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| Fruit Crop Advisory Team Alert newsletter | |||||||
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| Vol. 23, No. 9, June 3, 2008 |
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| In this issue Tree fruit news Borer damage sighted in many cherry orchards TNRC trapline data: Cranberry fruitwormSmall fruit news Disease control in grapes critical during and after bloom Small fruit meetingOther news Regional reports Weather news |
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| Borer damage sighted in many cherry orchards Background Borers, broadly grouped as insects whose larval stages feed inside the bark of woody plants, are key pests of fruit tree systems. Researchers have found that these insects contribute significantly to the decline or reduced vigor of stone and pome fruits. In Michigan stone fruit, the borer pest complex consists of three primary species: 1) greater peachtree borer (GPTB) (Synanthedon exitiosa (Say), 2) lesser peach tree borer (LPTB) (Synanthedon pictipes (Grote and Robinson), and 3) American plum borer (APB) (Euzophera semifuneralis (Walker)). Lesser peach tree borer and greater peach tree borer have similar life cycles, and the larval stage of all species cause the primary damage in cherry and other stone fruits. Lesser peach tree borer moths are active May through September, with peak emergence from early June to mid-July. Greater peach tree borer adults are active in early July through September, and this egg-laying period overlaps with the Michigan cherry harvest season - July through early August. Greater peach tree borer larvae are mobile yet found primarily on the trunks, while lesser peach tree borer larvae can be located in the trunks as well as in the scaffold limbs and branches. Greater peach tree borer can attack healthy tissue, but this pest has become much more prevalent with the onset of mechanical harvest. American plum borer is also a problem in cherry, but the peak adult flight is mid-May, around white bud or into bloom—much earlier than lesser peach tree borer and greater peach tree borer. American plum borer larvae also attack the cambium and can cause more severe damage or tree death due to their feeding habitats, and American plum borer has two damaging generations per season while the other species only have one generation per year. |
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| Prior to the discovery of American plum borer, most borer damage in stone fruit orchards was attributed to greater peach tree borer and lesser peach tree borer. Lesser peach tree borer is a pest of all stone fruits in the eastern United States. Similar to American plum borer, female lesser peach tree borer lay eggs in cracks or near injury and the onset of mechanical harvest has increased lesser peach tree borer populations. Lesser peach tree borer are also capable of causing tree mortality if populations reach damaging levels, but often American plum borer causes more damage than either lesser peach tree borer or greater peach tree borer as there are often more American plum borer larvae per wound and American plum borer only feeds horizontally, which girdles the trees more effectively than feeding in both horizontally and vertically. Greater peach tree borer are unique as females do not need damage to lay eggs, and these larvae feed on the cambium at or 6 inches below the soil line, which renders greater peach tree borer damage difficult to diagnose if it is underground. Although greater peach tree borer do not require tree damage for egg laying, it appears that trees previously infested with greater peach tree borer larvae or damaged by mechanical harvesters may be more desirable for egg laying by females. These results are based on studies that show plant derived semiochemicals play a role greater peach tree borer host recognition. Additionally, adult female greater peach tree borer respond to and deposit eggs more frequently on trees emitting gum, frass, or semiochemicals produced by larval feeding.
Recent observations Borer damage has been evident in many cherry and peach blocks throughout the northwest and west central regions of the state. We have observed many of the northwest infestations in Balaton® orchards while in west central, peaches have been a main target. Infestation intensity seemed surprisingly high, so we conducted orchard walks to provide an initial qualitative assessment of damage. Based on 15 Balaton® orchards in Leelanau County, we found borer damage that ranged from less than two percent to over 90 percent infestation (Table 1). Much of the damage was located in areas of the trunk with some type of injury, most likely shaker damage. However, we also observed damage at the soil line. Based on past information, we suspect the damage at the soil line was caused by greater peach tree borer. Infestations are located at the ground level or in areas with previous trunk damage. Soil line infestations can be difficult to see without removing the soil from around the trunk. Growers should be looking around the base of the trees, at the soil line, for gummosis and an orange colored frass (Photos 1 and 2). Frass can be seen in small piles, and its color contrast against a dark weed sprayed strip can be a good identifier of borer damage. For damage higher on the trunk, growers can peel back bark, which is much easier to do in damaged trees than in healthy ones, to find more gummosis, frass, and often larvae or pupae. This update is to alert growers to our recent findings and to be on the lookout for borer damage in his/her orchards, especially growers with Balatons®. Based on our preliminary assessment, we think Balaton® trees on Mahaleb rootstock may be particularly susceptible to borer infestations. However, we will continue to monitor trees and trap for all three stone fruit borers to give us a clearer picture of this emerging problem. |
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Lastly, we would add that although we have observed what seems like a lot of borer damage, the overall vigor of most of the surveyed cherry blocks looks good. Cherry trees appear to be more susceptible to borer damage in years three to five, and based on recent findings, mature trees can withstand higher levels of infestation. This observation in cherry is unlike peaches where borers cause more outright tree mortality. As we investigate further, we will refine our initial conclusions. Table 1. Percentage of damage to Balaton® trunks in 10 Leelanau County orchards.
