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| Vegetable Crop Advisory Team Alert newsletter | ||||
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| Vol. 22, No. 3, May 9, 2007 |
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In this issue Aster leafhopper and aster yellows testing 2007 Managing cereal rye cover crop to improve benefits in vegetable production Glyphosate-resistant horseweed confirmed in Michigan Management of glyphosate-resistant horseweed (marestail) Regional reports Weather news |
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Aster leafhopper and aster yellows testing 2007 Leafhoppers can be collected with sweep nets. After the leafhoppers are counted (to determine the number of leafhoppers per 100 sweeps), place them in a plastic bag or other container and keep them (preferably) frozen or refrigerated until shipping. Leafhopper samples should be enclosed in small box-like containers (for example, plastic containers used for storing food) and then shipped to Diagnostic Services via priority mail. Alternatively, the leafhopper samples can be delivered directly to Diagnostic Services on the campus. Each sample should be marked with location and date collected, and multiple samples can be shipped together. The aster leafhoppers do not have to be kept alive. However, we recommend that you avoid mailing the samples on Thursday or Friday so they do not sit in the post office over the weekend. Please fill out a submittal form for each sample. For more information on how to submit samples to Diagnostic Services, please see http://www.pestid.msu.edu/. |
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| Diagnostic Services will need a minimum of 40-50 leafhoppers to run a test. However, several smaller samples from nearby sites can be grouped and tested together. How will I receive results? Results will be provided to cooperators by MSU Vegetable Entomology. Cooperators should indicate which contact method (phone, fax, email, etc.) they prefer. Results will be delivered either the day of testing (in most cases) or the next morning. We will provide the estimated percent infectivity of aster leafhoppers and suggested treatment threshold for that crop for each sample tested. What is the cost for aster leafhopper testing? The cost of testing varies with the size of the sample. We recommend a minimum sample size of 40 leafhoppers; anything less will give unreliable results. Cost for 40 leafhoppers is approximately $25 to $30. More reliable results can be obtained with more leafhoppers. Each additional 8-10 leafhoppers increases the cost of the test by $5.00. For more information please contact: Beth Bishop (517) 355-5154 bishopb@msu.edu |
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| Managing cereal rye cover crop to improve benefits in vegetable production Cereal rye is among the most common cover crops used in vegetable production systems in temperate regions. Because of its ability to survive winter, cereal rye fits easily into most vegetable rotation systems. In early spring, rye grows slowly but as temperature increases, it quickly reaches its exponential growth stage in late April to early May. During the exponential growth stage, biomass accumulation increases rapidly. While biomass accumulation is desired to build soil organic matter and soil quality, it is important to remember that this may cause nutrient tie up in the cover crop residue if the cover crop is not managed adequately. Also, rye produces chemicals that have been shown to injure vegetable crops, including species established from transplants if residues are not managed properly. For no-till production systems, the objective is to maximize biomass production and to provide adequate soil cover for the entire growing season. This note deals mainly with rye cover crop management in conventional tillage systems. Here are a few tips for rye cover crop management. Kill rye cover crop when it is still tender Experienced growers would tell you that it is better to kill rye before it reaches your knees. Indeed, the cover crop should be killed at the vegetative stage when the tissue is still tender. Ideal stage would be at jointing during the initial phase of stem elongation but before flag leaf stage. When rye reaches boot stage, it becomes difficult to kill, the residue breaks down much slowler due to high C/N ratio, and there is greater potential for nutrient (especially nitrogen) tie up. If for some reasons rye cover crop gets out of control, consider mowing it to speed up tissue break down. Incorporate fresh residue into the soil Incorporating fresh residue into the soil will enhance the population of soil microorganisms that help break down the residues and release nutrients for the following cash crop. When residue is allowed to dry on the soil surface, as is the case for most herbicide-killed cover crops, subsequent residue and break down becomes slower. Allow enough time between incorporation crop planting Studies with many cover crops have shown that a period of about two weeks between fresh residue incorporation and crop planting is necessary to improve nitrogen availability to the following crop. This also reduces the risk of crop injury from allelochemicals released by the decomposing residue. Due to the high C/N ratio in rye, a longer period between cover crop kill and crop planting is mandated. This period will depend on the stage when rye was killed since younger tissue breaks down faster than mature tissue. Growers should be particularly careful when they are sowing small seeded vegetable crops. Chemicals released from the decomposing rye residue may lead to poor crop stand especially when rainfall is not adequate to leach the chemicals. In most vegetable production systems, benefits of rye cover crop are optimized when it is killed at a tender (vegetative) stage, incorporated into the soil as green manure, allowed enough time for residue breakdown before planting, and when rainfall or irrigation is adequate. |
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| Glyphosate-resistant horseweed confirmed in Michigan Editor’s note: The following article was published in the field crop edition of this newsletter and will interest many vegetable growers, too. Glyphosate-resistant horseweed (Conyza canadensis) has been confirmed in a Christmas tree plantation in Mason County, Michigan. This detection represents the 16th state in the United States with glyphosate-resistant horseweed (Heap 2006). Also known as marestail, horseweed is a troublesome weed in no-till field crops, fruit crops, tree plantations and nurseries throughout Michigan. For the past several years, MSU Diagnostic Services has been screening horseweed populations for glyphosate, ALS, triazine and PPO resistance utilizing greenhouse whole plant assays. ALS-resistant horseweed has been documented in 35 field crop locations and seven Christmas tree plantations spanning 14 Michigan counties. Triazine-resistant horseweed has been documented in two field crop locations, 12 Christmas tree plantations and 4 blueberry plantations spanning