Dan Pavuk...There are a number of caterpillar pests of tomatoes in Michigan, but certainly the most well known and largest in size are two species of hornworms: the tomato hornworm, Manduca quinquemaculata, and the tobacco hornworm, Manduca sexta. The caterpillars, or larvae, of these two species are called hornworms because they possess a prominent “horn” on the hind end (see Images 1 and 2).

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Dan Pavuk...The squash bug, Anasa tristis, is a major, widespread insect pest of pumpkin and squash throughout most of the United States, southern Canada and Central America. This insect is also very difficult to control in pumpkin and squash plantings. The key to effective control of the squash bug is early detection and control of the immature, or nymphal, stages of this pest.

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By Beth Bishop...The first European corn borers of the season are now flying in southern lower Michigan. Pheromone traps in several counties (Ingham, Macomb) have captured significant numbers of adult moths during the past week.

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Bill Steenwyk...White grubs from European chafer, Japanese beetle, June beetle (also called May beetle by some) have long been known as a major pest of turfgrass, and occasionally in agricultural fields, usually where significant grassy weeds are present, or where old sods were broken up for crop production. Last summer, however, I made the unexpected discovery of finding it as a major economic pest of late-harvested parsnip and carrot growing in virtually weed-free fields.

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By Fred Warner... Needle nematodes, Longidorus sp., are often very destructive nematodes. They are the longest plant-parasitic nematodes found in Michigan with the adults measuring six to eight millimeters (ca. one-third of an inch) in length. They possess very long stylets (used for feeding) which allows these nematodes to probe and feed upon cells inaccessible to most other ectoparasitic nematodes.

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By Fred Warner... Often the things we fear the most are things we don’t understand or can’t see. Does this include parasitic nematodes? Sure, parasitic worms sound quite frightening as we usually don’t see them, only the symptoms of the diseases they cause. In fact, nematodes can cause very serious diseases of both animals and plants.

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Beth Bishop...Sweet corn growers in Michigan experienced moderate “worm” pressure this season. In many locations the first flight of European corn borer moths was high, and early-maturing varieties had to be treated at tassel emergence to prevent larvae from entering the ear (see graphs below). In most locations the second flight was lower, but by then growers were protecting their corn from corn earworm (see graphs below). The second flight of European corn borer moths was pretty much over by late August, and we did not have a warm enough summer to produce a third flight.

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Beth Bishop...European corn borer second flight continues in most Michigan locations, although it is winding down in southern Michigan (see graphs below). Western bean cutworm flight has also ended. Some corn earworm moth migrants have entered the state on recent weather fronts, although the numbers are not as high as this time last year. Earworm moths may continue to migrate to Michigan, and given the active tropical weather, we can expect them to do so, although we don’t know when they will come or how many there will be.

 

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Beth Bishop...Several insect pests have been making a comeback in recent weeks. Corn earworm moth numbers increased, especially in southern and western Michigan, although they don’t come close to the hundreds of earworm moths caught during previous years. Weather conditions were conducive for migration of moths into the area and that is reflected in an increase in trap numbers.

 

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Beth Bishop...The second flight of European corn borer moths has begun in many areas of Michigan (see charts), although it remains to be seen how large it will be. Corn earworm numbers remain very low in pheromone traps and the number of western bean cutworms caught in traps has decreased. Despite low insect pressure, sweet corn with ears and snap beans and peppers with fruit should be protected by insecticide applications.

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Beth Bishop...Numbers of European corn borer moths captured in pheromone traps from July 22 to 29 have increased slightly, as the second flight has begun. No significant migration of corn earworm into the state has occurred during the past month and trap counts are low.

 

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Beth Bishop...We are still between flights of European corn borers, but the second flight will be starting soon in southern Michigan. We can expect egg-laying to begin about 1450 to 1500 degree days (base 50). Only a few corn earworm moths were caught in pheromone traps during the past week (e.g., Mason County, four moths; Ingham County, four moths; Monroe County, one moth Montcalm County; 13 moths; and Oceana County, four moths,). Although risk is low, there still are a few corn borer and corn earworm moths laying eggs, and any sweet corn with ears or snap beans or peppers with fruit are still vulnerable to corn borer infestation.