Management Most growers rely on handgun applications of insecticides for control of borers. The success of borer control using insecticides is heavily dependent on the timing and precision of applications. Moth captures in pheromone traps can be used to assess moth activity and to predict the time of egg hatch. Trunk sprays are most effective when applied at the start of egg hatch – generally two weeks after the start of adult flight. There are currently only two registered materials that provide adequate control of the borer complex. The most widely used material is the organophosphorous insecticide, chlorpyrifos. The other option is the lone chlorinated hydrocarbon registered for use in stone and pome fruits, endosulfan. Mating disruption is another option for managing two of the borer species, greater peach tree borer and lesser peach tree borer. The development of mating disruption for control of greater peach tree borer and lesser peach tree borer began in the late 1970s. These efforts were based on the identification of (Z,Z)-3,13-octadecadien-1-ol acetate (ZZA) and (E,Z)-3,13-octadecadien-1-ol acetate (EZA) as the major component of the sex pheromone of greater peach tree borer and lesser peach tree borer, respectively. A series of studies have demonstrated that high levels of disruption of greater peach tree borer or lesser peach tree borer orientation to pheromone-baited traps, as well as reductions in pest densities can be achieved through the application of synthetic pheromone sources. However, deployment of two types of dispensers may be required to achieve control of lesser peach tree borer and greater peach tree borer, one releasing primarily ZZA and the other releasing primarily EZA. Purchasing and deploying a full label rate of hand-applied dispensers for both species may have limited utility. Thus, we have initiated a research project aimed at identifying effective and economical approaches to disruption of lesser peach tree borer and greater peach tree borer. Currently, there is not a commercially available, American plum borer disruption product. The hand-applied formulations being tested are three types of polyethylene rope dispensers, Isomate GPTB, LPTB and GPTB Dual (ShinEtsu Fine Chemical Co., Ltd, Japan). Isomate-P is loaded with a 96:4 blend of ZZA:EZA and is specifically designed for control of greater peachtree borer. Isomate-LGPB is filled with a 73:27 blend of EZA:ZZA, and is designed primarily for control of lesser peach tree borer. Although pure EZA is the actual sex pheromone of this species, the blend is used because of the high cost of the pure pheromone. Additionally, ZZA is the major component of greater peach tree borer pheromone and thus, using a blend in the lesser peach tree borer dispenser allows for control of lesser peach tree borer and suppression greater peach tree borer. Isomate-GPTB Dual is filled with a 50:50 blend of EZA:ZZA, and is designed for control of both species. Our studies will primarily focus on demonstrating the effectiveness of either using the dual product, or using low rates of one or both single-species products. The strategies, if effective, would greatly improve the practicality of this control technique. |
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TNCR trapline data: Cranberry fruitworm
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Disease control in grapes critical during and after bloom Cane and leaf lesions have been showing up in vineyards. Each rainfall event now will lead to spore dispersal and can also lead to successful infection if the tissue remains wet for a sufficient amount of time. The optimum temperature for infection is 59-68ºF, at which time about six to10 hours of wetness are needed for infection. The longer the tissue stays wet, the more severe the symptoms will be. Since rachis and flower clusters are now fully exposed, we should be concerned with preventing Phomopsis infection of the rachis and fruit, especially in mechanically pruned vineyards and vineyards with a history of the disease. Rachis infections are most closely correlated with yield losses at harvest. If at this time you find a lot of lesions on the leaves and canes, infection pressure will be high for the fruit also. Best fungicide options for control of Phomopsis during and after bloom will be Abound, Sovran or Pristine (do not use Pristine on Concord grapes). Phosphorous acid fungicides such as ProPhyt and Phostrol area also good and cost-effective alternatives. These are systemic and will most likely provide some kick-back activity. In trials done in Michigan, ProPhyt provided very good control of Phomopsis when sprayed on a 14-day schedule. Tighten the schedule and increase the rate if disease pressure is high. Ziram is a moderate to good protectant against Phomopsis and can be a tank-mix partner with any of the phosphorous acid fungicides. EBDC fungicides are good protectants but cannot be applied after bloom has started in grapes grown for the National Grape Cooperative. EBDC’s have a 66-day pre-harvest interval. Powdery mildew No powdery mildew has been sighted in vineyards yet. However, we have had several occasions for primary ascospore release this spring. Ascospore discharge is initiated in the spring if 0.10-inch or rain occurs at an average temperature of 