A cold air mass from the Artic moved across Michigan and the rest of eastern North America last week creating havoc for fruit growers with colder than normal temperatures. Record-setting warm temperatures from the previous week made fruit crops even more vulnerable to the freezing and frost. Today’s issue of the Fruit Crop Advisory Team Alert and the May 7 issue will contain special features addressing a range of topics such as how low temperatures must get to cause damage and how to maintain a vineyard, orchard, or field after a crop has been lost.

Many crops grown in Michigan are not eligible for crop insurance policies written by private insurance providers. For those crops USDA has a legislated program referred to as the Noninsured Disaster Assistance Program (NAP).

Once a client has a valid CCC-471/Application for Coverage, additional responsibilities for producers include:

• Timely and accurately report the acreage and shares for all crops for which CCC-471 is filed.
• Certify crop production history for approved yield calculations.
• Complete CCC-502 "Person Determination/Payment Limitation" and supporting forms.
• Provide a certification for the $2 million gross revenue limitation for each "person" in an operation.
• Certify conservation compliance on AD-1026.
• File a Notice of Loss and application for payment, if applicable.
• Request a crop appraisal, as applicable.

Recent events have caused damage to some crops and not to other crops. The regulations state a producer shall file a Notice of Loss (CCC-576) within 15 calendar days after the date of the disaster condition occurred or when damage to the crop became apparent to the producer. This requirement is on an individual basis. Each grower is responsible to monitor crops they are growing and report loss conditions to USDA/FSA.

Notice of Loss forms should be filed whenever a weather event negatively affects the crop.

The local FSA County Committee must determine the damaging weather, adverse natural occurrence, or related condition must occur before or during harvest and directly cause, accelerated, or exacerbate destruction or deterioration of the eligible crop.

As a side note; if producers have a crop insurance policy with a private insurance company and their insured crops have experienced a weather-related event causing crop damage, they too should be filing a timely notice of loss with their private insurance company.

Fruit trees, grapevines and blueberry bushes require a certain amount of nitrogen (N) and potassium (K) to support vegetative growth and fruit production. If the fruit are lost to frost damage, the nutrient needs are also reduced. Here are some thoughts on fertilizing following frost damage.

The amount of nutrients that accumulate in the fruit of these crops is one estimate of how much fertilizer can be reduced if the crop is frosted out (Table 1). The N content of the fruit ranges from 8 lb per acre (blueberries, cherries) to as high as 50 lb per acre (15 ton per acre peach crop). The K contents range from 8 to 80 lb per acre. In the event of a crop failure, fertilizer rates can be reduced by at least these amounts. Since these plants obtain only part of their nutrients from added fertilizer (the rest from soil reserves), fertilizer rates can be reduced even more in some cases.

If the fruit of apples or grapes is lost to frost, N rates can be reduced by 50 percent (on lighter, sandier soils) to 100 percent (heavier, fertile soils) of typical applications. If the entire crop of cherries, peaches or blueberries were lost, N rates can safely be reduced by a third on sandier soils, to as much as a half on heavier soils. Reduce rates proportionately in the case of partial crop failures.

The effect of crop loss on K requirements is difficult to estimate. Fruit are strong sinks for K, so the K demand is clearly reduced when no crop is produced. Frost-damaged plantings on heavier soils likely will not benefit from K additions this year. Plantings on sandy soils with a low K reserve or where tissue analysis has indicated a need for K, may benefit from K, but will require lower rates, perhaps half of the typical application. Applications of K could be discontinued this year where K levels in the soil are moderate to high, and an annual maintenance application of K is typically applied.

1. Batjer, L., B. Rogers, and A. Thompson. 1952. Proc. Amer. Soc. Hort. Sci. 60:1-6.
2. Hanson, E. and G. Howell. 1995. HortScience 30:504-507.
3. Hanson, E. (unpublished data).
4. Hanson, E., and J. Retamales. 1990. Proc. N. Amer. Blueberry Res. Work. Conf.
5. Haynes, R., and K. Goh. 1980. Plant and Soil 56:445-457.
6. Retamales, J., and E. Hanson. 1989. J. Amer. Soc. Hort. Sci. 114:920-923.
7. Rogers, B., L. Batjer, and H. Billingsley. 1955. Proc. Amer. Soc. Hort. Sci. 66:7-12
8. Van Slyke, L., O. Taylor, and W. Andrews. 1905. NY Agric. Expt. Sta. Bull. 265:205-223.
9. Vang-Petersen, O. 1984 (Danish study).