 

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Beth Bishop...Tarnished plant bugs have been invading many vegetable crops, probably as a result of nearby alfalfa fields being cut. Tarnished plant bugs feed on a variety of crops, including many vegetables. In most crops they prefer feeding on flowers and fruit, but can also feed on the tips of asparagus fern, celery petioles and lettuce leaves. Adults are very mobile and can move in and out of fields before they are detected. Tarnished plant bugs have sucking mouthparts and insert a toxic saliva into plants while feeding. They can cause tip die back in asparagus, flower drop in peppers, snap beans and tomatoes, brown, sunken feeding scars or stings in lettuce and celery.

 

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Beth Bishop...The proportion of aster leafhoppers carrying aster yellows remains moderate. The latest test results from MSU Diagnostic Services indicate that the infectivity rate has decreased in many locations (see table). Because of the variability in infectivity rates, a range of conservative treatment thresholds is suggested.

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Beth Bishop...Numbers of European corn borer moths captured during July 15 - 22 are still very low, but should increase soon as the second flight begins. Also, very few corn earworm moths were captured last week. Although the risk from these pests to sweet corn, peppers, snap beans and tomatoes is low, another “worm” pest has appeared.

 

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Beth Bishop...The first flight of European corn borer moths is winding down in most areas. The number of moths caught in pheromone traps during the past week (July 1 - 8) has decreased in most locations (see charts below). However, any sweet corn with ears or snap beans or peppers with fruit are still at risk for corn borer infestation.

 

 

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Bruce MacKellar...Asiatic garden beetle is a new pest in southwest Michigan. The larval stage of this insect was first identified causing root-feeding injury in commercial corn in St. Joseph County and Elkhart County in Indiana in the summer of 2007. The pest contributed to the unevenness that was seen in the corn crop in the extreme southern portion of Michigan during last growing season. Corn fields that were the most severely impacted were rotated fields planted to soybeans the previous year.

 

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Beth Bishop...The first flight of European corn borer moths continues throughout Michigan. The number of moths caught in pheromone traps during the past week (June 17 - 24) has fallen in some locations (see chart) and we are past the peak flight in southern Michigan. However, moths are still flying, eggs are still being laid and growers and scouts report that a high percentage of sweet corn contains European corn borer larvae in the whorl.

 

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Beth Bishop...The severe weather during the first week of June brought more insect pests into Michigan. We continue to catch corn earworm moths in pheromone traps on campus. Last week (June 10-17), we caught 48 earworm moths in one trap and 54 in the second trap. This is very early for such high numbers of corn earworm to be present. Most sweet corn is not at risk for infestation, but any corn in silk is at risk.

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Beth Bishop...Aster leafhoppers collected last week from celery fields in southwest Michigan and carrot fields in Oceana and Mason counties were tested by Diagnostic Services for aster yellows infection. Four different leafhopper samples were tested and none of them carried aster yellows.

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Beth Bishop...Aster leafhoppers and potato leafhoppers have been reported in the state. These are largely migratory insects, although a few aster leafhoppers may overwinter as eggs in certain areas, and move into the state each year. Aster leafhoppers have been found over the past few weeks in western Michigan vegetable fields.

 

 

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Beth Bishop...In general, few insect problems have been reported in vegetables during the past week. The recent cool weather has inhibited growth and development of many insects, but is conducive for activity and egg laying of maggot flies (onion maggots, cabbage maggots, seed corn maggots). Adults have been captured on yellow sticky traps placed in and around onion, cabbage and sweet corn fields. Maggot damage has been found in cabbage fields in southeast Michigan along with diamondback moth larvae. Very low numbers of aster leafhoppers have been captured in celery fields in southwestern Michigan.