50ºF or more. This results in thorough wetting of the bark where the cleistothecia have overwintered. When the cleistothecia are sufficiently wetted, infectious ascospores are discharged within four to eight hours and are carried by wind to susceptible plant tissues. They can infect any green surface on the developing vine and do not need water for infection. The fungus then grows on the plant surface and produces a second type of spore (conidia) which are windborne and cause secondary infections. Under optimal conditions, the disease can spread rapidly, as the time from infection to production of conidia can be as short as seven days. Although infections can occur at temperatures from 59 to 90ºF, temperatures between 68ºF and 77ºF are optimal for disease development. Temperatures above 95ºF inhibit spore germination, and the fungus may be killed at temperatures above 104ºF. Berry age has a marked effect on susceptibility to powdery mildew. Researchers in New York showed that when clusters of ‘Chardonnay’, ‘Riesling’, ‘Gewürtztraminer’, and ‘Pinot noir’ were inoculated from pre-bloom to six weeks post-bloom, only fruit inoculated within two weeks of bloom developed severe powdery mildew. Berries became substantially resistant to infection by three to four weeks after bloom, resulting in diffuse, non-sporulating colonies on berries, and were virtually immune at six to eight weeks after bloom. Therefore, early sprays (from immediate pre-bloom until three to four weeks after bloom) are critical for preventing powdery mildew on the clusters. This usually coincides with critical sprays for black rot. For wine grapes, control of diffuse infections is also important as these can predispose the grapes Botrytis bunch rot and sour rot later in the season. Sulfur remains an effective and inexpensive protectant fungicide for powdery mildew control in non-sulfur-sensitive grape varieties. The most effective systemic fungicides for powdery mildew control are the sterol inhibitors (Nova, Elite, Vintage, etc.) and the strobilurin fungicides (Pristine, Sovran, Abound and Flint). Luckily, we do not have any reports of fungicide resistance to strobilurins in the powdery mildew fungus in Michigan, but in some vineyards where sterol inhibitors have been heavily used for many years, they appear to be less effective than they used to be. New fungicide options that provide excellent control of powdery mildew are Quintec and Endura. Therefore it would be best to not entirely rely on SI’s during the most critical period for fruit infection (immediate pre-bloom until three weeks after bloom) but alternate or tank mix with other effective fungicides. Last year, we did notice that Ziram as a tank-mix partner did improve control of powdery mildew in a spray program. Downy mildew Downy mildew primary infections start if rains occur (at least 0.4 inches) and temperatures are above 50ºF over a 24-hour period. Check the recent weather conditions at or near your location on the Enviro-weather website (www.enviroweather.msu.edu/). It takes seven to 12 days for the lesions to form after infection has taken place, so keep an eye out for downy mildew. Early in the season, downy mildew lesions may be confused with low-concentration Gramoxone and possibly Chateau herbicide injury, which also cause yellow spots on leaves. However, if no herbicide was used and no herbicide spots are present on lower leaves, the spots may be downy mildew. To confirm that you can enclose a leaf with lesion in a ziplock bag with a moist paper towel and leave it out in the dark overnight. If white sporulation appears on the underside of the leaf, it is downy mildew. A spray for downy mildew before or just after bloom is recommended for susceptible varieties, especially in vineyards with a history of disease. Early infections can lead to severe downy mildew infection and premature defoliation of the vine. Ridomil Gold MZ and Ridomil Gold Copper have excellent curative and protectant activity against downy mildew. Under moderate infection pressure, they will provide three to four weeks of protection. Of the strobilurins, Pristine, Abound, and Sovran are good choices. Other effective fungicides are mancozeb, ziram, and fixed coppers. ProPhyt and Phostrol are also good alternatives: they provide excellent curative and about seven to 10 days of protective activity. Under high disease pressure or when spraying after an infection period, use higher rates. |
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Small fruit meeting |
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Regional reports Last week’s temperatures were warmer with highs in the 60s and 70s, and lows near 40°F. There were scattered frosts on Wednesday and Thursday mornings that caused little damage. Friday was windy and cloudy and offered a little rain. Rainfall totals varied from a trace to a third of an inch. This was a disease infection period for some areas, depending on where the rains fell. Soils are really drying out and shallow rooted berry crops will benefit from irrigation. The weekend was warm. Temperatures will be cooler for the next couple of days near 70°F, with a good chance of rain. We expect hot temperatures at the end of the week with highs in the upper 80s. Our GDD totals are still lagging ten days behind normal.
