Vol. 20, No. 16, August 23, 2005

Weather news

David Epstein, MSU IPM Program; Carlos Garcia-Salazar, MSU Extension;
John Wise and Larry Gut, MSU Entomology

The incidence of unusually high daily temperatures and overall degree day accumulations registered this summer in Michigan will result in a third generation of codling moth (CM) for most of the state. Using photoperiod and temperature data from weather stations around the state, a model developed by Drs. Carlos Garcia-Salazar and Mark Whalon predicts full third generation CM activity for all growing regions of the state south of Bear Lake in Mason County (Table 1). Dr. John Wise, at TNRC in Fennville, reports that third generation began August 18 at TNRC.

The third generation is often referred to as a suicide generation, because under average Michigan weather conditions, the larvae that hatch from third generation eggs do not have enough time to mature to the overwintering fifth larval instar life stage. This year a large percentage of larvae will enter diapause and therefore contribute to the next season’s population.

Important considerations for third generation CM control include predicted harvest dates for different cultivars and associated pre-harvest (PHI) and re-entry intervals (REI) for the different control materials (Table 2). Options for controlling CM include conventional broad-spectrum insecticides, like the organophosphate (OP) compounds, Guthion and Imidan and a number of pyrethroid insecticides. These materials are applied primarily targeting CM egg hatch, beginning at 250 GDD post biofix. Apple growers should be aware that resistance to the OP compounds has been detected in Michigan orchards across the state, most extensively in the Fruit Ridge and southwest production areas. The levels of resistance detected were high enough that heavy dependence on OP's for CM control would likely have failed to protect the crop from infestation.

Among the newer insecticides for CM control registered over the past few years are the insect growth regulators Rimon and Intrepid. Rimon acts by suppressing development within the egg, as well as larvae that consume it. Hatching of eggs laid by treated adults will also be inhibited. Eggs are particularly susceptible to these products when laid on top of sprayed residue, thus sprays are timed earlier than most other CM control materials. Suggested timing for the first application is biofix plus 100 GDD.

Intrepid provides good control of CM with a residual action of about 10 to 14 days. This product is an insect growth regulator that primarily affects CM larvae, but also has some activity on eggs and has sublethal effects on adults. The best results have been achieved by applying the first spray at biofix plus 150 to 200 GDD to take advantage of the sublethal effects. The addition of an agricultural adjuvant is recommended to improve initial spray deposition.

The neonicotinoids, Assail and Clutch, are another group of compounds that have recently become available for CM control. Assail will provide good control of CM with a residual action of 10 to 14 days. Proper timing and coverage is required to achieve control. The best results have generally been achieved when the first application is made prior to the start of egg hatch (ca. biofix plus 150 to 200 GDD). Assail is labeled for CM control at the rate of 2.5 to 3.4 ounces per acre, but the high rate has shown better performance, especially for second generation CM.

Clutch, a new neonicotinoid registered for use in pome fruits, is a broad-spectrum material targeting CM as well as aphids, leafhoppers, PC, STLM, OFM and pear psylla. Trials conducted at the TNRC in 2004 showed Clutch to be most effective against CM applied at the egg hatch timing of 250 GDD and at the high rate of 6-oz/ac rate. Significantly less control was achieved using a lower rate of 3-oz/ac.

Danitol can provide good control of CM. It is highly active and fast acting on all live stages, though residual activity is limited.

SpinTor is not typically used for CM control, although its strong activity on eggs and its short PHI may be useful for third generation control considerations.

Sevin is a carbamate insecticide not typically used for CM control, but with a 3 day PHI, it may be useful for control of CM adults and larvae very near harvest.