 

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Beth Bishop...Degree-day accumulations (see table in this issue) are favorable for emergence of adults of the early-season maggots (seed corn maggot, onion maggot, cabbage maggot). These species overwinter as pupae in the soil and start to develop when soil temperatures near 40ºF.

 

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Beth Bishop...During the past week pheromone trap catches have ranged from about seven per night to over 200 per night! Sweet corn growers with fields in fresh silk and pepper, tomato and snap bean growers with fields in fruit, should be protecting their crop with insecticide applications.

 

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Beth Bishop...Aster yellows continues to be rare in southwestern Michigan celery fields. Aster leafhoppers collected from a field in Kent County were tested by MSU Diagnostic Services and were not infected with aster yellows. The treatment threshold for celery in this area continues to be 30 to 35 aster leafhoppers per 100 sweeps.

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Beth Bishop...There is good news and bad news this week. The good news is that the second flight of European corn borer is pretty much over. The bad news is that the corn earworms have arrived in force (view images)!

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Beth Bishop...During the past week, increased numbers of both European corn borer moths and corn earworm moths have been caught in most pheromone traps in southern and central Michigan (see charts). We are at, or nearing, peak corn borer flight for this generation of moths. All vulnerable crops (sweet corn at tassel and beyond, peppers and snap beans with fruit) should be protected by insecticides.

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Beth Bishop...Aster yellows symptoms are showing up in carrot fields in northwest Michigan.  Leafhoppers recently collected from carrot fields in Oceana and Mason counties have been tested and have an infectivity rate of 1.2 percent to 3.7 percent.  This infectivity rate (proportion of leafhoppers carrying the aster yellows disease) translates into a treatment threshold of 15 to 25 leafhoppers per 100 sweeps.

 

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Beth Bishop...The second flight of European corn borer moths has begun throughout most of Michigan, and the number of moths caught in pheromone traps last week increased (see charts). Female corn borer moths will be laying eggs on attractive crops for several weeks. Sweet corn at tassel and beyond, and peppers and snap beans with fruit, should be treated to avoid European corn borer damage.   

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Beth Bishop...In most areas of southern Michigan, the second flight of European corn borer moths has begun; the number of moths caught in pheromone traps last week was up slightly (see charts). In the more northern trapping areas (Oceana and Mason Counties), second flight has not yet begun, but can be expected in the next week or so. Right now, there is no way to determine how large this second flight will be.

 

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Beth Bishop...Scouts in West Michigan are reporting increased numbers of aster leafhoppers in some carrot and celery fields. In other fields, aster leafhopper numbers remain low. Leafhoppers infected with aster yellows were detected in two recent aster leafhopper samples. About seven percent of leafhoppers in a sample collected from Van Buren County celery fields were infected with aster yellows.

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Beth Bishop...Pheromone trap catches for European corn borer and corn earworm continue to be very low. In most areas of Michigan, we have not yet reached the 1450 degree-days (base 50) required for the second adult flight of corn borer moths. Because of high temperatures earlier in the season, this flight may start a bit later than 1450 degree-days. We don’t know yet how large the second flight will be.

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Beth Bishop...The second flight of European corn borer moths has begun in southern Michigan. The number of European corn borer moths caught in pheromone traps has increased during the last week, but remains fairly low. However, sweet corn with ears and snap beans, as well as peppers with fruit, should be treated to prevent corn borer infestation.

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Rufus Isaacs, John Wise and David Epstein Entomology The following is an article written for the Fruit CAT Alert that contains insecticide recomme...

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Beth Bishop...These beetles feed on over 300 different species of plants, although they have definite preferences and are primarily pests of fruit and ornamental plants. If you find large numbers of Japanese beetles in your vegetable fields, it is important to distinguish whether or not they are feeding on the crop. Adults tend to aggregate and numbers can be shockingly high, but if they are not feeding there is no need for control.

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Beth Bishop...Few moths of either species were caught in pheromone traps during the past week.  Weather conditions have not yet been conducive for corn earworm (which migrates from the south each year) to be carried into the state. For European corn borer, we are nearing the start of the second adult flight.

