Vol. 20, No. 11, June 21, 2005 In this
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| Summer leafroller control | As we approach the timing for obliquebanded leafroller (OBLR) egg hatch in many areas of the state, it is time to review the OBLR degree day model and insecticides used to control this pest. Leafroller activity can be predicted using degree day models, although the information is not as reliable as that provided by the codling moth model. Using GDD42 for OBLR, first adult emergence is at approximately 900, 1150 to 1200 for peak adult activity and 1250 to 1350 for first egg hatch. First sustained moth capture (capture on two successive dates) in pheromone traps is used as a biofix, thus if moth flight peaks between 250 and 300 GDD after initial biofix, the heaviest egg hatch should be about 400 GDD later. If the overwintering generation was effectively controlled earlier in the spring, then scouting orchards for obliquebanded leafroller larvae in actively growing terminals is the best way to judge whether infestations will require further control. This investment of time could result in saving several sprays. Optimal timing for summer sprays varies according to the product of choice. For conventional insecticides, like organophosphates (OPs), pyrethroids and carbamates, the first sprays should be targeted between 400 and 450 GDD to control hatching larvae before they can damage fruit. OBLR are resistant to OPs in most apple growing regions of the state, so they are not generally recommended for control. Bt's are most effective when applied during warm weather conditions (daily highs in the 70s). If Bt products are used, the latter timing (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 foliage treated throughout the long period of larval activity. Bt products are generally more effective with a lower tank pH. SpinTor has a similarly short residual (seven to ten days), but provides some contact efficacy, which 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 OPs and pyrethroids is failing to provide adequate protection. In contrast, 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. Intrepid can also be used later to protect 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. Good, thorough coverage is key to leafroller control with materials requiring ingestion to be effective. The addition of an agricultural adjuvant to Intrepid 2-F is recommended to improve spray deposition. Though usually targeted for the overwintering generation of obliquebanded leafroller, the insect growth regulator Esteem applied at obliquebanded leafroller egg laying timing will also provide some control. It should also be noted that use of SpinTor for the summer generation of obliquebanded leafroller will provide some control of codling moth, Oriental fruit moth and spotted tentiform leafminer. Intrepid applied at the earlier summer obliquebanded leafroller timing will also provide some added control for codling moth and tufted apple budmoth. Esteem will provide control of San Jose scale crawlers and some added control of codling moth. Bt's can also be expected to control other leafrollers when applied for summer generation of obliquebanded leafroller. As with many of our key apple pests, OBLR 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. For example, alternate the use of SpinTor and Intrepid. During periods of warm weather, Bt is an excellent option and a good resistance management strategy. To see a table of such insecticides, click here. |
Obliquebanded leafroller GDD Model
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| Pre-harvest disease control in cherry | Two primary diseases that affect cherries during the summer season are cherry leaf spot and brown rot. Powdery mildew can also affect tart cherries in a hot, dry year such as this one. Major constraints to an economically viable cherry production in Michigan include adequate control of these diseases. Cherry leaf spotThe fungus Blumeriella jaapii (Rehm) causes cherry leaf spot (CLS) in both tart and sweet cherries, although tart cherries show more susceptibility to CLS than sweets. CLS primarily infects leaves, but this disease ultimately decreases overall tree vigor and health. Purple lesions first show up on upper leaf surfaces, and eventually these spots turn brown. Wet weather causes whitish masses of conidia to grow on the undersides of the leaf in centers of the lesions. Often CLS appear as a one-dimensional spot, surrounded by a light halo on the top of the leaf, while the bottom-side lesion looks as if it is three-dimensional. A minimal number of lesions can cause the leaf to turn yellow and abscise. Trees severely defoliated prior to harvest produce light red fruit that have minimal soluble solids. These defoliated trees have difficulty forming buds and setting fruit for up to two years after severe infection; these trees are also less cold hardy and can die with low winter temperatures. Chemical control. Cherry leaf spot control revolves primarily around fungicide applications, as all cherry cultivars are susceptible to leaf spot. The first spray is usually applied as soon as the first leaves have unfolded. Sprays are often repeated on a 10 to 14 day (or seven day alternate row) interval