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| Vegetable Crop Advisory Team Alert newsletter | ||||
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| Vol. 22, No. 5, May 23, 2007 |
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In this issue  Insect update Diagnostic tests for managing nitrogen Avoiding losses due to black streaking disorder in celery SelectMax labeled for additional vegetable crops Regional Reports Weather news |
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Insect update 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). For the most part, migratory pests have not yet arrived in large numbers, although a moderate number of aster leafhoppers were found in celery fields in southwest Michigan. The insect migration forecast maps issued by Northern Illinois University (http://www.maplecity.com/%7Esand/cew/imrf.html) show a very low risk of insect migration from the southwest into lower Michigan over the next few days. The forecasted conditions are more conducive to sustained migration than any we’ve had so far this season. Growers are advised to scout their carrot, celery and onion fields for aster leafhoppers within the next week. |
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| Diagnostic tests for managing nitrogen Nitrogen (N) is a key nutrient for production of quality vegetable crops, and many vegetables are side- or topdressed with nitrogen during the growing season. Mid-season applications help match the supply of nitrogen with the requirement of the crop, and also minimizes the potential for loss of nitrogen by either leaching or denitrification. Depending on management practices, soil organic matter content, soil temperature and moisture conditions, the amount of nitrogen becoming available (mineralized) from the soil may vary from year to year and field to field. A soil nitrate test or a petiole sap nitrate test can provide information about the available nitrogen status of the soil. Nitrogen that becomes available in the soil due to microbial activity is nitrogen that does not need to be applied. Collecting soil samples to 10 to 12 inches deep prior to sidedressing and having the soil analyzed for the nitrate and ammonium nitrogen content, provides an indication of the available nitrogen status of the soil and provides a guide for how much additional nitrogen, if any, should be applied. Most soil testing labs, including the MSU Soil and Plant Nutrient Lab, will run the soil nitrogen test. The total nitrogen concentration in a plant is a good indicator of nitrogen available in the soil. The nitrate concentration in the petiole correlates well with the total nitrogen content, and is the basis of a quick test to determine the nitrogen status of the crop. The petiole sap nitrate test can be used in two ways. The best is to monitor the petiole sap nitrate concentration on a regular basis (every seven to ten days) and follow the change. If there is a large decrease from one time to the next that is an indicator it is time to apply more nitrogen. There are also general guidelines for various crops that test values can be compared with to use as an indicator of whether or not nitrogen needs to be applied. These guidelines will be published in the next vegetable newsletter. |
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| Avoiding losses due to black streaking disorder in celery For the last two years, celery growers have suffered severe economic losses due to a new physiological disorder named “black streaking.” The disorder makes the entire crop unmarketable. With celery being one of the most intensive and high value crops (about $8,000/A in 2005), many growers were severely affected because of the high production costs. To our knowledge, this was the first report of black streaking in celery. The cultivar ‘Dutchess’ was more affected than other cultivars. With most celery producing regions being affected, due to the unmarketable finished product, the farmers had to incur substantial monetary losses. Symptoms Celery plants with this defect look perfectly healthy in the field; however, when cut, some petioles show “black streaks” in the lower half or throughout the entire length of the petiole. Symptoms in large plants were more pronounced than in smaller ones. Cause The problem is a physiological disorder, and is not caused by a pathogen. Studies conducted in 2006 showed that the symptoms can be triggered under field conditions by high temperatures. The number of petioles with black streaking symptoms increased as temperature in our experiment was increased. The cultivar Greenbay exhibited high levels of tolerance to the disorder. Tips for avoiding losses in 2007 In both 2005 and 2006, black streaking occurred on celery plants that were in their exponential growth phase (active growth) during the month of July. Both 2005 and 2006 weather data indicate that during that time air temperatures exceeded 90ºF for a couple of days. With a zero tolerance for this problem in 2007, growers should be particularly careful in programming and scheduling their crop. Our current suggestion, based on the 2005 and 2006 experience are as follows: |
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| SelectMax labeled for additional vegetable crops SelectMax, a postemergence graminicide, has been labeled for several additional vegetable crops. It now may be used on asparagus, snap beans, herbs, leafy greens and peas. The normal use rate for SelectMax is 9-16 fl oz per acre. Use the high rate for control of perennial grasses and annual bluegrass. The preharvest interval for asparagus is one day; 21 days for snapbeans, 14 days for herbs, 14 days for leafy greens, and 21 days for succulent shelled peas. SelectMax is a new formulation of clethodim (Select), which may be more active on a volume basis than Select. All the postemergence grass herbicides have a similar mode of action on grasses, but each is slightly different on each grass weed. It is a good idea to alternate postemergence grass herbicides when more than one are registered on a crop. |