With this year's predicted crop losses in some of the growing areas of Michigan, it appears that some blocks will not have enough fruit to justify the expense of harvest. If this ends up being the case, growers should start the year off by trying to minimize expenses wherever possible. Reducing the spray bill is the logical place to start.

There are disadvantages, though, in reducing the pesticides that one applies to their orchard. The reduction in control of diseases or insects this year may well lead to higher levels of those pests the following year. Thus, next year your spray bill could be higher than normal. This may, in part, offset the advantages of reducing your input costs this year. Having said that, the following are some key areas to consider in designing this year's spray program for tart cherries, if that crop is not to be harvested.

Some weeds in the fall are okay - The main time that weeds compete with the trees is in May and June. Fall weed cover does very little to hurt the trees, except in drought situations. Tight mowing in the fall will reduce cover for voles.

Foliar nutrients - In a year with little to no fruit on the trees, growers should only consider foliar nutrients in situations where they have either chronic problems or leaf analysis has shown a deficiency. Typical foliar maintenance programs of zinc, potash, nitrogen and magnesium can be avoided in most cases. Boron should be spared with the exception of post harvest applitcations.

Bloom Sprays for blossom brown rot - Even in cropping years these sprays are of questionable value in many locations. If your crop is so short that harvest will not take place, they should be avoided.

Cherry leaf spot control - Keep the leaves for as late into the fall as possible. Carbohydrate reserves are necessary to aid in the set of the crop in 2003. Without a crop this season, however, the reserves will be higher than normal going into the winter. So, if you defoliate somewhat earlier than you usually like to, it shouldn't make much difference. Expect a heavy set with lots of early vegetative growth next spring. The bloom will have lots of green in it next spring, due to the high level of carbohydrates that is pushing lots of large blossoms and foliage as well.

Petal fall - Typically it is early in the petal fall period when the first leaves are fully expanded and thus susceptible to the cherry leaf spot fungus. Early control is important to prevent the buildup of inoculum early in the season within the orchard. Chlorothalonil (Bravo) is by far the best material for controlling cherry leaf spot and should be used at this time in a full cover spray. The rate could be reduced to some degree based on the limited amount of leaf material in the orchard at this time. Keep in mind that this is a protectant and will not provide any back action, so the material has to be applied prior to any infection periods - particularly high and moderate ones.

Shuck split - Chlorothalonil should again be applied at the higher end of the rate. Depending on rainfall and coverage, the material can be applied full cover or half cover. Full covers are preferred, as you will see benefits from this spray well into the future.

Bravo formulations labeled for use on cherry read, "Bravo is NOT TO be applied after shuck split and before harvest." In the case where no harvest is taking place this obviously leads to a gray area that growers will have to interpret for themselves.

Post shuck split - Once the grower has decided to switch away from Chlorothalonil he should consider going to a reduced rate of a sterol inhibitor fungicide plus three lbs of Captan. This provides the best control on a protectant basis and I believe the most economical for the benefit you get. You will also get some mildew control if Elite or Nova is used. An example would be four oz of Elite plus three lbs of Captan.

Post Harvest - The time of harvest with no crop could certainly be considered as soon as the first tart cherries in your area are mature. At this time growers should evaluate their blocks. If it is clean of leaf spot, growers may want to consider bypassing any further sprays. If there are any levels of leaf spot in the orchard, then he should consider one final "post harvest" Chlorothalonil applied as a protectant.

Recent freezes raised questions about the capacity of sprinkler systems to protect blueberry flowers (and other crops) from cold injury. Here are some facts that may help.

Swelled but closed buds tolerate 15-20° F. At "tight cluster" (individual flowers visible but still tight in bud), injury will occur between 18° and 25° F. Once flowers have separated but the corollas (petals) are still closed, 25-28° F is lethal. Fully open flowers are killed between 28° and 31° F. The most sensitive stage is just after the corollas drop, when 31° F will cause damage. These temperature ranges are general and will vary depending on the duration of exposure, wind, humidity, and possibly temperatures immediately preceding the freeze. Varieties at the same stage of development differ little in tolerance.

The freeze protection from sprinkler systems is limited by the irrigation rate. More water is needed to protect at lower temperatures and higher wind speeds, as summarized in the accompanying table.