Granulosis virus is another material with a very short REI and PHI. This is a naturally occurring virus that goes by the scientific name of Cydia pomonella granulovirus (CpGV), and is only active on the larval stage of codling moth. Two CpGv products were available for use last year, Cyd-X and Virosoft. Our MSU on-farm trials and grower feedback indicated both performed well. Consult June 1, 2004 Fruit CAT Alert article for a detailed discussion of CpGv and its use. Our overall experience is that frequent application of a low rate of product is the best approach for using this biopesticide. (Figure 1)

* For apples only

** 21 day PHI if more than 2 lb rate of Guthion 50W

Amy Irish-Brown

The year 2005 is going to be the year of the insects – the warmer than usual weather has pushed many insects into overdrive. There are several insects that can cause injury to apples late in the season – particularly in a season like this one. While a third generation of codling moth will be the most significant insect to be aware of in apples this fall, other insects such as European corn borer and dock sawfly could show up as well – particularly in apple blocks under mating disruption for codling moth, because general cover sprays are not used as routinely in these blocks.

European corn borer can be a sporadic pest in apples. Typically, it is of more concern where apples are growing next to a cornfield. When the corn is harvested, there could be some migration to nearby apples as a secondary food source. However, European corn borer does occur even where corn is not grown adjacent to orchards.

Corn borer excavates rather large tunnels in apple fruit, feeding in the flesh. The larvae tunnel into fruit, usually entering at the calyx end and feeding inside until early fall. This differs from codling moth damage, which makes a smaller tunnel extending to the seed cavity. Typically, this pest is a problem when weeds such as pigweed and lambsquarters grow up into the canopy. Weeds should be mowed to reduce the risk of problems from this pest. Problems develop in late August and September, as cornfields dry down and orchard spray programs wind down. The damage is usually confined to the border rows. Since it is difficult to predict which orchards will be damaged, it is wise to check the fruit for damage as harvest nears. Corn borers have also been found to tunnel into the shoots of young, non-bearing trees, causing dieback. Where corn borers have been a problem in apples, maintain insecticide spray programs later in the season, especially in the border rows of the orchard.

Dock sawfly can also cause late season damage in apple by burrowing into the fruits. This insect is usually only a problem in orchards with poor weed control and where hollow-stemmed weed species, such as dock, are found growing up into the canopy. Dock sawfly is seeking an overwintering location and generally chooses hollow-stemmed weeds, but if apples are nearby the weeds, they have been known to burrow into the fruits as well. They usually don’t become evident until the bins are removed from CA storage – when the larvae become active again and begin to emerge from fruits. Adequate weed suppression via herbicides or mowing is the best prevention for damage from dock sawfly. The insect is far too unpredictable to try to manage with insecticides.

Rufus Isaacs,
Entomology

In recent years, harvesting of some fall Michigan fruit crops has been complicated by the presence of Multicolored Asian Ladybeetles (Harmonia axyridis). The adult beetles can damage fruit in the field, act as a contaminant of the harvest and can even bite pickers. This growing season, the population of Asian ladybeetles is very high in soybean fields across southern Michigan, fueled by high populations of the new soybean aphid. The long, dry summer has also been good for aphids on other plants, including trees where these ladybeetles congregate. Because of this, the potential risk from Asian ladybeetles to fruit crops is high this year.

Recent research in Ohio has found that ladybeetles start searching for overwintering sites, getting into houses and fruit crops during fall weather patterns. Beetle movement from their summer habitat happens when temperatures drop quickly followed by a sunny day, typically in mid- to late September. For growers of fall fruit crops concerned about ladybeetles, watching for this kind of weather and scouting fields regularly for the first signs of the beetle can provide peace of mind about whether the beetles have started their fall movement to overwintering sites.

If crops become infested with these ladybeetles prior to harvest, growers’ options are restricted by the need for materials with a very short PHI. Laboratory trials conducted at MSU last year found that Evergreen EC 60-6, an MGK Co. pyrethrum insecticide with a 12 hour reentry interval provided the best activity to flush beetles out of grape clusters. While some of the beetles eventually recovered, this type of activity might help growers remove beetles from their crop and harvest the fruit with reduced potential for contamination.

