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| Vegetable Crop Advisory Team Alert newsletter | |||||||
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| Vol. 23, No. 13, July 23 2008 |
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| In this issue Western bean cutworm: a new corn “worm” Aster leafhoppers and aster yellows Watch for tarnished plant bug Recent foggy, humid weather favors downy mildew Potato disease update Starane Ultra labeled for onions in Michigan Informational meeting on new water use legislation Agricultural field sanitation requirements in Michigan Regional reports Weather Next issue July 30 |
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| Western bean cutworm: a new corn “worm” 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. Western bean cutworm has been a pest in the western Corn Belt and, in recent years, has been expanding its range eastward. For the past several years Dr. Christina DiFonzo, MSU field crops entomologist, has been coordinating the Michigan component of a pheromone trapping network that tracks its spread. The first western bean cutworm captured in Michigan was caught in Cass County in 2006. In 2007, moths were caught as far east as Eaton County and so far in 2008, low numbers of moths have been caught in many different counties as far east as Ingham County. |
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| For detailed information on western bean cutworm identification and biology, consult the Field Crops CAT Alert. To summarize, there is one flight, or generation, each year, which usually begins in early to mid-July and continues until mid-August. Females are attracted to corn in the whorl to pretassel stage. Eggs are laid in clusters on the upper surface of leaves. Eggs are white when first laid, but turn purple before hatching. European corn borer egg masses are white at first, but flat, resembling fish scales, unlike the rounded eggs in a western bean cutworm egg mass. Upon hatching, larvae feed on the tassel in the whorl and after the tassel emerges move down to the silk. They feed on the silk for a while and then enter the ear. Unlike corn earworm, the larvae are not cannibalistic, and there can be many western bean cutworm larvae in a single ear. Sweet corn growers in areas where western bean cutworm are flying should be scouting their fields for egg masses. Check the upper leaves of 20 plants in five different locations in the field. Be sure to check different varieties and corn at different growth stages. Chris DiFonzo has recommended a threshold for field corn of five percent of plants with egg masses. However, the tolerance for worms in sweet corn is considerably lower. Growers with silking corn should already be on a preventative program for European corn borer and corn earworm. However, remember that western bean cutworm prefers corn at the pretassel stage. If western bean cutworm egg masses are found in sweet corn at the whorl or pretassel stage, an insecticide should be applied at tassel emergence. Western bean cutworm larvae are difficult to control when in the silk and impossible to control once in the ear, so insecticides must be timed to tassel emergence. A number of insecticides are registered on sweet corn for control of western bean cutworm, including pyrethroids (Asana, Capture, Baythroid, Mustang Max, Proaxis, Pounce), organophosphates (Lorsban, Penncap-M), Sevin, etc. Western bean cutworm is not controlled by most varieties of Bt sweet corn. It is also a pest of dry beans, but that crop is less preferred. I have not heard of any reports of western bean cutworms on snap beans, although that is always a possibility later when the population increases and corn becomes less attractive. |
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| Aster leafhoppers and aster yellows 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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| Watch for tarnished plant bug 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. Treatment thresholds have not been established in most crops for tarnished plant bug. In celery, Ontario recommends a threshold of 0.2 tarnished plant bugs per plant for celery up to three weeks before harvest and 0.1 tarnished plant bugs per plant for celery less than three weeks before harvest. Because of this pest’s mobility, inspecting plants for damage may be necessary. Tarnished plant bugs are effectively controlled by a number of insecticides, including pyrethroids, neonicitinoids, and carbamates. Consult bulletin E312: 2008 Insect, Disease, and Nematode Control for Commercial Vegetables for insecticides registered to control tarnished plant bug on your crop. |