Table 1. Irrigation rate (inches/hour) to protect buds under different wind and temperature conditions (from U. of Florida Exten. Circ. 287)

Many sprinkler systems in Michigan blueberries are designed to provide about 0.12 to 0.15 inches of water per hour. This volume protects plants to about 22° F with no wind or 24° to 25° F with a light wind. Most systems cannot easily be changed to deliver more water and protect to lower temperatures. Increasing the operating pressure is not advisable because the volume is not increased substantially (increase from 60 psi to 80 psi may provide only15 percent more water). Higher pressure may break lines and also generates considerable mist and may compromise the uniformity of application. Larger nozzles can be installed in some systems, but only if the capacity of the mainlines, well and pump can handle the added volume. For example, 9/64-inch nozzles that deliver 0.12 inches water per hour require 60 gallons per minute per acre of blueberries. Switching to 5/32-inch nozzles would deliver 0.15 inches per hour but require 68 gallons per minute per acre. Even if systems can provide adequate volume to protect from temperatures in the low 20’s, breakage from ice accumulation can be considerable.

Some frost avoidance can be achieved by keeping the soil surface clean of vegetation, moist, and packed. Soils have a large heat capacity, so they can capture and store considerable heat energy during sunny days, and release heat to maintain air temperature during cold nights. Weeds, sod, and plant residues insulate the soil from the sun and reduce heat capture. In addition, tall grass and weeds raise the effective ground level. This is important since cold air is heavier than warm air, and settles along the ground and in the lowest areas of fields. If fields are covered with foot-tall grass or weeds, flower buds a foot higher in the canopy may be injured during a frosty night.

The other consideration is that wet or moist soils have a higher heat capacity than dry soils, and packed soils are able to absorb more heat than recently cultivated soils. Some growers attempt to irrigate during the day prior to predicted frosts in order to increase the capacity of the soil to absorb heat. This may be of some value if warmer well water is applied, but cold water will also reduce soil temperatures initially. This practice may temporarily raise the humidity in the air surrounding the plants, but it likely has little effect during the following night, particularly if wind is present. The bottom line is that clean, moist, and packed soil surfaces will absorb more radiant energy during the day, and protect from frost by releasing this heat during the night.

As a result of last week's frost, many grape growers are looking at vineyards that will not produce an economic crop this year. Following on the heels of last year's poor crop, growers will not want to spend much money on their vineyards. It is tempting to just ignore your vineyards this season and cut your losses. An important thing to remember is that many of the buds that push now may be fruitful. It is important to get a handle how much crop you may actually end up with. Areas that look like a disaster now may have a marketable crop at harvest. The vines will also be growing wood for next year. With little fruit on these vines, their energy will go into shoot growth. Like last year we will end up with lots of shaded wood that makes for poor fruiting canes. Shaded buds have reduced fruitfulness. In frost-damaged vineyards you need to keep costs down and develop good wood for next year.

I think one of the most important things growers can do is shoot positioning or combing this summer. Positioning shoots outward decreases shading and eliminates running brush. Positioning the shoots downward slows their growth, preventing excess wood development. Lots of growers will be doing mechanical pruning next year to save money and this is very effective on vines that are set up for it rather than a mess you walked away from last year. Combing will also increase the effectiveness of the pesticides that you apply.

Do not eliminate your pesticide program. The pre-bloom and post-bloom sprays are still vital, especially if you think you might have a crop. Determine your spray needs by scouting in your vineyards for pests and diseases. Certainly in some vineyards with little or no crop we can let foliar pests and diseases take their toll and thereby reduce the vigor of the plants but I think that all of you will need to spot spray some areas in your vineyards where pest and disease pressure explode.

The same goes for herbicides. Stick to your scheduled herbicide applications to keep weeds in the trellis row down. You still want to maintain a clean vineyard. Suckering is expensive and many growers will just burn them off, but this frost does give you a good opportunity for trunk renewal in your vineyards. Many growers will reject this out of hand as too expensive in the middle of two bad crop years. Many of our vineyards would benefit from this and you might choose one or two vineyards to improve this year. You might make back your losses later with increased yields.

Many growers will cut back on their fertilizer program. Most growers have already put on part of their nitrogen and all of their potash. I do not see a reason to put on more nitrogen after last year's growth and what looks like two years of light crop. I would recommend applying nitrogen only and only to vineyards where shoot growth is poor. I do not see a need for other nutrients.

