty for application of sprays. We are still in the grips of the primary apple scab season, but it is winding down with 90 percent of the ascospores or sexual spores, estimated to have been released from their overwintering structures. The rain we received over the weekend caused a predicted light to moderate infection period in most of the region. Protectants to prevent apple scab should continue to be applied. The fire blight model has slowed EIP accumulation due to the cooler weather, which is predicted to last through Wednesday. Most varieties have finished blooming, but we have been seeing a great deal of tag bloom which needs continued protection for fireblight. Strep applications are recommended to treat fire blight in northwest Michigan where resistance is not yet present. Plum curculio continues to be caught in orchards around the region. Spotted tentiform leafminer numbers are down, and we are well beyond peak emergence. We are catching approximately 30 codling moths per trap at the research station, and oriental fruit moths are emerging in elevated numbers (19-22 per trap). Cherry leaf spot is still predicted in the region based on Saturday and Sunday’s rainfall. If growers applied a protective fungicide, such as Pristine or Gem, these are locally systemic and rainfast after two hours, the foliage in these cases should be protected. If fungicides have been applied on alternate rows, then the interval between sprays should be shortened by two to three days. We are seeing a great deal of bacterial canker in sweet cherries at the Northwest Station, particularly on those in low-lying sites that were hit hard by the freeze after Memorial Day weekend. Powdery mildew is also showing up on tarts at the station. We continue to see plum curculio stings on cherries. We are continuing to catch American plum borer and lesser peach tree borer at approximately 15 per trap. We are also catching low levels of greater peach tree borer in our station traps. In grapes, we have been seeing potato leaf hopper and an unusual insect, grape plume moth. Grape phylloxera, Daktulosphaira vitifoliae (Fitch) was sited in one of our commercial vineyards. These insects rarely make serious pest status in areas with our sandy soils; they are considered to be more problematic in regions with heavier clay soils. Despite the fact we rarely see damaging numbers of phylloxera in the north, we remind growers to be vigilant about control. This caution should be particularly noted in choosing a phylloxera-resistant/tolerant rootstock for newly planted vines. If populations reach high enough levels, the foliar or aerial part of the phylloxera life cycle can result in premature defoliation, reduced shoot growth, and reduced yield and quality of the crop. We often observe foliar damage on wild grape, labrusca and some vinifera vineyards as raised galls on the undersides of leaves in the eastern part of the U.S. The root form of phylloxera stunts the growth of susceptible vines and can kill them, but this form prefers vines grown in heavy clay soils. Phylloxera damages the roots by feeding on growing rootlets, which then swell and turn yellowish; dead areas eventually develop at the feeding sites. |
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Weather news A large area of training thunderstorms (storms which form and move repeatedly across the same areas) brought torrential rains and widespread flooding to sections of northwest lower Michigan last Thursday and Friday (June 12-13). More than six inches of rain fell from Mason and Manistee counties northeastward into Wexford, Lake, Osceola, and Missaukee counties. There was an observation of 11 inches in the Ludington area from roughly 9:00 PM on Thursday through 7:00 AM on Friday. If this observation stands, it would be a new state record for precipitation in both the 12 hour and 24 hour periods (the old record of 9.78 inches was set in Bloomingdale in 1914). To put the magnitude of this event in further historical perspective, the statistical 100-year, 24 hour precipitation event (an event expected to occur on average only once every 100 years) for Michigan ranges from about four inches in far northern and eastern sections of the state to about seven inches in the extreme southwest. A very rare and extreme event indeed! In contrast to the turbulent and quickly changing weather experienced during the past couple of weeks in Michigan and across much of the Midwest, the forecast for this week is relatively simple and straightforward. An upper air trough across the Great Lakes region is expected to result in a cloudy and cool weather pattern through much of this week. A series of weak disturbances moving counterclockwise around the trough will bring a chance for showers and a few thunderstorms Tuesday, Wednesday, and Thursday, especially during the afternoon and early evening hours. The best chances for rainfall will be in northern and eastern sections of the state closest to the center of the trough. Daily rainfall totals will generally remain in the 0.10-0.25- inch range where rain occurs, with most areas expected to remain dry. Temperatures during the next few days will remain well below average, with highs Wednesday through Friday generally ranging from the upper 50s north to the low 70s south and lows from the upper 40s north to the mid-50s south. Look for slowly moderating temperatures by Saturday, with highs back into the 70s and lows in the 50s across most areas of the state. A cool front is expected to pass from northwest to southeast through the region Saturday, and will bring the next chance for significant precipitation beginning late Friday in northwestern sections of Michigan and spreading south and east by late Saturday. In the medium range forecast, the National Weather Service 6‑10 day and 8-14 day outlooks covering June 22 through June 28 and June 24-30, both call for precipitation totals to remain at below normal levels. Mean temperatures are forecast to remain at below normal levels during the 6-10 day period, moderating to near normal levels during the 8-14 day time frame. |
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