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| Fruit Crop Advisory Team Alert newsletter | |||||||
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| Vol. 23, No. 5, May 6, 2008 |
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| In this issue San Jose scale biology and control in fruit crops New MSU web resource for cherry growers TNRC trapline data: Spotted tentiform leafminerIntrepid 2F blueberry use directions updateTopsin M Section 18 request for blueberries still pendingCorrection: PropiMax fungicide is not labeled for strawberriesSpartan 4F receives Section 18 label for Michigan strawberries for 2008Small fruit meetingsHow to use the Enviroweather Fire Blight ModelRegional reportsWeather news |
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| San Jose scale biology and control in fruit crops In 2007, we observed large populations of San Jose scale on sweet cherries in the northwest, and now they are showing up on tree fruit across the state. In the northwest, populations were not readily identified because branch and tree dieback were masked by ethephon damage due to hot and dry weather prior to harvest in 2005-2006. This type of epidemic has never been seen in sweet cherry in Michigan. Sweet cherries are considered hosts of this introduced pest, but more commonly, we see San Jose scale in apple, peach, pear and plum. Scales are unusual insects with a very unique life cycle that makes them difficult to control. Adult females live underneath a waxy, turtle-like covering, giving birth to live young rather than lay eggs. These nymphs are the crawler stage of the life cycle. Because the crawlers’ stage does not possess any waxy covering, this is one optimal stage for control. Crawler females will develop wax coverings; males develop wings for dispersal (Figure 1). |
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| San Jose scale feed on sap of trees and a large population is needed to cause injury. Depending on the size of the population, scale can kill a young tree in two to three years. Older trees can also be killed by scale, but they do withstand more feeding damage than young trees. In addition to bark feeding, San Jose scales can also feed on the fruit and leaves. Feeding on fruit causes bright red spots, most commonly seen on apple. San Jose scale spend the winter as partially grown scales where they adhere themselves tightly to the bark. When the sap begins to run in the spring, the scales grow, and they reach full grown status in late May. At this time of the year, male scales come out from under the scale to mate with females. Females will start to produce young, and are each capable of bearing 150-500 offspring. These crawlers start to suck sap with their needle-like mouthparts. In three weeks, the young crawlers molt and lose their old skins, legs, and antennae to become a flattened sac with waxy caps (Figure 1). They remain attached to the trees with their mouthparts. Because these insects have two generations per year, we have two optimal timings for control. An oil application during pre-bloom is highly effective at targeting adults. Insecticides applied mid-June and mid-August target crawlers before they mate. Table 1 and Figure 2 list the insecticidal activity of several compounds in research conducted at the MSU Trevor Nichols Research Complex in Fennville, Michigan.
Table 1. Insecticidal Activity on San Jose Scale
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| New MSU web resource for cherry growers We have rolled out a new cherry website for this season that is designed to concentrate all of our MSU cherry-related resources into a “one-stop shopping” location. Please check us out on the web at www.cherries.msu.edu. Throughout the year, we will continue to expand this site. Presently, you will find:
Also, look forward to an apple website in the near future. |
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| Intrepid 2F blueberry use directions update An updated set of use directions has been released by Dow AgroSciences for Intrepid 2F for control of Lepidoptera larvae infesting highbush blueberry. The recent label approved for Intrepid in blueberry originally contained a 16oz/acre rate for fruitworms, which is a high rate. The new label update provides greater flexibility and guides blueberry growers to use a rate range of 12-16 oz/acre for fruitworm control, 10-16 oz/acre for leafrollers and spanworms, 8-16 oz for cutworms, and 4-8 oz for gypsy moth. The 12 oz rate of Intrepid is expected to perform very well against fruitworms, and we will be running trials this spring to verify this. Intrepid 2F is an insect growth regulator insecticide, so it must be eaten to be effective on the insect. For this reason, the label guides application to be done to achieve excellent crop coverage. For this reason the label recommends application using 30 gallons of water by ground application and 10 gallons of water by aerial application. The updated label can be downloaded here, which also provides information on the other application restrictions, such as the 7-day PHI. |