The unique situation in Michigan grapes this spring has created a need for growers to consider an adjusted insect and disease control program for frost-damaged vineyards. The comments below are intended to help growers reduce pest management costs while maintaining a program to address critical needs for vine protection.

If a crop is to be harvested from a vineyard, regular scouting can help avoid any more surprises. At the very least, checking vineyards post bloom, in mid-July, and in early August can provide the minimum of information regarding development of key insect pests and diseases. If the cost of hiring a scout seems too much, try negotiating a lower price before canceling this service. Alternatively, walking the rows once a week can help you keep up to date on vine and pest development and will cut down the cost of this service. It may not seem worth it to spend any time in some badly affected vineyards, but consider this an investment in the long-term future of the vineyard.

Decisions for insect control in 2002 will depend on the expected yield from each vineyard. If it is expected to be close to normal, a typical insect control program should be maintained to guarantee the expected yield and quality.

If a lower than normal crop will be harvested, juice grapevines can tolerate leaf damage and still ripen the reduced crop. Because of this, it will be much less important to control Japanese beetle, rosechafers, and leafhoppers than normal. If no post-bloom insecticide application is made, leafhopper infestation can be checked in mid-July to determine the need for controlling this pest. The threshold for juice grapes with a full crop at this time of the season is ten percent of leaves infested. Although thresholds have not been developed for situations with a reduced crop, they are likely to be much higher as the crop load decreases. As mentioned above, the need for foliage protection will be low this year, so only those vineyards where a high leafhopper infestation is discovered will need treatment. If no crop will be harvested this year, the cost of protecting vines from leafhoppers and beetles is unlikely to be economical in juice grape vineyards.

Hybrid and Vinifera vines are less tolerant of insect feeding than juice grape varieties. If bearing vineyards of these varieties are infested by foliage pests, leaf protection remains important for achieving fruit ripening and vine maturation. Regular scouting can be used to determine the need for, and timing of, interventions to control foliage pests.

A program for control of grape berry moth, which is the main pest of grape clusters, should remain a priority if any grapes are to be harvested. This will help minimize crop loss this year, and will reduce the risk of high infestations next year. Application of a post-bloom insecticide to vineyards that have a history of high GBM infestation is warranted if the vineyard will be harvested. Sampling again in the third week of July (same time as leafhopper samples above) can be used to determine whether the cost of further insecticide applications is warranted. It is worth keeping the sprayer on hand after veraison, in case populations of grape berry moth continue to develop close to harvest (as they did in 2001). If this occurs and berries are at risk from infestation, a well-timed effective insecticide may be warranted prior to harvest to minimize risk of infestation in harvested berries.

If grape berry moth infestation is restricted to wooded borders, cost savings may be achieved in some vineyards by applying border sprays to the outer ten rows. Cluster sampling in mid-July can help identify vineyards where this strategy would be worthwhile.

The main foliar diseases that Michigan juice grape growers need to worry about are powdery mildew in Concord and downy mildew in Niagara grapes. If no fruit will be harvested, foliar diseases are the only diseases that need to be considered. As with insects, vines with a small crop load will be able to tolerate more foliar disease. Control of powdery mildew in Concord grapes may not be needed at all, unless there is a lot of disease leading to a concern about excess inoculum production for next year. In that case, one or two mid- to late-season applications of a sterol inhibitor fungicide will probably be sufficient to reduce further infections and inoculum production. Highly susceptible Vinifera varieties and hybrids may need closer monitoring and control. Sulfur (for non-sulfur sensitive varieties) and JMS Stylet Oil are lower-cost alternatives for control of powdery mildew. However, they may need more frequent application.

Downy mildew can be more harmful than powdery mildew, as it can lead to severe defoliation and reduced winter hardiness of the vine. Even though vines with a small crop load can withstand more downy mildew than heavily cropped vines, it should not be allowed to go completely out of control. This is also important from the standpoint of overwintering inoculum for next year. I would recommend scouting of vineyards in mid-July. If downy mildew lesions are common, an application of Ridomil can be made to eradicate the disease and stop further spread. Scout again 2-3 weeks later to check if further control is needed. Protectants such as copper (for non-copper sensitive varieties), Bordeaux mixture, and ziram are less costly alternatives, but these will not eradicate the disease. They will only serve to prevent further infections and may need to be reapplied if weather conditions are conducive to the disease.

