| Time to have your obliquebanded leafroller traps up | The beginning of the month of June marks the time that growers should have their pheromone baited traps for the obliquebanded leafroller (OBLR) placed in their orchards to monitor the activity of this pest insect. The OBLR is capable of inflicting considerable damage to the external surface of developing fruit. Failure to control OBLR can result in badly scarred fruit not suitable for the fresh market. Seasonal activity of male obliquebanded leafroller can be monitored using 1 pheromone-baited trap for every 10 acres of orchard. There are two periods of adult activity. In Michigan, the first adult flight typically begins in early June and lasts about six weeks. A second flight takes place from early August to mid-September. Moth capture in pheromone traps is not a good indicator of leafroller abundance or potential damage, but is essential for tracking biological development with the OBLR degree day model for proper timing of control measures. To get information on OBLR abundance, a scout must look for leafroller larvae or at least signs of their presence. Larvae are green with brown to black head capsules and are about 25 mm long when fully grown. Often, a scout will detect signs of leafroller activity rather than the actual larva. The name leafroller comes from the larva’s habit of rolling leaves to form a shelter. These feeding sites are most often found at the tips of growing shoots. Larvae will also use silk webbing to attach two leaves or a leaf and fruit together to form a shelter. The presence of webbing is a good clue that leafrollers are around. Unfortunately, one of the best signs of leafroller activity is the feeding damage they inflict on the fruit. Damage occurs at three periods during the growing season. Larvae of the overwintering generation will feed on young fruit in May and June. Fruit that do not abort will be deeply scarred and deformed. Young, summer generation larvae will feed on fruit before moving to growing shoots. Several shallow feeding sites within a small area characterize a leafroller-damaged fruit. Late in the summer, young larvae will feed on the fruit prior to seeking overwintering sites. The pinhole-size feeding sites are difficult to detect at harvest, but become noticeable as the fruit ripens in storage. Growers usually apply a pre-bloom or petal-fall insecticide if leafrollers damaged the crop the previous season. Obliquebanded leafroller larvae are more easily detected in the summer. At this time, insecticides are only applied if larvae are found or if visual signs of their presence are detected. Degree day models can aid in timing insecticide sprays by predicting key events in the leafroller’s life, such as the start of egg hatch. Using these models relies on the establishment of a biofix and daily temperature records. Biofix is the date when the scout records the first sustained catch of moths in pheromone traps, the first date at which moths are captured in traps, provided that moths are trapped on two successive trapping dates. The model is set to zero, and degree days are accumulated from this date forward based on daily temperatures. The obliquebanded leafroller model calculates degree days based on a minimum developmental threshold of 42°F. We will provide an article updating summer leafroller management control materials as timing for treatment approaches. You can also reference the June 8, 2004 CAT Alert article Summer Leafroller Management available on-line at: http://www.ipm.msu.edu/CAT04_frt/F06-08-04.htm |
Obliquebanded leafroller
GDD42 (Post biofix) |
Event |
Action |
Tight cluster |
Majority of larvae have emerged from shelters |
Examine fruit buds for larval activity |
0 DD° = biofix (~900 DD° after Jan 1) |
1st sustained moth captures |
Set DD° = 0 |
220-250 DD° |
Peak moth flight - overwintering generation |
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400-450 DD° |
Start of egg hatch |
Timing for treatment |
1000 DD° |
End of egg hatch |
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2300 DD° |
Peak moth flight - 2nd generation |
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2750 DD° |
Start of 2nd generation egg hatch |
Timing for treatment |
