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| Fruit Crop Advisory Team Alert newsletter | ||||
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| Vol. 22, No. 4, May 1, 2007 |
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In this issue |
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Fire blight, blossom blight |
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The fire blight pathogen is exceptionally adapted to growing on the stigmatic surface of blossom pistils. Populations can readily reach 1 million to 10 million cells per blossom. Each open blossom is only susceptible to infection for a few days; however, the pathogen is adapted to successfully infect blossoms during this window of time. After explosive growth on stigmas, rain or dew facilitates the movement of pathogen cells to the hypanthium (floral cup) where infection occurs through nectarthodes.
In addition, other major factors important for the occurrence of blossom blight include:
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| Fire blight and streptomycin resistance in Oceana County George Sundi and Gayle McGhee Plant Pathology In 2006, we detected streptomycin-resistant Erwinia amylovora, the fire blight pathogen, for the first time in orchards in Oceana County, Michigan. The pathogen was present in apple orchards at frequencies of 20 to 30 percent. Growers in Oceana County should use a tank-mix of Streptomycin and Mycoshield at full rates for blossom blight control under high disease pressure. Other materials such as Serenade MAX can be utilized under low to moderate disease pressure. Apogee (prohexadione calcium) is another tool that can be used for shoot blight control and is particularly useful in orchards with streptomycin resistance problems. See the 2007 Michigan Fruit Management Guide for information on rates and timings of spray applications. |
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| Applying Apogee There are four points that I would like to make about applying Apogee in apples. First is timing, second is rate per acre, third is thinning relationships and fourth compatibility. Timing. Apply Apogee when vegetative shoot growth is less than 3 inches. This is about a 7 to 10 day window commencing at the king bloom petal fall stage. Most years all varieties can be treated at this time. The second application should be applied two weeks later and the third application two weeks after the second. Sometimes a fourth application is needed, but that is optional based on crop load and tree vigor. Excessive rainfall and light crops will promote vegetative growth; therefore an additional fourth application may be needed. Rate. Rate per acre is usually calculated on a tree row volume basis and adjusted to 2/3 of the label full rate. This 2/3 rate/acre is a season long rate per acre. For example, if your trees are 75% tree row volume then 24 ounces per acre is the seasonal rate (48 * .75 * 2/3). Best results occur when seasonal rate is split into three or four sprays. For example, 8 + 8 + 8. When fire blight is a severe risk, the first application at king bloom petal fall timing should be increased, perhaps as much as 150% of a split rate. For example, increased from 8 ounces per acre to 12 ounces per acre. Subsequent sprays, the second and third sprays could be reduced, so the seasonal application would be 12 + 6 + 6 = 24 ounces per season. Thinning. Apogee tends to increase fruit set, therefore more aggressive thinning is needed. Increase your thinning by 10 or 15%. Compatibility. Apogee is not compatible with calcium or boron in the tank. Also, we suggest that Apogee be applied after a thinner. If the two-week timing interval is also the ideal time to thin, make your thinning application first and then a couple days later follow with Apogee. Remember to include the label recommendations for AMS and surfactants. In a summary; Apogee is an excellent tool to help control vegetative growth and especially suppress fire blight spread among shoots and within shoots. Follow these tips to get the most out of Apogee. |
