|
Vol. 19, No. 3, June 15, 2004 In this
Issue |
|
Bracing for a possible cherry leaf spot epidemic
|
We've been receiving samples and hearing reports of cherry leaf spot infections in tart cherry blocks throughout the state of Michigan. Leaf spot is a cause for major concern at this time with harvest still several weeks away in much of Michigan. The occurrence of symptoms right now indicates that leaf spot will be exceedingly difficult to control this year. The initial symptoms of cherry leaf spot are small (1 to 3 mm) red-to-purple leaf spots on the upper leaf surface (Looking at leaves with back-lighting is helpful.). These spots will then turn brown (Photo 1). In heavy infections, spots can overlap producing larger areas of dead leaf tissue. Leaves accumulating lesions will soon begin to turn yellow. On the underside of these leaves, whitish spore masses are usually visible on each lesion (Photo 2). These spore masses are a sign of the pathogen and represent inoculum for new infections. It does take a few days after leaf spot is visible for spore masses to become evident. We've recently received samples showing leaf spot symptoms with no sporulation. After incubation in the laboratory, viable spores were produced from these lesions. Leaf spot symptoms are also showing up on pedicels of fruit (Photo 3); we currently do not have data to know if these lesions affect fruit size or quality. Leaf spot is usually effectively controlled early in the season. In years with extended drier weather, such as in 2003, leaf spot symptoms were not initially seen in most orchards until August-September. We recommend scouting the tops of trees for yellow leaves because infections are usually initiated there due to spray coverage problems. However, in this season, symptoms are not necessarily limited to the tops of trees and may be observed throughout the foliage. The occurrence of leaf spot infection on bract leaves (Photo 4) is also evidence of early season infections. Record rainfall combined with several extended wetting periods this season has fostered the rapid proliferation of leaf spot. What is the best action plan to attempt to manage leaf spot in orchards with visible leaf spot infections? We recommend the use of a sterol-inhibitor (SI) fungicide (i.e., Elite, Indar, Nova, or Rubigan) at the maximum label rate combined with Captan used at the maximum (4 lbs. / acre) rate for your next cover spray. The SI fungicides have some back action in controlling new infections and will greatly reduce sporulation from existing infections. Captan is a protectant that is also used for fungicide resistance management concerns. Because of the extremely high disease pressure conditions, it is critical to use the maximum label rates of fungicides and also to cover entire orchard blocks; i.e., do not use an alternate middle row spray plan. Dodine could be substituted for Captan as the tank mix since dodine is a better leaf spot fungicide than Captan. However, we do not know the current status of dodine resistance in the cherry leaf spot fungus population, therefore, dodine should be used with caution. If dodine has been used with success in your orchards and used sparingly, this fungicide could be used as a mixing partner with an SI. We recommend using two consecutive applications of the SI/Captan or SI/dodine cover spray keeping the interval to seven days, using the maximum label rates, and covering entire orchard blocks. These sprays should be followed up with a strobilurin at the full label rate that would be effective for prevention of new infections. The interval should be kept to seven days unless we experience significantly drier weather that would allow stretching the interval to no more than 10 days. Again, with the high pressure we are experiencing, cover entire orchard blocks. Leaves currently exhibiting a number of lesions are almost sure to defoliate. The amount of leaves remaining on trees is a critical factor for fruit ripening. A rule of thumb is that trees need at least two healthy (non-yellow) leaves per fruit to properly mature the fruit. If the ratio is less than two leaves per fruit, maturity may be delayed and trees with ratios of less than one leaf per fruit may not produce mature fruit. The goal of this management plan is to limit the infection of currently healthy leaves by eradicating new infections and protecting against subsequent infections. The cherry leaf spot spore load will probably be high in most orchards for the remainder of the season. These blocks must be intensively managed for the next several months. |
Pre-harvest fungicides for blueberries |