| Control of borer insect pests in tree fruit | Dogwood borer in apple The dogwood borer is a problem in some apple orchards in Michigan, mostly those that are four to nine years of age. Initially the dogwood borer larvae feed inside burr knots (adventitious roots), which can develop on the exposed aboveground portion of clonal rootstocks. Feeding in the burr knot does little damage to the tree but feeding can continue below the bark where it is much more destructive and may eventually girdle the tree. Burr knots are aggregations of partially developed root initials that usually occur in clusters at or below the graft union. Reddish frass on the surface of a burr knot is a visible sign of infestation. Burr knots are fibrous and permit entry of some insecticides such that larvae are readily exposed to a lethal dose while still within the plant tissue. The larvae can be controlled with trunk applications of Lorsban 4E at a rate of 1.5 quarts per 100 gallons of water. This must be applied directly to the trunk from a distance of no more than 4 ft using low volume handgun or shielded spray equipment. Do not allow spray to contact foliage or fruit. A single spray timed for the peak egg hatch in late June to mid-July will provide good control. Work in New York (Agnello & Kain) has shown that prebloom and post harvest application will provide decent control as well. Another strategy for managing dogwood borer (Ron Perry and Larry Gut of MSU) is to use sand or soil and mound it up around the tree union infested by the borers. When larvae escape as adults, they can’t get back in later to lay eggs later this year. The sand should be checked and removed from the union area if there is evidence that scion rooting is underway. Peach tree borers in stone fruitThe greater peach tree borer can be a serious problem on cherries and peaches because it attacks and feeds on the root system. No evidence of frass or feeding is seen unless the soil is dug around the base of the tree (Photo). Trees infested with greater peach tree borer show wilting and loss of vigor. Unlike the lesser peach tree borer, the greater peach tree borer does attack young, healthy trees. While cherry trees can survive many lesser peach tree borers infesting the scaffold limbs, a single peach tree borer can cause serious injury to the root and affect the vigor of the tree. Multiple infestations of peach tree borer in the root can kill the tree. Applying Lorsban 4E or Lorsban 75WG in late June for lesser peach tree borer, taking special care to spray the lower scaffolds, crotch and base of the trunk, will also control greater peach tree borer. Lorsban 75WG is less economical but has a much less objectionable odor than Lorsban 4E, an emulsifiable concentrate formulation. Lorsban 4E will cause foliar and fruit injury on sweet cherry. Summer peach tree borer sprays should be applied with a handgun sprayer and applied to the trunk and lower scaffold limbs. Do not apply materials to foliage or fruit. Do not apply more than one application of Lorsban per year in peaches and nectarines. Lorsban is not registered for borer control on prunes or plums. |
Reduced risk insecticides are being tested for ability to control tart cherry insect pests in a statewide on-farm trial. A total of nine sites were established for this study and are located in the three key tart cherry regions of Michigan. Five sites were located in the northwest region (1 in Antrim County, 1 in Benzie County, and 3 in Leelanau County), two in west central (1 each in Mason County and Oceana County) and two in southwest (both in Van Buren County)
Two 10-acre blocks have been established on each site. One block received reduced risk insect control strategies (RAMP block). Control decisions in the RAMP block are based on insect monitoring and scouting. A second 10-acre block was used to compare reduced risk control strategies with each grower’s standard pest control strategies (COMP block).
| Table 1. Insecticides used in reduced risk insect management program | |||||
Insecticide |
Active ingredient |
Label rate |
Target insect |
Spray timing |
REI |
SpinTorTM 2SC |
spinosad |
4 - 8 |
Green fruitworm |
Late bud burst/open cluster |
4 h |
Avaunt®** |
indoxacarb |
5 - 6 |
Plum curculio |
Shuck split, |
12 h |
ActaraTM 25 WG |
thiamethoxam |
4.5 - 5.5 |
Cherry fruit fly; plum curculio |
12 mm fruit |
12 h |
Provado® 1.6 Flowable |
imidacloprid |
4.0 – 8.0 |
Cherry fruit fly |
20 – 22 mm fruit |
12 h |
** Not currently registered for use in cherries. Experimental Use Permit obtained through EPA.
In 2004, spray programs varied widely depending on differing pest pressure observed in each block. The number of insecticides applied to RAMP blocks ranged from three with one half cover to five.