Tree fruit Insect activity increased last week. We are now in the treatment window for Oriental fruit moth. Few fresh plum curculio egg-laying scars were found. Leaf roller larvae are feeding on the leaves and are common in some orchards. Codling moth biofix was set as May 26 for most of the region. For a May 26 biofix, we are at 100 GDD50. We expect codling moth egg hatch at 250 GDD past biofix, which is around next Monday. Apricots are about one to 1.25 inches in diameter. Bacterial spot lesions have been found. Peaches are 16 to 19 mm in diameter. The peach crop looks lighter every week, although some blocks have a good crop. No Oriental fruit moth shoot strikes have been reported. Oriental fruit moth was biofixed at SWMREC on May 4 at 310 GDD45. Egg hatch should end at about 646 GDD45 after biofix (956 GDD45). Peach fruit needs to be protected from rusty spot (powdery mildew) until pit hardening. Growers can consider trunk sprays for lesser peach tree borer or greater peach tree borers after hand thinning is done. A post harvest spray for borers can be done instead. Pheromone disruption of these pests is also effective and eliminates the need to balance hand labor in the orchard with pesticide sprays and restricted entry periods. Sweet cherries are about 16 to 18 mm in diameter. Sweet cherries are always susceptible to brown rot. Brown rot requires warm, wet conditions, five to six hours of wetness at 70°F. We may see warm and wet conditions this week when it rains. The rain event Friday was cherry leaf spot in central Berrien and southern Van Berrien counties, depending on where it rained. Tart cherries are 12 to 14 mm and the pits are hard. The tart cherry crop looks pretty good. The crop is throughout the tree, with lots of doubles. Few fresh plum curculio egg laying and feeding scars were found. Friday’s rain was a moderate cherry leaf spot infection for some areas. Japanese plums are about 16 to 18 mm. European plums are about 14 to 16 mm. Growers still need to protect against black knot and plum curculio. Apple fruit size is generally in the 14 to 18 mm range. King fruit are generally 15 mm or larger. Apple scab symptoms are very common on unsprayed trees and have also been found in sprayed orchards. The new symptoms are probably from the May 14-16 infection period. Friday’s rain was a moderate scab infection in Central Berrien and Southern Van Berrien counties. We are near the end of primary scab season. Almost all the scab spores have been released. We need a good rain to bring the last of the spores out. Scab protection will be necessary at least through the next rain event. Last week’s cool weather kept bacterial populations low, so Friday’s rains were not fire blight infections. Some growers reported canker blight symptoms of systemic fire blight, wilting stems near overwintering cankers. Other growers also reported blossom blight symptoms Sunday. We do not expect to see blossom blight symptoms from the May 26 infection until Thursday. A few southern Berrien County orchards biofixed for codling moth on May 14 at 278 GDD50, more commonly other orchards in the region Biofixed May 23 at 284. We are at about 140 and 112 GDD50 after biofix for those two dates on Monday, June 2. Codling moth Biofix was set as May 26 for most of the region. For a May 26 biofix, we are at 100 GDD50. We expect codling moth egg hatch at 250 GDD past biofix, about next Monday. The application timing of control materials varies greatly (see the article on codling moth in last week’s Fruit CAT Alert). Spotted tentiform leafminer sap feeders are out and will form leaf mines soon. European red mites are moving about. San Jose scale adults are flying. Sprays for San Jose scale crawler should be targeted for 300 to 530 GDD50 after biofix (June 1). Due to the cooler weather this year, sprays for crawlers will be a week or two later than last year. We can now see initial fruit set. Side fruits are about 2mm smaller than the kings. Many growers applied thinning sprays, but fruit set is still heavy and the thinners do not appear to have been very effective in the cool weather. We have had several short, two day warm periods offering good apple thinning windows. Apparently growers have applied their thinners too early in the cool periods (50 to 60°F) before these window. The wet and windy weather forecast means that we will not have another good apple thinning windows until Thursday when conditions are good for spraying. Unfortunately, the temperatures will be very warm in the mid- to upper 80’s. We recommend a moderate thinning strategy using 1/2 to 2/3 rates due to the very warm temperatures, which favor over thinning. These high temperatures with high thinner doses will be very effective. Use aggressive rates only with large fruit size (over 18mm), with heavy set and lots of fruits in the cluster. Pear fruit are 12 to 14 mm in diameter. The crop is variable. Pear psylla adults and nymphs can be found in unsprayed trees. Leaf and fruit symptoms of pear scab have been reported. Growers should continue to protect against pear scab, through the next rain. Small fruit Blueberry bloom is ending. There is still bloom in most fields as well as green fruit. Many growers irrigated for Wednesday and Thursday mornings’ freeze when temperatures dropped below freezing in cold areas, especially where the soils were dry. There were losses in cold sites. Overall, it looks like we will have a very large blueberry crop. Growers with trickle irrigation should be irrigating. It is hard to catch up with trickle irrigation when you fall behind. Rainfall has been spotty and soils are dry. Blueberries can use 0.2 tenths of an inch of water a day or more in June and July when the sun is up from 6:00 AM until 9:00 