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| Topsin M Section 18 request for blueberries still pending The Section 18 (emergency exemption) request for Topsin M in blueberries is still pending with the Environmental Protection Agency (EPA). Do not use this fungicide unless we obtain approval for use this season. In making its decision, the EPA considers all other fungicides that are available for disease control in blueberries and the risk of major losses to diseases in the absence of Topsin M. In addition, it considers the toxicological profile and the overall “risk cup” for the product in question. We expect a final decision this week and will inform the growers immediately. |
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| Correction: PropiMax fungicide is not labeled for strawberries A few weeks ago, I introduced a new fungicide called PropiMax (propiconazole), a systemic sterol inhibitor fungicide with the same active ingredient as Orbit. PropiMax recently received a supplemental label for disease control in berries (blueberries, raspberries, blackberries, currants, gooseberries, lingonberries and a whole range of other berry crops). However, it should be clearly stated that the label does not include strawberries. The PropiMax label lists the following target diseases: mummy berry, rusts, powdery mildew and Septoria leaf spot. PropiMax has a 30-day PHI. |
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| Spartan 4F receives Section 18 label for Michigan strawberries for 2008 On April 21, the US EPA issued a Section 18 label (specific exemption) for use of Spartan 4F on strawberries in Michigan for 2008. The label is similar to the Section 18 labels we have had for the past several years. A maximum of 1,000 acres of strawberries may be treated with Spartan in Michigan in 2008. The label is effective June 25 to December 15, 2008. Spartan 4F may be applied to strawberries at renovation or after the plants have gone dormant late in the season. The primary target weeds are mayweed chamomile, puncturevine, redroot pigweed, common groundsel, field pansy, white campion and yellow woodsorrel. Spartan will control many other broadleaves and grasses as well. Four to eight fluid ounces of Spartan 4F may be applied in any one application. A maximum of 12 fluid ounces may be applied per year. There is a 70-day preharvest interval (PHI), but this should not affect Michigan production, since Spartan is applied after harvest is finished for the year. Spartan may be applied in tank mixes with Sinbar and postemergence herbicides such as 2,4-D, Stinger, Poast or SelectMax. The postemergence herbicides will kill emerged weeds and the residual herbicides will maintain weed control until fall frost. Copies of the label will be available from chemical dealers and suppliers. As soon as we receive a copy, we will post it on the MSU vegetable website: www.veginfo.msu.edu. This is the seventh year that Michigan has had a Spartan Section 18 label for strawberry. We hope to have a tolerance and label soon. To continue the Section 18 process, the Michigan Department of Agriculture must interview several growers who use it and obtain their reports on the effectiveness of the use. We encourage growers to cooperate with MDA personnel if and when you are called for a report. Growers for the interviews are chosen randomly from users around the state. |
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| Small fruit meetings
Blueberry twilight IPM meeting Topic: Bloom meeting Van Buren County, Cornerstone Ag (Bodtke’s) For more information, please contact: Paul Jenkins, Rufus Isaacs or Annemiek Schilder. Southwest grape IPM meeting May 21 from 10:00 AM to 12:00 PM Lawton, MI (Cronenwett Farms) 2:00-4:00 PM Benton Harbor (Berrien County Extension office) For more information, please contact: Paul Jenkins, Mark Longstroth, Rufus Isaacs or Annemiek Schilder (schilder@msu.edu). Northwest grape IPM “First Friday” meetings May 9 at the Lenny Ligon’s Farm, Paolo Sabbini will be discussing viticulture practices. The meeting will take place from 3:00 to 5:00 PM. For more information, please contact: Erin Lizotte, Nikki Rothwell, Duke Elsner or Paul Jenkins. |
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| How to use the Enviroweather Fire Blight Model Nikki Rothwell, NWMHRS George Sundin, Plant Pathology, MSU Bill Shane and Amy Irish-Brown, MSUE educators Growth of the fire blight pathogen is favored at temperatures over 65ºF. Degree hours using a base of 65ºF (DH65) are used to estimate fire blight bacterial population growth. To reach a level where fire blight can cause problems in the orchard, 198 degree hours (base 65ºF) from first bloom are needed to increase the population to a potentially dangerous level. These fire blight bacteria grow on the tip of the flower pistil (the stigma, which receives pollen grains), and once the population has built up on the stigma, a rain or heavy dew can wash the bacteria deep inside the flower where infection can take place. The fire blight blossom model is based on the EIP value (Epiphytic Infection Potential), which is a way to express this heat unit accumulation on a 0 to 100 scale. ("Epiphytic" = plant surface). The EIP is calculated by dividing the current DH65 accumulation by 195 and then multiplying this by 100. If the DH65 reaches 195 (which also means that the EIP is 100), the bacteria have built up to a dangerous level, and a rain or heavy dew at this time will wash the bacterial down into the infection site and cause infection. The current blossom blight model on Enviroweather also has the capacity to reduce the EIP value under cooler weather conditions by figuring in blossom life. In addition, the model reduces the EIP