| Orchard scouting Weekly scouting was conducted on 10 trees in both the RAMP and the COMP blocks during the 2004 field season. On each of the ten trees, leaf and fruit damage was assessed and the canopy was inspected for insects and mites. In addition to the 10-tree sample, plum curculio and cherry fruit fly (CFF) were monitored with traps. Pyramid and screen traps baited with plum essence were deployed in late March to early April to monitor for plum curculio. Four of each trap type were deployed on the border of RAMP and COMP blocks. Traps were monitored weekly through fall. Only a few plum curculio were captured in monitoring traps and did not help in making control decisions. Better lures are necessary to make these traps effective for commercial blocks. Cherry fruit fly were monitored using Pherecon AM yellow sticky traps. Ammonium carnbonate and ammonium acetate baits were compared. Traps were deployed in late May to early June. Two of each trap type were placed in a border row and one of each type was placed in the center. Yellow sticky traps baited with ammonia carbonate caught CFF earlier and in higher numbers compared to yellow sticky traps baited with ammonia acetate. Traps deployed on the border tended to perform better but there are some sites where traps deployed in the interior of the orchard performed better. Therefore, we recommend that traps are deployed both in the border and interior of the orchard. In these trials, two border traps and one interior trap performed gave us a good indication of when CFF began to fly and when populations began to increase. Damage samplingPlum curculio, green fruitworm and leafrollers. Two extensive samples were conducted to determine plum curculio, green fruitworm and leafroller damage. The first damage sample was conducted within seven days after shuck split and the second was conducted approximately one week before harvest. For the early damage sample, 600 (100 in lower canopy and 50 in higher canopy in each directional quadrant) were examined on every other border tree and 25 randomly selected interior trees. The extensive border sample was conducted so that we could determine where plum curculio hot spots are located and return to these sites for the harvest sample. In general, insect damage was low and we saw no statistical difference between RAMP and COMP blocks. In the case of plum curculio, there were numerically more oviposition scars in RAMP blocks compared to COMP blocks in five out of nine sites. However, in four out of five of these sites, damage was below 0.1 percent and there was no statistical difference between RAMP and COMP blocks in all five of these sites. Harvest damage samples were conducted within one week before harvest. For these samples, we selected 20 border trees (including trees with damage at shuck split) and five interior trees. At least 100 fruit were jarred from trees and fruit were examined for insect injury. Only one fruit was found with a plum curculio sting in all of the blocks. This fruit was from a RAMP block in west central and did not have a larva inside the fruit. Cherry fruit fly. Fruit were also sampled to determine if cherry fruit fly (CFF) larvae were present in the fruit at harvest. Since CFF oviposition cannot be visually detected on the fruit, 600 fruit were collected from both the RAMP and COMP block twice before and twice after harvest. These fruit were placed in containers and pupae were allowed to drop out of the fruit. No pupae dropped out of fruit that were collected before harvest. One site in the southwest had larvae in the fruit after harvest with 3.75 percent infested fruit in the RAMP block and 1 percent infested fruit in the COMP block. |
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| Cranberry fruitworms laying eggs in blueberry | Catches of cranberry fruitworm moths have increased in our monitoring traps with the warm weather. We now have found our first cranberry fruitworm eggs in scouting this week in commercial blueberry farms in Van Buren County. One of these eggs had already hatched, and some early fruitworm feeding was found on berries. This feeding could be from early cranberry fruitworm infestation, but it could also be from cherry fruitworm, which have been laying eggs for at east one week in some farms in southwest Michigan. The take-home message is that growers who have fields with a history of fruitworm infestation and damage should be scouting fields over the coming weeks and selecting appropriate insecticides to protect from fruitworm infestation. For more information on fruitworm insecticide selection, please refer to the May 31, 2005, issue of the Fruit CAT Alert. |