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| Gibberellin to enhance blueberry fruitset Eric Hanson Horticulture Compared to most fruit crops, a high percentage of blueberry flowers normally produce fruit. When bees are numerous and weather is warm and calm, 80-95 % of flowers may set fruit. However, cold, rainy weather during bloom restricts honey bee activity and pollination, resulting in lower fruit set and often reduced berry size. Flowers that are not pollinated within 3-5 days after opening are unlikely to set fruit. After normal pollination, berry growth is dependent on the production of gibberellin and perhaps other growth promoters in the ovary tissues and viable seeds. If flowers are not pollinated, they abort. If only a few ovules are fertilized, the fruit may set, but not contain enough seeds to grow to full size. When pollination is limited by poor weather, gibberellin (GA) sometimes improves % set and berry size. Several GA products (ProGibb, GibGro) are labeled for highbush blueberries. GA may result in retention of some seedless (parthenocarpic) fruit that normally drop, and increases the size of berries with low seed numbers. GA can be applied in a single spray during bloom (80 gram active ingredient per acre) or two 40 g sprays, one during bloom and the second 10-14 days later. Higher spray volumes (40 to 100 gallons per acre) may improve coverage and effects. Slow-drying conditions also increase absorption. Also make sure your spray water pH is not above 7.5. Since the cost of 80 g of GA is over $100, it is important to know when to use GA. If weather has been reasonable good for bee activity and the white corollas fall easily from the bushes, pollination is probably adequate. Keep in mind that blueberries can bloom over a long time, and often only a few days on good conditions is enough to provide adequate pollination. Consistently cold, rainy and/or windy weather through bloom causes pollination problems. If the corollas stay on the bushes longer than usual and turn red/purple before eventually dropping, pollination may have been inadequate. The corollas of pollinated flowers drop readily while still white. Varieties with fruit set problems (Jersey, Coville, Earliblue, Berkeley, Blueray) are most likely to benefit from GA. Jersey, for example, is relatively unattractive to honeybees, and berry numbers and size are often limited by inadequate pollination. GA does not always provide a benefit, and effects can be subtle. A key to learning about GA benefits is to leave non-treated check rows. This is the only way to tell if your money was well spent. 2006 Trial. Because weather during bloom was poor, we treated Jersey bushes at the Southwest Michigan Research and Extension Center with ProGibb applied twice at 40 g a.i./acre (17, 27 May) or applied once (17 May) to a single application of 80 g/acre on. On 17 May, 30% of Jersey petals had fallen. Treatments were applied in 50 gallons spray per acre. Results were fairly typical for years when there is a response to ProGibb. The 80 g rate applied once increased yield by about 30% over control plots, and there was a trend towards a response from the 40 g treatment as well (Table 1). The higher yield appeared to result from more berries rather than an increase in average berry weight. During the week prior to the first ProGibb spray, measurable rain occurred every day, and maximum daily temperature exceeded 60oF only on one day. These are the type of conditions when growers are likely to see benefits from ProGibb.
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| Strawberries may need extra nutrition this season Bob Tritten SE District Fruit Educator Many strawberry fields that I have observed over the last two weeks across east Michigan appear to have a lack of vigor as they have begun to grow. I feel that some of this lack of vigor is related to cooler than normal and fluctuating soil temperatures this spring, as a result of our off and on season. While it is typical for me to recommend to strawberry growers that they apply light rates of nitrogen in springtime, this year I am suggesting extra nitrogen be applied immediately to strawberry fields to help improve their vigor and to be prepared for our fruiting season. The typical rate of fertilizer that I would suggest on strawberries growing on our heavier soils of east Michigan is in the range of 10 lbs to 15 lbs of actual nitrogen per acre. This year, I am recommending doubling that rate to 20 lbs to 30 lbs per acre to help overcome this lack of vigor. I would suggest that you leave a small area untreated to determine the effect of this extra fertilizer application. |