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| Recent foggy, humid weather favors downy mildew The wet, foggy and humid weather that occurred over the weekend and extended through the early part of this week will cause downy mildew to increase rapidly and spread. This year’s weather is much more favorable for downy mildew than what we experienced last year. That means that if you were able to control downy mildew on cucumber last year by spraying every 10 days you should not assume that the same approach will work this year. Since the weather is cooler and wetter than last year, fungicide sprays will need to be applied to cucumber more frequently than every 10 days in order to adequately control downy mildew. It is currently recommended that all cucumber growers apply a fungicide at least as often as every seven days. For cucumber growers who find downy mildew in the field, the sprays will need to be tightened up to five-day application intervals. At this point, there have not been additional fields found with downy mildew beyond those identified earlier in Monroe and Allegan counties. However, given the increasing spore counts as determined by the spore traps, cucumbers in other fields or in homeowner gardens must be infected with downy mildew, but are not being reported. Updates on the movement of downy mildew in Michigan and spore counts can be found on the internet (http://plantpathology.msu.edu/labs/hausbeck/ForGrowers.html). Since even seedlings at the cotyledon stage can become infected, it is critical that all fields be scouted frequently so the spray interval can be tightened as needed if downy mildew is found. We have received some cucumber samples with downy mildew-like symptoms, but found alternaria leaf blight only. We welcome all samples that appear to have downy mildew-like symptoms. We can look at the leaves under the microscope and determine within a few minutes whether there is downy mildew. In some cases, we can arrange to pick up the samples if the location is near the spore trap sites. Given the extremely favorable weather for downy mildew and the increasing spore counts in some areas of the state, all melon growers should be certain to be using downy mildew fungicides at a spray interval of every 10 days. Melon growers in Monroe and Allegan counties should consider downy mildew fungicide sprays every seven days since the disease is present in those counties and the weather has been very favorable for disease. In previous years, melons have become infected with downy mildew, ranking second behind cucumber in susceptibility to the disease. I’ve had a lot of questions about how to use the new fungicides Presidio and Revus. Presidio can be used for both downy mildew and Phytophthora crown and fruit rot. The label for Presidio specifies that another fungicide needs to be mixed with Presidio. When using Presidio for control of downy mildew either Bravo of Dithane can be used as a mix partner. When using Presidio to target Phytophthora crown and fruit rot, fungicides such as Gavel or Acrobat can be considered as tank-mix partners. Revus is best used for control of Phytophthora. While I do not think that Revus is one of the top downy mildew fungicides that we have available, it is a good choice for Phytophthora control. Squash, pumpkin, and zucchini growers can continue to use downy mildew fungicides every 10 days, but should be scouting fields for any early downy mildew infections. In the last few years, downy mildew has not been an especially difficult problem in squash, pumpkin, or zucchini fields. Melon, pumpkin and squash growers need to remember that powdery mildew has also been found in the state and will need to be scouted and treated. The products used to treat powdery mildew are different than those used to treat downy mildew. So, those growers who are on a downy mildew program will need to make adjustments in their spray program to be protected from both downy mildew and powdery mildew. |
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| Potato disease update The main diseases to appear in Michigan fields in 2008 have been Rhizoctonia stem canker, bacterial soft rot and seed-borne fusarium dry rot. Spring and early season conditions have been ideal this year for the sporadic appearance of these diseases although Snowden has been particularly affected by soft rot issues. The disease has not been confined to seed from any single seed lot or grower, but has been a varietal issue. We are investigating this further. In 2008 – 2009, we intend to start a fusarium dry rot survey to revisit the species and fungicide sensitivity of these species and isolates to determine if there has been a population change, since the last work was done in Michigan about 25 years ago. Some states are reporting an increase in discoveries of potato dry rot caused by fusarium graminearum (the wheat head scab pathogen). This pathogen may be sensitive to fungicides that we do not currently recommend and there may be opportunities in the future to better manage this disease. Foliar diseases such as early blight and brown leaf spot are starting to appear now and first reports of early die. Growers have been challenged by frequent rain this year and conditions have been ideal for late blight in many areas, especially the southwest and southeast growing areas of Michigan. To date, we have only sampled one suspected plant from southwest Michigan, but this did not turn out to be late blight. With the prevalence of volunteer potatoes throughout Michigan in 2008 and the continuing conducive conditions for late blight development, it will be prudent for growers to remain on at least a seven-day schedule at the highest recommended rate of protectant residual fungcides such as chorotahlonil (Bravo, Equus, Echo) or EBDC fungicides (Manzate, Penncozeb, Dithane, Polyram). In addition at this time when white mold sclerotia are likely to germinate and produce air-borne ascospores, white mold fungicides should be applied such as Endura and Omega. Omega is also an effective late blight fungicide. Full recommendations for management of these diseases and others can be found at http://www.potatodiseases.org/index.html. Daily updates of potato late blight risk are available at http://lateblight.org for all the MAWN sites in Michigan and updates at Extension meetings held throughout the state. |