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Beth Bishop...Thrips are reported in cabbage fields. Thrips populations can build up rapidly in hot, dry weather. Be aware that the Bt materials (Dipel, etc.) applied for control of “worms” are not effective against thrips. Consult Bulletin E-312, 2007 Insect, Disease and Nematode Control for commercial vegetables insecticides registered for control thrips on cabbage.

 

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Beth Bishop...Squash vine borer adults and squash bugs have been reported on vine crops in Southeastern Michigan (view images). Squash vine borer moths are day-flying moths with a 1.0 to 1.5 inch wingspan. In flight, they look like wasps. There is one generation each year and adults emerge in late June/early July. They lay eggs at the base of squash plants, and upon hatching, larvae bore into stems (where they are protected from insecticides). Unless you scout fields for evidence of eggs or larvae, the first sign of squash vine borer infestation can be wilting vines in July and August. By that time, it is too late to do anything.

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Beth Bishop...The numbers of European corn borer moths caught in pheromone traps were low again last week in most locations except for the site in Macomb County. Sweet corn growers with corn about to tassel should check their fields for corn borer larvae. When tassels emerge, these larvae move down the stalk to the developing ears. If 20 percent or more of the whorls have larvae or feeding damage, apply insecticides to the whorl four days or less before tassel emergence.

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Beth Bishop...With the recent reports of soybean aphids being captured in suction traps throughout Michigan, vegetable growers are concerned about virus transmission. Very small numbers of soybean aphids have been caught so far in 2007, but we don’t expect large numbers until later in the year. You can track the soybean aphid flight in Michigan by checking the NCR IPM Regional Soybean Aphid Suction Trap Network at http://www.ncpmc.org/traps/index.cfm.

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Beth Bishop...Aster leafhopper numbers remain low in carrot and celery fields in west Michigan. The percentage of leafhoppers infected with aster yellows has also remained low so far this year. Most fields have too few leafhoppers to require insecticide treatment. Treatment threshold is 30 to 35 leafhoppers per 100 sweeps for celery, 40 to 50 leafhoppers per 100 sweeps for carrots and 20 to 25 leafhoppers per 100 sweeps for lettuce.

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Beth Bishop...The numbers of European corn borer moths caught in pheromone traps last week were low in most locations (exception, Macomb County--see Table) We are nearing the end of the first moth flight (see degree-day totals, base 50) in this issue of the Vegetable CAT Alert or visit MSU’s Enviroweather at http://www.enviroweather.msu.edu. However, some sweet corn is at risk from corn borer larvae that are now feeding in the whorl.

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Beth Bishop...A few corn earworm moths were caught in pheromone traps in Ingham County. These probably migrated into the area on the weather front last Thursday, June 7. Sweet corn is not vulnerable to corn earworms until green silks are present. However, corn earworms also lay eggs on tomatoes and larvae (which are also known as tomato fruitworm) feed on developing fruit.

 

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Beth Bishop...The numbers of European corn borer moths caught in pheromone traps were down last week, compared with the previous week, at all locations in Michigan (see Table). However, degree-day totals (base 50) indicate that moths are still laying eggs (consult degree day table in this issue of the Vegetable CAT Alerts or visit MSU’s Enviroweather at http://www.enviroweather.msu.edu).

 

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Beth Bishop...Damage from cutworms was reported in several southeastern Michigan tomato and vine crop fields. We were not able to obtain a specimen for identification, but photos suggested these were cutworms that overwinter as eggs, perhaps dark-sided cutworm. In this species, eggs are laid by female moths in the fall and are attracted to weedy areas, fields of grass or pastures.

