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| Fruit Crop Advisory Team Alert newsletter | ||||
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| Vol. 22, No. 8, May 29, 2007 |
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| In this issue Tree fruit news  Block specific monitoring of codling moth is key to decision-makingSmall fruit news Managing grape berry moth – timing, activity and coverage Blueberry scorch, shock and sheep pen hill virus quarantineOther news Statewide pre-harvest strawberry/raspberry meeting TNRC trapline data: Codling moth Regional reportsWeather news |
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| Block specific monitoring of codling moth is key to decision-making Another cool wet spring in Michigan has pointed out the difficulties inherent in timing early season codling moth controls and moreover, in deciding whether or not an early season spray application targeting codling moth is warranted. Our goal here is to address some of the confusion that exists over what constitutes codling moth biofix, and to discuss the use of treatment thresholds based on moth captures in traps, in conjunction with growing degree-days (GDD) for codling moth, to optimize the timing of insecticide applications. Management guidelines developed by MSU entomologists over the past decade, have advised growers that the best way to understand how to manage codling moth on your own farm is to have pheromone-baited traps in each of the blocks on that farm. The 2007 season has provided us with a good lesson in how variable codling moth catches can be from one farm to another, and from one block to another on the same farm. This is not surprising considering that the extent of early season codling moth activity in an orchard is typically associated with how well the pest was controlled in the previous season, and we suspect that control was not the same in all blocks in 2006. Traps for monitoring codling moth adult flight should be set before bloom in Red Delicious with two objectives: to help establish codling moth biofix, the start of adult activity, and as a measure of codling moth activity to assist with determining if and when insecticides need to be applied. Regional information is a part of understanding codling moth activity, but the use of monitoring traps in every block of your orchards is the only accurate way to know what is happening on your farm. |
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| The accumulation of growing degree-days from the establishment of biofix is used to determine the relative proportion of each codling moth life stage developing over the course of a generation. For example, 250 DD predicts that 3 percent of the egg hatch has taken place. Keep in mind that this is a proportion; the actual numbers of eggs hatching depends on how big the population is in a particular block. If few moths have been captured, therefore, it is likely that 3 pecent egg hatch is a very small number and applying a spray would not provide much bang for the buck. As was discussed earlier this season in the Fruit CAT Alert article of May 8, there are control materials targeting the adult, egg and larval life stages of codling moth. By combining the establishment of biofix with the use of the growing degree-day model, these varying life stages can be accurately predicted to properly time spray applications. What has consistently been omitted from the decision-making process on many farms is weekly monitoring information on population numbers and whether treatments are necessary at that particular time. MSU treatment thresholds for codling moth advise that a cumulative catch of five to seven moths in any one trap over time, may indicate the need for a treatment (Table 1). This value is for orchards not deploying codling moth mating disruption. In pheromone-treated orchards, a more conservative threshold should be used. A supplement insecticide treatment is probably warranted following a cumulative catch of only two to three moths per trap. Table 1. Example of determining cumulative moth capture in traps
Over the past few seasons, early season codling moth activity in Michigan has been impacted by cool wet weather. This weather pattern has led to low codling moth activity in many orchards for the first few weeks after the establishment of biofix, making it difficult to decide if a treatment should be made when the GDD model indicates a timing window is current. The situation in southwest Michigan in 2007, provides a good example of how considering a treatment threshold can help in making this decision. Biofix for several Southwest counties was set on May 9, but moth captures in traps on five out of seven farms being intensively monitored as part of a codling moth area wide project in the region, have indicated no need for treatment in any of the blocks on these farms. So, even though the growing degree-day model tells us that enough degree-days have been accumulated to time a treatment, that treatment should