The Asian Ladybeetle Fact Sheet For Fruit Growers can be found at:
http://www.ipm.msu.edu/beetleFruit.htm

Annemiek Schilder,
Plant Pathology

While fire blight is most common in pears and apples, it also affects raspberries and blackberries (Rubus spp.). We recently confirmed a case of fire blight on red raspberries (K81-6) in northern Michigan. At the same farm, the variety Boyne was also showing similar symptoms. Certain varieties are particularly susceptible. Losses result from berry necrosis and from tip dieback of primocanes. Fruit losses of 65 percent or more have been reported on thornless blackberries in Illinois.

Symptoms
The most obvious and striking symptom are blackened cane tips, which bend over and die, resulting in a “shepherd’s crook” appearance. Infections may proceed down the cane for up to eight inches and may produce cream-colored bacterial ooze under high moisture conditions. As the disease progresses down the cane, the veins of leaf veins and portions of the leaf surrounding the midvein turn black. Entire leaves may wither and die. Typically, discoloration and dieback is limited to succulent young growth. In addition, the disease can affect fruit clusters. Infected peduncles (the stalks of fruit clusters) turn black and the young developing berries become brown, dry and very hard. Entire fruit clusters may be infected, but generally a few berries in each cluster remain healthy.

Cultivar resistance
Fire blight affects both red and black raspberries and blackberries. The susceptibility of purple raspberries is unknown. While there has been no thorough study of resistance to fire blight among commercially available cultivars, Latham, Boyne, K81-6 and Fallgold raspberries are known to be susceptible.

Purchase and plant only certified, disease-free plants from reliable nurseries.

Practice good sanitation. Remove and destroy diseased canes from the planting as soon as you see them. Pruning is best done during dry weather to avoid spread of the disease. Disinfest pruning shears in a 10 percent household bleach solution (containing 1 part bleach and 9 parts water) between each cut to avoid transmitting bacteria to healthy canes. Isopropyl alcohol (70%) or quaternary ammonia may also be used, but the bleach solution is more effective.

Manage insect pests to avoid a possible means of moving the bacteria from plant to plant.

Avoid over-fertilization. Vigorous, succulent growth is very susceptible to the disease.

Orient rows and prune and thin plants to maximize air circulation. This will help lower the relative humidity within the plant canopy.

Destroy wild or abandoned brambles growing nearby. These plants may serve as inoculum sources for fire blight and other pathogens, particularly viruses.

Apply copper as a preventative material, starting before or as soon as the first symptoms appear.

Regional reports

1 – Southwest

Mark Longstroth
Bill Shane
Al Gaus

Peach harvest continues with Loring and Glowing Star. Oriental fruit moth trap catches are high, and the third generation is flying. We set biofix as July 27 at 2259 GDD45 and egg hatch will continue to about 3200 GDD45. Brown rot is showing up here and there. Several growers have reported San Jose scale

Cherries look good. There is still little sign of cherry leaf spot. Mites have caused bronzing in many orchards.

Early plum harvest has begun. Stanley plums are coloring. Growers should protect against brown rot.

In apples, we are harvesting Paula Red, Ginger Gold for the fresh market and early Mac types for processing. Gala and Jonathan harvest will begin next week in some orchards. We caught fewer apple maggots last week. We biofixed on codling moth July 20, at 1581 GDD50, we are now at 2336 GDD. I expect the second generation to end about 2330 GDD50, and I also expect a third generation of codling moth to beginning flying soon. See the articles in this week’s Fruit CAT Alert. Trap catch for Obliquebanded leafroller was up last week indicating the overwintering generation is out. I set biofix for this generation as Friday, August 12, at 3100 GDD42. Redbanded leafroller flight is up. Leafroller larvae are common. Oriental fruit moth trap catches are down indicating the flight of the third generation is tapering off. Growers need to protect against Oriental fruit moth and codling moth for several more weeks. Many growers have applied treatments for European red mite. If you have seven mites per leaf you should control European red mite. White apple leafhopper nymphs are easy to find. Examine 50 leaves from 10 different trees and treat if the average is more than one nymph per leaf.