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| Starane Ultra labeled for onions in Michigan The Michigan Department of Agriculture has approved an SLN (Section 24c) label for use of Starane Ultra (fluroxypyr) on dry bulb onions in Michigan. Starane Ultra is a hormone-type herbicide that is taken up by the leaves of a plant and disrupts the normal plant growth system. Starane Ultra gives good control of several broadleaf weeds, including common chickweed, common ragweed, eastern black and hairy nightshades, horseweed, mustards, and volunteer potato. To control broadleaves, apply 0.35 pt of Starane Ultra to weeds less than four inches tall. Please note that only the new formulation of Starane Ultra, which is a 2.8 lb ae/gal formulation, is labeled for onions. The original formulation, Starane 1.5 lb ae/gal, is not labeled for onion. Volunteer potatoes should be four to eight inches tall for optimum control. Application to onions may be made as a broadcast over the top spray from the 2- to 6- leaf stage. After the 6-leaf stage, Starane Ultra should be applied with drop nozzles as a directed spray. Do not use an adjuvant with Starane Ultra on onions. For heavy weed infestations, make two applications 10 to 14 days apart. Do not exceed two applications per year. Do not apply within 42 days of onion harvest. Applicators must have a copy of the label when making applications. The label can be printed from the MSU vegetable website: www.veginfo.msu.edu. |
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| Informational meeting on new water use legislation
Attend one of these informational meetings during August to better understand the new water use legislation signed into law by Governor Granholm on July 9, 2008. There are four locations to choose from: August 13 9:00 AM to Noon August 18 9:00 AM to Noon August 21 9:00 AM to Noon August 22, 9:00 AM to Noon A pdf of this information is available at www.ipm.msu.edu/cat08veg/pdf/7-23wateruselegislation8-08.pdf. |
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| Agricultural field sanitation requirements in Michigan The Michigan Occupational Safety and Health Administration (MIOSHA) has updated enforcement procedures for field sanitation standards in 2008. Inspections may be based on complaints or referrals, as well as, programmed inspections, which are conducted by MIOSHA personnel as time permits where they see hand-labor operations in the field. Drinking water Clean and safe potable water must be readily accessible to all employees. Heat-related illness can be reduced or prevented by drinking enough water and taking other precautions, including suitable clothing. Farm workers experience the highest risk of heat-related illness of all occupations. Where 11 or more employees have worked on any day during the last 12 months, the water must also be suitably cool for the temperature conditions and dispensed by single-use cups or by fountains. Toilet and hand washing facilities Toilet and hand washing facilities must be provided whenever work time plus transportation time to and from the field exceeds three hours. One toilet and hand washing facility shall be provided for each 20 employees or fraction thereof. The facilities shall be located together and as close as practical to the work location. For small operations, where the 11 or more employees rule does not apply, the facilities must be either provided as above or available to employees by using employer furnished transportation. Employees must be given reasonable opportunity to use these facilities. Toilets shall be ventilated and screened, have self-closing doors lockable from the inside, and constructed to ensure privacy. Toilets shall be operational and include an adequate supply of toilet paper. Hand washing facilities must have an adequate supply of potable water, soap, and single-use towels. All facilities must be maintained in clean and sanitary conditions and waste shall be disposed in a sanitary manner. Where the 11 or more employees rule does apply, employers must inform all employees about the importance of good hygiene practices to minimize adverse health effects. More information is available at www.michigan.gov/miosha, and by calling the MIOSHA General Industry Safety and Health Division at 517-322-1831 or the district supervisor at 616-447-2650. Free consultation and compliance assistance is available through the MIOSHA Consultation Education and Training Division (CET) by calling the Lansing office at 800-866-4674. CET publications can be accessed at http://www.michigan.gov/dleg/0,1607,7-154-11407_30453---,00.html. To read Dr. Bitsch’s complete newsletter go to her website at http://www.msu.edu/user/bitsch. Under “News” click on “Agricultural Field Sanitation” or click on “Agricultural Labor Issues in Michigan” for a list of available newsletters. Please remember that these newsletters serve educational purposes only and do not constitute legal advice. |