not be automatically triggered. Growers need to weigh the evidence of moth activity measured by monitoring traps to decide if treatment is justified in terms of cost and time. Another consideration to be factored in for Michigan growers, is the spike in late first generation codling moth activity that has been seen over recent years. Delaying early first generation controls, when monitoring shows that treatment thresholds have not been reached, can leave more resources available to target late first generation codling moth, preventing populations from building up as the season progresses. Based on the above discussion, what advice can be provided to growers that will help them make good decisions over the next few weeks? Catches in pheromone traps appear to fall into two general patterns; a typical start to biofix a few weeks ago and continued activity above threshold since, or no to low catches throughout the past few weeks following biofix. Under the first scenario, a treatment is warranted and growers should time their sprays as outlined in the May 8 Fruit CAT Alert article. The second pattern of codling moth activity is the one that leads to a less than clear-cut process for deciding whether and when to apply first generation control treatments. Using a treatment threshold based on block-specific moth captures really helps in this situation. In some cases, the threshold will eventually be reached, although after the suggested optimum DD timing for a particular material. For example, 300 DD have passed and the grower planned to use a larvacide that typically is applied at 250 DD. Under this scenario, the grower should apply the larvacide as soon as the threshold is reached. Some growers may be fortunate enough to not reach the threshold throughout the first generation flight. Suggested options if this is the case are: to not treat if the grower is willing to take a risk, or treat at a delayed timing of 350-450 DD after the first moths were captured. This timing would be targeting the predicted peak of activity. The use of biofix and the GDD model for codling moth are key tools for helping growers properly time control measures to manage this pest, but it is only when combined with site-specific monitoring information to help determine when damaging levels of codling moth are present, that growers can best manage scarce resources to achieve the best results. |
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| Managing grape berry moth – timing, activity and coverage Effective control of grape berry moth with the currently available insecticides leaves less room for error in both timing and coverage than was possible in the past. This is because the remaining products either have shorter duration of residual control, or they are specific to fewer life stages of the pest than the broad-spectrum insecticides that had vapor action. Maintaining control of grape berry moth requires a combination of good timing, high insecticide activity and excellent cluster coverage. Our ongoing research addresses each of these components of berry moth IPM, and this update will cover them in turn. Timing To time sprays for this pest, monitoring traps and weekly scouting of vineyards can be used to know when moths and larvae are active. This can be focused on vineyard hot spots, but it is useful to spread scouting across your farm to know where grape berry moth activity is greatest. Most growers know hotspots on their farm, but this monitoring can also tell you when the pest is active in different blocks. Generation 1 Moths emerge in late April or early May, usually around 200-250 growing degree days (GDD base 50) from March 1. This year, we saw the first moths in traps on April 22 in Lawton and April 27 in Scottdale. In recent years in a trial in Paw Paw, we have found the first eggs on clusters around 650 GDD, which typically occurs when the number of moths peaks in traps and when the vines are at trace bloom. This year is no exception, as the first few grape berry moth eggs have been detected in a farm in Berrien County where the warm weather has brought the vines and the insect activity forward. Egg-laying by the spring generation moths increases during bloom, and so if using a broad spectrum insecticide, the 10 days post bloom spray will be an effective way to control the larvae and eggs present at this time. Treatments applied earlier than the post-bloom timing can be washed off or degrade before most of the egg-laying and are unlikely to protect the clusters from feeding by berry moth larvae. If growers are aiming to reduce costs in vineyards where a crop is expected, scouting clusters just after bloom can be used to determine the level of infestation by this pest and whether an insecticide is warranted at the post-bloom timing (Photo). Although there is no formal threshold developed for first generation berry moth, if only a small proportion of clusters have larvae or if the level of feeding is low, there will be minimal effect on yield. Since