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| Honey bee CCD update If you have been listening to radio or reading papers the last few weeks, chances are that you have already heard about the alarming honey bee die-offs around the country. The phenomenon is officially named Colony Collapse Disorder (CCD). This disorder has the media all excited because it is large in scale (27 states are affected), came in quick (Colonies that were fine in August or September became collapsed around October and November.), and hit people hard (Many beekeepers with hundreds to thousands of colonies are losing 50 to 90 percent of their colonies.). Nationally, it is estimated that we have lost about 600,000 colonies. The worst of all, we do not yet know what causes it! The symptom seems to be for bees simply to disappear. That is why initially peopled called it disappearing disease (or fall dwindle disease). A colony with 30,000 bees checked one week ago – apparently healthy with lots of honey and pollen – suddenly has nothing, or a handful of bees with a queen left, but with lots of food and many frames of capped brood left. Very few dead bees are found inside the hive or near the entrance. Strangely, wax moths, small hive beetles, and robbing bees are slow in moving into such newly abandoned colonies – two to three weeks later – while normally they move into defenseless colonies right away. I just attended an emergency conference in Washington, DC a few days ago and we had a brainstorming session on possible causes of CCD, what we should research and where to obtain the funding. The short answer is that we still do not know what is the cause of CCD. A list of culprits include nosema ceranae (a protozoan parasite that infects adult bee mid-gut), viruses, varroa mites, or a new pathogen. Tracheal mites, pesticide use, various supplemental feeds are tentatively excluded. It is interesting that someone at the meeting reprinted an article published in 1897, complaining about the same symptoms seen in Colorado as what we are seeing today: most workers gone with a queen and some workers with lots of brood left in colonies. That was prior to both the varroa and tracheal mites, prior to the use of neonicotinoids (and organophosphates and pyrethroids). It seems almond growers in California, who need about half of the bees in the country (about 1.2 million colonies) did not have an obvious shortage of bees for pollination, but they did see a $15-25 per colony increase in price. Blueberry growers in Maine are experiencing a 50 percent increase in bee prices, one grower told me. I do not think Michigan will be as bad, but I would not be surprised if you see a $10 per colony increase in price. |
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| Locating a local beekeeper for fruit pollination Zachary Huang Entomology Even though Michigan has not been hit hard with CCD (compared to the loss of 25 percent of bees nationally), some beekeepers lost 50-80 percent of their bees during the overwintering process. This might make it difficult for growers to keep their existing relationship with beekeepers. This is where pollination contract becomes useful, if done correctly. Most California almond growers have contracts in the fall the previous year, specifying the number of colonies needed, colony strength, delivery date and consequences of not meeting the conditions. Usually there are monetary damages for either side not to meet the contract. This way the grower can be rest assured that he or she will get the specified colonies at the right time, at the pre-specified price. The beekeeper or the provider (in California there is now a new form of business for people just to hook up beekeepers with growers) will have to rent other bees if they do not have enough the bees to meet the contract. A sample copy of a pollination contract is at http://maarec.cas.psu.edu/PDFs/Pollination_Contract.pdf. Here are the instructions for finding a beekeeper at my web site, http://cyberbee.msu.edu
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| Application technology for small acreage producers Roberta Dow Northern District Water Quality Educator Michigan Groundwater Stewardship Program Michigan State University Extension June 14 from 6:00 - 9:00 PM |
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Regional reports Last week temperatures were cool with lows in the 40s. Monday and Tuesday (April 23-24) were nice with highs near 70. Wednesday and Thursday (April 25-26) were cold and rainy with highs near 50. The last two days have been warm and pleasant with highs climbing into the 60s on Sunday, April 29. We accumulated between one to two inches of rain. Soils are moist. Scattered thunderstorms brought scattered light hail Monday. This week’s forecast is for cooler, dry weather with lows in the 40s and highs near 60. Warmer temperatures are forecast for the weekend.