| Blueberry insect control meeting scheduled for June 15 | Michigan blueberry growers are faced with the challenge of protecting their fruit from multiple insect pests to meet the quality standards demanded by the public and the food industry. At the same time, the threat of losing some of the organophosphate and carbamate insecticides creates a potentially uncertain future for maintaining insect pest control. New insecticides are being registered for use by blueberry growers, but the strategies for using these compounds can be different than when using broad-spectrum insecticides. A four-year MSU research project at commercial blueberry farms aims to identify the opportunities and challenges of transition to these new insecticides. This research project is comparing the effectiveness of IPM programs that integrate selective insecticides with that of standard grower practices. Results from the first two years of this project will be highlighted at two meetings at grower-cooperator farms on June 15. The meetings are open to anyone interested in blueberry insect management. Updates on new pesticide registrations, fruitworm management with new insecticides, potential natural enemies for control of blueberry pests, update on blueberry maggot and Japanese beetle management. Discussions and tours of the research sites will be led by MSU Extension team members Rufus Isaacs, Carlos Garcia Salazar, John Wise, Mark Longstroth and Keith Mason. Restricted Use Pesticide Applicator credits have been applied for, and refreshments will be provided at both meetings. Contact Rufus Isaacs at (517) 355-6619 or isaacsr@msu.edu for more information. Morning meeting A morning meeting from 10:00 AM to noon will be hosted by Larry Bodtke of Cornerstone Ag Enterprises. His farm is on the left side of 57th Street, a quarter mile north of CR 388 (Phoenix Road). 57th Street crosses Phoenix Road a few miles west of Grand Junction. Afternoon meeting This meeting will run from 2:00 to 4:00 PM and will be hosted by Al Ochoa of A&L Blueberries at his farm on the left side of 144th Ave about 1 mile north of M-45 in Grand Haven. |
| Orange rust – a colorful nemesis of brambles | Symptoms and biology The main rust disease that affects blackberries, dewberries and black raspberries is orange rust. Red raspberries are immune to the disease. Characteristic symptoms are bright orange, powdery blisters on the undersides of leaves (Photo). Before the blisters burst open, they look waxy or shiny, as if covered with lacquer. Young shoots are often spindly and clustered, new leaves are misshapen and pale green to yellowish. On black raspberries, the rusted leaves start to wither and drop in late spring to early summer. New leaves produced towards the tips of canes may appear normal, giving the impression that the plant has “grown out” of the disease. However, such canes will remain infected and will produce a mass of spindly shoots with no blossoms the following spring. The plant becomes systemically infected and remains so for the rest of its life. Orange rust is not known to kill plants, but it can significantly reduce vegetative growth and yield. The disease can be caused by either of two closely related fungi, Arthuriomyces peckianus and Gymnoconia nitens. The orange aeciospores are spread by wind and can infect leaves of healthy plants with long periods of leaf wetness provided by rain or dew. Orange rust if favored by relatively low temperatures (50-70°F). The fungi overwinter and survive in the crown and roots of infected plants, leading to the production of new infected canes every year. Cultural control While there were no chemical control options for this disease up to recently, we now have several excellent fungicide options. This does not mean that we should abandon cultural practices, such as establishing new plantings from disease-free nursery stock, which will also help in avoiding virus diseases. If any plants show signs of the disease during the spring in which they were set out, this means they were already infected at the time of planting. Upon inspection of plants each spring, any infected plants, which are economically worthless, should be dug up and destroyed promptly before rust pustules mature and spores are liberated. The location of those plants should be clearly marked, and any new suckers arising from root pieces left in the ground should be removed and sprayed with an approved systemic herbicide. It is also prudent to remove infected wild brambles in nearby wooded areas and fencerows. Management practices that improve air circulation, such as thinning out canes within the row, pruning out floricanes immediately after harvest, and effective weed control, aid in disease control by reducing leaf wetness duration. Some blackberry cultivars (e.g., Eldorado, Raven, and Ebony King) are reported to show resistance to orange rust, but no black raspberry cultivars are known to be resistant. Fungicide options The best fungicide options are Nova (myclobutanil), Pristine (pyraclostrobin + boscalid) and Cabrio (pyraclostrobin). While Abound (azoxystrobin) is labeled for use on brambles, it does not have orange rust (or any other rust for that matter) on the label. Nova may have a bit better curative activity than the others because of its greater systemicity, which would make it the material of choice during or after a rainy period with inoculum already being present. Each of the above-mentioned fungicides will also control various other cane, leaf and fruit diseases. Since Pristine has two active ingredients, it has the broadest spectrum of activity. None of these fungicides will cure an already infected plant. However, they can prevent healthy plants from becoming infected. Since infected plants will continue to be sources of inoculum over their lifetime, it is best to remove and destroy them altogether and replace them with healthy plant material from a reputable nursery. Apply fungicides upon first discovery of the blisters, preferably before they burst open and release the spores. If the field has a history of the disease, sprays may be initiated before blisters appear. Since infections can also originate from wild brambles near the field, one should keep an eye on these as well if possible. |
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| Slimy things in the vineyard | Reports of slimy things always make me think of the blob-from-outer-space scare in Dallas, Texas in 1973, when an innocent slime mold of nearly a meter across appeared on someone’s lawn and convinced locals that an alien invasion was underway. Luckily the following report will not create such an upheaval, and besides, Michiganders do not seem particularly prone to hysteria. However, it is nice to know what the various slimy things reported from grapevines are, lest growers think they are harmful in some way. The first report we had this spring was of yellowish “sap” on a grapevine trunk in late April (Photo 1). The grower feared that this was somehow related to crowngall that was also present in the vineyard. However, crowngall would not result in yellow exudate, so I concluded that it was a slime mold growing on the bark of the grapevine trunk. Slime molds are not actually molds but are microbes that in some ways behave like fungi and feed on dead organic matter. Their growth is favored by moisture and moderate temperatures. In the early stages, they grow in expanding (usually yellow) slimy colonies that spread over wood mulch, leaves or other dead plant material. Some types of slime molds common on wood chip mulch can grow to about 1 foot across and may appear like someone got rather sick after a night of drinking beer and eating cheese pizza. Later on, the colony dries up and turns brown and powdery: these are the spores. Slime molds are harmless, although they have been known to affect the marketability of strawberries when they grow over the fruit surface. The second case involved orange slimy blobs on grapevine pruning stubs (Photo 2). The blobs were identified as a Fusarium fungus. While some species of Fusarium are plant pathogens, this one appears to be a harmless saprophyte growing on the pruning wounds. You may ask why the fungus is growing there. The two main requirements for fungal growth are water and nutrients. Late pruning and moderate temperatures can cause profuse bleeding of the wounds, thus providing a continuous source of moisture and sugars for fungal growth. Interestingly, the fungal colonies on the pruning wounds themselves contained some fly maggots as well as non-pathogenic nematodes, both of which appeared to be feasting on the fungus spores. Yum! Is it necessary to spray for these slimy creatures? No. They are not harmful and live on dead plant material for the most part. They do not infect or damage the vine. In fact, they may even be beneficial. The Fusarium fungus may actually protect pruning wounds from infection by wood pathogens, such as Eutypa lata. |
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Regional reports 1 – Southwest |
Weather
Last week was hot with highs in upper 70s and 80s with a high Sunday (June 5) in the low 90s. Low temperatures were in the 60s. A cold front moved through the region on Sunday dropping temperatures 20 degrees. Scattered thunderstorms accompanied this front. Precipitation from this storm varied from over an inch to less than a third of an inch. Hail fell in some areas of Northern Berrien and Western Van Buren counties. Cover crops were wilting but topsoils now have been recharged. This moisture will last less than a week under these hot, windy conditions. Soil temperatures are about 75. This week’s forecast is for continued hot weather with highs in the 80s. There is a chance of thunderstorms this week with a better chance during and after the weekend.