Pear harvest has begun.

Grape veraison is almost complete. Grape berry moth egg hatch increased sharply last week with the beginning of the third generation flight. Insecticide sprays to control egg hatch should be applied. See the article in the July 26 Fruit CAT Alert titled Controlling mid-season grape berry moth. Disease pressure this dry summer has been light and there is little need for fungicides mixed with the insecticides needed to control grape berry moth.

Strawberry growers should protect against leaf diseases and potato leafhopper.

Fall raspberry harvest continues. With heavy dews every night, growers need to protect against fruit rots especially gray mold and botrytis.

Bob Tritten

Paula Red harvest is wrapping up and Gingergold harvest is about 0.75 quarters complete. Peach harvest is about 85 percent complete. Fall red raspberry harvest is now underway. Blueberry harvest is nearly at an end.

Tree fruit
Apples continue to size well despite the dry weather. Many apple varieties are now at 3.5 inches in diameter with Red Delicious being around 3.25 inches. Insect trap catches have been all over the board over the last two weeks. Codling moth trap catches are generally low and steady with a few blocks having high numbers in non-mating disruption and very low trap catches in mating disruption blocks. Stay tuned for additional information on a partial third generation of codling moth, and look for the in-depth codling moth article in today’s edition. A later than normal insecticide application will most likely be needed this year to continue this threat. Apple maggot trap catch continues with many farms having numbers in the five to eight maggots per yellow board. Very few apple maggots have been caught on red traps over the last two weeks. Oriental fruit moth trap catches are generally low, however there are still some farms that are catching some good numbers of Oriental fruit moth. Trap catch numbers are not as high as two weeks ago, where we saw trap catches in the range of 40 to 50 per trap. However, at a few farms trap catch numbers have been in the range of 12 to 20 per trap. Wooly apple aphid populations continue to build slowly but steadily in many problem apple blocks. However, there are also many farms where wooly apple aphids have not been detected. Most other aphids are under control with a few being left on terminal leaves. Some European corn borer adults have been caught in obliquebanded leafroller traps, however the numbers have been fairly modest over the last two weeks. Japanese beetle adults continue to be seen, however their numbers are declining. European red mite populations are still high in a few selected apple blocks, however at most farms they seem to be under control. At this late date it is questionable as to the effectiveness of controlling European red mites. Twospotted spider mite populations continue to build in several blocks with a few isolated blocks where numbers are very high. We are still seeing good numbers of fallacies mites and green and brown lacewings. Asian lady beetle populations continue to build with fewer of our traditional lady beetles being seen over the last couple of weeks. Velvet mites are being seen in increasing numbers. Generally predator populations have begun to decline with the lack of food sources.

Sooty blotch and fly speck started to show up late last week in some blocks that had reduced fungicide programs this summer. Bacterial spot continues to be seen in light amounts on Crispin. Cedar apple rust continues to show up at very light levels in many blocks. A fruit rot that appears to be black rot started to be seen late last week in a few apple blocks. No twig (branch) or leaf symptoms were observed.

Pears are sizing quite nicely with most being around 2.5 inches. We are at least a couple of weeks away from Bartlett pear harvest.

Peach harvest is wrapping up fairly quickly. I estimate that we are about 80 to 90 percent through the harvest season. Many growers have moved through varieties rather quickly this year. Bacterial spot continues to be seen in many blocks of peaches, as does X-disease. Twospotted spider mites continue to be seen in many peach blocks, however, it is late enough in the season that it is not a serious problem.

Sweet and tart cherry blocks continue to show yellowing leaves from leaf spot infections. I encourage growers to scout closely and possibly to apply a second fungicide to control this disease.

Plums have begun to size more over the last two weeks and have colored a great deal over the last week. Most growers have a light to moderate crop of Stanley type plums this year.

Raspberry harvest for fall red raspberries is now underway for varieties ahead of Heritage. Autumn Bliss and Autumn Britton harvest started about ten days or so ago, and Red Wing just started harvest over the weekend or early this week. Heritage harvest appears to be about a week or so away. There are no major new pest problems to report on raspberries.