As harvest is fast approaching, take note of the pre-harvest interval (PHI) for the various fungicides. Most fungicides you would use at this time of the year have a 0-day PHI, but Topsin M has a 7-day PHI. Also note that while Ziram 76 DF (Cerexagri) had 14-day PHI under a Section 24C in the past, we are still waiting for the renewal of this 24C. Pending the approval of this request, both Ziram 76 DF and Ziram Granuflo cannot be sprayed later than three weeks after bloom. Also, the maximum rate per acre per application is 3 lb under the old label. The main diseases of concern at this time of the year are fruit rots, such as anthracnose (orange wet spore blobs) and Alternaria fruit rot (green velvety layer of spores). Botrytis fruit rot (gray mold) is usually not a problem in Michigan, but can occur, especially in a year as wet as this. Anthracnose is often a problem in cultivars such as Bluecrop, Jersey, and Rubel, while Alternaria fruit rot is more common in Bluecrop. The cultivar Elliott is moderately resistant to anthracnose. While fruit rot is usually not visible until the berries ripen, it is prudent to assume you will have a fruit rot problem if you had problems last year. This year's rainfall also would have increased disease pressure, particularly of anthracnose fruit rot, as well as reduced the efficacy of fungicides due to wash-off and suboptimal spray timing. If the first blueberries are starting to show rot, fungicide sprays can limit the spread of the spores from the rotten berries to neighboring healthy berries. Often, these berries look healthy at harvest, but start to rot soon after in the lugs while awaiting processing. Rot may be slowed down by refrigerated storage, but will resume on the supermarket shelves, lowering fruit quality. Applications within several weeks of the first harvest can still be beneficial in preventing these late infections. In fact, an application between the first and second harvest may be recommended as well under high disease pressure. Examples of fungicides that can be used during
the pre-harvest period are discussed in the following text. A spray
at first blue fruit is recommended. The strobilurins (Abound, Cabrio,
Pristine) are all highly effective against anthracnose with Pristine
having the most broad-spectrum activity since it contains two different
active ingredients. However, it probably is also the most expensive
of the three. Pristine will also have excellent activity against
Phomopsis, while Cabrio has good and Abound fair activity against
this disease. All have moderate to good activity against Alternaria
fruit rot and become quickly rainfast since they are locally systemic.
Switch (cyprodinil and fludioxonil) also has some systemic properties
and provides simultaneous control of anthracnose, Alternaria, and
Botrytis fruit rots. Thus, it may be a good choice if several fruit
rots are a concern, e.g., in 'Bluecrop.' Captevate (captan and fenhexamid)
at the high rate will provide good control of anthracnose as well
as Botrytis fruit rot, but this disease tends to be less common
in Michigan. Aliette (fosetyl-Al) is a highly systemic fungicide
that provides good control of anthracnose, Alternaria fruit rot,
and Phomopsis. Of course Topsin + Captan can still be used, provided
the 7-day PHI of Topsin is taken into consideration. While Topsin
is very active against Phomopsis, Captan will do most of the work
against anthracnose. Therefore, if anthracnose is the disease you
wish to control, a Captan or Captec spray alone may suffice. Just
remember that Captan is a protectant that can be washed off in heavy
rain. This means that under rainy conditions, it will have to be
applied more frequently than the other fungicides (e.g, every 7
days), while the strobilurins and Switch are rainfast and have at
least 10 to 14 days of forward activity. |
Pre-harvest gray mold control in strawberries |
Gray mold, caused by the fungus Botrytis cinerea, is one of the most important fruit rot diseases affecting strawberries. Cool, wet weather is conducive to development of this disease. Typical symptoms include a brown discoloration of the fruit and the presence of a gray fuzzy mold, which can rapidly develop and spread to neighboring healthy berries. Even if berries look perfectly healthy at harvest, they can start to show mold symptoms within several days. Botrytis cinerea sporulates on old leaves and plant debris. The spores are airborne and can travel long distances by wind. Remember that in strawberries, primary infections take place almost exclusively through the flowers. This is why gray mold control in strawberries is focused on the bloom period. If the bloom period was dry or good fungicide coverage was maintained during bloom, incidence of gray mold at harvest is expected to be low. However, if Botrytis is starting to show up before or at