Peach bloom is ending. We should have a good assessment of the peach crop as it emerges form the shuck in the next few weeks. Oriental fruit moth adults are being caught in good numbers in pheromone traps. Biofix was Saturday, April 21 at 230 GDD at SWMREC. Pesticide sprays are targeted for 150 to 200 GDD base 45 after Biofix; this timing would be this weekend. The first generation of tarnished plant bug adults has been seen in trees during warm weather. Last week’s rains could have caused brown rot infections (48 hours at 50F for infection). Blueberries are at pink bud. In many fields, there is a heavy set of fruit buds. Mummyberry mushrooms are out, so last week’s rain was probably an infection period. Growers should check the new Blueberry IPM Newsletter at the MSU Blueberry Site. No cranberry or cherry fruit worms have been caught yet and scouts should be setting out pheromone traps for these pests. For grapes, Concord buds are at bud burst and vinifera grapes are at late swell. Once the buds have opened, there is less damage from cutworms and flea beetles. There are many live buds swelling in the vineyards. We are catching a heavy flight of grape berry moth. These are early males and there is no need to treat for these moths. There are no fruit clusters available to damage at this time. Growers should begin their early season disease control programs. Growers should apply protectants before the next rain. Be sure and check the MSU Grape website (grapes.msu.edu) for scouting updates. Strawberries are at white bud. Wild strawberries have begun to bloom. Fall raspberries are putting up new shoots. Summer raspberries are leafing out and some flower buds are visible in some fields. Some varieties were severely affected by the Easter cold snap. Blackberries were severely damaged by winter cold (early February) and the Easter freeze. Advanced shoots were damaged or killed, but new growth is emerging. Cranberries are beginning to green up on the edges of the beds and buds are beginning to swell. Currents and gooseberries are blooming. Meetings The next Monday Fruit Update meeting will be Monday, May, 5:00 PM, at the Fruit Acres Farm in Berrien County. We will discuss apple thinning. There are RUP credits available for the Monday Fruit Updates. |
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2 -- Southeast It seems as if our stop and go season has continued over the last week. We’ve had four days of cool weather with few, if any degree day accumulations, and then a few relatively warm days with a good number of degree day accumulations. Our season is still running about three to five days ahead of normal in terms of degree day totals, but based on phenology of flowering, we are about a week ahead of normal. The region received between a 0.5 and 1.75 inches of rain over the last week, with most farms receiving around a 1 inch. While this rain did slow up tree planting and other field work, as of yesterday many growers were back at it again. I am pleasantly surprised to see the amount of bloom in most of our tree fruits over the last several days. It appears that the Easter freeze event was not as dramatic as what we had originally thought. While there is still significant damage in sweet cherries and some in tart cherries, at this point in time it appears that overall we have a pretty good crop of tree fruit. The notable exception would be peaches that in many areas, with the exception of Romeo, are very thin this season. Look for more details on the Easter freeze event later in this report.
Tree fruit Apples have moved along quite fast in the last few days, with most varieties being at bloom or near bloom in the south and in the Flint area. Spotted tentiform leafminer trap catches have jumped up a bit, with numbers in the range of 35 to 200 per trap. Spotted tentiform leafminer egg laying has started over the weekend. Oriental fruit moths are starting to be caught as of Monday. Redbanded leafroller trap catches are down to 25 to 40 per trap, where as they were 75 to 100 last week. European red mite egg hatch occurred as of yesterday in several apple blocks; however, overall, European red mite eggs are scarce this spring. Apple rust mite adults are also scarce this year, which is a dramatic downturn from last year’s very high populations at this time. Green fruitworm larvae are starting to be seen. There has been no codling moth trap catch as of yet. Most growers had an apple scab infection late last week on April 28, with most of the reporting stations having a high infection. Symptoms from this event should start to show up mid- to late next week. I have not seen any apple scab lesions. I continue to get apple scab spore discharge with each rain event. For the most part, it appears that we have an excellent crop of apples coming along this year. In cutting flower buds since the Easter freeze event, it was apparent that there was damage in individual blocks and varieties; however that varied from block to block across most farms. Even in blocks that appeared to have a good percent of flower bud loss, it now appears