Blueberry harvest is nearing an end. Berry size is now diminished to a point where picking conditions are less than ideal. Blueberry maggot adult emergence continues as a reduced pace from three to four weeks ago.

Amy Irish Brown
Phil Schwallier
Carlos Garcia-Salazar

weather station, degree day totals continue to run 12 days ahead of average for GDD42 and 14 days ahead of average for GDD50. Tree and fruit growth appear normal at this time, in fact, growers are concerned about apple size being too large for some varieties. Harvest has begun for Gingergolds and Paula Reds. Fruit quality – especially flavor – is very good at this time.

Tree fruit
Codling moth trap numbers continue to be elevated and we are most likely past the peak adult flight and egg hatch. Cover sprays will be important for another week for any late trap catches that were over threshold. Trap numbers have been varied for this second generation of flight and growers should use their average trap numbers and spray accordingly where they are over the threshold of five moths per trap per week. It appears that there will be a significant third generation of codling moth this year and growers, scouts and consultants should continue to monitor codling moth for another month, at least. See the article in this issue for more information.

Obliquebanded leafroller adults have begun to fly again. A second biofix was set for August 12. Cover sprays will be important for early larvae control where damage is evident from earlier feeding. Be sure to watch the PHI on pesticides as we get closer to harvest dates. This is a good time to monitor OBLR activity closely to help with decisions for control.

European red mites are present in all life stages and numbers continue to be very high in many blocks. Bronzing is easy to see now and eggs are being laid on the calyx end of apples.

Apple maggot have been down over the past two weeks. Even with the rain we’ve had, trap numbers are low. Continue to monitor maggot traps and spray accordingly.

Retain applications should be timed for 30 days prior to anticipated harvest.

Mira Danilovich

Weather
The weather in the last two weeks has followed the familiar pattern… still quite warm and very humid. The new development is we have had a few rain showers that came at the right time to help alleviate drought conditions and help with fruit development. So far, August is turning out to be the rainiest month yet this season.

GDD totals: March 1 to August 21

In apples, the first selective harvest of Paula Reds has started. Honeycrisp and Galas are coming along nicely. Their harvest is expected in about three to four weeks. For our main varieties, the estimated peak harvest dates for the CA storage for Ludington area are: McIntosh September 8, for Jonathan September 30 and for Red Delicious October 8. Apple maturity testing will commence in two weeks. Our trap line is indicating heavy insect activity. We are particularly concerned with the high number of codling moths. In the last two weeks we were averaging about 13 moths per trap. The peak flight for the second generation was August 13 with the average catch of 17 moths per trap. There are indications that we might have third generation of this pest. It is going to be very important to continue with tight coverage to control the pest. Scouts are reporting very high numbers of leafrollers particularly obliquebanded leafrollers (small larvae and a few pupae) and medium to large redbanded leafroller larvae. There are a fair number of Japanese beetles present in orchards throughout the area. The disease situation seems to be under control for the most part. We are finding a few scab lesions scattered through the area but not enough to create major concern. Fire blight strikes are being reported in a few blocks. The overall situation is not alarming though a few blocks are hit quite heavy with fire blight.

Crop size of pears varies from block to block. Generally, it is on a light to medium size. Fruit size is satisfactory. Harvest has started this week.

Peach harvest is underway. Fruit size and quality is good. It looks like a good crop. Powdery mildew and brown rot are of concern. The weather is conducive to disease development. Greater and lesser peachtree borer numbers have increased significantly and are now reading in two digit numbers. Oriental fruit moth numbers have increased sharply, particularly in the last week, averaging 30 moths per trap.