harvest, the emphasis has to be on preventing new infections of ripening berries, which become more susceptible the riper they are. So where possible, remove sporulating berries from the field and destroy them to limit inoculum availability. During picking, also avoid handling infected berries, since spores can be transferred on hands to healthy berries. Timely harvesting and rapid post-harvest cooling may also help to reduce losses to Botrytis gray mold. There are several excellent fungicide choices out there for control of gray mold close to harvest. Elevate (fenhexamid) is a protectant fungicide that becomes rainfast quickly. Captevate is a pre-mix of captan and fenhexamid and has a broader spectrum of activity than Elevate alone (i.e., it also protects the fruit against anthracnose and other fruit rots), especially at the higher rate. Switch (cyprodinil and fludioxonil) and Pristine (pyraclostrobin and boscalid) are also excellent products for gray mold control. Topsin M + Captan also is a good fungicide combination against gray mold, but remember that captan can be washed off by rain or irrigation water. Thiram (thiram) similarly is effective but not rainfast. Cabrio (pyraclostrobin) and Quadris (azoxystrobin) are NOT suitable for gray mold control, but are effective against anthracnose and other fruit rot and leaf spot diseases. All fungicides mentioned above have a 0-day pre-harvest interval, except Topsin M (1 day) and Thiram (3 days). |
Strawberry insect and slug control update |
This season there are a few new insect control products registered for strawberry, and the recent wet weather is cause for concern when thinking about slugs and sap beetles. This article will update growers on these issues. Slugs do well in damp, cool weather, and we have had plenty of that this year. As fruit ripens, slugs can damage the fruit making them unmarketable. In the past few years, the Small Fruit Entomology Program has compared the standard Deadline Bullets slug bait product with a new one called Sluggo that contains iron phosphate as the active ingredient. One of the potential benefits of Sluggo is that the bait is light brown in color making it less visible to pickers, and it is expected to have fewer side effects because of the different active ingredient. It is also biodegradable and safe to humans, animals, and natural enemies. We compared the two products at a farm in Sutton's Bay, Michigan during 2002 in a replicated field trial. Deadline Bullets at 25 lb per acre provided excellent control of slugs over the month-long period between application and harvest, and reduced damage to harvested fruit by 95 perent, compared to the untreated areas. Sluggo at 40 pounds per acre did not significantly reduce slug populations, but it did provide protection of berries from slug damage (79 percent control), that was not significantly different from Deadline Bullets. It seems that the Sluggo has a less rapid toxic effect, but it does stop the slugs from feeding, which eventually leads to their death. Insecticide registrations have been received in the past few years for a few new products for use in strawberry. SpinTor 2SC is a new insecticide class (naturalyte) with activity on moth larvae. This product will provide control of strawberry leafroller, and applications need to be applied when larvae are beginning to develop. Provado 1.6F received registration last year, and this insecticide (neonicotinoid class) is highly effective against sucking insects, particularly aphids, spittlebugs, and whiteflies. Control of leafhoppers may also be possible on leaves that receive treatment, but new foliage that grows out after the spray will be untreated and a new influx of leafhoppers could become established on new growth. This product should be banded onto the strawberry plants to get the maximum effect from your investment. We are currently testing activity of Provado on potato leafhoppers in a Michigan planting. While Provado is labeled for use on foliage, a soil-applied formulation of this insecticide called Admire 2F provides strawberry growers with a much-needed option for grub control, with potential benefits to the foliage too. Admire is labeled for use against white grubs in the soil and against aphids and whiteflies. To control white grubs, this product needs to be applied to a field just in advance of the start of egglaying of the target pest and then irrigated in. As the eggs hatch in the soil and young larvae (grubs) emerge, they will be killed by the insecticide as they start to feed on the roots. Because this product is systemic, treated plants will draw the insecticide into the leaves, thus protecting them from feeding by aphids and whiteflies. Trials are underway to evaluate