Black rot and Phomopsis are the main cluster diseases to control if there is sufficient fruit to harvest, especially if there is a lot of overwintering inoculum (fungi are typically not affected by a freeze). If very little disease was present last year, fungicide applications are not as critical. Black rot control should be focused around bloom, with the first and second post-bloom sprays being most important. If there is a lot of overwintering inoculum and conditions are conducive, an immediate prebloom spray may also be warranted. However, there is generally no need to protect the fruit beyond the second postbloom spray, because the berries become naturally resistant to infection.

Phomopsis control becomes important as soon as the flower clusters become visible, which will happen a little bit later this year as the secondary buds are only starting to push now. If there is a lot of overwintering inoculum, Phomopsis spores will be released during most rain events until about bunch closing. If there was not much disease the previous year, Phomopsis sprays may only be necessary until pea-size berry. If you don’t know how much disease there was last year, the amount of overwintering inoculum can be estimated from the number of lesions on current-season young shoots and leaves. During a dry spell, fewer sprays are necessary as well. Last year, there was no benefit from sprays beyond the first post-bloom spray. The EBDCs are cost-effective materials for use prior to bloom, and Ziram can be used after bloom.

Botrytis bunch rot is primarily a concern in Vinifera and hybrid grapes. Protection may be needed if conditions are cool and wet in the period between bunch closing and harvest, with veraison being a critical time. A bloom spray typically is not cost-effective. One or two applications of a fungicide like Vangard are most effective for control of this disease.

Because cluster protection is the main focus of a reduced insect control program, it is best to target sprays to the fruiting zone to maximize the effectiveness of sprays. For effective grape berry moth control, spray deposits must reach the whole cluster. This becomes more challenging as the vine canopy grows and so as the season progresses, spray volume should be increased and every row should be treated. Although this will take more time, getting the maximum effect out of every spray is particularly important when yield is expected to be low.

Under times of financial challenge, the temptation may be to choose the least expensive option to achieve control. This may seem the best choice, but it is good to keep in mind other factors. For example, is the product effective under the current and predicted weather conditions; how long does it last; and how well will it control the target pest or disease? In the long run, it may be more cost effective to use a slightly more expensive product that lasts longer than the cheapest option. Depending on existing pest and disease pressure, a lower labeled rate may be used, though.

When cutting back on sprays, make every one count. Making sure that applications are made at the optimal stage for control of your target pest is another way to help cut costs. It may take a little more time to check vineyards closely every few days, but doing this can be a cost-effective way to improve the impact of your spray program. By doing this, you may also find that pests and/or diseases are not as bad as expected, and the cost of an application can be saved.

Apple thinning is the most important practice an apple grower needs to perform each year. Thinning can be somewhat unpredictable, but in general, good results can be achieved by applying thinners under good weather conditions. All thinners work best when applied during warm temperatures (80’s for highs). The two to three days after a thinner application needs to be warm to achieve good thinning. Also, apply thinners early to achieve good results, such as maximum fruit size and increased return bloom.

Difficult to thin varieties are prime candidates to consider starting a thinning program at petal fall. As the petal fall stage approaches, evaluate your potential crop. First, consider last year’s crop. A prior year’s heavy crop will be easier to thin this year. Second, has frost damage occurred during pre-bloom and bloom period? If so, reduce the aggressiveness of the thinning application or consider delaying the thinning application altogether. Third, evaluate the health and strength of the bloom, the pollination conditions and the bee activity. If these factors are good or excellent, be ready to start thinning at petal fall only if warm conditions are forecasted.

To summarize, thin early, starting at petal fall where appropriate, and apply thinners at the beginning of a forecasted warming trend. Use mild or aggressive thinning rates based on your best judgment of the potential crop set. Use your past year’s experience with your block to help select your program.

Abnormally cold temperatures on April 21-23 caused major damage to a variety of crops in Michigan. The cold temperatures were associated with a large Arctic-origin air mass moving across eastern North America. Conditions on April 21 and 22 were best characterized as a "black frost," where the sub-freezing temperatures were accompanied by cloudy skies, light to moderate winds, and no visible frost formation on soil or vegetative surfaces. Minimum temperatures in the 28-32° F range were common across northern Michigan the evening of April 21 through the morning of April 22.