There is very heavy load on the plum trees. Crop looks excellent. Fruit has good size and is already showing color. Early varieties are being harvested. Stanley plum is still green though it is showing a good color. In the last three weeks I have been evaluating plum varieties and found that across the 70+ varieties there is one common thread this year…cracking of both fruit and pits. Fruit has dry cracks, mainly longitudinal but in more severe cases the crack appears to have a “tri-star” shape. I have also found quite a bit of abortive seeds in them. This is related to boron deficiency and accentuated by the dry weather conditions. Similar situation is in other fruit crops as well. In apples, one could find brown streaking throughout the flesh. It looks like internal breakdown. Pears have dry scar cracks. The first step in eliminating this problem is to detect it to find out how much of boron is there and how much is missing. Leaf analysis will provide the answers to these questions. If needed, boron could be sprayed yet this fall. It will be absorbed and preserved in the tissue (buds) and will help the next season. Blocks that have boron deficiency need to be closely monitored so the appropriate steps could be taken when needed.

Nikki Rothwell
Jim Nugent
Jim Bardenhagen
Duke Elsner

GDD accumulations at NWMHRS
GDD 42            3120
GDD 50            2120

Tree fruit
In apples, codling moth trap catches were an average of 10 moths per trap. Obliquebanded leafroller moth catches are at 13.6 moths per trap. We still have not captured apple maggot on yellow boards or sticky red spheres, but there are reports of isolate captures in the area. We are surprised at the lack of flies this season.

We have seen very little cherry leaf spot in any cherry blocks in the area. American plum borers are down to 4.6 moths per trap. No lesser or greater peachtree borers were reported this week. Twospotted spider mite counts are still high in many orchards, but populations are declining despite low predator mite populations. The likely reason for the population decline at this time is that these mites are "ballooning" off the trees as the food value in cherry leaves is decreasing. This habit is particular to twospotted spider mite, which survive on a wide range of host plants. By contrast, other mite species, such as European red mites and plum nursery mites, survive on a much more limited range of hosts. We are still catching cherry fruit flies, and the average is 12 flies per trap.

Peach harvest is underway, and Bartlett pear harvest will begin later this week.

In grapes, veraison has begun. Growers need to begin scouting for botrytis and other fruit rots, and for grape berry moth in vineyards with a history of this pest. Many vineyards have been netted for bird management.

Jeff Andresen,
Agricultural Meteorology
Geography

High pressure centered over the Great Lakes region Tuesday morning (August 23) will only slowly drift eastward during the next few days, setting the stage for a mostly fair and dry week across Michigan. Cool and dry air associated with the high pressure led to some of the coolest temperatures observed since May on Tuesday morning, with some mid- and upper 30s and isolated frost reported in sections of the Upper Peninsula. The cool air moving across the relatively warm waters of the Great Lakes (Water temperatures were as high as the low 70s recently.) also led to extensive lake effect cloudiness and some scattered lake effect rain showers Monday and early Tuesday. As the high pressure drifts eastward during the next couple of days, winds will shift to the southwest, leading to a gradual warming trend into the weekend.

A weather disturbance currently moving into the Pacific Northwest region is expected to make its way across the northern Great Plains and into the Great Lakes region by Friday, bringing the next chance for rainfall. Given relatively weak dynamics and limited moisture, however, rainfall areal coverage and amounts are expected to be scattered at best with many locations remaining dry. Scattered showers and thundershowers will be possible Friday statewide, continuing into the weekend across southern sections of the state.

Temperatures will gradually warm from highs ranging from upper 60s north to low 70s south on Tuesday to the upper 70s north to mid-80s south this weekend. Low temperatures will range from the 40s north to low 50s south Wednesday, warming to the upper 50s to low 60s by Saturday.

Further ahead, latest medium-range forecast guidance suggests upper air troughing across western North America and ridging across the east. This pattern would lead to a return of warmer than normal temperatures and likely to an active storm track across the Upper Midwest. NOAA CPC 6-10 day and 8-14 day time outlooks, covering August 28 through September 1 and August 30 through September 5, both call for above normal temperatures statewide. Precipitation is forecast to range from near normal levels in southern sections of the state to above normal levels elsewhere during both time frames.