Tree fruit Apricot fruit have bacterial spot symptoms appearing. Peach fruit are almost an inch in diameter. June drop continues and pit hardening has not begun. Rose chafers are out and often attack young peach fruit. Oriental fruit moths are laying eggs. Biofix for the first flight was April 15 in southern and central Berrien County at 175 GDD45. We are now at 764 GDD, almost 600 GDD past biofix. For the rest of the region, Oriental fruit moth biofix was May 6 at 320 GDD45 and we are about 450 GDD past biofix. The expected end of Oriental fruit moth egg hatch is at 650 GDD after biofix. Tarnished plant bug feeding scars have been found on young fruit. Plum curculio should be attacking peaches with the warm weather. In sweet cherries, early varieties are coloring. Birds are sampling the ripening fruit. Tart cherry fruit is yellowing. Leaf symptoms of bacterial canker were found in both tart and sweet cherries. Fruit symptoms were found on sweet cherry fruit. This warm weather will stop that disease. Cherry leaf spot symptoms were found in sweet and tart cherries. Sunday’s rain was a cherry leaf spot infection period. Growers protect against plum curculio. Apple fruit are differentiating into several size classes. This warm weather will hopefully cause many of the smaller fruit to fall and increase the June drop. Blossom blight symptoms of fire blight appeared this weekend. The storm Sunday was a trauma infection period for fire blight, especially where there was hail. Green apple aphids are out and can spread the infection to healthy trees. No new apple leaf scab symptoms were found. Symptoms from the May 22 infection should visible. If scab lesions are found in the orchard, growers should continue to apply protectant materials to suppress fruit scab. Growers need to protect the fruit from plum curculio. European red mites are scarce. Redbanded leafroller trap catches are zero indicating the end of the first generation. Oriental fruit moth trap catches are declining and the first generation should end soon. Spotted tentiform leafminer sap feeders and mines can be found in some orchards. No obliquebanded leafroller adults have been caught. Growers and scouts should get their traps out this week. Codling moth trap catches are high. We biofixed for codling moth on May 20 at 334 GDD50. We are now at 522 GDD, almost 200 GDD past biofix. Traditional control materials are applied at about 250 GDD after biofix. The warm temperatures forecast for this week mean that we will be picking up 20 GDD50 for much of the week and controls should be applied before the end of the week. Small fruitBlueberries are larger than peas on early varieties. Cherry fruitworm and cranberry fruitworm egg hatch has begun and feeding damage has been reported, so insecticides should be applied for these pests. Plum curculio egg laying scars are also reported in some fields. Tussock moth larvae are out. Blueberry aphids are becoming more numerous. Fungicide applications should focus on anthracnose fruit rot. Grapes are blooming. Rose chafers and rose chafer feeding damage were found Monday (June 6). Grape berry moth adults are being trapped, but egg laying has not begun, so insecticide sprays are not needed now. Thursday’s rain was a black rot infection. Phomopsis, black rot and downy mildew symptoms can be found. Growers should be protecting the flower clusters from diseases with bloom sprays or post bloom sprays before our next rain. There are upcoming blueberry meetings see the article in this weeks Fruit CAT Alert. Strawberry harvest has begun in Berrien County and will start soon in Van Buren and Allegan counties. Most summer raspberry varieties are blooming. Later varieties have not begun to bloom. Blackberries are blooming. Orange rust is abundant on wild raspberries and has been reported in blackberries. Cranberries are in the jewel stage, just before the flower buds open. Cranberry shoots are 3 to 4 inches long. Pre-bloom sprays to reduce fruit rots should be applied before the flowers open. Meetings The next Monday Update meeting will be Monday June 13, at the Overhiser Fruit Stand in Allegan County at 5:00 PM. There will be one MDA restricted use pesticide recertification credit available at this meeting. |
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| 3 – Grand Rapids Area | GDD accumulated in West Central Michigan
Weather According to 30-year averages from the Sparta weather station, degree day totals are running about two to three days ahead of average for both GDD42 and GDD50. There was some rain that moved through the Grand Rapids area over the weekend, but actual rainfall totals were quite variable – some areas had no rain, while other locations had over two inches. Hail was reported in very light amounts at only a couple of isolated blocks around Grand Rapids. Tree fruit Regarding fire blight, risk for blossom blight infections is still there in newly planted trees that are just coming into bloom and they should be covered as long as bloom is present. No blossom blight symptoms have been reported, but they should start to show up at any time. The weather this week could be favorable for some severe weather including hail and high winds – watch the weather closely. Several events are coming together at once this week