PM. A full-grown plant needs four gallons or more of water a day during the fruit growth. For light sandy soils, frequent light irrigations of about an inch of water twice a week will wet the root zone and avoid leaching fertilizers and nutrients below the roots. Leaves are greening up with the warm weather. Trap catches of cranberry fruitworm and cherry fruitworm have been spotty. These pests lay their eggs in the calyx cup of the fruit and no eggs have been found yet, but growers have been applying Confirm and BT formulations. These applications are too early. Cranberry fruitworm biofix was expected at about 350 GDD50 with egg hatch following at 85 GDD50 after biofix. Only the warmest sites in the region have 485 GDD50. Growers should scout for eggs in the calyx cup of fruit. Sprays of bee-safe materials are planned when the weather warms up if there is still open bloom and bees are in the field. Post bloom fungicide sprays should target anthracnose. Grape growth increased dramatically with warmer temperatures. Freeze damaged vineyards still look pretty ragged. Concord and Niagara shoots vary a lot; primaries are 16 inches or longer, secondary shoots are about 12 inches, sprouting from the base of primaries live primaries. New shoots from the base of the canes are four to eight inches long. Many primary shoots have three clusters. Shoots in mechanically pruned vineyards are shorter and generally only have two clusters. Secondary and tertiary shoots have one or two flower clusters. There has been no growth from nodes killed in the April 30 freeze. Flower clusters on primary shoots are beginning to elongate and the flower clusters are separating. Wild grapes are beginning to bloom and Concords and Niagara will follow as soon as the weather warms later this week. Growers need to apply their prebloom fungicide sprays to control bloom infections. The conditions generally have been too cool for powdery mildew and, downy mildew. Friday’s rain was a black rot infection in many areas and also probably a good phomopsis infection too. Phomopsis lesions have been reported at the base of this year’s shoots. We are trapping grape berry moth, but controls can be delayed until the first post bloom spray. Strawberry bloom is ending. Primary fruit are an inch or more in diameter and starting to color. The secondaries have thimble-sized fruit. Pre harvest fungicides should be applied to reduce fruit rots such as gray mold. Early harvest may begin this weekend. Raspberry flower buds are separating in the cluster. Early varieties such as Prelude and Nova are starting to bloom. In Blackberries bloom has begun in early varieties such as Washita. Primocanes in fall bearing raspberries are 12 to 18 inches tall. Cranberry shoots are elongating and flower buds are visible. Active growth before bloom is time for a protectant fungicide spray to protect new foliar and reduce fruit rots. Miscellaneous The next Monday Fruit Update meeting will be Monday, June 9 at the Fruit Acres Farm in Berrien County. There is a Blueberry IPM meeting this Wednesday, June 11 at Cornerstone Ag. 1240 57th Street, north of Phoenix Road, west of Grand Junction. A series of twilight grape scouting IPM meeting will start in two weeks. The dates and locations are: June 19 at Tim Seppala's farm, southeast of Lawton, July 24 at Bob Dongvillo's farm, south of Scottdale; and August 28 at Lemon Creek Vineyards, west of Berrien Springs. These meetings start at 6:00 PM. For more information, on these meetings call Mark Longstroth at (269) 675-8313. |
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2 -- Southeast Another round of frost/freeze occurred in southeast Michigan last Wednesday morning, May 28. It appears that this event roughly affected fruit growers to the north and west of Flint. There was also a localized frost/freeze event on the morning of Sunday, May 25, this event primarily affected strawberry growers, and again was a very localized frost. Low temperatures on May 28 at the Enviro-weather stations were mostly recorded in the 25°F to 27°F range for the Lapeer and Bath weather stations. Temperatures at most of the stations to the south and east were mostly in the range of 32 to 34° F. While these low temperatures affected strawberries, they did not impact tree fruits nearly as much. This second frost/freeze event affected apples, pears, peaches, blueberries and possibly did some fruit scarring on sweet and tart cherries, as well as plums. Fruit that were affected were mostly in the fruit set to 5 mm to 10 mm in size. The affected fruit has taken on an off-color of the skin, and the flesh is of light grey to brown color. I predict that a good amount of this fruit will drop to the ground in the next two weeks or so. Again this second frost/freeze event was very site specific, and even varied a great deal within orchards. Dry soils are the other continuing concern at many fruit farms across the region. A few fruit growers received 0.75-inch of rain from slow moving thundershowers over the weekend, mostly Friday night and early Saturday morning. However most of the region received less than .10-inch of rain. Rainfall totals varied greatly, and depended on where the thundershowers moved over your farm in terms of total precipitation from the event. Farms a half mile away might have received no rain and to 0.75-inch. Fruit growers are generally irrigating newly planted tree and small fruits on a regular basis to help them become established. We did have some hot temperatures Monday, June 2, but with that exception our season still remains about three to five days behind normal in terms of degree day totals, and a few days behind normal when I look at pest development as well as the phonology of our fruit crops.