Admire 2F against pests in Michigan strawberries. Sap beetles continue to be a problem for some growers. While there are no new options for control of this pest, it is important to remember that field sanitation is the foundation of sap beetle control. Try to get unpicked berries out of the field wherever possible. With the wet weather we have had this year, this will be even more important as fruit may be more likely to rot in the field. There are still some insecticides registered for control of this pest, but once the beetles get established in fruit, it is difficult to get control because they are protected inside or under the berries. Finally, we are still searching for a strawberry field with white grub problems to conduct some experiments this year after harvest. If anyone has a site where we could use a corner for a spray trial, please contact me at (517) 355-6619. |
Bush berry growers now have Admire registered for white grub control |
The soil-applied insecticide Admire 2F (Bayer CropScience) is now registered for use in blueberry and other bushberry crops for control of white grubs. This product has had three years of emergency registrations for use in blueberries against Japanese beetle under Section 18 labels in Michigan. This full registration provides growers with a new tool for managing white grubs in the soil and can provide assistance with protection against some foliage feeding insects. Of particular interest to Michigan growers, this product has shown excellent efficacy against Japanese beetle grubs in field trials conducted by MSU in the past three years, and has been highly effective against aphids in research conducted by Rutgers scientists. A new type of insecticide option Admire for Japanese beetle grub
control Admire for reducing Japanese beetle
feeding In experiments during 2003, application of Admire under blueberry bushes led to a 45 percent reduction in Japanese beetle injury to blueberry leaves compared to untreated bushes. In contrast, when applications were done only in the row middle, there was no protection of foliage on nearby bushes. So, to get the benefit of foliage protection against beetle feeding, application under the bushes is required, but this will not place the insecticide in the correct place for targeting grubs in grassy row middles. Admire recommendations and restrictions Another formulation of this insecticide for application to the foliage of bushberries has recently been approved. For a recent article on the use of Provado see the June 1, 2004 issue of the Fruit CAT Alert. |
Diverging patterns of fruitworm activity in blueberries |
In most years the cranberry fruitworm (CBFW) and cherry fruitworm (CFW) have similar enough biology that they can be managed together. They both are Lepidopteran pests, they both have one generation per year; they both first emerge as moths in the spring and lay eggs on blueberry fruit; and the larvae of both species feed inside fruit. That is why in blueberries we typically refer to them as the fruitworm complex. In some years, however, the climatic conditions are such that the patterns of their life cycles diverge and they need to be managed separately to maintain adequate control. This year is an example of that phenomenon. CFW moths not only emerged several weeks earlier than CBFW moths, but in many locations CFW egg laying and egg hatch occurred long before the CBFW. What does that mean for management of these pests? Even though the primary period for control is over, there are several things to yet consider. First, even though they both infest blueberry fruit, the CFW generally spends its complete larval period within one fruit. Therefore, once it is inside the fruit there is very little opportunity for control. This is not the case for CBFW. As the CBFW larva grows, it moves from the initially infested fruit to another and another, tying the cluster together into a messy mass of webbing, berries, and frass. Therefore, even if you could not prevent the initial infestation, every time the larva exits a berry there is additional chance for control. This opportunity diminishes as the cluster is further webbed, so persistent effort at control is important. It is this fully-webbed cluster that brings the greatest threat of a "load rejection" at the processing plant, or unhappiness by U-pick customers. Fruitworm infestation is of particular concern for early-ripening cultivars where infestation is likely to be present at harvest, whereas in late harvest varieties infested berries may drop off the bush before harvest. Special note: When considering insecticide options for fruitworm control, note that Guthion 50WP has a label restriction of only two applications allowed per season. The most effective alternatives to Guthion for fruitworm control include Imidan, Sevin, and Asana. |