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| Regional reports 1 -- Southwest Ron Goldy Weather Temperatures have been near normal for the period with lows from 60°F to 69°F and highs from 72°F to 89°F. There was 1.5 to over 2.0 inches of rain across the area. High rainfall has made it difficult for field activity in some fields. Crop report Sweet corn harvest volume has increased as more fields come into production. Some fields are showing signs of rust and smut, and tassel feeding born corn borers. Aphids are present in some fields. Tomato harvest continues with volume also increasing. Hornworm and fruit worms can be found in some fields. Phytophthora symptoms can be found in pumpkin and fall squash fields. Otherwise plants are growing and runnering well. Early cucumber, zucchini, and yellow squash fields are finished and are being removed with some being replanted. Early virus symptoms are showing up. Cantaloupe harvest began this week. Watermelons are continuing to size well with harvest at least two weeks away. Peppers and eggplants continue to grow well with few problems. Harvest is also about two weeks away. Tarnished plant bugs are present on many crops. There will be an open house for the High Tunnel system July 31 from 7:00 PM to 9:00 PM at SWMREC. |
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| 2 -- Grand Rapids Area Bill Steenwyk Weather Rainfall for the past week varied from less than 0.1 inch in Belding to one or more inches south of Allegan County. Much of the area received 0.50 to 0.75-inch. Crop report Celery is being harvested steadily, with the early crop down about 20 percent from normal. On individual farms, yields range from excellent, to nearly nothing where earlier flooding damage was severe. Fusarium blight is present in a number of fields. Some onion fields look very good with bulbs sizing beyond two inches. I saw one field where the leaves have dropped. The early June floods, followed by repeated wet periods have produced bacterial blight in a number of west Michigan onion fields. It is the worst where plants were submerged the longest and non-existent on areas with slightly higher elevation. Growers should spray with copper hydroxide or copper sulfate-containing products. Some growers have been sold fungicides to combat this problem. These will not work because the pathogen is one of several bacterial species. Harvest of the second radish crop is underway, and appears to be good. Recovery of some severely flooded red beet seedlings has been surprisingly good. Sweet corn harvest has just begun. No major problems are being reported. Cabbage harvest continues at a good pace. The tomatoes and peppers that I have seen look good, and no reports of problems have come in. The have been reports of phytopthora in some of our vine crops. Growers should go to www.ipm.msu.edu/cat08veg/pdf/7-23buyinwaiver08.pdf to see a copy of a new USDA announcement entitled "2008 Crop Year Buy-in for Disaster Assistance Programs". This describes how growers have been given extra time to go to their county USDA Farm Service Agency office to purchase "catastrophic risk protection" insurance (CAT), or "Noninsured Crop Disaster Assistance Program" coverage (NAP), to be eligible for USDA crop disaster funds. The cost is $100 per crop, but not more than $300 per producer per county, or $900 total per producer, for all counties, less any previously paid fees for CAT and/or NAP. Contact the local USDA, FSA office for full details. |
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| 3 -- Oceana County Norm Myers Weather Weather has continued to be dry this last week and irrigation is underway where it is available. Crop report The first flush of fern on full season asparagus fields is now fully expanded. Most growers have put down their first fungicide cover. Purple spot and rust are both active and TOM-Cast sensors are building Disease Severity Values quickly because of the foggy mornings. In carrots, foliar diseases continue to be a big concern in these weather conditions. Some aster yellows are beginning to show up now and aster leafhopper numbers are rising. Harvest of processing zucchini is under way. Growers are treating for powdery mildew as needed. Cucumber beetles are still a big problem in many fields. Powdery mildew is also beginning to show up on most pumpkin fields. Unfortunately, we had our first virus case confirmed by MSU Diagnostic Services with both zucchini yellows and watermelon mosaic type II identified. This isn’t too surprising since Dr. Chris DiFonzo found winged soybean aphids in Mason County last week. Summer snap bean plantings appear to be growing normally in most areas. In sweet corn, European corn borer traps were up just a little, but this is the first week that I caught zero corn earworms. Western bean cutworm flight has been way up with one trap catching 103 moths in a week. Egg masses were over threshold on the two field corn sites I scouted, but not on the sweet corn field I scouted. |
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| 4 -- Mason-Newaygo counties Jim Breinling Weather Temperatures continue about normal with highs averaging about 80°F and lows in the low to mid-60°F range. Even though rainfall amounts were low, the humidity levels remained high during the week. Actual rainfall recorded for the week was 0.69-inch at the Ludington Enviro-weather station with most of that measured on July 16. At Fremont only 0.15-inch was reported, but during the week, however thunderstorms formed in the area on July 22, and about 0.25-inch was reported in the Grant area. Crop report Even though incidence of leaf blight is reported, foliage of carrots in Newaygo County is healthy and growing well. Root diameter in fields for processing is now one to one and a half inches. Harvest for one packing plant is scheduled to begin on August 11. Onions continue to progress and bulbs are sizing at one to one and a half inches in diameter. Growers report normal insect