clusters set only about a third of the potential berries produced, clusters can withstand some feeding and this is worth considering when weighing up the cost of a spray. Generations 2 and 3 These generations are harder to time sprays for because there is less likely to be a distinct increase in moths in traps and the generations overlap. From our detailed sampling for eggs in borders of high risk vineyards for grape berry moth, we see some egg-laying during the first half of July and a period of more intense egg-laying that starts around berry-touch in early August and continues through until harvest. This may be partly from moths moving into vineyards from the woods, and partly from the offspring of the earlier generations. Insecticide activity When selecting an insecticide, there are many options for berry moth control. Some of these are selective for this pest, while others will also provide control of leafhoppers, rose chafer and other insects that can occur during bloom. The selective insecticide Intrepid has shown good effectiveness against berry moth, and we have tested it in the mid-season timings in July and August at the 12 oz rate. Although this is more expensive than many standard insecticides, the product lasts a long time (two to three weeks depending on the rate) and is resistant to wash-off. This helps make it an effective tool to use against the high pressure of egg-laying seen late in the season, when maintaining control would otherwise require multiple sprays. This works on the molting system of the larvae, disrupting normal development and because it is selective, Intrepid will not control leafhoppers or beetles. It also has a 30-day PHI. Another selective insecticide to consider is B.t. (Dipel, Javelin, Deliver etc.), which only targets the larvae of berry moth. Both of these selective insecticides need to be eaten to be effective, so their activity is greatest when temperatures are above 70ºF. Intrepid is quite stable and resistant to wash-off once sprayed providing good residual control, whereas B.t. formulations degrade under ultraviolet light, providing three to five days of activity. Most pyrethroids are inexpensive insecticides with broad insect activity. They have relatively short residual control in the hotter summer weather when growers might be spraying for the second or third generation of grape berry moth. In our 2006 trials with Danitol, Baythroid and Capture, the lower rates of these products declined in activity against grape berry moth after nine days. If using a pyrethroid to control grape berry moth along with Japanese beetle in the hot sunny conditions of July or August, using the full rate will provide the best residual control. Despite the temptation to look only at the price per acre when making decisions, be sure to rotate this class with other chemical classes to avoid resistance developing. Excellent control of grape berry moth has consistently been seen in our spray trials using either Danitol at 10.6 oz/acre or Imidan at 2 lb/acre (and buffered to pH 6). Venom provided good control of the lower, early season populations and is now registered for this use. We also have tested programs containing the new pyrethroid Capture in the first half of the growing season, and this has performed as well as the standard insecticides. Coverage Getting cluster coverage with your spray material is essential for berry moth control. As the canopy becomes denser after bloom, increase the water volume and slow down to ensure the pesticide has a chance to contact the pest. If the spray doesn’t hit the cluster, a significant investment of time and money is being wasted. To illustrate this, our research in a mature Niagara vineyard found that an airblast sprayer operated at 20 gallons of water per acre gave only half the control of grape berry moth compared with one running at 50 GPA. These results emphasize the need to make sure your sprayer is getting good coverage of the clusters, because it can make a big difference for control. |
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| Blueberry scorch, shock and sheep pen hill virus quarantine In 2002, the Michigan Department of Agriculture (MDA) established a quarantine for blueberry planting material to prevent the introduction into Michigan of blueberry scorch virus (BlSV), blueberry shock virus (BlShV), and Sheep Pen Hill virus (BlSV-NJ). These viruses are known to infect blueberries in Oregon, Washington, New Jersey and British Columbia (Canada). Cranberry plants can also be infected by blueberry scorch virus. Recently, blueberry scorch virus was also found in highbush blueberries in Connecticut and Massachusetts. These viruses spread from one geographic location to another over long distances through infected planting stock. To date, these viruses have not been found in Michigan, and it is therefore very important that we are vigilant and keep them out as they can wreak havoc on our blueberry industry. Blueberry scorch is caused by the blueberry scorch virus