if the maximum temperature for a day is below 64ºF, because the fire blight bacteria require warm temperatures to grow. The EIP value is reduced by one-third by one cool day, another third by a second consecutive cool day, and to zero with a third. A day with freezing temperatures reduces the EIP to zero. However, once the EIP reaches 200, cool weather no longer reduces the accumulation. The fire blight model is very different from other pest models in that it is based on degree “hours” rather than degree “days.” Since the threshold temperature for fire blight is 65ºF, we often go above that temperature for many hours in one day, so it takes a lot less time to collect degree hours above the threshold compared to collecting “daily” temperatures that average above 65ºF. Growers must be particularly diligent about checking the model because when temperatures change drastically during the day, the EIP can rise quickly and warrant a fire blight spray. Therefore, at this time of the year, we need to be on the look out for weather conditions that favor fire blight, especially in susceptible varieties (See list of susceptible varieties). Infection can occur with a small amount of rain (or dew) following a warm period that allows bacterial populations to reach critical levels. The Enviroweather website has a reliable chart growers can use to determine if a fire blight control spray is needed:
At this time of year, it is particularly difficult to gauge fire blight infection potential as we often have warm and rainy weather, but we don’t want to waste an antibiotic spray if it is not truly necessary. If the fire blight model’s EIP is close to but not at 100, there are a few rules of thumb to determine if an antibiotic application is warranted: 1) a block with a history of fire blight, 2) susceptible varieties, or 3) visible cankers are all good reasons to go into a rainy period with an antibiotic spray. Susceptible varietiesGala, Fuji, Jonathan, Rome, Idared, Ginger Gold, Mutsu (Crispin), Rhode Island Greening, Paulared
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| Regional reports 1 -- Southwest Mark Longstroth Bill Shane Weather A freeze on Wednesday, April 30, with lows in the 20ºF to 29ºF range, caused wide spread damage, but the severity of damage varied from extensive to very little. Every freeze is different. A great deal depends on the crop’s stage of development, the characteristics of the fruit site and the duration of cold temperatures. This freeze was radiation freeze similar to freezes in 2002, 2004 and 2006. Apples, grapes and sweet cherries were the hardest hit. Southern Berrien County did not get as cold as other parts of the region and suffered less damage. Good pollinating weather with high temperatures near 70ºF and lows near 50ºF followed the freeze. Rain fell in the region May 2. Rainfall amounts varied greatly, from an inch to less than a tenth of an inch. These rains represented infection events for some diseases where more than a tenth of an inch fell. Soil moisture varies quite a bit depending on soil type. Light sandy soils are dry, and heavier soils are still very wet. We expect cooler temperatures this week. The forecast is for dry conditions with highs in the 60s and lows near 40ºF. Rain showers should begin Friday with a wet weekend.
Tree fruit Tree fruits were not damaged as much as one would expect from the reported lows during bloom. Insect activity increased last week. Oriental fruit moth were caught and biofixed last week on Thursday (275) and Sunday (305). Redbanded leafroller and spotted tentiform leafminer are flying. Apricots are in the shuck. Shuck split has begun in early varieties. Damage was slight on good fruit sites. Peach bloom is ending. Damage is generally light at good sites in the major production area of Berrien County. Early non-showy types were hit hardest. Unopened flowers were not damaged. A good crop remains for most varieties, but some varieties suffered and there might be times when flow to the market is light during peach season. Oriental fruit moth were caught and biofixed Sunday at 330 GDD45. The main worry during bloom is brown rot. This disease requires wet and warm conditions, 5 to 6 hours of wetness at 70ºF. Peaches are less susceptible after bloom. Sweet cherries are in the shuck. Damage seems to be variety specific, varying from heavy to light. Better sites and later varieties suffered less damage. Many growers have enough cherries to feed the birds; others will have a good crop. Sweet cherries are always susceptible to brown rot. Since the leaves are out and developed, they are susceptible to cherry leaf spot. The rain May 2 began a cherry leaf spot infection in some areas. Tart cherries are at full bloom. Damage is generally light. Tart cherries seldom get blossom brown rot unless the conditions are very warm and wet. As the leaves emerge, growers need to protect against cherry leaf spot. In plums, Japanese plums are in the shuck and were damaged by the freeze. European plums are at petal fall. Stanley plums are full bloom and suffered some damage. As shoot growth begins, growers need to protect against black knot. Apples are at king bloom. Damage to apples was severe in some sites. Early and late varieties were damaged and the damage seems very variety specific. Rain on May 2, was an apple scab infection for some sites. Symptoms from the April 19 infection should be