that could make the risk for trauma blight very high – cankers are oozing and blossom blight will be showing up at any time. When you add in the high temperatures and some trauma from hail or high winds, fire blight could become a problem in a hurry. All of the primary apple scab spores should be mature at this time, but rainfall amounts where equipment is located was very light over the weekend and only a very light number of spores were found. Spore numbers have been declining with the last rain events, but they are still present, so growers need to continue to protect leaves and fruits for the next rain event at least. There are some scab lesions showing up from the infection periods back in late April and mid-May but only in isolated blocks. Plum curculio egg-laying scars were found in apples over the weekend, but numbers are light and sporadic. They should be active with the warmer weather. Codling moth trap numbers have been steady over the last week and are still quite high in some high pressure areas. A regional biofix was set on May 19 – we have accumulated 228 GDD50 from this regional biofix. Some growers and consultants have very different biofix dates than this regional date – it’s important to scout individual blocks and set local biofix dates whenever possible. Small fruitBlueberries are in petal fall. After several weeks in the low 70s, we are finally seeing temperatures above the 80s and with these a rapid development of plant health and insect problems. One single issue that remains as a major concern for growers and pest consultants is the outbreak of diseases in most fields across the blueberry growing area. In late May, we reported an abnormal growth and development during the bloom period for some varieties, especially in Jersey. Plants in affected fields showed a normal bud break and beginning of the bloom period. However, at some point in time, buds and blossoms stopped their development and shoots in which they developed started to show symptoms of dieback (Photo). These symptoms were more evident in older canes that in younger shoots. This condition also was prevalent in older fields with a history of winter damage. Two weeks ago, with the beginning of high temperatures, entire fields began showing similar symptoms accompanied by wilt and dieback of shoots that at the beginning of the season looked normal. However, in the past week we observed the collapse of plants affecting entire fields. A preliminary investigation indicated that the damage is caused by a combination of factors including Phomopsis twig blight and canker. So far, this condition affects approximately 200 acres of blueberries in Ottawa County. The most affected variety is Bluecrop. One thing in common shared by affected fields is that in the past (two years ago) they were severely affected by winter damage and drought. Presently, we are evaluating the magnitude of the problem and investigating long-term solutions to ameliorate this situation. In the meantime, there are few options available to control this problem. One immediate action is to protect the new growth from further infection. Therefore, it is necessary to continue with fungicide treatments according to the program outlined in the 2005 Michigan Fruit Management Guide. In addition, collapsed canes and dead plants should be pruned and infected wood removed from the field and burned to prevent further infections. Fields with history of Phomopsis and fruit rots should be closely monitored for symptoms of wilt and poor growth and initiate preventive measures as soon as the first symptoms of Phomopsis appear. Don’t wait until the symptoms appear in the entire field. The accompanying pictures show the progress of the disease |
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| 4 – West Central | Weather For the first time this season we had several days of summer-like temperatures with highs in mid- to high 80s. The radar images were showing that the hot air mass from the south was dominant over the Great Lakes region creating suitable circumstances for some severe weather development. When the cold weather front reached our region the two weather fronts collided creating a lot of atmospheric turbulences resulting in tornados and severe storms with heavy rains and hail all around our area. We were in a “void,” though it would have been really beneficial to have some precipitation. The only rain we received was Sunday morning (June 5) in a form of a very brief and not very intense shower. The rainfall amounts were barely measurable. The weather stations recorded 0.05 inches in Manistee, 0.01 inches in Ludington and 0.04 inches in Hart. Our drought spell continues, and the trees are showing signs of stress. GDD totals Since March 1 as of Sunday, June 5