and has a devastating effect on blueberry plants. In the spring, young flower clusters and shoots suddenly turn brown and die (Photos 1, 2). Blighted flower clusters and shoots can be confused with mummy berry and Botrytis blight. The disease starts on one or two branches before it spreads to the whole bush in succeeding years. The symptoms are expressed in infected plants every year and plants do not recover. The production begins to drop off rapidly and the bush eventually dies. Neighboring bushes often appear healthy. Some cultivars also show marginal leaf chlorosis (Photo 3). The Sheep Pen Hill virus is a strain of blueberry scorch virus that occurs in New Jersey. Symptoms are similar for both strains, except that a red line pattern is sometimes seen on leaves of bushes infected by the Sheep Pen Hill virus (Photo 4). The disease can spread rapidly throughout a planting due to movement of aphids, which transmit the virus. Aphid transmission occurs over relatively short distances (less than a mile). All cultivars can be infected by blueberry scorch virus, but some do not show symptoms. Symptom-less infected bushes can still serve as a source of infection for nearby bushes. Blueberry shock, caused by the blueberry shock virus is very similar to blueberry scorch in its symptoms, including a sudden blighting of blossoms and leaves (Photo 5). However, the plant then apparently recovers and produces a second flush of leaves. By the end of the season, the bush looks normal except for the absence of fruit. The plant may exhibit this “shock” reaction for one to three years and may be symptom-free thereafter, but will carry the virus. All cultivars are susceptible. Blueberry shock virus is pollen-borne. Transmission of the virus occurs when pollinators, especially honeybees, transfer infected pollen to flowers on healthy plants. The MDA quarantine regulations stipulate that no plants, buds, vegetative cuttings or any other blueberry planting material should be brought into Michigan from regulated areas (WA, OR, NJ, BC) unless it has been certified virus free by a virus-free certification program recognized by MDA. Planting material shipped into Michigan must be accompanied by a State Phytosanitary Certificate or Certificate of Quarantine Compliance, indicating its point of original propagation or production and labeled or stamped to show compliance with terms of this quarantine. Violations of the quarantine regulations can lead to fines and destruction of uncertified or virus-infected plant material as well as revocation of the special permit to ship to Michigan. |
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| Statewide pre-harvest strawberry/raspberry meeting This year’s Pre-harvest Strawberry Meeting will take place at Rowe’s Produce Farm, 10570 Martz Road, Ypsilanti, Michigan. The farm is located between Ann Arbor and Detroit (close to Metro Airport), just south of I-94. The meeting will be June 7 from 4:00 to 6:00PM. This year’s meeting is designed to help strawberry and raspberry growers learn the latest recommendations in varieties, insect, disease and weed management. We have an excellent farm to host our meeting this year and a great deal to see and talk about. Topics featured
For more information or details about this meeting, contact Bob Tritten at 810-732-2177 or email Bob at tritten@msu.edu. |
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| Regional reports 1 -- Southwest Mark Longstroth Bill Shane Greg Vlaming Weather Last week was hot and windy. Highs were in the upper 80s until a cold front moved through the region on Friday May 25, with overnight rain and a rainy Saturday. Precipitation totals were about one to 1.5 inches of water. A long wetting period of over 24 hours at about 60ºF was a major infection period for all fruit diseases. A fire blight trauma infection was possible due to hot windy conditions before the storms. The forecast is for warm weather with temperatures above 80ºF to return with thunderstorms possible the rest of the week. Cooler temperatures with lows in the 70s are forecast for the weekend.
Tree fruit Peaches are 20 mm in diameter and growers are hand thinning. We are finding shoot flagging from Oriental fruit moth larvae feeding in the shoot tips. Oriental fruit moth trap catch is down. We are nearing the end of egg hatch. Biofix was April 21 at 230 GDD at SWMREC. The end of egg hatch is about 646 GDD base 45 after biofix, so the end of egg hatch will be about 975 GDD base 45. Growers should protect susceptible varieties from peach mildew or rusty spot. Tart cherries are 14 mm in diameter. With the light crop, growers need to maintain protection for plum curculio and cherry leaf spot. Cherry leaf spot symptoms are easy to find on unsprayed tart cherries. Sweet cherries are 16 mm in diameter and some fruit is coloring and being shed. Growers need to protect against plum curculio and brown rot. Bacterial canker symptoms are appearing on fruit and leaves. Black cherry aphids are curling the