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| Regional reports 1 -- Southwest Michigan Research and Extension Center Ron Goldy Weather Temperatures during the week ranged from highs of 53 to 85oF and lows from 35 to 57oF. The area received no rain for the week and has had 4.71 inches since April 1 and 0.9 inches since May 1. Soil temperatures are in the mid to upper 60s. Crop reports Planting and transplanting continue. Dry conditions have made irrigation essential for seed germination. Windy conditions have made good coverage of overhead irrigation difficult. Dry soil has also lead to difficulty in laying plastic. Some asparagus fields are finished, especially newer plantings. Growers will begin applying post-harvest weed control and fertilizer this week. Asparagus beetles continue to be active. Tunnel-grown cucumbers, squash and tomatoes are in early bloom. Sweet corn growing conditions have been excellent, and germination and emergence is rapid (less than seven days) providing moisture is present. Earliest plantings are 8 to 12-inches tall. |
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| 2 -- Grand Rapids Area Bill Steenwyk Crop reports Planting progress continues at a good pace. No significant frost damage has occurred. Plant growth is rapid, with no widespread pest problems. With essentially no rainfall since May 15, the lack of topsoil moisture is the only limiting factor. Farmers are expending considerable time managing crop irrigation. Lettuce, leeks, beets, onions, cabbage, radishes, squash and celery all look good. Sweet corn size ranges from spike to 2-3 leaf stage. Weed seedlings, primarily broadleaf, are establishing themselves. Few post-emergence controls are available for some vegetable crops, so cultivation/rotary hoeing will be needed soon. In onions, barley companion crops have been killed in most fields. Where oilseed radish and other brassica species have been established as a cover crop on muck soils, growth and vigor are excellent. |
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| 4 -- Mason-Newaygo counties Jim Breinling Weather Rainfall amounts have been minimal during the past 14 days with only 0.14 inch reported at the Fremont MAWN station. Amounts have been slightly higher in the Mason County area with 0.66 inch at the Ludington MAWN station during the same period. Temperatures have for the most part remained seasonal. Low temperatures recorded on May 18 were 33.7ºF at Fremont and 29.4 ºF at Ludington. High temperatures recorded on May 22 were 83.7 ºF at Fremont and 82.3 ºF at Ludington. Crop reports Early plantings of carrots are at 2-3 true leaf stage. Herbicide applications are being made to kill barley cover and broadleaf weed control in some fields. Initial sweeps for aster leafhoppers this week very few found. First onion plantings at 3 leaf stage. First plantings of slicing cucumbers have emerged. Soil temperatures at the Fremont MAWN station have been consistently above 50 degrees since May 8. ECB traps were placed at a snap beans field site in Mason County on May 21. The field is scheduled for planting May 24-26. Growing degree days (base 50) are at 292 for the area on May 22. Planting of winter squash will begin this week with favorable soil temperatures and moisture conditions. |
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| 5 -- Macomb, St. Clair and Lapeer counties Hannah Stevens Weather and crop conditions After some light rainfall one week ago, following the heavy rains on the evening of Tuesday, May 15, it has been a dry week with windy conditions that are drying wet soils. Widespread light frost on May 18-21 may not have caused too much damage, as many transplants have yet to be put out and seeded crops are just beginning to emerge. For many growers, field work resumed early this week and is moving at a fast pace. Some soils, particularly untiled fields, are still too soggy to plant. On wet fields, it has been a challenge working sown rye cover crops, which are beginning to head. Crop reports Cabbage growth is excellent. In some areas, the outer leaves were marked by hail a week ago. Sweet corn first seedings are about 6 inches tall. Those that were planted in May have caught up with April seeded corn. Seeding is in full swing. The tomato crop is mostly under cover and needing some warm night time temperatures. Fresh market beans are emerging with no leafhopper activity reported yet. Squash, in some early fields, is emerging with no beetle activity reported. Onions and carrots on muck soil barley cover crops are about 60 percent sprayed. |
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| Weather news Jeff Andresen Agricultural Meteorology Geography Unseasonably warm air moving northward around a large area of high pressure just off the eastern coast of the United States, will lead to another day of summer-like weather across Michigan and much of the central United States. Look for high temperatures to remain from the upper 70's far north to the mid and upper 80's Thursday, May 24, with some southern areas of the state approaching 90EF. Low temperatures will generally remain in the upper 50's to mid 60's Thursday morning. A cold front is forecast to move west to east across the state beginning Thursday evening, which will lead to the next chance for rainfall. Given that the front will be passing through most of the state during the late evening or early morning hours, rainfall area coverage is expected to remain on the scattered side, with some areas remaining dry. Best chances for rainfall late Thursday will be across far northern sections of the state. Cooler and dry weather is expected Friday statewide. |
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