Blueberry Extension event |
We will be having a blueberry extension event at the Trevor Nichols Research Complex on Wednesday, June 30 from 2:00 PM to 5:00 PM. The field day will focus on the importance of spray coverage for different pesticides and pests in blueberries with a sprayer demonstration activity. The event will be hosted by West Central MSUE small fruit agent Carlos Garcia-Salazar, John Wise, Rufus Isaacs, Gary Van Ee and Mark Longstroth. See our Web page for directions: http://www.maes.msu.edu/tnrc/ |
Regional reports |
1 - Southwest |
Weather
Tree fruit In apricots, bacterial spot symptoms are appearing on leaves and fruit. Peach growers still are thinning fruit. Disease symptoms found last week include rusty spot or powdery mildew of peach, fruit symptoms of peach leaf curl, X-disease, and bacterial spot. Bacterial spot is causing leaf drop in susceptible varieties. Oriental fruit moth biofix was April 29 at 300 GDD45. We are now at 1065 GDD, 965 GDD45 since Biofix. Second generation Oriental fruit moth should be emerging at 950 GDD45. Trap catches in some areas have already started to rise. Plum curculio and damage can be found on peach fruit. Mowing of cover crops and adjacent hay fields can move tarnished plant bug into fruit trees where they will feed on the fruit. We are now catching both peach tree borers. Sweet cherry fruit are coloring and fruit cracking is a problem. Birds are eating the red fruit. Growers need to protect against brown rot, cherry leaf spot, and plum curculio. Cherry fruit flies have not been trapped. Tart cherry fruit are coloring. Yellow leaves are appearing in tart cherry orchards. Carefully check the leaves for the symptoms to determine the cause of leaf drop. Cherry leaf spot symptoms are showing up in Van Buren County, but are less common in Berrien County. Some yellow leaves are due to sour cherry yellows virus; others are due to bacterial canker. Growers need to protect against cherry leaf spot and plum curculio. Plums are an inch. Growers should maintain plum curculio sprays. Fresh plum curculio damage was found on plum fruit on Monday (June 14). We are now catching both peach tree borers and growers may want to apply trunk sprays. White apple and potato leafhopper have been reported in the region and growers should protect young trees. Apples are over an inch in diameter. Apple scab is defoliating unsprayed orchards. Flyspeck and sooty blotch sprays are not yet needed. We usually start treatment for these diseases after we had accumulated 200 to 250 hours of leaf wetness after the end of scab season. Fire blight symptoms are easier to find. Dieback is now easily visible from the road. New shoot blight symptoms are appearing that may be due to insect spread of the bacteria. In young orchards, prune out strikes as soon as they are seen. Be sure to cut a foot or more below all visible symptoms. See the articles in the Fruit CAT Alerts May 18 and May 25, 2004. Some growers are applying copper. We biofixed codling moth on May 7 at 235 GDD50, our current total is 765 GDD, 535 GDD after biofix. We had an increase in trap catch last week so growers should continue their spray program to protect against the egg hatch this week, which should be strong. Most growers are applying their second spray for codling moth control. There are leafroller larvae feeding on the shoot tips. We are catching obliquebanded leafroller across the region. Biofix for Southern Berrien County was May 27, for Northern Berrien and Van Buren about May 30 or June 4 when temperatures were warm. See the article on summer apple pests in the May 25, 2004 Fruit CAT Alert. Neonicotinoids have not been thoroughly tested against obliquebanded leafroller so growers will not want to depend on them for control. European red mite and aphid numbers are building. White apple leafhoppers are out and potato leafhopper damage has been found. Growers should protect young trees. In pears, late first generation codling moth can attack pears at this time. Small fruit In grapes, Concord bloom has ended and shatter of the clusters has begun. The crop
got a lot lighter last week. Berry
numbers are low. Rose
chafers are out. Grape
berry moth trap catches are up sharply with the warm weather
last week. Expect a heavy egg hatch this week. Grape
berry moth larvae are feeding in the clusters. Black rot and Phomopsis symptoms are easy to
find in some grape vineyards. Downy
mildew and anthracnose
were found in Marquis table grapes. Growers should be applying their
post bloom sprays. The very wet conditions we have had will favor
downy mildew. Downy mildew symptoms are common in Niagara suckers.