The second event was a more typical, radiation-type of frost. Clear and relatively calmer conditions on the evening of April 22 allowed temperatures to fall to sub-freezing levels over all but southeastern sections of the state (where clouds persisted for much of the night). Air temperatures and wind speed from the Michigan Automated Weather Network station at Fremont, MI (Figure 1) are representative of this radiation-type freeze event across western Lower Michigan. The air temperature fell off quickly during the evening hours of April 22, and quickly approached the dew point temperatures, which were in the mid-20's by early morning on April 23.

(Figure caption) Figure 1. 5-minute air temperatures (° F) and wind speeds (mph) between 18:00 EDT April 222002 and 12:00 April 23 2002, Fremont, MI.

Rapid tree growth and increased pest activity often mark the bloom period in apple, with a greater diversity of pests being visible. Many of the pests first seen at the tight cluster to pink stage are now becoming more prevalent. The focus of orchard management at this time is disease control and ensuring good pollination. Protection of pollinators will limit insecticide use to those compounds that will not harm bees. Just the same, the pest information gathered at this time will be critical for good insect management decisions at the petal fall stage. Fireblight control measures are critical in the bloom period if conditions become favorable for infection.

Monitoring for fireblight entails use of models that integrate moisture, temperature and tree phenology to predict when potential infections may occur. In the field, it is important to look for overwintering cankers on twigs, bacterial oozing from these cankers, and new blossom infections. Any visible symptoms should be reported immediately.

Apple scab and powdery mildew are increasingly active during this period as foliage expands and temperatures rise. Apple scab lesions will become larger and may be found on both upper and lower leaf surfaces. Powdery mildew can cover entire leaves or terminals.

The insect and mite pests that we will visually scout for are rosy apple aphids, green apple aphids, leafrollers, and European red mite nymphs. Rosy apple aphid colonies are expanding, and feeding damage is visible as curled leaf clusters and petioles exhibiting a reddish discoloration. Rosy aphids will now take on a deeper red body color with a dusty covering. Green apple aphids will continue to colonize clusters, but without the distinctive damage seen with rosies. Obliquebanded leafroller larvae are now larger and more active, moving throughout the expanding flower cluster and consuming more leaf surface. European red mite eggs have mostly hatched by this time and nymphs will be readily visible on leaves. Spotted tentiform leafminer eggs have now hatched and are becoming visible as sap feeding mines on the underside of older spur leaves.

Leafminer flight is now in decline, and trap information is less important as a management tool.

Continue to monitor traps for Oriental fruit moth, and note the first sustained catch for biofix purposes. If pheromone-baited traps for codling moth have not been placed, then they need to go up now. Plum curculio adults are also beginning to emerge from their overwintering sites. Traps for this pest can be placed in the orchard at this time to provide preliminary information on movement of adults into trees and to estimate population levels.

The tarnished plant bug spends the winter as an adult and on warm spring days can be seen feeding on flower clusters. High populations of tarnished plant bug may cause limited injury to flowers. Most economic injury to the fruit will occur over a two-week period beginning at petal fall.

Inspect flower clusters to assess pest populations. Select a total of 100 flower clusters from inside and outside of 10 to 20 trees throughout the block. Inspect each cluster and record the damage and the total number of each kind of pest present.

The weather for the upcoming week is forecast to be cool and wet. There is still a danger of frost whenever we have clear skies and calm conditions at night. Soil moisture conditions are good. Soil temperatures are about 48.

In apricots, there was only moderate damage from Tuesday's (April 30) freeze. In general, fruit set looks good.

In peaches, we still have a good crop in most sites. No signs of peach leaf curl yet. Just like the previous week there were Oriental fruit moth caught one night last week but cool weekend temperatures generally kept the catch at zero. We are delaying declaring biofix until we have a sustained catch for several days. We believe that the cool weather this week will keep moth flight low until warm weather returns.

In cherries, crop losses to freezing were significant in sweet cherries. Crop losses in tart cherries were light. Tart cherries have a scattered bloom. Cold windy weather means pollination will be poor. A long drawn-out bloom period means the crop will be fertilized over a long period of time and crop maturity will be strung out making harvest more difficult. Fruit set will be a problem. The final crop size will probably be average for the region. Blossom blight is rare in tart cherries. As the leaves unfold they become susceptible to cherry leaf spot. Growers should be protecting against this disease as weather warms. Sweet cherries are always susceptible to brown rot.