until harvest. There are many chemicals labeled for CLS, but MSU research from 2003-04 has shown CLS to be developing resistance to one class of fungicides – the sterol inhibitors (SI’s: Elite, Funginex, Indar, Nova, Orbit and Rubigan). This research suggests that Michigan growers need to shift from SI's to alternative chemistries for leaf spot control, which includes chlorothalonil (Bravo), strobilurins (Flint), strobilurin + Boscalid (Pristine), copper compounds, dodine, ziram and captan. Bravo is the chemical of choice prior to shuck split and post-harvest, as this chemistry provides good CLS protection and does not have resistance potential. A tank mix of ziram and captan is an option for covers. Dodine is also an effective chemical where resistance has not yet occurred. Strobulirins work well against CLS, and Pristine is an excellent chemistry if powdery mildew is also a problem in the orchard. New research has also suggested that copper compounds are effective against CLS in tart cherries only. When using an SI, always tank mix with another chemistry such as captan. For a complete table of recommended CLS control strategies, please see the May 3, 2005 Fruit CAT Alert. Brown rotWarm, wet or humid weather is conducive to brown rot (Monillinia fruticola) development, and brown rot is a major disease of stone fruits. Sweet cherries are particularly susceptible to brown rot. Once the fruit begins ripening and changing color, it becomes more susceptible. This pathogen can gain easy access to fruit when any type of injury (insect damage, hail injury, bird pecks, bruised and/or cracked fruit, etc.) is present. Once the pathogen becomes established, soft brown spots appear on the fruit (photo 1). These spots rapidly expand into lesions covered with powdery masses of creamy-tan colored conidia (photo2). Under favorable conditions, the entire fruit may rot within 48 hours. Eventually, fruit that remains on the tree dries out; these fruits are often referred to as “mummies,” and they become source for future infections. Disease management. As it is true with any disease, reducing inoculum level will lower disease pressure. Control of blossom infection is important to minimize disease inoculum for fruit protection. Fruit injury should be minimized to reduce the fruit’s susceptibility to M. fruticoloa. Insect damage to the fruit should also be curtailed to decrease disease outbreaks. Chemical control. There are several good fungicides that provide adequate control for brown rot disease. Protectants (captan, Wettable Sulfur) may be an adequate option in low-pressure situations. Materials from this group must be applied prior to the expected wetting event. Sterol-inhibitors (Elite, Indar, Orbit) will provide excellent control of fruit brown rot, but these materials should be used judiciously as resistance has been reported with these products in cherry leaf spot disease. SI products are best applied before the onset of the infection, but some of these fungicides have a limited back action of 24 to 36 hrs (Indar, Orbit). SIs are again best applied in a tank mix with a protectant such as captan. Strobilurins (Flint, Pristine) adequately control brown rot, and they are currently an option for fungicide resistance management. They must be applied prior to the wetting event since there are no available data as to their kickback action. Other options are available for brown rot blossom blight control such as Rovral and Bravo that cannot be used for summer control. Powdery mildewTart cherries are particularly susceptible to powdery mildew (Podosphaera clandestina) during hot, dry weather. When mildew first infects young leaves, it looks like a whitish felt-like patch (mycelium) on the bottom of the leaf. The top of the leaf usually boasts a wrinkle, and there is a halo-like appearance where the mycelium is growing on the underside of the leaf. These powdery lesions can spread quickly and can soon cover the entire leaf. Eventually, small brown to black globular bodies develop in the mycelium. Fungal spores are spread from leaf to leaf when temperatures hit 68°F. Powdery mildew takes hold of an orchard when temperatures are high and moisture is generally low but spiked with times of high humidity. Mildew can spread rapidly throughout an orchard if inoculum levels are high. Heavily infected terminal leaves tend to shatter during mechanical harvesting. Disease management. Increasing airflow in the orchard is the best cultural control for powdery mildew. Pruning trees to improve air circulation will create a less optimal environment for powdery mildew development. Chemical control. Powdery mildew is often controlled with fungicide applications. Since this disease is most often a problem in hot and dry years, every season may not require a powdery mildew fungicide application. However, powdery mildew is important to control at the onset of the problem as this disease progresses rapidly and can overtake the orchard in a short amount of time. The disease is best controlled during the first cover to the pre-harvest period. Flint and Pristine are both excellent against powdery mildew. Nova, Rubigan and Elite (SI’s) are all fair to good against mildew, but their use should be minimized due to resistance concerns. Sulfur provides some control of powdery mildew. |