Tree fruits Apples are mostly at 12 mm to 15 mm in size, with Red Delicious appearing to be very typie this season. We have had a significant amount of new growth this year, with many apples having an average of 10 to 12 inches of new growth.. A lot of thinning has taken place over the last week, with many growers applying two thinners in the southern part of the region, and mostly one application in the north. This is one of the most difficult thinning seasons that I have seen for apple growers. This is primarily due to the fact that we have had a wide range of a cold damage within most blocks of apples, and have experienced a long bloom period. For the most part, I have been advising growers to take a moderate approach to thinning, with the exception of a few varieties like Jonathon, Jonagold and Golden Delicious, where we have a heavy crop load in most blocks. Now is the time to keep an eye on whether or not fruit that you desire to remove from chemical thinning slowing its growth rate, or stopped growth entirely. Most growers in the mid- and northern part of the region will have one more window of opportunity for thinning. Codling moth emergence is now widespread across the region and most growers biofixed on May 26 or 27. Oriental fruit moth adult flight is down significantly across the region. Mullein bug is still being seen, however the numbers are much lower and it is now most likely a predator. Plum curculio is still active, and I have seen some recent oviposition scars in apples. San Jose scale crawlers have not been seen yet, however the adult females are ready to release them. Oyster shell scale crawlers continue to be seen. There are a good number of aphids feeding in all tree fruits this week, including a few rosey apple aphid, wooly apple aphid, apple grain aphid and green apple aphid. White apple leafhopper nymphs are seen fairly commonly, as are many of the leafrollers, most notably obliquebanded leafroller and green fruitworm. European red mite adults are being seen in slightly higher numbers, as are two-spotted spider mites feeding in weeds and seedlings under apples and peaches. Apple rust mites were seen in apples for the first time of the season. There continues to be a good number of predators being seen throughout many blocks of apples. Apple scab spore discharge has continued even with the light rain events at both of our trapping stations. So, while the number of spores being caught is decreasing, until I get a couple of rains without any spore discharge, I am not ready to call an end to our primary apple scab season. Apple scab lesions were just starting to be seen late last week and early this week on both the top and bottom of leaves. Most of the lesions appear to be burned out. There are a few possible fireblight strikes that I am seeing around, however it is a bit early to determine for certain if they are fireblight, so I am keeping an eye on them. According to the Enviroweather models, we have not had any fireblight infections this season. Powdery mildew was seen for the first time last week infecting terminals of apples. Pears are mostly at 15 mm, again with some crop loss with farms to the west and north of Flint. There has been a fair amount of drop in pears over the last week. Pear psylla continue to be seen in all stages, most farms have controlled the adults fairly well. Peaches are at 12 mm to 14 mm in size, and some fruit continues to drop. We are not at pit hardening. There is a fair amount of variability in terms of crop load on peaches across the region. Bacterial spot seems to be affecting the leaves on peaches at a few farms. Some oozing is coming from trunks. Sweet cherries are not at pit hardening yet, and are mostly at 15 mm to 18 mm in size where fruits are generally light due to frost and freeze damage earlier in the spring. Some bacterial spot continues to be seen on sweet cherry’s leaves. Tart cherries are mostly at 11 mm to 13 mm in size. There is some off coloration of fruit at farms that had a second freeze event. Plums are mostly at 12 mm to 15 mm in size for Stanley and related strains. Plum curculio feeding continues to be seen in many blocks of plums. Small fruits Strawberries are mostly ending bloom to thimble size fruit in the south and about 80 percent to 90 percent bloom in the north. I anticipate some harvest to begin at farms in the south over this coming weekend, with most of those farms starting to be open a week from now. Farms to the north appear to be 10 to 14 days away from the beginning of harvest. Low numbers of two-spotted spider mites being seen in strawberries. Raspberries are at first bloom at many farms across the region, and about 12 to 15 inches of new growth on fall bearing raspberries. There appears to be some blocks that have two-spotted spider mites, however those are limited to a few farms. A few raspberry plants are starting to show signs of anthracnose disease. Blueberries are at fruit set for the most part with some farms that had frost and freeze damage showing a 40 percent to 60 percent crop loss. |