leaves of terminal shoots. Cherry leaf spot can be found in the area. Plums are about 14 mm in diameter. Growers should be protecting against plum curculio black knot and brown rot. Apples are 12 to 20 mm in diameter. We have not seen a heavy drop and some growers are considering follow up spray thinning. Many blocks do not need thinning. Fire blight and apple scab symptoms are becoming common. The Enviroweather website is forecasting that all the apple scab spores are mature and the weekend rain probably removed almost all the primary spores. Growers should check their orchards for scab lesions on the leaves and determine if they should maintain fungicide protection. The fruit will still be susceptible to scab infection for several weeks. Plum curculio will be attacking fruit during this warm period. Growers should consider materials that have activity against both plum curculio and codling moth. Codling moths began flying May 5, and were biofixed on Wednesday, May 9 (325 GDD50 at SWMREC). We are now catching moths widely and have a sustained flight. It is now over 250 GDD past biofix and time to spray conventional materials such as Guthion, Danitol or Warrior. A few Oriental fruit moths are still being caught in pheromone traps, but egg hatch of the first generation is ending. European red mites and rosy apple aphids are out and growers and scouts should be looking for sap feeding spotted tentiform leafminers and the first mines. Pears are 18 mm in diameter. Pear psylla nymphs are feeding in the axils of leaves. Pear blister mite symptoms have appeared. Pear scab is similar to apple scab, and pear scab symptoms should appear this week as with apple scab. A good scab program usually controls Fabraea leaf spot, but the infection period lasts longer than pear scab. We expect rose chafer to emerge soon. Potato leafhoppers have been reported in the region. Fresh plum curculio damage is fairly common on edges of some peach, plum and apple blocks. We expect peak egg laying for plum curculio this week in Southwest Michigan. Small fruit Blueberries are small green fruit. Many growers have treated for cranberry and cherry fruit worms. Growers should apply fungicides to reduce anthracnose fruit rot later. In grapes, Concord flower clusters are separating. Wild grapes are past full bloom, so bloom could begin late this week. Vinifera shoots are 8 to 12 inches long. Growers are applying the last pre-bloom disease control materials. Growers who did not have materials on for the May 26 rain should consider materials with back action. The rain over the weekend was an infection event for all grape diseases. Phomopsis lesions were found on grape leaves and shoots. There was some scattered frost injury on Friday, May 18. Treatment for grape berry moth should be timed for the end of bloom. Grape leafhopper adults are flying low in the canopy. We expect to see rose chafer soon. Strawberries are beginning to color, and harvest of berries on and under plastic have begun. Summer raspberries have green fruit, and the crop looks good. Fall raspberry shoots are about 24 inches high. Orange rust has been reported. Cranberry shoots are elongating. Now is the time for pre-bloom fungicide treatments. Upright dieback has been common in the fields. Miscellaneous The next Monday Fruit Update meeting will be Monday June 4, 5:00 PM, at the Fruit Acres Farm in Berrien County. There are RUP credits available for the Monday Fruit Update meetings. |
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| 2 -- Southeast Bob Tritten Weather Heat over the last week has resulted in the emergence of many insects. Rainfall over the weekend brought a high apple scab infection period for apple growers and generally another round of spraying for fruit growers. Rain on Friday, Saturday and Sunday generally totaled about ½ inch across the region. High winds were also a concern with some of these storms that moved through the region over the last three days. Our season is still running about five days ahead of normal in degree day totals and a few days ahead of normal of phenology or tree growth. Southeast Michigan growing degree day totals for March 1 to May 28
Tree fruits Apples are mostly at 15 mm to 16 mm for Red Delicious, Empire at 19 mm and Ida’s at 20-22 mm for the Flint area. I’ve not seen any drop as a result of thinner applications that were applied over the last 10 days or so. Golden Delicious is the only variety that appears to be consistently light this year, with Red Delicious consistently the only variety that appears to be fruiting on the heavy side. New pest problems reported on apples include; codling moth biofix at many farms, plum curculio adult and egg laying scars being seen more commonly and first visible fireblight strikes. Codling moth trap catches are generally low this year, however many apple growers biofixed for codling moth mid to late last week. With the continued warm day and night temperatures, I expect to see a sustained flight of codling moth as we move through