that we have a crop of bloom. In some blocks that were over cropped last year, there is also a notable lack of bloom. I feel that this is due more to over cropping in the 2006 season as opposed to loss from the Easter freeze event. Pears are at king bloom, with a good crop of pears coming along. Pear psylla adults were seen yesterday in much higher numbers than last week. Egg laying has been going on for several weeks. Egg hatch occurred as of this morning. Peaches are at full bloom where we have a crop. The color of the bloom is off a bit this year at many blocks. There are also a good number of blocks that have an extensive amount of flower bud kil, primarily due to cold events in January and February. In blocks where there is a full crop of peaches, growers can go ahead and prune normally. In blocks where there is heavy bud damage, this may be an opportunity to bring the height of peaches down to more of a manageable level. Also in these blocks of peaches without a crop, I would encourage growers to cut back their fertility program for the season. Sweet cherries are at bloom to early petal fall. It appears that most farms have about 50 to 60 percent of a crop of sweet cherries at this time. This is a crop that I think was affected most from the Easter freeze event. It may be a good recommendation to apply copper to reduce bacterial canker in blocks that have a poor crop this year. Tart cherries are at bloom for the most part, however there is a fair amount of delayed bloom that may have been injured from the frost and freeze event. At this time, it appears that we have about 60 percent of a tart cherry crop. Plums are at full bloom, with the exception of early flowering types, which are at early petal fall. Small fruit Strawberry flower trusses have started to emerge from the ground. See the strawberry nutrition article in this issue for details on the extra nutrition recommendation this year. Raspberries continue to rebound from the Easter freeze event. Many of the leaf buds, which were at green tip at that time, were burned off. There may be some delayed Easter freeze injury on summer red raspberries, which will show up as they begin to fruit. Fall red raspberries are at 2 to 3 inches of new growth. Most of this new growth has reemerged since the growth that was present at the Easter freeze was burned to the ground. This may delay harvest of fall red raspberries by a few days this fall – time will tell. Blueberries are at pink for earlier flowering types. It appears that there was much less damage to flower buds than I originally predicted. Grapes are at bud burst for Concord types. Most growers are now finishing pruning grapes for the year. |
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3 -- Grand Rapids Area Growth over the last week has been more normal due to some average or slightly above average temperatures. Apples are at open cluster to pink stage depending on the variety. There are a few king blooms open on early varieties like Ginger Golds and Ida Reds. Sweet cherries are mostly in full bloom. Peaches are blooming also. As we get closer to bloom, freeze damage to apples still doesn’t appear to be extensive. There are some varieties and some blocks with more damage than others, but overall, the apple crop from the Grand Rapids area should be at a full crop potential right now. Now that sweet cherries are in full bloom, they still seem to be at about 30 to 50 percent of a crop at this time, depending on site and variety. The damage to peaches is still the most variable – from no damage to 100 percent bud kill or even tree death. Time will tell for sure, but overall, peaches should harvest out at 50 to 60 percent of our area’s normal harvest. Most of the damage to peaches most likely occurred during the cold weather in February rather than the April extreme cold. Now that we know more about the crop load, ground applied fertilizer applications are beginning. Growers are also adding foliar nutrients to their regular cover sprays to boost bud health. Tree planting is ongoing. Tree fruit Apple scab has had two infection periods over the past week for all areas around Grand Rapids. Spore numbers have been low and we should be at about 45 percent ascospore maturity at this time, so we could see some high spore discharge numbers over the next few weeks. With bloom coming on, apple growers will need to think about adding a mildewcide in the tank for powdery mildew in the next week or so for those varieties that are susceptible to it. Brown rot sprays on sweet cherries and peaches in bloom should be applied – these rainy days during bloom will promote brown rot at harvest time. Oriental fruit moth should begin flying at anytime, but no reports of activity at this time. Apple grain aphid can be found, but in relatively low numbers for this time of year. Rosey apple aphids are being found in low numbers in non-sprayed blocks and should be present in commercial blocks as well. Green fruitworms are flying. Overwintering European red mite eggs are still very difficult to find at this time, but there have