and disease pressure with crop development possibly a little behind normal at this time due to the cold early season temperatures. In cucurbit crops, slicing cucumber harvest began this week. Butternut and other winter squash for processing are growing well with first bloom appearing. Striped cucumber beetles were observed in some bloom. Irrigation is being applied at this time on a number of the squash fields. Pumpkin fields in the area are now well established and starting to grow well. Local sweet corn is now available in Newaygo County. Corn earworm trap catch at the Mason County site this week was zero in the small trap. There were four western bean cutworm moths in the trap also located in Mason County. Snap bean fields in Mason County are now 30 days in the ground and at the third trifoliate. Some local areas of root rot can be found in the field where the European corn borer traps are located. Eurorpean corn borer counts this week were 0 – 0 – 0. A number of Japanese beetles were also in the traps. |
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| 5 -- Macomb, St. Clair and Lapeer counties Hannah Stevens Weather and crop conditions |
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| 6 -- Monroe County Sudeep Mathew Weather It was dry during the past week. Humid conditions have provided favorable environments for disease development and spread. The Enviro-weather station near Dundee received a total rainfall of 0.14 inches. Soil temperatures ranged from 70°F to 84°F. Relative humidity averaged 78.76 for this past week. Crop report Sweet corn is silking in many fields and harvest is going on in early planted fields. There was some fall armyworm feeding on harvestable sweet corn ears. Japanese beetles are everywhere. They are present in the fields of sweet corn, cucumbers, peppers and tomatoes. There weren’t any European corn borers or corn earworms found in our traps in the past week. Cucumber picking is taking place. All the commercial growers are on a continuous spray schedule to restrict further spread of downy mildew. Cucumber beetles (Photo 1) are present in many fields in moderate numbers. Pumpkins are growing steadily. Cantaloupe and melons are being harvested this week. There were few corn borer-type injuries on mature melons and cantaloupe fruits. I found one squash vine borer in the trap. Cabbage harvest is in full swing. I have seen sclerotinia (white mold) symptom on fully formed heads of cabbage (Photo 2). Cabbage planting is continuing on the fields where sweet corn is harvested. I have learned from many growers that it will continue beyond this week. Green bell peppers and Hungarian peppers are maturing for harvest. European corn borer feeding was evident on some green bell peppers. Harvest of market tomatoes began this past week. I saw symptoms of bacterial speck and spot (Photo 3) in the vines of the staked tomatoes. Processing tomatoes are looking good although many plants lost some flowers during the cool nights of this season. Potatoes are growing well with green vines and completing canopy closure. There is not much disease pressure at this time. Colorado potato beetles are found in mild to moderate numbers in Monroe and moderate to heavy numbers were found in the Washtenaw area fields. There were 16 variegated cutworm moths found in our trap.
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| Weather news Jeff Andresen Agricultural Meteorology Geography A nearly stationary frontal boundary across the eastern United States, has resulted in several rounds of showers and thunderstorms across Michigan since last weekend. This front will finally move off to the south and east by late Wednesday (July 23) and be replaced by a large area of high pressure. A few showers will still be possible Wednesday afternoon and evening in eastern sections of the state, otherwise, most areas will remain dry. The high pressure system will lead to fair and dry weather Thursday. An area of low pressure is forecast to approach Michigan from the southwest by Friday afternoon, with the chance for more showers and thunderstorms Friday evening and during the day Saturday. At this point, widespread rainfall is not expected with this system, with only scattered 0.10 - 0.25-inch accumulation where rainfall occurs. Some areas of the state will remain dry. High temperatures Thursday and Friday should range from the low 70s far north to the low 80s south with lows in the 50s into the low 60s. Similar temperatures are expected this weekend, with highs from the mid-70s north to the low 80s south and lows from the mid-50s south to low 60s far south through Sunday. Further ahead, high pressure is forecast to dominate weather across the region early next week, with fair and slightly cooler than normal conditions expected. In the medium range period, forecast guidance suggests upper air troughs across northwestern and northeastern sections of the United States, with a broad ridge across the Great Plains region. The National Weather Service 6 ‑ 10 day outlook covering July 28 through August 1 calls for mean temperatures to range from near normal levels across the western section of the Upper Peninsula, to below normal elsewhere across the state, and for below normal precipitation totals statewide. The outlook for the 8 ‑ 14 day period (July 30 B August 5) calls for temperatures to warm to above normal levels statewide with precipitation continuing at below normal levels. |
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