Systemic fungicides that control downy mildew such as Ridomil, Prophyt,
and Abound will work better than a protectant such as Ziram in very
rainy weather.
Strawberries harvest continues. Fruit rots are a problem due to the wet, poor harvest conditions. Raspberries harvest has begun with the harvest of the early variety Perlude. Leafrollers are common in both summer and fall raspberries. Cranberries are blooming. Miscellaneous |
||||||||||||||||||||||||||||||||||||||||||||||||
2 - Southeast |
Weather
Tree fruit The only
new pest to report this week are wooly apple aphids, which are being
seen at a few farms. Wooly apple aphid was particularly troublesome
the year before last at many fruit farms. This year we are finding
it at isolated farms. It is most often a spotted problem when these
insects congregate around old pruning scars and on suckers or spurs
on the insides of trees. Green apple aphid and rosy apple aphid
populations are slowly building. While both Oriental fruit moth
and codling moth trap catches remain low, they are beginning to
rise around the district. This will be the second generation for
both. I continue to see Oriental fruit moth flagging in terminals
of apples, as well as some peaches. Plum curculio are still being
found at several farms. Last week we found some fresh stings from
plum curculio. These fresh stings most often occurred on apples
stung previously this spring. It is interesting to see plum curculio
hang around so long this year. Spotted tentiform leafminer mines
are mostly empty at this time. There was a fair amount of predation
that was done to first generation leaf feeders this year. Potato
leafhopper continues to be seen, however numbers seem to be fairly
stable in tree fruits. This is not the case for strawberries. White
apple leafhopper levels are low. Tarnished plant bug are still visible,
however their numbers have not increased over the last three weeks.
Mullein bug injury has now been reported at several other farms
mostly on Red Delicious. While mullein bug is a fruit-stinging pest
early in the season, it is a later season predator feeding on European
red mites and green apple aphids. So once you see damage, it's generally
too late to target controls. Check the June
8, 2004 issue for a nice article on mullein bug. Dogwood borer
adults continue to be caught in traps. Apple maggot traps are being
set around the region. European red mites continue to be seen, however
the numbers are fairly low. Apple rust mites also continue to be
seen with low numbers as well. Many apple predators are being found
in increasing numbers. These include lacewing adults and eggs, ladybird
beetles, Stethorus punctum, Amblyseius fallacis, minute pirate bugs,
and assassin beetles. Apple scab
sheet scab symptoms are starting to show up at a few farms. I can
find apple scab lesions from primary apple scab at just about all
farms across the region. Leaf drop from apple scab is starting to
be seen in unsprayed blocks. Fireblight strikes are starting to
show up in a few more apple blocks, however the level is very low
this year. Nectria twig blight infected twigs continue to show up
at several farms across the region. Pear growers need to continue to watch for pear psylla damage as well as codling
moth. No fireblight strikes have been seen on pears. Peaches continue to size nicely around the region with most being around 1.25
inches to 1.5 inches in size. Many peach growers are having to do
an extensive job of thinning this year. Peach harvest should be
ahead of last year's schedule. Bacterial spot symptoms are showing
up on foliage at several farms across the region. Oriental fruit
moth infected shoot tips continue to be seen. Symptoms from peach
leaf curl continue to show up. Twospotted spider mites continue
to be seen in a few peach blocks, however their numbers are fairly
low. Green peach aphid numbers continue to build at a few farms. Sweet cherries continue to size and turn straw-colored and
even beginning to turn red. I expect to see sweet cherry harvest
begin in a few weeks. Birds have been feeding on some of the early
maturing fruit. Bacterial canker infected fruit and leaves are common
across the region. There has been a fair amount of drop in sweet
cherries over the last three weeks or so, mostly due to bacterial
canker. Tart cherry fruit are mostly around 14 mm in size and are turning straw-colored with
a few beginning to show some red color. Cherry leaf spot symptoms
continue to be seen, particularly in tart cherries. Small fruit Fall red raspberries are now about 18 inches in length. Leafroller
damage continues to be seen, as do raspberry cane borers. Summer red raspberries have small fruit on them, and I continue to
see Phytophthora-infected root rot plants wilt down. Blueberries continue to size very well with a good crop coming along this year. I have seen Phomopsis twig blight in the last week at several farms. |
||||||||||||||||||||
3 - Grand Rapids Area |
GDD accumulated beginning January 1 in West Central Michigan. Totals are about 5 to 6 days ahead of the 30-year averages.