this week. Mullen bug fruit damage has been seen now at several apple farms across the region, with sightings more numerous than other years. Plum curculio adults and fruit egg laying scars have been seen in light amounts at many farms across the region. Oriental fruit moth trap catches remain high at many farms across the region with some in the range still of 150 to 170 per trap. I expect to see these numbers drop off this week. Tarnished plant bugs continue to be seen in fairly low numbers, as do potato leaf hopper adults. Larvae of many leafrollers continue to be seen in fairly low numbers. Rosy apple and green apple aphids continue to be seen in fairly light numbers, as do woolly apple aphids. European red mites have been slow to move thus far this year, with mostly low populations of adults. Growers need to do a good job of scouting at this time, as populations could begin to build quickly with this hot weather. We have a good number of predators being seen on a regular basis in many apple blocks this year. Rain on Saturday generally brought a high apple scab wetting infection period over the entire region. We are still catching apple scab spores with each of these rain events, so I’m not ready to call an end to primary apple scab season at this time. Stay tuned for details as we move throughout the week. Apple scab lesions are now being seen on leaf tops in light amounts at many farms across the region. Fireblight strikes first started to show up last Tuesday, and were more evident as we moved through the middle and the end of the week. I’ve seen fireblight strikes in many varieties, including Jonathon, Cortland, Rome and Empire. Streptomycin burn has been seen fairly commonly at many farms across the region. Pears are mostly at 16-18 mm in size. Pear psylla adults continue to be seen in good numbers at a few farms. I’ve seen just a few fireblight strikes in pears over the last week. Peaches are mostly at 15-16 mm for Red Haven. Peaches continue to size fairly rapidly. Green peach aphids are being seen in high levels at a few farms and at low to moderate levels in many others. Sweet cherries are currently at 13-15 mm in size and are now at pit hardening. Black cherry aphid was seen in high levels in a few blocks, however they are being seen quite commonly at lower levels across the region. Plum curculio scars continue to be seen at low levels in many blocks. Bacterial spot affected foliage is becoming more apparent. Tart cherries are mostly at 10-11 mm in size, with some as large as 13 mm. We are not at pit hardening yet on tart cherries. There are some low levels of black cherry aphids on tart cherries. Plums are sizing quite nicely, with most being in the range of 15 to 17 mm in size. Low levels of plum curculio have been seen over the last week. Small fruits Strawberries have had a long bloom period this year, with some fruit now thimble size in the Flint area. Tarnished plant bugs and strawberry clippers continue to be seen in fairly low levels, most strawberry growers have applied an insecticide to control both of these pests. Gray mold fungicide sprays were applied for a second or third time over the weekend or early this week. Weed issues are becoming more apparent in many strawberry fields over the last week. Raspberries are in bloom for summer raspberries and fall raspberries are now about 16 to 18 inches in length and look fairly good with no pest problems to report at this time. Blueberries are mostly at petal fall to early fruit set. We’ve had a good bloom in blueberries this year. Many blueberry growers are applying insecticides to control petal fall pests as well as fungicides for early disease control. |
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| 3 -- Grand Rapids Area Phil Schwallier Amy Irish-Brown Carol Garcia-Salazar Tree fruit Many apple fruits are at the 12 to 15 mm size, with early varieties being quite a bit larger than that. Quite a bit of thinning will be done this week with the much warmer temperatures being predicted. By next week, fruits will be too large for thinners to work. We should be at 100 percent apple scab spore maturity now, but only 90 to 95 percent of those spores are most likely discharged at this time, and we need a few more rain events to discharge them all – primary scab fungicide rates are still very important. The last apple scab infection was from the rain on May 26 – a moderate to heavy infection depending on which weather station data you use. I did catch ascospores with this last rain event – a low amount, but that tells us we’re still in primary apple scab for at least another rain or two. Some fire blight is showing up in non-sprayed trials, but none has been reported in commercially cared for blocks. It looks as through growers have done a good job protecting from blossom blight this year. A regional biofix for Oriental fruit moth was set for Grand Rapids area on May 10. Adult numbers have consistently been increasing in traps over the last 10 days, and we should be