 

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Beth Bishop...Low numbers of aster leafhoppers are still being detected in celery and carrot fields in western Michigan. Diagnostic Services tested two additional samples collected from celery fields in Allegan County. Both samples tested negative for aster yellows. Given the low infectivity rate and the low numbers of aster leafhoppers, most Michigan fields are below threshold (see the May 30, 2007 issue of the Vegetable CAT Alert for thresholds)

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Beth Bishop...The number of European corn borer moths caught in pheromone traps increased for the week of May 30 to June 5 (see table). Most areas in Lower Michigan are at or above the 450 to 500 degree days base 50 required for the first flight (consult degree day table in this issue of the Vegetable CAT Alert or visit MSU’s Enviro-weather at: http://www.enviroweather.msu.edu

 

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Beth Bishop...The first European corn borer moths were captured in pheromone traps in southern Michigan last week. An average of five moths per trap were captured in pheromone traps in Monroe County and 51 moths per trap were captured in Ingham County. In these locations, degree-day accumulations (base 50) have exceeded the required 450 to 500 for the first moth flight. Locations farther north have not yet reached this threshold, but with the warm weather predicted over the next week we can expect moth flight to start in many locations.

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Beth Bishop...With the advent of warmer temperatures, insect activity has increased. Species that overwinter as adults, such as common asparagus beetle and Colorado potato beetle, have emerged and begun feeding. Early-season pests (e.g., onion maggot, cabbage maggot, cabbage butterfly) remain active. Other resident pests, such as European corn borer, have not yet emerged; the required degree-day accumulation has not yet been reached (450 to 500 DD50 for corn borer).

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Vicki Morrone...Most leaf blowers have the capacity of serving as a vacuum and a blower. There is very little conversion needed to use a leaf blower to suck up insects for sampling purposes, or to provide an eco-friendly way to remove them from crop plants.

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Walter Pett...Diamondback moth larvae have been found in recently planted cabbage fields in southeast Michigan. Adults are small, grayish moths with a wingspread of about half an inch. The light green larvae are about a quarter of an inch in length and their bodies are tapered at both ends. The larvae will wiggle rapidly when disturbed and often drop from the leaf on a silken thread. Larvae feed on the foliage and produce a “windowpane” type of damage by consuming all but the outer layer of leaf tissue.

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Beth Bishop...In 2000, we began to test a new method to accurately and quickly determine the proportion of leafhoppers that were carrying aster yellows. This proportion, along with absolute numbers of leafhoppers present, determines the risk of aster yellows to a particular crop and, in turn, determines whether an insecticide application is warranted. Prior to 2000, to estimate aster yellows risk, it was necessary to collect aster leafhoppers, place them on plants and then wait several weeks for aster yellows symptoms to develop.

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Beth Bishop...Early season maggot flies (onion, cabbage and seed corn) are active and laying eggs. (view images) These insects are adapted to cool weather; they are more of a problem early in the season. Adult flies look similar to small houseflies. They are very mobile and do not spend much time in the field. Control methods should be directed toward protecting seeds, seedlings and young plants.

 

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Beth Bishop...The corn flea beetle is a small, black beetle that feeds as an adult on a variety of grasses, including sweet corn. (view images) Feeding by corn flea beetle produces linear scars along the leaf. Usually corn flea beetles do not directly damage corn. They do, however, vector the bacterial disease, Stewart’s wilt. This disease can cause wilting, stunting, and reduced stand and yield in sweet corn.

 

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Beth Bishop...Growers are still busy managing this year’s crops. However, now is the time to begin reducing your insect pest problems for next season. Mortality during the winter months has a huge impact on Michigan insect populations. Although insects that live here year-round are somewhat adapted to cold weather, their ability to tolerate cold weather is limited. In general, the colder the overwintering habitat, the higher the winter mortality.

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Beth Bishop...European corn borer numbers remain low, but corn earworm moths continue to be captured in pheromone traps, although numbers have decreased. The moths will readily move from senescing crops (for example, sweet corn with brown silk), to younger, more attractive crops. Growers should be vigilant and protect vulnerable crops (sweet corn with fresh silk, tomatoes and snap beans with fruit) for the rest of the season.

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Beth Bishop...Very high numbers of corn earworm continue to be caught in pheromone traps throughout the state. During the past week, 123 corn worms were caught in a pheromone trap on the MSU campus (Ingham County) and a record 958 were caught at a site in Mason County.