Tree fruit It appears that apple scab was controlled very well in many orchards this year. There are some problem blocks with scab in them, but considering all the rainy days in May and how difficult it was to keep an adequate fungicide cover on, I fully expected to see more primary scab than we are. Regarding codling moth, we're 422 GDD50 past my regional biofix of May 11. When we near 500 GDD50 past the biofix, we should be at peak egg hatch. Cover sprays will continue to be very important over the next week or so. Moth trap numbers have declined over the past few weeks, but I would expect we might hear reports of a slight increase in trap numbers from the warm temperatures late last week. Obliquebanded leafroller started flying last week. I'm setting a regional biofix for June 4. We have accumulated 276 GDD42 from the biofix and are probably about 5 to 7 days away from our target for early timed sprays or 400 to 450 GDD42 after the biofix. Hearing some additional reports of damage to small apples from Campylomma. or mullein bug - more than last week and especially in Red Delicious. Dogwood borer started flying in this area and trunk sprays should be applied sometime in early to mid July to target small larvae as they hatch. Lesser and greater peach tree borers started flying over the last two weeks and trunk sprays should be applied to stone fruits in the next 10 to 14 days. American plum borer adults are also flying. Small fruit Another problem that has been brought forth by the warm weather is the presence of Phomopsis twig and canker blight. We are seeing an increased number of fields with collapsed plants due to Phomopsis. And again, that is happening mostly in fields weakened by winter damage and drought conditions. In some of the most affected fields, we established several observation plots where we recommended a especial fungicide treatment against Phomopsis. The treatment was a combination of several applications of Topsin M + Captan after bloom followed 14 to 21 days later by an application of Cabrio or Pristin. The last application was repeated 14 days later. This treatment was compared with the standard fungicide program base on Indar and Topsin M + Captan that most growers follow. Preliminary observations indicate there was a substantial decrease in the incidence of Phomopsis under the recommended program. Regarding insect problems, the cherry fruitworm flight is almost finished in most fields. Moth captures decreased from one to eight per trap during the past week to zero during the present week. No new eggs were found in all sampled fields. However, most old eggs found in the Fennville area were parasitized. In addition, we observed fruit damage and a high number of first and second instar cherry fruitworm larvae in blueberry fields across Allegan and Ottawa counties. On the other hand, the highest peak of cranberry fruitworm adult emergence occurred the past week around Fennville and the captures remained high during the present week (up to 60 moths per trap in a three-day trapping interval). The number of eggs also remained high: 10 to 12 eggs per 50 fruit clusters. In Ottawa County, the populations of cranberry fruitworm remained low (one to two per trap per sampling interval) and one to two eggs per 50 fruit clusters. During the present week, we are observing a large number of first instar cranberry fruitworm larvae in all fields. Fruit damage due to fruitworms in non-commercial fields was on average 5 percent. However, in commercial fields the damage was less than 1 percent. The proportion of fruit damage caused by cherry fruitworm was approximately 32 percent, and 68 percent by cranberry fruitworm. The percentage of larvae corresponding to cherry fruitworm and cranberry fruitworm was 36 and 64 percent. |
3a - CHES organic apple block report |
Ground system Sprays Disease Insect report |
4 - West Central |
Weather GDD totals Since March 1 as of Sunday, June 13
|