In plums, frost thinned the crop, but we should still have a good crop. Plum growers need to protect new shoot growth against black knot.

In apples, earlier varieties were hardest hit losing the king bloom and some of the side bloom. Later varieties suffered little damage. We still have good crop potential but chemical thinning will be much harder. The northern areas of Berrien County suffered the worst damage. An apple scab infection occurred on April 27. The symptoms of this infection should be visible on about May 16. Scab spores are being caught after each rain. Scab spore release is about 50 percent complete. Most scab spores are released in the period from pink to petal fall. Growers need to maintain protection against scab. Powdery mildew will become a problem as bloom nears. There is no insect activity to report: cold weather has shut them down. Codling moth and Oriental fruit moth were flying last Wednesday (April 24). Growers are planning their pink sprays. Scout your orchards for leafroller larvae and European red mite eggs. Growers and scouts report lots of ladybugs and little else. It appears that the ladybugs are eating everything they can find. Growers may not need to apply early season pink sprays.

In pears, there was little damage. Pear psylla are hard to find. Look for ladybugs.

Concord grapes suffered greatly. It appears that only the highest sites have any crop. We lost 75 to 90 percent of the crop. The highest sites recorded temperatures of 27° and 28° F and had little damage. In lower vineyards almost all the buds froze. Secondary and tertiary buds will now push, and time will tell if there are many flowers in those buds. It seems unlikely that growers will harvest many acres this fall. Wine grapes suffered less because they begin growth later and are usually in better, higher sites. Chardonnay buds are at bud burst. It appears likely that depending on the site we have lost about 50 percent of the crop. Cool, wet conditions should favor phomopsis. No black rot infection periods yet. The grape growing degree-day total base 50 from April 1 to April 28 at Lawton is 165.

In strawberries, the frost caused little loss, since the flower buds were below ground. Fields that wintered under plastic were beginning to bloom and suffered losses.

Raspberries and blackberries have little damage.

Cool and more typical spring-like temperatures have helped to slow our season down. We are now only a few days ahead of normal spring fruit development. Many areas of Southeast Michigan were close to receiving bud-damaging low temperatures last Tuesday morning (April 23). However, in cutting buds over the last and this week in the many areas of the region, it appears that we have not had any frost or freeze injury in any of our fruit crops. This cool, cloudy weather has kept insect activity to a minimum. However, most areas did experience an apple scab wetting period over the weekend. Cool, wet weather is forecast for the next five days or so, and there is still a danger of a frost or freeze event occurring. Soil temperatures are now in the mid-40’s most days, which is cool for this time of the year. Many fruit growers have commented on a surprising lack of soil moisture while doing planting over the last week.

Pears are mostly at popcorn. As reported last week there is little to no pear psylla to be found this year.

Peaches are at bloom to early petal fall. Peach pollination may be a concern this year. We have an excellent crop of blossoms this year. Now is the time for peach growers to wrap up their brown rot control sprays.

Sweet cherries are in full bloom and tarts are just a few days behind. Applications for brown rot control and cherry leaf spot have been made at most farms. It is apparent that we have an excellent crop of sweet cherries coming along.

Raspberry growth was rapid early in the spring, but has slowed due to cool weather. New canes for fall raspberry bushes are about two to three inches long and summer raspberries have one to two fully expanded leaves. There has been little to no winter injury to cane tips in most summer raspberry plantings this year.

Blueberries are mostly at early pink bud. Leaves are unfolding. It appears that we have a nice crop of blueberries at this time. Mummy berry trumpets were detected mid to late last week at fairly low levels.

Degree accumulations are running near to slightly above normal for much of the Grand Rapids region. GDD42 are 260 and GDD50 are 145.

Sweet cherries are coming in bloom for many varieties.

Cooler than normal spell continues. We had two frosty nights but without significant bud damage. Our major concern is with the pollination or lack of there off. Apricots, peaches and sweet cherries are at risk of not having a good crop not necessarily due to the frost damage but to the fact that the daily temperatures are so low that are hindering normal pollination and fertilization. The concern is that even if we do get some more favorable weather for bees to fly by the end of the week, we still may end up with inadequate fertilization as a result of the age of the flowers. Ovules are viable eight days and it takes two days for pollen tube to reach the ovule so the effective pollination period is six days. Keeping that in mind, if the pollen is deposited on stigma between days one and six, fertilization will occur. If the pollen reaches stigma on day seven it will be too late; pollen tube will reach the ovule on day nine but by then the ovule would not be viable any more. In general, the sooner pollination can occur after a flower opens the greater the likelihood that the fertilization of the ovule will occur. As the time elapses, the stigma receptivity, ovule and pollen viability diminish.