nearing peak adult activity this week. Flagging of peach and other stone fruit shoots should be seen at any time and cover sprays are recommended. A regional biofix for codling moth was set for May 20. It might be too late or too early for a few blocks, but it should work for the majority of acres around Grand Rapids. We have accumulated just over 100 DD50 since May 20 and nearly 180 DD50 since May 15. European red mites are relatively common this year, and many blocks have a petalfall miticide on this year. Adult European red mite can be found, but no new egg-laying reported yet, but should start at any time. The continued warm weather this week could really drive red mite populations where no controls have been put on. Plum curculio have been actively making ovipositioning scars in stone fruits and apple. Damage should continue for another week or two, and cover sprays in apple should be well maintained this year for another 10 to 14 days for plum curculio. |
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| 4 -- West Central Mira Danilovich Weather and crop development A cold front made its way to our area by the second part of last week dropping the temperatures down into the mid 60’s and low 70’s. The same front brought strong winds and rain across the district with the highest amounts recorded in Oceana County. The crop continues to develop nicely. Growers have been taking advantage of a few warm days to do early apple thinning. Except for the early bloomers, most varieties are just reaching the optimum size for thinning (Red Delicious is 8-9 mm). The very early window of opportunity was between Tuesday and Thursday, when the temperatures were well into the 80’s. Though it is still early to evaluate the results of these applications, it appears that there is quite a bit of variation among the varieties. Red Delicious seems to have responded very well having mostly two fruit per blossom left; Cortlands do not show any signs of distress. They still have all (and very strong) fruits in a blossom; Golden Delicious has not responded strongly to this early thinning. Pears are about 15-16 mm in diameter. Peaches are 15+ mm. Plums are 15-16 mm. Tart cherries are 12-13 mm. Sweet cherries are 14-16 mm. West Central Michigan growing degree day totals since March 1-May 28
Tree fruit Out of the two rain events this week, only the rain of May 26-27 was long enough to develop into moderate infection periods for both apple scab and cherry leaf spot. Each rain event produced spore discharge. The good news is that the numbers are declining. We have had 100 percent mature spores for a week now and would need some more rain to flush them out. Lesions from the previous infections on apples and cherries are being found on occasion. Bacterial canker symptoms are showing up on the leaves and the fruit on sweet cherries. Codling moth numbers are increasing. Biofix is being set on block-by-block basis. For many blocks in Mason and Manistee Counties, biofix was set for May 18 at 255 and 277 DD50, respectively. Many growers have chosen Rimon for the early control of the first generation, and the applications are going on at this time based on the post biofix degree-day accumulation. Applications for oriental fruit moth control have started a few days ago following the degree- day model, though we are still catching a fair number of adults. Scouts are reporting finding a significant number of brown weevils in apples that have been identified as European leaf weevil. Though they might be numerous in the block, they are leaf feeders and do not inflict damage to the fruit. At any rate, some of the regular sprays will take care of them too. Plum curculio numbers are getting higher. Egg-laying scars are being found. It appears that the cool evenings have slowed them down. Forecast for the reminder of the week is calling for the warmer evening and nighttime temperatures, which will increase plum curculio egg-laying activity. We are finding tarnished plant bugs and first symptoms of potato leafhopper feeding. |
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| 5 -- Northwest Nikki Rothwell Duke Elsner Growing Degree Day Accumulations at NWMHRS Apples are at 9 mm fruit. Pears: Bartlett is at 9 mm fruit. Sweet cherries: Hedelfingen, Gold, and Napoleon are at 11 mm fruit. Tart cherries: Montmorency and Balaton are at 11 mm fruit. Apricots are at 29 mm fruit. Plums are at 9 mm fruit. Grapes: Chardonnay are at 10 – 16 inch shoots. Weather The Memorial Day weekend was fairly cool in the north. We had some rain on May 26, which resulted in infection periods for all diseases. The most noticeable weather event for the past few days has been the extremely high winds. The forecast for the next few days predicts spotty rain showers and thunderstorms throughout the region. Tree fruit In apples,after much discussion about codling moth biofix so far this season, the NWMHRS biofixed for this pest on May 14. As of today (May 29), we are at 136 GDD post biofix. We have also seen