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| Can plant pathogens tell the difference between dew and rain? | A relatively dry season has kept diseases fairly well at bay and lessened the need for fungicide sprays, providing a well-deserved break for growers weary from last year’s rainy season. Many diseases currently showing up are from pre-existing infections (e.g., orange rust in brambles, Eutypa dieback in grapes, viruses and Phomopsis canker in blueberries). Is the absence of rain a guarantee against disease development? Read on. Spore dispersalMost plant pathogens, particularly fungi and bacteria, require moisture for dispersal and infection, which is why diseases pose more of a problem in rainy years. For many of the diseases we deal with, e.g., powdery mildews, apple scab and black rot in grapes, thorough wetting is required to release the ascospores that cause primary infections. Once the ascospores become airborne, they are carried to susceptible tissues by wind currents. Rain is generally more effective than dew or fog in promoting release of ascospores. Often, within a few hours of the commencement of a light rain or cessation of heavy rain, ascospores are airborne. Greater numbers of ascospores are associated with longer periods of rain. Heavy rains may actually depress the numbers of airborne ascospores by washing them out of the air. In the case of apple scab, discharge of mature ascospores is initiated within 30 minutes after the start of rain and is largely completed within three to six hours. For pathogens with fleshy (e.g., mushroom-like) fruiting bodies, high humidity is often sufficient for release of ascospores. While dew and fog are generally not sufficient for release of ascospores, overhead irrigation can certainly provide the moisture required. For powdery mildew on grape, rain, sprinkler irrigation or fog can induce ascospore discharge. Interestingly, an apple scab study in Norway showed significant releases of ascospores after some dew events. If a dew event followed a fairly dry period and many ascospores had matured in the meantime, these ascospore release events could constitute at least 10% of total seasonal ascospore discharge. However, dew-induced ascospore release was only considered an infection risk when large numbers of ascospores were released and continued wetness occurred due to poor drying conditions, promoting infection. Otherwise, ascospore release due to dew was more likely to deplete the ascospore supply with no consequent increase in the overall risk of disease. In the case of pathogens that rely on rain splash for dispersal of spores in all or part of their life cycles (e.g., Colletotrichum, Phomopsis, bacteria, etc.), dew is a poor substitute for rain. A heavy dew could potentially carry spores or bacterial cells to susceptible tissues by run-off, but the spores would not be distributed very far. However, overhead irrigation can function just like rain in providing splash dispersal of fungi and bacteria. For pathogens with wind-dispersed spores (e.g., Alternaria, Botrytis), moisture is only needed to induce sporulation, and the source of the wetness is not very important. In fact, dry, windy conditions following a moist period are more conducive to spore dispersal in this case. Once spores have been released and reach susceptible tissues, most fungal pathogens require free water for spore germination and infection of the plant. This is certainly true for pathogens with zoospores (swimming spores) but also most other pathogens, including bacteria. The only exceptions to this are the powdery mildews, which do not need free water for infection and can infect plants between 40 to 100 percent relative humidity. In general, the duration of wetness required for infection varies by the pathogen, temperature and type of tissue it is trying to infect. For instance in strawberries, Phytophthora cactorum zoospores can infect fruit within 30 minutes, whereas Colletotrichum acutatum needs at least 13 hours of wetness. The moisture required for infection can originate from rain, dew, fog or irrigation water. In fact, frequent or prolonged irrigation during dry weather or for frost protection may increase the chances of infection, especially if the tissues do not dry off between wetting periods. In blueberries, overhead irrigation increases the incidence of fruit rots. It is therefore important to allow overhead irrigation to overlap with natural dew or rainy periods, to reduce plant wetness duration to the minimum time possible. So for infection, the origin of the wetness does not seem to matter as much as the timing and duration. Now, in the case of downy mildew on grapes, it appears that dew could actually be more conducive than rain in some cases, since the infections take place on the undersides of the leaves and that is where most of the stomata are. Since a light rain may not wet the undersides of leaves well, especially in Labrusca varieties with hairy leaves, dew may be a better source of water for infection. This may explain why we often see downy mildew after heavy dew events, particularly later in the season. Fungicide coverage |