In apples, wetting events last week produced spore discharge but did not result in scab infections due to the low temperatures. Scouts are reporting finding very few mite eggs. They are finding very few aphids, some leafroller larvae. No spotted tentiform leafminers yet.

Apricots are in full bloom to early petal fall.

Pears are in open cluster. No significant damage from the frost events. Pear psylla eggs are very difficult to find.

Peaches are in 50 to 80 percent bloom depending on the variety. No significant frost damage but crop may still be low due to poor pollination weather. Oriental fruit moth has not been caught yet.

In plums, brown rot and black knot are of concern at this time.

Sweet cherries are in bloom 50 to 80 percent depending on the variety. Blossom blight is of concern as well as leaf spot. After the first catch of plum curculio during the warm spell, we are continuing to find them in small numbers. They have been found in the blocks with resident populations, mainly abandoned blocks.

Tart cherries are in open cluster. As the leaves unfold they become susceptible to the leaf spot. The rain events up to this point did not result in infection periods.

GDD42 193

GDD50 103

The major weather events that have affected the potential fruit crops in Northwest Michigan are:

1) Record high temperatures in the 80's during the week of April 14 advanced cherry buds to a vulnerable stage for cold injury ahead of normal.

2) Freezing northeasterly wind at temperatures of 26° to 28° F occurred for 10 to 11 hours during the night of April 21 and early morning of April 22. This freeze caused extensive bud damage in cherries, particularly at higher elevations (temperatures were lower at higher elevations and potential exposure to wind was greater).

3) More typical inversion types of freeze further damaged fruit buds, particularly in low areas, on the mornings of April 23, 25, 26 and 27.

4) The extent of the damage in cherries was very likely accentuated because last year's severe drought and large crops caused trees to go into this spring in a weakened state. This reduces the hardiness of buds, resulting in higher bud losses at given temperatures than normal.

Apples came through the wind freeze in good condition. We expect to see some damage in low areas from inversion freezes, but have not yet assessed conditions in these areas. The apple growers' main concern so far is apple scab. A long, cool wetting period just ended, resulting in an infection period only for Northport. It was humidity that carried this infection through, so growers in other areas that have relatively higher humidity – particularly low areas or spots near bodies of water, should treat this as a light infection. The next spray for apples should include either a sterol inhibitor or a strobilurin fungicide for mildew control. These products also have up to four days of back action. Dr. Alan Jones' research has shown that the strobilurins perform better when used on a protectant basis. Spotted tentiform leaf miner is flying and laying eggs on the few warm days we've had. European red mite egg numbers are low in most blocks. Oil can be applied to kill eggs, but the timing should be frost free for 48 hours both sides of the application. Oil may prove difficult to fit in this year due to cold temperatures and wind.

In pears, pear psylla egg numbers are low as well, likely due to low overwintering adult populations and unpleasant flying conditions for the adults. Eggs are darkening as they approach hatch time. Oil sprays can be applied to deter egg laying. Surround can also be applied to deter egg laying on both organic and standard orchards.

Abnormally cool conditions will continue over the entire region as the jet stream troughing feature currently in place across central North America persists into the upcoming weekend. Combined with the threat of rain and possibly some snow in central and northern sections of the state Wednesday and Thursday (May 1-2), conditions will likely remain poor for pollination.

High temperatures will reach only into the 40's and 50's with low temperatures remaining in the 30's. Frost and freezing temperatures will be a possibility late this week, although low temperatures are expected to remain above the 30° F mark. There is currently expectation for a major jet stream over the region change by the end of the weekend or early next week with the movement of the trough currently over central and eastern sections of the country to the west and the formation of a ridge in its place.

The NOAA 6-10 outlook for May 5-9 reflects this upper air change, and calls for temperatures to increase to normal to above normal levels statewide. For the 8-14 day period covering May 7-13, the outlook calls for near normal temperatures. With southwesterly flow across much of the Midwest region, an active storm track is also a good bet, so both the 6-10 and 8-14 outlooks call for normal to above normal precipitation totals. Unfortunately, with this type of pattern, severe weather will also be a possibility across much of the central U.S.