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Beth Bishop...Numbers of European corn borers captured in pheromone traps continue to decrease (see charts), and we are nearing the end of the summer flight in most areas. Right now the biggest threat to snap beans, tomatoes and sweet corn is corn earworm, and insecticides applied to control earworm will also control corn borer.

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Beth Bishop...Over the past week, corn earworm moths again migrated into the state. The number of moths caught in pheromone traps increased, in some cases dramatically (see accompanying table). Growers are reporting larvae in sweet corn ears. Growers in all areas of the state should consider vulnerable crops (corn with fresh silk, snap beans and tomatoes with fruit) to be at risk for corn earworm infestation for the rest of the season.

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Beth Bishop...European corn borers are still being captured in pheromone traps throughout the state, although numbers are decreasing (see charts). According to degree day accumulations, we are nearing the end of the summer flight. For the most part, the summer flight was lower than the spring flight. Sweet corn, snap beans and peppers may still be at risk for corn borer infestation, though, and should be protected if at a vulnerable stage. The generations are less defined later in the season.

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Beth Bishop...The latest results from Diagnostic Services are shown in the accompanying table. We are finding a lot of variability between locations, which is typical for this late in the season. Leafhoppers collected from carrot fields in Newaygo, Oceana and Mason counties continue to be more infected with aster yellows than leafhoppers from celery fields in southwest Michigan.

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Beth Bishop...We continue to catch high numbers of corn earworms in pheromone traps (see accompanying table). Growers should protect vulnerable crops (corn with fresh silk; snap beans and tomatoes with flowers and fruit) now. For more details, see the August 9 issue of the Vegetable CAT Alert.

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Beth Bishop...We have received results of tests on aster leafhoppers collected from celery fields in southwestern Michigan ( Ottawa, Allegan and southern Newaygo counties) during July 15-19. None of these leafhoppers tested positive for aster yellows. We recommend a treatment threshold of 35 aster leafhoppers per 100 sweeps for these areas.

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Beth Bishop...The second flight of European corn borer is well under way in most Michigan locations (see graphs). Sweet corn in tassel and beyond, peppers and snap beans with fruit should be protected. European corn borer larvae can be controlled by insecticides used for corn earworm, and this is where growers should be targeting their effort.

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Beth Bishop...The weather front that moved through a week ago brought insect migrants into the state, including many corn earworm moths. Pheromone trap catch numbers jumped in almost all areas, sometimes dramatically (see accompanying table). Growers should protect vulnerable crops (corn with fresh silk; snap beans and tomatoes with flowers and fruit) now.

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Beth Bishop...The second flight of European corn borer has begun throughout most of Lower Michigan. Numbers caught in pheromone traps during the period of July 25 to August 1 were higher than the previous week, but still fairly low (an average of 13 per trap in Ingham County, 10.5 per trap in Macomb County, 5 per trap in Mason County and 0.3 per trap in Oceana County.)

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Beth Bishop...Aster leafhopper numbers have increased in many carrot and celery fields throughout Michigan. The percentage of aster leafhoppers infected with aster yellows varies between < 1% to 5.6%, depending on location. The table below shows the latest test results from Diagnostic Services and associated treatment thresholds.

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Beth Bishop...Degree day accumulations throughout most of Lower Michigan are at or near the threshold for second flight of European corn borer moths. (view photos) Few moths were caught in pheromone traps during the week of July 18-25, but numbers could increase significantly in the next week, especially with the projected warmer temperatures.

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Beth Bishop...The number of European corn borers caught in pheromone traps during July 11-18 remained relatively low in most locations throughout Lower Michigan. The exceptions were traps at two different sites, one in Mason County and the other in Macomb County, at which 15 and 13 moths per trap were captured. One trap at each of these sites has captured consistently high numbers of corn borer moths throughout the season, probably because these traps are located in extremely favorable habitat for European corn borer moths.