Tree fruit A brief shower Sunday morning did not produce enough moisture to impact the spore discharge of apple scab. Though we are very near the end of the primary that could not be confirmed at this time. We are finding a few scab leaf lesions from the previous infections. Maryblight is indicating that the canker blight symptoms should start appearing shortly. So far, there has been only one report of blossom light symptoms coming from the southern part of the district. Powdery mildew is quite readily found in apple blocks throughout the district. Regional biofix for codling moth was May 27 with 265 GDD50. Based on a regional biofix, we are still in the window for use of Calypso or Assail for first generation control. Application of OP’s should be targeted for about 515-520 GDD50. We are finding a small number of green apple and rosy apple aphids as well as the various leaf roller larvae. European red mites are starting to be more numerous. Sweet cherries are growing rapidly. Fruit is from 13-15 mm in diameter. Pit is starting to harden off. Tart cherries are 13-14 mm in diameter with pit starting to harden off. Peaches are gaining in size measuring 15-16 mm in diameter. Bacterial leaf spot is found quite readily in cherry, apricot, plum and peach blocks. Cherry leaf spot symptoms are present in a very few blocks. Scouts are reporting finding plum curculio scars on the fruit. Blocks need to be covered. |
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| 5 – Northwest | GDD accumulations at NWMHRS GDD42 807 GDD50 422 Weather The past week has been warm and dry at the NWMHRS. GDD42 at the NWMHRS a week ago were 32 GDD ahead of the past 15-year average, and they are now 100 GDDs ahead of average. Soil moisture is getting unusually dry for this early in the season due to low precipitation in the region this growing season. Temperatures have been very good for applying apple thinners. Isolated apple scab symptoms have been reported in Benzie and Leelanau counties. Fire blight still remains a concern in susceptible varieties for the remainder of the week as long as tag bloom lingers in trees. Codling moth catches are on the rise this week, and Oriental fruit moth has also made a big jump with an average of 60 moths per trap. Obliquebanded leaf roller larvae are in high numbers in abandoned apple orchards. Spotted tentiform leafminers catches are still on the decline. Small amounts of cherry leaf spot were found in isolated areas in Leelanau County. Plum curculio oviposition scars have been detected in multiple stone fruit orchards, and we are seeing green fruitworm leaf and fruit feeding. We are still capturing American plum borers. Lesser peachtree borers have been captured for the first time, and we averaged 25 borers per trap. Sweet cherry fruit set in northwest Michigan is generally heavy. Tart cherry fruit set varies considerably. Trees that bloomed during the warm weather on May 8 and 9 generally set good crops, whereas orchards in cooler areas that crept into bloom during the cold period from May 11 to 17 have not fared so well. |
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| Weather news | Last weekend, the jet stream pattern across North America flip-flopped from the recent western ridging/eastern troughing pattern to western troughing/eastern ridging. This change allowed warm and humid air from the Gulf of Mexico back into the Great Lakes region after an extended absence, culminating in a round of turbulent weather across the state on Sunday (June 5) when severe thunderstorms spawned several tornadoes, high winds and widespread power outages. A stationary frontal boundary marking the edge of warm, tropical air to the south and cooler, drier air to the north was ran west to east across the central Lower Peninsula Tuesday morning (June 7). This front will very slowly wander north- and southward across the state during the next several days, setting the stage for an almost daily chance for shower and thunderstorms well into the weekend. Best chances for rainfall during the next couple of days will be in northern sections of the state, where some scattered 0.5-1.0 inch totals are possible. A weather disturbance currently over the central Great Plains will move towards Michigan by Friday, bringing a better chance of rainfall to central and southern sections of the state by late in the week. Overall, while rainfall probabilities will likely be limited to 30 or 40 percent probability on any given day, the extended number of days with possible rainfall should result in significant precipitation to most of the state by the beginning of next week. Temperatures will vary from north to south across the state during the next several days with daytime highs ranging from the upper 60s in northern lakeshore areas to the low 90s in some southern locations. Low temperatures will range from the 50s far north to the 60s in the south. In the medium range time frame, forecast guidance is having trouble identifying a dominant jet stream pattern, resulting in discontinuous and variable outlook of lower than normal confidence. The 6-10 day outlook (for June 12-16) calls for above-normal temperatures and for precipitation to range from near normal over the Lower and eastern Upper Peninsulas to above normal in the western U.P. During the 8-14 day time frame (covering June 14-20), the outlook calls for below normal temperatures and for precipitation to range from below normal levels in southern sections of the state to near normal in the north. Again, given major differences among the individual tools used to create the outlooks, forecaster confidence is considered lower than normal. My personal guess is that warmer than normal temperatures will continue over most sections of the state during the majority of both forecast periods. |