been some reports of early red mite activity in known hot spot areas. Spotted tentiform leafminer adults should start flying at any time, especially with some warmer nighttime temperatures. Climbing cutworm damage to buds could be seen at any time. Pink sprays are going on in commercial apple blocks where warranted. There is still time to get them on in later blooming varieties, but be sure you are aware of neighboring blocks that may have bees set out already. Small fruit Blueberries in west central Michigan are showing a range of development from a ¼ inch green to early pink stage. The low temperatures and raining conditions occurring during the past week prevented blueberries from further development. Thus, although we observe some temperatures below freezing, no freeze or frost damage has been reported, yet. However, growers need to be alert because there are some chances of light frosts within the next five days. Therefore, frost protection plans and preparedness to start frost protection should be in place. For a complete frost protection action program visit our web site http://www.ipm.msu.edu/FruitFrost.htm. As of April 30, growing degree days (GDD, base 50 °F) accumulation in west central Michigan is around 160 with an average daily accumulation of 7 GDD. Cumulated rainfall for the last 5 days ranges from 1 to 1.1/4 inches. So far, insect pest activity is non-existent due to the prevailing low temperatures, but we need to remind growers that it is time to install cherry and cranberry fruit worm pheromone traps. At this time, it is critical that traps be monitored twice a week to be able to detect the beginning of the moth flight and to time our pest scouting activities. In the past we have observed that cranberry fruitworm eggs appeared 120-130 GDD (base 50 °F) after the beginning of the moth flight. Therefore, if we are going to use GDD to predict the fruitworm activity detection of the beginning of moth flight is critical. |
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4 -- West Central The weather has been nice and seasonable. We had quite a spread of temperature, from mid 40’s to the 70’s. Nightly temperatures were in low to mid 40’s with the exception of Saturday and Sunday night (April 28-30) when the temperatures dropped down into the mid30’s. Some low-lying areas might have had some frost. In the past seven days there were four rain events. It appears that the heaviest precipitation was in the southern parts of the district, then diminishing as it progressed north. The combinations of moisture and warmer temperatures have stimulated vegetation development. Apples are in various stages of phenological development depending on the variety. Idareds are in pink. Red Delicious is in open cluster, Jonagolds are showing early pink king blossom and McIntosh is in early pink, etc. Pears are in open cluster showing early white blossoms. If the warmer temperatures continue, I would expect them to start opening flowers in a couple of days. No doubt they will be in full bloom by the end of the week. Peaches are in full bloom. Plums are starting to bloom. Stanley plums have about 10 percent with open flowers. In plum rootstock trial, NY6 on Julior, Myrobalan H29-C, Prunus besseyi 9431, M2624 and M-40 are in full bloom, while only 50 percent on Myrobalon seedling. Tart cherries are just starting to open their flowers. Sweet cherries are in full bloom. West Central Michigan Growing Degree Day Totals since March 1 – as of Sunday, April 29.
Tree fruit Rain on April 26-27 in combination with heavy fog that lasted most of the day on April 27 provided favorable conditions for a heavy apple scab infection period in the whole district. As predicted, another wave of precipitation rolled into the area yesterday late afternoon. At the time of this report we have had an ongoing wetting for more than 12 hours. By 10:00 AM (on May 1), all the requirements will be satisfied for low infection. Spore discharge has been increasing. At this time there are about 40 percent mature spores with estimated 14 percent discharged. Rapid green tissue development must be taken into consideration when deciding on spray options. Best control will be achieved by using a combination of materials that would have a component capable of providing post infection, curative action. Captan or one of the EBDC fungicides in combination with Vangard could be one such option. Vangard is pre-bloom material that works better under cooler conditions and, given the current weather conditions, it could make a good fit. Vangard is a protectant with some after-infection capability if applied at full label-recommended rate up to 48 hours post infection. Other possibilities would be strobilurins (Flint, Sovran, Pristine), SI’s (Nova, Rubigan). Any of these materials should be applied in combination with protectant fungicides to maximize disease control and delay fungicide resistance development. Leaves are unfolding indicating a need for protection from cherry leaf spot. Last year this area had quite a few blocks with very heavy disease presence causing early