plum curculio moving around in minimally managed apple blocks. The Saturday rain event resulted in low to moderate scab infections for all stations in the region. We have not seen apple scab lesions from previous events. Based on the apple scab model, the NWMRHS is at 100 percent spore maturity and 87 percent spore release. We have noticed that we have had quite a few apple scab infection periods considering we have had so little total rain accumulation this season. Apples at the NWMHRS are at 8 mm for Red Delicious and 6 mm for Gala and Golden Delicious, which means growers should be planning their thinning strategies this week and into next week. Temperatures are predicted to be warm this week – a good forecast for thinning. In cherries, plum curculio are moving around in stone fruits, and we have detected egg-laying scars in unsprayed sweet cherries. However, we have seen minimal scarring in conventional cherry blocks. If growers are using the Postponed Insecticide Treatment Strategy for plum curculio in tart cherry, we are at 189 GDD post biofix at the NWMHRS. The biofix for this delayed treatment strategy is full bloom. Remember, this model only works for tart cherries and is only recommended for growers that are actively scouting their blocks. With the warm temperatures predicted and with the cherries at a susceptible stage, growers should be diligent about plum curculio control. We had a cherry leaf spot infection period throughout the region on May 26. We have also saw some cherry leaf spot lesions showing up in blocks that had a missed spray. Small fruit Most grape varieties are now at 8-12 inch shoot length and clusters are clearly visible. No symptoms of powdery mildew or other foliar diseases have been seen in unsprayed vines at NWMHRS. No potato leafhoppers have been reported in the Northwest, but they have been seen in West Central Michigan. Adults of potato leafhoppers could arrive in our area at any time. A few eight-spotted forester moths have been seen; larvae typically appear just before bloom, but they are seldom numerous enough to be a concern. Injury from grape erineum mite has been reported in Grand Traverse County – more next week. A number of clearwing borer adults closely resembling grape root borer were trapped this past week. If this tentative identification is verified, this will be the first record of this pest, which is a serious problem in other eastern United States growing regions. For additional information please go to the http://www.grapes.msu.edu website and click on “View latest 2007 Scouting Report.” |
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| Weather news Jeff Andresen An upper air trough across the northern Great Plains on the morning of Tuesday, May 29, will very slowly edge eastward towards the Great Lakes region by the end of the work week, setting the stage for several days of summer-like weather with an almost daily chance for showers and thunderstorms. Given the lack of a focusing mechanism for convection, any rainfall that develops through Friday will be scattered in nature, with most areas remaining dry. Best chances for rainfall will be during late afternoon and early evening hours. Temperatures through Friday will range from highs in the upper 70's in lakeshore areas to the upper 80's inland, with lows generally in the upper 50's to low 60=s. As the upper air trough approaches this weekend, there will be a better chance for rainfall, especially Saturday. Temperatures will fall back to highs in the 70's by Saturday, with lows in the 50's. Cooler and drier weather is expected early next week. In the medium range time frame, the official NOAA 6‑10 day and 8-14 day outlooks for June 3-7 and June 5-11, both call for near normal mean temperatures statewide. During the 6-10 day period, precipitation is forecast to range from below normal levels in western sections of Upper Michigan to above normal in far eastern sections of Lower Michigan. Precipitation totals during the 8-14 day period are forecast to range from below normal levels in southwestern sections of the state to near normal in the northeast. New long lead outlooks NOAA long lead outlooks for the next few months call for the gradual development of cooler than normal sea surface temperatures (La Nina conditions) in the equatorial Pacific. However, any related impacts in the United States, at least for the remainder of the summer and fall seasons, are expected to be only minor. For Michigan and the Great Lakes region, the official outlooks for June and the June-August periods both call for the climatology scenario of near equal odds of below-, near-, and above-normal temperatures and precipitation. By late summer and fall, the outlooks are a bit less vague, calling for increased chances for above normal temperatures across most of the region, with no direction on precipitation. The outlooks also call for milder than normal temperatures during the upcoming winter season. |
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