visible. Fireblight should not be a problem for the next few days. Not enough heat units have accumulated since the freeze to pose a risk of infection. Now is the time to apply Apogee sprays to reduce the spread of fire blight. A single application at petal fall for king bloom is most effective in reducing the spread of fireblight after an infection. To control vegetative growth longer into the season, applications are spread out over the next 6 to 8 weeks. Pears are at full bloom. Pear psylla are laying eggs. Growers should protect against pear scab. Small fruit Blueberries are at pink bud and suffered little damage. Early varieties are nearing bloom and a few petals were damaged and may not open. Few growers used sprinklers to protect their plantings. Mummyberry mushrooms had dried out, but I expect more to emerge after this weekend’s storms. Many growers sprayed for mummyberry sprays immediately following the freeze. Symptoms from this infection should be visible in about 10-14 days. No mummyberry shoot strikes have been reported. Grapes buds are opening. Juice grapes shoots are 2 to 3 inches long with one to two leaves out. Wine grapes are a little behind. Damage to juice grapes in the Paw Paw area was severe. In Berrien County damage varied. It was not unusual to see the buds at the tip, which had burst to be killed by the freeze and buds at the base of the shoot at bud swell undamaged. Southern Berrien County suffered much less damage. In wine grapes, damage varied greatly by variety. Some French hybrids were advanced enough to be hurt, but other varieties were not damaged. Vinifera grapes were at swollen bud and suffered little damage. Strawberry flower trusses are out and bloom has begun. Many strawberry growers protected their crop with sprinklers. Growers have spread straw between the rows. Fungicides during bloom can reduce fruit rots at harvest. Raspberry and blackberry shoots are growing. Damage from the freeze was minor. In fall bearing plantings where all the shots have been removed, the new primocanes are about 6-inches tall. Cranberry beds are greening up and tip buds have burst. Miscellaneous Last week growers were planting trees and applying fungicide sprays. The next Monday Fruit Update meeting will be Monday, May 12 at the Fruit Acres Farm in Berrien County. |
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2 -- Southeast The frost/freeze event on the night of April 29 and the morning of April 30 is the big news of the week. I have made a concerted effort to visit as many fruit farms as possible over the last week to gain a greater sense of the impact of that frost/freeze event on our fruit crops. Every frost/freeze event is unique in terms of the damage to our fruit crops; this one was different than any that I have experienced. Please understand that this is still a preliminary assessment, as the true effects of this frost/freeze event are several weeks away from being fully determined. Cold temperatures started late in the night of Tuesday, April 29 and continued through sunrise on the next morning of April 30. The length of the cold is as much a factor as the actual cold temperature in this event. At most of the Enviro-weather stations we had between 3 and 7 hours of temperatures below 28ºF degrees. The low temperature recorded at our Enviro-weather stations ranged from 23ºF to 27ºF. We did sustain injury to apples, sweet cherries, tart cherries and pears. There appears to be no visible damage at this point in time to peaches, plums or blueberries. There is extensive frost/freeze damage to the apples across the region, even on late flowering varieties like Northern Spy that were at ½-inches green to tight cluster with about 10 to 12 days away from bloom. Idared, Empire, McIntosh and Red Delicious seem to be the varieties which were affected the most. Damage to varieties varies from farm to farm. Low sites were hit the worse. At some farms, I have seen a complete kill of the king bloom with much of the side bloom remaining undamaged. There is damage in other varieties that were not as far along as Idareds, however that damage is usually limited to a king bloom. So, at this time, I am stating that we have had more than a thinning frost/freeze event, but we still have the potential to have a nice apple crop across the region. Pears were damaged, but not quite as significantly as apples. Around 40 percent of the buds have been damaged. Peaches were at early bloom at most farms across the region. It appears that there is little to no damage in peaches. Sweet cherries were at full bloom at many farms and sustained a fair amount of injury. It appears to me when I cut sweet cherry buds there is about 50 percent crop loss. I think the real story in sweet cherries was the lack of good pollinating weather as blooms were opening. Tart cherries were just coming into bloom when this frost/freeze event hit. I estimate that we had a 20 to 30 percent bud kill. Plums were just coming into bloom; it appears that there was not much damage. Blueberries were at early pink bud at most farms, and it appears at this time that they were undamaged. Blueberries are a bit tricky and will need a couple more weeks to determine if there was injury. With spring like temperatures over the last week, our growing season was slowed a bit back to more of a normal range. The on again-off again season has been very difficult for fruit growers to determine insect and disease stages. Most of the region had their first true apple scab wetting event on Friday and Saturday of last week, with infection occurring at three-quarters of the Enviro-weather stations. The amount of rainfall from this event was about 0.3 to 0.5-inches, it was not enough to do what growers needed to replenish the surface moisture supplies. Things continue to be rather dry at fruit farms across the region. Southeast Michigan growing degree day totals for March 1 to May 5