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| Enhancing beneficial insects with native plants | For many years, entomologists have recommended conserving insect predators, parasites and pollinators around the farm or garden to help suppress pests and increase crop yields. But what can you do to promote these beneficial insects? MSU research is investigating the role that native plants may play in helping to enhance the abundance and performance of these helpful arthropods. Many beneficial predators and parasites (AKA natural enemies) and all pollinators rely on plant nectar and pollen to help sustain them. In addition to these food sources, plants can also provide needed alternative prey and shelter from adverse environmental conditions. For example, one important parasite of the European corn borer in Michigan, the wasp Eriborus terebrans, will live for over 14 days in corn fields if provided with a nectar substitute, but only two days if sugar is denied. Further research indicated that these food resources were typically not present in Michigan cornfields but that wasps needed to travel to field edges to find them. Survival of E. terebrans was even greater if it could find flowering plants in hedgerow and woodlot edges where temperatures were moderated. Similar observations have been repeated in various cropping systems with many different types of natural enemies. This has resulted in recommendations for habitat management that include maintaining or planting species that provide floral resources in or near crop fields, orchards and vineyards. One curious fact about these recommendations is that the plants most commonly cited for this purpose, such as buckwheat (Fagopyrum esculentum), sweet alyssum (Lobularia maritima), faba bean (Vicia faba), dill (Anethum graveolus) and coriander (Coriandrum sativum) are all annuals and none are native to the United States. We were interested in learning if native Michigan perennial plants could provide similar resources. Furthermore, we wanted to determine if a succession of flowering species could be found that provide floral resources over much of the growing season. We selected 46 native Michigan plants based on their reported bloom period and ability to survive in agricultural habitats. All of the species selected historically grew in prairie or savanna habitats (scattered trees with an understory of prairie species). Native species were established as plug or 1qt size plants in the fall of 2003 and contrasted to the non-native annuals planted as seed the following spring. During the 2004 growing season, we counted the number of open flowers at each plant species weekly to determine bloom order and time of peak bloom. We also collected, counted and identified natural enemy insects at each plant species weekly during peak bloom. Results from 2004 showed that plant bloom periods do overlap, which means that we can pick a subset of the most attractive plant species and still provide nectar and pollen to natural enemies during the entire summer. During the early season (May through mid-June), the native cow parsnip (Heracleum maximum) attracted three times more natural enemies than the next most attractive plant, the non-native sweet alyssum. Other attractive native plants blooming in May were Virginia strawberry (Fragaria virginiana) and round-leaved ragwort (Senecio obovatus). During the mid-season (July through mid-August) the non-native faba bean, buckwheat and coriander were the most attractive plants, followed by the natives yellow giant hyssop (Agastache nepetoides) and hoary vervain (Verbena stricta). During the late season (mid-August through September), the native boneset (Eupatorium perfoliatum) was more attractive than any plant, followed by sweet alyssum and the natives: New England aster (Aster novae-angliae), Riddell’s goldenrod (Solidago riddellii) and smooth aster (Aster laevis). The total number of natural enemies in a sample increased dramatically throughout the growing season. During the early season, up to 12 natural enemies were collected per sample, while during the mid-season we collected up to 33 and in the late season up to 83 natural enemies per 30 second sample, respectively. The first full growing season for these perennial plants was 2004. Already in 2005 we are seeing that many species are far more robust and are producing greater floral area than in 2004. As these species mature, it is likely that they may compare even more favorably to the non-native annuals. While this research is just beginning, we have found several Michigan native plants that are very attractive to natural enemies and show promise for habitat management. On-farm demonstration/research has been initiated to determine if these plants can be reliably established as strips in crop fields and if this translates into improved pest management. An additional benefit of this approach is that while formerly common, many of these prairie and savanna species have almost completely disappeared from our agricultural landscapes. If proven effective, we may once again enjoy the subtle beauty of these native Michigan plants in our agricultural landscapes. For more informationAttend the August 10 MSU Field Day on Enhancing Beneficial Insects with Native Plants. Additional field day information and registration forms are available at: http://ipm.msu.edu/plants/home.htm |