defoliation. The inoculum presence is heavy and vigilant approach and aggressive control is necessary to avoid a repeat of last year’s performance. The current rain event has not yet reached the 20 hours of wetting necessary to trigger infection. According to the forecast, rain will stay over the west central part of the state over most of the day and expending into tomorrow morning indicating that the first infection of the season is imminent. Young leaves are at the highest risk. Spray options include, but are not limited to, Bravo, Indar and Pristine. Bravo is excellent cherry leaf spot material that will extend the protection against blossom brown rot. It is a very good fit at this time due to label restrictions allowing it to be used only up to the point of shuck split. Some of the other options are Indar with excellent ratings against leaf spot and blossom brown rot and Pristine that provides excellent control for leaf spot and powdery mildew. Plums are susceptible to leaf spot infections. Conditions are favoring disease development requiring protection at this time. Spray options are Elevate, Bravo, Rovral, Vangard, Orbit, Pristine, Captan and Topsin-M. As stated in the last week’s report, now is the prime time for brown rot/blossom blight, bacterial leaf spot and black knot requiring full attention and prompt control. Insects are still relatively quiet. Very few European red mite eggs have been observed. Pear psylla is the only one showing significant activity. No reports of oriental fruit moth flight yet, though I would expect to have a catch this week. There are very few spotted tentiform leafminers in the orchards at this time. |
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5 -- Northwest
Weather and crop development Last week, April brought in its usual showers, and we look forward to the start of May with warmer and dry weather, except for Tuesday, May 1 in the morning. Growth Stages at NWMHRS (4/30/07—8:00 AM) Warm weekend weather is moving the trees along. In pears, we are at late green cluster for Bartletts and white bud in Potomac. All apples are in tight cluster. In tart cherries, we are at bud burst and late bud burst for Balatons. In sweet cherries, we are seeing some differences between varieties: Hedelfingens are at bud burst, Golds are at early white bud, and Napoleons are at 10 percent bloom. Apricots are at petal fall, while plums are at early white bud. Grapes are at early bud swell. Not too much to report in the insect world, except for low levels of two-spotted spider mites and green apple aphids. We have seen a few blocks with lots of apple rust mites. We have not seen any European red mite eggs. We have also trapped a few (about 10) spotted tentiform leafminers at the research station. We have a new experiment in place to investigate plum curculio overwintering and spring migration, and we have observed movement in the weevil population this past week in our emergence traps. In other words, plum curculio are up and moving. However, primary migration into the orchard occurs for up to six weeks after bloom, with the biggest flush of movement happening up to 14 days after petal fall. This movement indicates the beginning of migration. With the wet weather of last week, all eight weather stations reported wetting events that resulted in a low to moderate apple scab infections. As of Tuesday morning, May 1, the Bear Lake and Benzonia weather stations are reporting wetting events, which have both resulted in low infection periods at those sites. Small fruit For grapes, a few climbing cutworms have been seen at the NWMHRS vineyard, but they were not feeding on buds; some were seen feeding on the bleeding sap from pruning cuts. Numbers were relatively low, about 1 per 70 vines. Growers should be scouting vineyards for symptoms and signs of last year’s powdery mildew infections, making notes on relative levels of overwintering powdery mildew on canes. If dormant sprays are planned for powdery mildew control, these need to go on soon. |
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| Weather news Upper air ridging and high pressure will move into the Great Lakes region Wednesday (May 2), setting the stage for an extended period of fair and dry weather. Following normal to below normal temperatures during the mid-week period, look for a gradual warming trend by late week. Readings will return to above normal levels again by the upcoming weekend. Daytime temperatures will remain in the 50's to low 60's Wednesday, gradually warming to the upper 60's to the mid or upper 70's by Saturday. High temperatures may reach the 80 degree mark in some locations by Sunday. Low temperatures will range from the 30's to the low 40's Thursday and Friday mornings, warming to the 40's to low 50's by Sunday. Given a very dry air mass in place across the region with relatively clear, calm conditions, some scattered frost is possible later this week – mainly in low-lying areas on Thursday or Friday morning. Most areas should remain well above freezing. |
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