Plums are at full bloom. Small fruitsStrawberries have grown very well over the last week. The flower tresses are now up and exposed. In scouting done on Monday, I have not seen any evidence of strawberry clipper or tarnished plant bug. Other species of plant bugs are starting to be seen in fence rows and other plants around strawberries, so expect to see tarnished plant bug to show up in about 7 to 10 days. Most strawberry growers to frost protected during the frost/freeze event on Tuesday and Wednesday of last week. Some were close to needing frost protection on Sunday morning; however most did not need to in the end. Raspberries were burned back with the cold event of last week and much of the new foliage was damaged. Raspberries will regrow very quickly and not show any significant long term damage. Fall red raspberries have not grown very much over the last week most canes are 2 to 4-inches in length. I have also seen damage to the terminal growing points in many fall red raspberries fields. Blueberries are at early to late pink bud at most farms across the region. As mentioned earlier, there does not appear to be any frost/freeze damage of blueberries at this time. |
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3 -- Grand Rapids Area Amy Irish Brown Weather and crop development A heavy apple scab infection was recorded for the general Grand Rapids area. Rains started Friday, May 2 and the wetting period was on and off again until it ended on May 4. Apple scab spore counts were quite high. Average per rod was over 4,500. This is a rather high number of spores, but a little more than half the number caught in the first infection back on April 24th. According to degree days for apple scab spore development, we were at about 35 percent spore maturity when the infection started, so we’re just getting started. The models suggest we’re at about 45 percent spore maturity as of May 5. As we move into bloom, growers will need to be ready for potential fire blight conditions that would lead to blossom blight. The weather forecast over the next several days is not looking very favorable for building up fire blight bacteria on the flowers, but a couple of days of warmer weather could change things in a hurry. European red mite eggs can be found, but numbers appear to be normal so far. Some egg hatch has been reported. Obliquebanded leafroller larvae have been observed feeding in terminals, but they are very difficult to find in most blocks. Redbanded leafroller continue to fly in normal numbers. Aphids are active. Both apple grain aphids and rosy apple aphids have been seen. Rosies are curling up in the leaves and pink sprays are advised in blocks with more than one rosy apple aphid per terminal. Oriental fruit moth should start flying at any time. |
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| However, for blueberry fields located around Fennville, Michigan and north Ottawa County, GDD accumulation is only 157-157, and the daily accumulation averages is about 6.5 GDD per day. According to our cranberry fruitworm phenology model, we recommend to install the pheromone traps at approximately 300 GDD accumulated since March 1. Once the first sustained moth trapping occurs, the model is biofixed and the first application of insecticides is programmed to be applied 100 GDD after biofixing. Prices for fresh blueberries continue to be high. In the past five days, prices for fresh blueberries remain around $24 and $30 per flat (12 4.4 oz cups), and most blueberries in the market are from Florida and Georgia. |
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4 -- West Central Last week’s freeze-events between April 27-30 have left their mark on the crop. Based strictly in the temperature report and the flower bud cold tolerance, it appears that the temperatures reached critical lows (low 20’s) in Oceana and Manistee counties on Tuesday through Wednesday night. The coldest night of the three for Mason County was Sunday through Monday night with the temperatures around 26ºF. Sweet cherries have suffered the most all across the area. Reportedly, there are significant varietal differences: Sams have had the highest bud damage while Hedelfingens come out of the event in pretty good shape. Tart cherries are looking good with very little damage. Any damage to the peaches is mainly from the winter injury. This last cold spell did not cause damage other than to the low-lying blocks. Apples in the flats have lost kings and a few side blossoms. On better sites it appears that the main damage occurred on the lower part of the canopy. Apples are in pink. In the southern part of the district, a few surviving kings in Idareds are starting to open up. Pears are in white bud. In peaches, Redhavens are from 50 percent bloom in the southern areas to less than 5 percent bloom further north. Plums are in white bud. Tart cherries are at 30 to 50 percent bloom. Sweet cherries are entering full bloom. West Central Michigan growing degree day totals from March 1 to May 4