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| Changes in Diagnostic Services fee schedule | Due to increases in costs, Diagnostic Services has had to increase fees for samples. The new fees are listed below and are effective immediately. The fees are per sample. (Charges for out-of-state samples are double – herbicide resistance and pesticide analysis are increased by 50 percent for out-of-state samples.) The cost for visual inspection for infectious and non-infectious diseases, insect injury and herbicide injury; pathogen culturing; pH and soluble salts as well as in house ELISA tests is now $20 and Bacterial identification by BIOLOG ä is now $25.00 Weeds and plants Common plant identiciation will still be done for no charge and keyout plant ID is now $10.00. Standard herbicide resistance tests for a single site of action is now $50.00 with an additional $20.00 for each additional site of action. Contact the lab for pricing of more extensive tests. Nematodes Basic nematode analysis is now $20.00 and total community nematode analysis is now $50.00. Hg type testing is $50.00. Verticillium analysis (for potato stem/soil) by wet sieving is $20.00 and by dilution plating is $15.00. Both Verticillium analyses on a single sample is $35.00. Insects and arthropods Charge for common insect ID remains no charge while keyout insect ID is now $10.00 Pesticide analysis Costs for individual pesticide tests / multi-pesticide tests are as follows:
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Regional reports 1 – Southwest |
Weather
Tree fruit Codling moth and obliquebanded leafroller trap catches continue. Rose chafer is still about. Potato leafhoppers have been found. We are now catching greater and lesser peach tree borers and growers should be thinking about trunk sprays for borer control. The second generation of redbanded leafroller is beginning to fly. Early apricot varieties are beginning to ripen. Peach fruit are 1.25 inches in diameter. June drop continues and pit hardening has begun. Early varieties are hard, but later varieties are still soft. Rose chafers are out and still pose a threat to the fruit. The second flight of Oriental fruit moth should be starting and trap catches are up in Berrien County. We are catching peach tree borer adults and growers should be thinking about trunk sprays. Sweet cherry harvest has begun. Tart cherry growers are applying Ethrel, and harvest should begin the middle of next week. Cherry fruit flies are being trapped in abandoned cherry plantings. No symptoms of cherry leaf spot have been found. Apple fruit are still dropping. Fruit set is heavy in the tops of some trees and growers are complaining that they over thinned or that they need to hand thin. Fire blight is not common but some orchards are severely affected. Green apple aphids are becoming common and can spread the infection to healthy trees. The treatment threshold for green apple aphid is when three to four leaves per terminal are infested. Codling moth trap catches are still high. We biofixed for codling moth on May 20 at 334 GDD50. We are now at 816 GDD, 480 GDD past biofix. Activity for the first generation of codling moth should end at about 1000 GDD after biofix, so we are only about halfway though the first generation. Obliquebanded leafroller biofix was June 6 at 935 GDD. Egg hatch begins at 400-450 GDD past biofix about 1350 GDD42, so egg hatch is beginning. See the article in the June 7, 2005 Fruit CAT Alert. The second generation of Oriental fruit moth is emerging in southern Berrien County. European red mites are hard to find. Spotted tentiform leafminer mines are easier to find. Small fruitBlueberry fruit are coloring. Harvest of early varieties will start late next week in the southern Berrien County. Cherry fruitworm flight is winding down but cranberry fruitworm trap catches are increasing. Fruit worm egg hatch and feeding continues. Tussock moth larvae are out and causing severe damage in some fields. Blueberry aphids are becoming more numerous. Cane collapse due to phomopsis is common in some Allegan County blueberry plantings but not common in Van Buren County. Preharvest fungicides should target both anthracnose and alternaria fruit rots. See the article in last week’s Fruit CAT Alert. Grape berries are buckshot-sized. Vinifera bloom is ending. Rose chafer numbers are down. Grape berry moth egg hatch and feeding have begun. Phomopsis, black rot and downy mildew symptoms can be found. Growers should be protecting the flower clusters from diseases with bloom sprays or post bloom sprays before our next rain. Strawberry harvest is moving quickly. Heat will end the harvest soon. Anthracnose fruit rots have been reported. Early summer raspberries varieties are being harvested. Many varieties look poor due to winter injury. Cranberries are blooming. A second fungicide application to control fruit rots is targeted for the end of bloom on rapidly growing pinhead fruit. Meetings The next Monday Update meeting will be Monday, June 27 at the Overhiser Fruit Stand in Allegan County at 5:00 PM. There will be one MDA restricted use pesticide recertification credit available at this meeting. |