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Walter Pett...Hot and dry weather conditions are favorable for rapid increases of thrips populations. Adult thrips are very small (ca. 1/16 inch), yellowish, slender and have fringed wings. The immatures look like small wingless adults. Thrips reproduce very rapidly at high temperatures, and we may have five to eight generations per year.

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Beth Bishop...Large populations of tarnished plant bugs are reported in southwestern Michigan. Tarnished plant bug feeds on a variety of vegetable crops, including asparagus, snap beans, lettuce celery and others. The adults are approximately one-third of an inch long, are bronze-brown with black markings and are extremely mobile. Adults may fly in and out of fields quickly (Most flight occurs in early morning and late afternoon/evening.), leaving only plant damage as evidence of their presence.

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Beth Bishop...Low to moderate numbers of aster leafhoppers are present in most carrot and celery fields in west Michigan. Recent test results for aster yellows infectivity (conducted by MSU Diagnostic Services) reveal low infectivity rates for leafhoppers collected from celery fields in southwest Michigan. Infectivity rates for leafhoppers collected from carrot fields continue to be higher and are variable. I feel comfortable recommending a treatment threshold of 30 to 35 aster leafhoppers per 100 sweeps for celery fields in southwestern Michigan.

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Beth Bishop...The numbers of European corn borer moths caught in pheromone traps remain low throughout most of Lower Michigan. Some locations (Montcalm County, Mason County, Macomb County) are still catching several moths per trap while others (Ingham County, Oceana County, Monroe County) are catching none (or nearly so).

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Beth Bishop...The number of European corn borer moths caught in pheromone traps are very low throughout most of lower Michigan. An average of 0.7 moths per trap were caught in Ingham County, 0.7 in Oceana County and none were caught in Monroe County during the period of June 27 to July 4. An average of 16 per trap were caught in Mason County. Although high, this number is down considerably from the trap catch last week. In the southern part of the Lower Peninsula, the first adult flight is over, and it is nearing the end in the north.

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Beth Bishop...Scouts are reporting low numbers of aster leafhoppers (3-7 per 100 sweeps) in celery and carrot fields in western Michigan. (See table for more areas.)

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Beth Bishop...European corn borer moths are still being caught in pheromone traps throughout Michigan; although numbers are lower than in previous weeks (see accompanying charts). The current degree-day accumulations (base 50) indicate that the first corn borer flight is nearing its end, although significant numbers of moths are still laying eggs, especially in central and northern Michigan. Growers should continue to protect vulnerable crops.

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Beth Bishop...The latest aster leafhopper test results for aster yellows infection are shown in the accompanying table. Very low infectivity rates are still being found in aster leafhoppers from celery fields in southwestern Michigan. Higher infectivity rates are still occurring in leafhoppers from carrot fields in west central Michigan. The recent weather patterns are favorable for bringing new insect immigrants into the state.

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Beth Bishop...The first seasonal flight of European corn borer moths is still occurring in most of Michigan. Corn borer moths were captured in pheromone traps during the period of June 13 to 20 (see graphs). Many sweet corn fields are now vulnerable to corn borer damage. Growers should protect any fields with developing ears. When corn borers hatch, they feed very briefly on the plant surface before boring into the plant. Once inside the plant (most often the ear or the fruit of peppers and snap beans), corn borers are protected from insecticides.

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Beth Bishop...During the past two weeks, aster leafhoppers were collected from celery fields in various locations in Michigan and were tested for aster yellows infection by Diagnostic Services. Leafhoppers from all sites (Newago County, central and southeastern Ottawa County, and eastern Allegan County) tested negative for aster yellows. An appropriate treatment threshold for celery in these areas is 35 aster leafhoppers per 100 sweeps.

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Beth Bishop...European corn borer moths continue to be caught in pheromone traps throughout Michigan. During the week of June 6-13, pheromone traps in Ingham County (MSU campus) captured an average of 8 moths per trap. An average of 50 per trap were caught in Monroe County, 2 per trap in Oceana County, 7 per trap in Montcalm County, 10 per trap in Mason County, and 9 per trap in Macomb County.