An apple scab wetting event from May 2 to May 4 resulted in a heavy apple scab infection in Manistee County and moderate infections in Oceana and Mason counties. Spore discharge was massive with 19,261 spores per rod. A cherry leaf spot wetting event resulted in a low infection period for Oceana and Mason counties and moderate infection in Manistee/Bear lake area. Black knot is a cool season disease that affects plums and tart cherries. Infections are very likely at this time. Spores may come from the infected choke cherries or wild cherries in the surrounding areas or from the knots within the blocks. Sanitation, knot removal, is a very important step in disease suppression. Fungicide (Bravo) treatments during the spore release provide some control in preventing black knot infections. |
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5 -- Northwest GDD42 272 GDD50 125 Weather Although the weather has seemed chilly, our growing degree day (GDD) accumulations are similar to last year’s GDD: 125 base 50 this year compared to 127 base 50 in 2007. The numbers are likely due to the extremely warm temperatures in the third week of April. However, temperatures have dropped since then, and the last week of April and first of May have remained cool. Average temperatures have been in the mid- to upper 40’s. On April 28, 29 and 30, cold overnight temperatures were recorded in the mid-20’s to low 30’s. Growth Stages at NWMHRS as of May 5 at 8:00 AM Apples are in tight cluster. Bartlett pears are in green cluster. Sweet cherries: Hedelfingen are at 80 percent bloom. Napoleon are at full bloom. Gold are at first bloom. Tart cherries are at early white bud. Apricots are at full bloom. Plums are at early white bud. Grapes are at early bud burst. Crop report The cold overnight temperatures varied in the northwest regions last week, but overall we believed there was minimal damage to cherry or apple buds. However, as we have been cutting buds and hearing grower reports, we may have sustained more damage than our original assessments indicated. In some tart cherry blocks, we recorded about 50 percent damage, while adjacent blocks sustained no damage. King bloom in some apple blocks was impacted by the cold temperatures, and sweet cherry damage appears to be minimal in many tested blocks. With time, we will have a better assessment of overall damage. Things are starting to move along in the region despite the consistently low temperatures of the past week. Plum curculio began emerging in Northport orchards late last week. Here at the Northwest station, Oriental fruit moths have been captured in pheromone traps and obliquebanded leafroller larvae have been detected in apple. European red mite eggs are at low to moderate levels in the region, and the first two spotted spider mites have been found on the underside of apple leaves and are laying eggs despite the temperatures. Aphids have also been observed in apple blocks. Over the weekend, a moderate apple scab infection was forecasted for most of the northwest region, and as sweets leaf out, the cherry leaf spot infection levels are now a concern. |
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Weather news A relatively zonal, west to east jet stream pattern is expected across North America during the next one to two weeks, which should lead to an unsettled weather pattern across the Midwestern United States including Michigan. In the short term, the cool front that moved across the state Monday is expected to stall near the southern border of the state and serve as a focusing mechanism for showers and thunderstorms through the middle of the week. Best chances for rainfall will shift from northern sections of the state late Tuesday, May 6 into towards central and southern sections Wednesday and Thursday. Precipitation totals and areal coverage are expected to be greatest across southern sections of the state where precipitation totals through Friday morning may exceed 1 inch. Fair and drier weather is expected again by Friday continuing into the weekend. New NOAA long lead outlooks for the upcoming few months reflect a significant weakening of the La Niña event that has been in place across the equatorial Pacific region since last fall. The outlook for the month of May calls for a continuation of an active storm track across the western and Midwestern United States leading to a forecast favoring cooler and wetter than normal conditions for Michigan and the Great Lakes region. However, given the recent weakening of La Niña conditions in the Pacific, there have been additional changes in the longer lead forecast periods (mainly moderations in precipitation forecast). For May through July, mean temperatures and precipitation totals in Michigan and much of the Midwest are forecast to remain in the climatology scenario with near equal odds of below, near and above normal values. The outlook for the middle and latter parts of the upcoming summer is identical for Michigan, with more of the climatology scenario expected for both mean temperatures and precipitation. In a change from previous outlooks, only some western sections of the Midwest (e.g. sections of Nebraska and Kansas) are expected to remain drier than normal through the middle of the upcoming growing season. |
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