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| 3 – Grand Rapids Area | Weather According to 30-year averages from the Sparta weather station, degree day totals are running about seven days ahead of average for both GDD42 and GDD50. There has been little rain over the last week, but tree and fruit growth appear normal. Tree fruit June drop in apple is ongoing. Fruit set appears to be an average crop with a few varieties being too light and others are still too heavy and will need hand thinning. Blossom blight strikes from rain events back in mid-May should all be present if they are there. So far fire blight doesn’t appear to be too wide spread this year and is really only a problem in blocks that have had a history of the disease. Growers should still be concerned about the potential for trauma blight situations – trees are still susceptible until they set terminal buds. Primary apple scab is over for 2005, but some new scab lesions are still being found – continue to scout closely for lesions over the next week or two as fungicide rates are lowered for the summer. Plum curculio activity has been light this season, but should still be scouted for. Codling moth trap numbers have started to decline over the last week and we should be getting towards the end of first generation adult flight. Cover sprays will continue to be important for at least another week to 10 days. Obliquebanded leafroller are flying in normal numbers. Green apple aphids are very high in number this year – there are some predators in colonies, but they don’t seem to be keeping up with the aphids and many growers have had to input some kind of control. |
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| 4 – West Central | Weather There was a slight cool-down in temperatures over the course of the week. Currently, temperatures are on the rebound and are back into the 80s. The whole district continues to be dry. Except for a very light rain on Wednesday (June 15) there has been no precipitation. We are from 4.5 inches to more than 5 inches below normal. Trees are showing signs of stress. GDD totals Since March 1 as of Sunday, June 19
Tree fruit Apples are sizing well despite the dry soil conditions. Fruit is mostly over an inch in diameter. While there is still some fruit drop, it appears that the crop outlook is very good. The reported wetting event has flushed the remainder of the scab spores, thus the end of the primary scab infection can be announced. Generally, scouts are reporting finding very few leaf scab lesions throughout the area. Spray programs have been mainly based on use of protectant fungicides so in a few instances where the growth rate was not the part of the equation, we ended up with newly developed tissue that had been left unprotected and subject to infection. Overall, most of the blocks look “clean.” Weather conditions were favorable for powdery mildew (Podosphaera leuctrcha) development that accounts for common sightings of symptoms throughout the area. The new “arrivals” on the orchard scene are nectria twig blight (Nectria cinnabarina, Tode, Fr.) found on Rome and Golden rush varieties and alternaria leaf blotch (Alternaria alternata, pt. mali) reported on Red delicious. Nectria is often confused with fire blight since the symptoms are very similar. New shoots wilt and die. At the base of the dead shoot there are small sunken cankers. Under the favorable conditions (warm and humid) salmon-colored spores will start to appear on the surface of the cankers. When spotted, these dead shoots need to be removed. That would help in reducing the available inoculum for further infections. Alternaria appears as rather large brown leaf spots with purplish margins. It is often mistaken for another leaf spot known as frogeye (Botrisphaeria obtusa) or necrotic spots due to Captan injury. While Captran injury and frogeye spots are localized, alternaria leaf spot/blotch is quite evenly distributed on the trees and throughout the block. Insect pests are quite active. Codling moth numbers are still very high. Egg hatch continues, thus it is important to maintain block coverage to prevent fruit injury. Scouts are finding increased number of European red mite eggs and twospotted mite eggs that will result in higher mite presence on the leaves with the onset of hot and dry weather. Plum curculio stings have been found on the apples. The green apple aphids and rosy apple aphids are building up colonies. Increased numbers of tentiform leafminer mines and larvae have been found in the blocks but still below threshold. Pears are sizing well exceeding an inch in diameter. Pear psylla does not seem to be much of a problem. Some blister mite injury is beginning to show. Sweet cherries are not gaining in size. If anything, they may have lost some size due to the droughty conditions. Fruit is coloring and harvest is not that far off. At this time, fruit brown rot (Monilinia fructicola, G.Wint.) is of major concern. Any injury (insect injury, mechanical injury, etc.) may lead to development of brown rot lesions. Humid, warm weather will facilitate disease development. Uses of SI’s (Elite) or strobilurines (Flint) are some of the options at this time. Tart cherries are affected by the drought as well. Fruit is coloring, but there is no size gain. Ethrel applications will start to go on possibly early next week. Eastern parts of the district are going to start with the harvest about 7/7-8. Scouts are reporting finding very few cherry leaf spot lesions (Blumeriella japii, Rehm. Arx). No significant incidence of powdery mildew (Podosphaera clandestine, Wallr.:Fr.). Scouts are reporting finding rose chafers, and a call came in on June 21 for the first catch of cherry fruit fly. |