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Chris DiFonzo...Why should vegetable growers care about this network? In previous years, large numbers of soybean aphids taking flight from soybean fields in late July and early August are thought to have spread viruses to a variety of vegetable crops (including vine crops, snap beans and peppers). Soybean aphids, like other aphid species, find new fields by flying, landing and “tasting” plants with their mouthparts and then flying on if the plant is not to their liking. During this “tasting” behavior, plant viruses are both acquired and spread.

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Beth Bishop...Large numbers of adult striped cucumber beetles have been reported feeding on young vine crops. The mild winter plus the recent heat and moisture have resulted in a high population of overwintered beetles. Cucumber beetles can severely damage or kill young plants. They also transmit bacterial wilt disease through their feeding. Cucumbers, melons, processing pumpkins, butternut squash and hubbard squash are susceptible to bacterial wilt.

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Beth Bishop...The first flight of European corn borer moths is occurring in most of south and central Michigan. An average of 78 moths per trap was caught in pheromone traps in Monroe County during the week of May 31 to June 6. At a second site in Monroe County, an average of 23 moths was caught. We caught 13 moths per trap on the MSU campus in Ingham County; 6 moths per trap were caught in Montcalm County, 11 moths per trap were caught in Macomb County and less than 1 moth per trap was caught in Oceana County.

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Beth Bishop...The recent warm weather has caused the sudden appearance of many insect pests in vegetable fields. Insects that overwinter in Michigan need two major factors to emerge: adequate degree day accumulations and adequate moisture. The cool, wet weather we experienced in mid-May provided sufficient moisture. The very warm weather during the past week has meant a rapid rise in degree days. Consequently, some insect pests such as Colorado potato beetle and European corn borer (see photo), which would normally emerge during several weeks of moderate temperatures, emerged all at once, in high numbers in the hot weather.

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Beth Bishop...Diamondback moth larvae have been found in cabbage fields in southeast Michigan. The small (1/4 inch or less), pale green caterpillars consume foliage and produce a “windowpane” type of damage. When disturbed, they dangle from a silken thread. Larvae are sometimes imported into Michigan on southern transplants, and these can be resistant to several classes of insecticides.

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Beth Bishop...A few aster leafhoppers have been caught recently in celery and carrot fields in Michigan. At this point, the numbers are very low and they are not likely to cause problems. Aster leafhoppers spread the disease aster yellows. The risk to a particular crop depends on the inherent susceptibility of the crop, the percentage of leafhoppers that carry the disease, and the number of leafhoppers present. To assess risk and determine whether an insecticide treatment is warranted, all three factors must be known.

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Beth Bishop...Colorado potato beetles have emerged from overwintering and are feeding on potatoes in many areas of the state. (see photo) In most cases, growers applied at-plant neonicitinoid insecticides to control these overwintered beetles.

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Beth Bishop...Because cool conditions have slowed growth in vegetable crops, cutworms are becoming a concern. Cutworms are the immature stage of a particular family of moths. There are many different species of cutworm. In general, most cutworm species are active in cool weather and, therefore, are more of a problem in the spring. Cutworms typically “cut” seedlings and young plants off at soil level (thus their name), but some species are “climbing” and may feed on foliage.

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Beth Bishop...The recent normal to above-normal temperatures have resulted in good growth of vegetable crops and early emergence of some vegetable insect pests. Cabbage butterflies have been active for several weeks and are laying eggs on cole crops and wild mustards. The butterflies are small and white with one or two black dots on the forewing. Females lay eggs singly, usually on the underside of leaves. The bullet-shaped eggs are white when laid and turn yellow when they are close to hatching. The cabbageworms that hatch from these eggs are green and hairy with a very thin line of yellow down the back.

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Beth Bishop...White cutworm damage has been reported on asparagus in Oceana County. White cutworms overwinter as partially mature larvae and are active at low temperatures. They feed at night by climbing on the spears and chewing the tip or the side of the spear.

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