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3 -- Grand Rapids Area Degree day accumulations at the Sparta weather station continue to be right at or slightly below average now. It continues to be dry. A half to three-quarters-inch of much needed rain fell on May 30, but we could use more. Tree fruit Most apples are in the 10 mm stage, but there is still some bloom out there on one-year-old wood of some varieties. We are currently in a significant thinning window, but growers are apprehensive from the effects of the cold weather mid-last week. The last apple scab infection for the greater Grand Rapids area was still back on May 14. Some rain fell on May 30, but was short by a couple of hours for an infection to occur. There were some light showers moving through the area this Tuesday, June 3, but it’s drying off now and it might not result in an infection. Lesions from earlier infections are being reported. A light number of spores were caught with the May 30 rain, so primary scab is still a concern for at least one more good rain event. For any susceptible varieties with open bloom on them, MaryBlyt is calling for several days of possible blossom blight infections over the next week. Growers will also want to be ready for the possibility of trauma blight if any of the rain events predicted for the next several days have hail or high winds included. A few egg laying scars from plum curculio continue to be found in non-sprayed apples, but there are no reports of damage to commercial blocks. Growers will want to continue to scout closely for any damage in small apple fruits. Apples are subject to plum curculio damage until they are about 20 or 25 mm. European red mite eggs should all be hatched. No new eggs have been seen yet, but could be reported at any time. Monitor mites closely to determine if early controls are needed. Codling moth flight has been reported in high pressure blocks for about two weeks now. The warmer weather over the holiday weekend has caused a push of codling moth flight in other blocks as well. A regional biofix has been set for the Grand Rapids area for May 24. We’ve collected 110 degree days base 50 since that biofix, so the timing is right for those early egg-timed materials to go on. Obliquebanded leafroller are mostly all pupated, and flight for the summer generation could begin at any time. Oriental fruit moth is flying, with numbers still sporadic in some locations. A regional biofix has been set on May 8. We have accumulated 275 degree days base 45 since that biofix, so egg hatch is probably well underway. Now is the time to apply control materials in stone fruits for early larvae if you haven’t already. Flagging of new growing shoots could be seen at any time in stone fruits. Small fruit Because of the low temperatures that prevailed during the last weeks, blueberries in the Central Region, north of Van Buren County, are in different bloom stages. There are blueberry fields in which we find blossoms still in full bloom, while in the same bush there are fruit clusters in the early green fruit stage. Despite the freezing temperatures observed on May 28, little damage has been observed in most blueberry fields. If the weather conditions remain above the freezing temperatures, we may have another large blueberry crop similar or bigger than the last year’s blueberry crop. In 2007, Michigan produced 93 million pounds of blueberries, the largest crop so far. Lack of rain has been an issue that may affect some fields, however during the past week there were some rains mainly in Ottawa County where the amount of rain reported was 0.82 inches. In Allegan County, only a small (0.25 inches or less) amount of rain was reported during the same period. So far, the growing degree-day accumulation in South Allegan is about 462, and around Fennville, the accumulation is of 331 degree-days. In Ottawa County, degree-days accumulated since March 1 are 355, approximately. The blueberry harvest has continued in North Carolina, Georgia and Florida as well as in Mississippi and California. However, most blueberries in the market are from Florida, Georgia and California. During the past five days blueberry prices in terminal markets of Chicago and Detroit fluctuated from $3.00 (flat 12 4.4 oz cups w/lids) to $4.50 (12 6 oz cups w/lids) per pound. |
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| 4 -- West Central Mira Danilovich Weather and crop development Before the frost event of Tuesday and Wednesday night (May 28 and May 29) this region had good crop set and potential for a very nice crop. Wednesday morning revealed a picture that was not so bright. We expected to see some damage from the frost, but not to the extent that we are finding. Hour-by-hour temperatures indicate the loss of cloud cover around midnight on May 27 in Mason County, then a couple of hours later in Manistee County. Oceana County had the cloud protection the longest, but not long enough to prevent frost/freeze damage. The first night on May 28 was the worst of the two. The sub-freezing temperatures stayed over the area for a very long time. Though our official temperature readings registered by the Enviro-weather stations were showing from 25.9°F to 27.5°F, growers were reporting temperatures as low as 19° F and 18°F. There was a slight wind (less than 2 mph) during that period, but it was coming from the wrong direction, east, northeast, east-northeast and south-southeast depriving us of the air warming benefit of the lake. Where we had the cloud cover, wind machines were useful in bringing the warmer air from the higher elevation down into the canopy. Once the clouds were gone, any warm air that was there dissipated into the clear sky and radiation freeze did the rest. Radiation freeze had done most of the damage in Mason and Manistee counties. Crops did not fare well. By my assessment and the grower accounts, apples, sweet cherries and plums have sustained the biggest losses. Overall, perceived damage is about 50 to 60 percent, though in certain spots that damage is almost 100 percent. Tart cherry loss is about 60 percent. Pears are looking better than expected, though they too sustained significant crop reduction. Apples have been hit hard, particularly in the northern parts of the district and the lake-shore throughout the district. A few grape growers in the area are reporting significant damage up to 100 percent. Peaches are holding surprisingly well for now. Plums are just about a total loss. Overnight temperatures report –hourly average temperatures for May 28