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| 5 – Northwest | GDD accumulations at NWMHRS GDD42: 1192 GDD50: 696 Weather Northwest Michigan received some rainfall this past week, but amounts were generally quite low. At the NWMHRS, rain for the month of June has totaled only 0.47 inches. This follows two months with only about 1.5 inches per month. Above normal temperatures keep advancing this season relative to normal. Degree day accumulations at both GDD42 and GDD50 are now ahead of every year since 1999.Tree fruit Since we have been very dry this last month, we have seen low incidence of apple scab. A wetting event was reported on Thursday (June 16), which resulted in an apple scab infection throughout northwest Michigan. Primary scab was predicted to be over as of Monday (June 13), but we recommended that growers keep covered for the June 16 rain event in case of remaining scab spores lying in wait for wetting period. We caught our first OBLR adult last week, but all other apple insect pests are on the decline. We have been seeing high numbers of snail case bagworms in apple, and they are causing some damage to the leaves. Very little cherry leaf spot has been reported in the area due to the dry conditions, but the June 16 wetting event resulted in an infection period. We have detected powdery mildew in tart cherry blocks, as expected with the hot and dry conditions. We captured our second cherry fruit fly of the season this Monday, which makes two flies in two weeks. Drought responseConditions are getting very dry in many areas in Michigan's fruit belt. At the NWMHRS we have received the lowest amount of precipitation during the April, May and June (to date) period of any year since we began keeping records in 1982! The rate of water demand has also been above normal this year, due to the above normal evaporation rates and heat. In general, plants with limited root systems are the first to suffer from drought stress. The most susceptible trees and vines are the newly planted stocks. Next to be impacted will be young plants and those on the most dwarfing rootstocks. The two most appropriate responses to the drought are to apply water where possible and maintain exceptionally good weed control. Mulch can also help maintain better soil moisture, but it does not add moisture to the already dry soil. Small fruitWine grapes are in or approaching bloom and still look to be very free of disease pressure. Potato leafhopper nymphs can now be found on shoot tips. Rose chafer is very numerous this year, especially in vineyards near grassy old field sites. A few forester moth and hornworm larvae have been seen, but it is still early for the bulk of these to appear. |
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| Weather news | Just in time for summer solstice, midsummer day, and the arrival of astronomical summer, a upper air ridge will build across the Midwest, bringing summer-like weather to Michigan for much of the upcoming week and possibly longer. As the ridge becomes established, a weak cool front will move from northwest to southeast across the state Tuesday (June 21), setting off scattered showers and thunderstorms. Unfortunately for those areas of the state in need of rainfall (Rainfall deficits and dryness are greatest from northwestern Lower Michigan southward to southwestern and south central sections of the state.), this system is not expected to produce widespread rainfall (only scattered 0.10 to 0.25 inch totals are expected) and best chances for rainfall will once again be in northeastern sections of the state. Drier, somewhat cooler weather is expected Wednesday, followed by a return of warmer than normal temperatures once again Thursday through Saturday. A second frontal system will approach the state once again from the northwest late Friday into Saturday, bringing another chance for rainfall. Just like the system on Tuesday, moisture ahead of the front will likely be limited and only scattered aereal coverage precipitation is expected. Temperatures will warm from daytime highs from the low 70s north to near 80 south Wednesday to the 80s to near 90 Thursday through Saturday. Low temperatures will warm from the 40s to low 50s Wednesday morning to the upper 50s to mid 60s by Saturday. Medium range forecast guidance calls for the upper air ridge mentioned above to become the dominant weather feature in the one to two week time frame. The NOAA Climate Prediction Center 6-10 day (for June 26-30) and 8-14 day (covering June 28 through July 4) outlooks both call for above normal temperatures state- and region-wide. Precipitation totals are forecast to range from below normal levels across much of the Lower Peninsula to above normal in western sections of the Upper Peninsula. |