The second frosty night of May 29 had slightly higher but still sub-freezing temperatures, but the damage had been done a night before. In the next week or so, after careful damage assessment, growers will be making decisions whether or not there is economic justification for continuing with the full insect and disease protection programs. In many cases, they might choose to put one more fungicide sprays to get them through the apple scab primary and then go to a bare minimum in order to preserve the foliage and work on next-years crop. West Central Michigan GDD totals from March 1 as of Sunday, June 1
The rain that started early Friday morning and for the most of the district, ended Saturday morning, May 31 was an infectious rain for Mason and Manistee Counties with moderate rating. Oceana County did not get an infection out of this wetting event. The apple scab ascospore maturity guide is showing that 99 percent of the spores are mature. Roto rods picked up 75 spores per rod during the rain from the beginning of the rain until noon when the rods were replaced. The rain that came afterwards was responsible for release of additional five spores per rod. The indication is that we are near the end of the primary. It is quite possible that the next rain may exhaust the spore supply. With all this rain forecasted for the rest of the week, the expectation is that we will be out of primary by early next week. This same wetting event of May 30-31 is responsible for the low (Manistee) and moderate (Ludington) cherry leaf spot infections. We did not have fireblight infections during the bloom period. This freeze event reset the Maryblyt model to zero. Our EIP numbers have been well below the threshold for the most of the season. The old fireblight cankers are becoming soft and with predicted rain, will start to ooze any day now. It appears that starting towards the end of the week and all next week, we will have high temperatures facilitating disease development. Bacterial leaf spot, bacterial canker and European brown rot are present in some stone fruit blocks. There is increased potential for brown rot development in all the stone fruit blocks affected by the recent frost/freeze injury. Damaged fruit that does not drop will present brown rot hazard. Insect activity is picking up. Scouts are reporting increased activity in lesser peachtree borers. American plum borers are still very active. Trap catches have gone up significantly for both species since last week. Codling moth catches have exploded. The average trap catch has reached two-digit numbers. Biofix dates are being established on block-by-block basis for the growers that have scouting service or are monitoring codling moth emergence themselves. Our regional biofix was set for May 24. Codling moth: GDD accumulation post biofix as of June 1.
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| 5 -- Northwest Nikki Rothwell Duke Elsner Erin Lizotte Rob Sirrine Growing Degree Day Accumulations at NWMHRS
Growing stages at NWMHRS June 2 at 4:00PM GDD50 271 Growth Stages at NWMHRS June 2 at 4:00 PM
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| Weather news Jeff Andresen Summer is on the way... Last week, I mentioned the gradual change of the upper air configuration across North America to a western trough, eastern ridge pattern. As of the morning of Tuesday, June 3, that transition is under way with the development of southwesterly flow aloft and very summer-like weather conditions expected across the Great Lakes region during the next couple of days. A stationary frontal boundary stretching from the central Great Plains eastward through the Ohio Valley to the Mid-Atlantic region Tuesday will begin to move northward as a warm front Wednesday, bringing a very warm and humid air mass into Michigan for Thursday and Friday. The front will also bring a good chance for showers and thunderstorms across central and southern sections of the state Tuesday evening into Wednesday, and across northern sections of the state Wednesday night and Thursday. The front will temporarily move back south and eastward across the state late Friday and Saturday as a cool front, bringing more showers and thunderstorms. Fair and drier weather is expected Sunday, but more rainfall is possible next Tuesday as the front returns northward as a warm front once again. Rainfall totals during the next five days are expected to be highly variable, ranging from 0.25 inch in some locations to more than one inch in others. Some one to two inch totals are possible, especially across far northern sections of the state. Temperatures during the next few days will warm to above normal levels with highs Wednesday in the mid-60s to mid-70s increasing to the upper 70s to upper 80s on Thursday and Friday and lows from the mid-40s to mid-50s Wednesday morning increasing to the mid-50s to mid- or upper 60s Thursday and Friday mornings. Some 90EF high temperatures are possible in southern sections both Thursday and Friday. Humidity levels behind the warm front will also increase with dew point temperatures Thursday and Friday reaching the 60s to near 70EF in some spots, leading to uncomfortable conditions especially during afternoon and early evening hours. The medium‑range forecast guidance calls generally for the upper air pattern mentioned above with a broad upper air ridge expected across central and eastern sections of the United States. The National Weather Service 6‑10 day outlook covering June 8 through 12 calls for mean temperatures to range from near normal levels across northern sections of the state and for above normal levels across the south. Precipitation totals are forecast to range from near normal levels across extreme southeastern sections of the state to above normal levels elsewhere. The 8‑14 day outlook for June 10 through June 16 is similar, calling for near normal temperatures across northern and central sections of the state and above normal levels across the south. Precipitation totals are forecast to range from near normal levels in eastern sections of the state to above normal levels in the west. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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