five Michigan counties. While glyphosate resistance was suspected by the growers in some of these populations, herbicide resistance proved not to be the case until now. The initial greenhouse screen of this Mason County horseweed population yielded survivors of glyphosate at 1X and 4X the labeled rate (22 and 88 oz/A Roundup WeatherMAX 5.5L, respectively, plus AMS at 17 lbs/100 gallons). These plants were stunted and delayed in development, but were able to bolt and produce seed. Seed was collected from these survivors and subsequent dose response experiments were established with the original field population and greenhouse population. Horseweed plants were treated with glyphosate at 0.01X, 0.1X, 0.25X, 1X, 4X, 10X and 100X the labeled rate (0.22, 2.2, 5.5, 22, 88, 220, and 2200 oz/A Roundup WeatherMAX 5.5L, respectively, plus AMS at 17 lbs/100 gallons) when rosettes were 2 to 3 inches in diameter. Visual weed control ratings and dry weights were taken 21 days after treatment. While GR50 values have not yet been tabulated, these experiments consistently show the ability for this population to survive glyphosate at 1X, 4X and occasionally 10X the labeled rate. The attached picture shows representative plants for each treatment and population. Testing for herbicide resistance If herbicide resistance is suspected in any weed species, samples may be submitted to MSU Diagnostic Services for a resistance screen. In most circumstances, a whole plant pot assay established from seed will be the standard test for herbicide resistance confirmation. Mature, high quality seed or seedheads should be collected from suspicious plants in late summer or fall and submitted in a paper bag or envelope. Do not seal plants or seed in plastic! Generally, fees associated with herbicide-resistant weed testing are $50 per sample per herbicide site of action (i.e. ACCase inhibitors, ALS inhibitors, Photosynthesis inhibitors). Each additional site of action is $20 per sample. However, costs associated with horseweed samples submitted by Michigan soybean producers are covered by check-off dollars through the Michigan Soybean Promotion Committee. Samples submitted from out-of-state producers are $75 per site of action and $30 for each additional site of action. Please contact Steven Gower (517-432-9693, sgower@msu.edu ) with any questions regarding resistance confirmation or sample collection. Samples can be mailed to: Michigan State University Diagnostic Services - Attn: Steven Gower 101 Center for Integrated Plant Systems East Lansing, MI 48824-1311 |
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Management of glyphosate-resistant horseweed (marestail)
Management of glyphosate-resistant horseweed
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Regional reports Temperatures during the week ranged from highs of 63o to 80oF and lows from 44o to 60oF. Soil conditions are extremely dry in the top four inches and soil temperatures are in the lower 60s. We have had no rain over the reporting period and are in need of rain for some field activities to continue. Conditions have been good for transplanting and seeding providing irrigation is available. Crop Reports Transplanting and direct seeding continues. Early transplants are being set outside of tunnels. Dry soil has slowed plastic laying in some areas. Asparagus harvest continues with some purple spot symptoms showing up, which is not surprising given the weather conditions the area experienced over the past two weeks. Other crops are progressing well with no problems evident at this time. |
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2 -- Grand Rapids Area Until today's rain, tilling, planting and spraying has been continuing at a rapid pace, especially on muck and coarse-textured mineral soils. Crop reports Most of the onions are in the ground, with many acres emerged in Allegan, Kent and Ottawa counties. Onions planted late March in Ottawa County muck fields were subjected to the cold and snow that followed, but are up three to four inches and doing well. Perhaps a third of celery transplants are in the ground. Radish, parsnips, and leeks, among many others, have been planted as well. Some fields were being irrigated to maintain new transplants placed in the drying upper inches of topsoil. Some report that cabbage transplanting has been somewhat delayed this year, but sweet corn planting seems to be more on-schedule, with some beginning to emerge. Many acres of upland vegetables, especially on medium- and fine- textured soils, have yet to be planted. No incidences of significant pest problems have been reported. |
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3 -- Oceana County We are getting rain this morning, May 9. I had a quarter of an inch in my gauge before I left home, but Hart appears to have had less rain. Night-time temperatures have risen into the 50s the last couple of nights and winds have dropped, which has allowed growers to get on some sprays. While there is still plenty of subsoil moisture, dry, easterly winds have dried out the surface moisture allowing area growers to get in and plant some fields that were formerly too wet. Crop reports Asparagus is growing well. The first couple of pickings have had little or no purple spot and hasn’t suffered from sand damage, even though winds have been high. Exceptionally heavy rye cover crops are probably responsible for holding sand in place. Weed control in most fields is excellent. Much of it got put on before the one-inch rain we received on May 1. Growers with year-old plantings have mostly finished taking the two to three pickings we customarily take on those fields and are letting fern develop. Planting of new fields continues. We should have enough new fields that have had the Cannonball soak to get a good handle on how well that will work. Early cutworm problems were taken care of with insecticide sprays. I did have my first report of a common asparagus beetle adult yesterday. Fresh prices are good enough that some growers were moving all of their early pickings to fresh packers. Processing prices are also up somewhat, and demand from processors is strong so far. Labor is still a problem, although the shortages are spotty, with one grower having plenty of labor and the next one being very short. The real test of our labor supply will be when we get a prolonged period of 80 degree weather. Carrot growers are finishing up planting. Some fields emerged during the wet period last week or the windy period early this week and no pre-emergent Lorox was put on them. Stands are reported to be good. |
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4 -- Mason-Newaygo counties No official record of precipitation was recorded during the past seven days at the Ludington and Fremont MAWN stations. Rainfall is occurring at this time on May 9. Strong winds during the latter part of the week of April 30 dried the soil surface resulting in soil blowing in some fields on May 5. Temperatures generally remained seasonal during the past week. A warming trend resulted in 80 degree temperatures on May 8. Crop reports Onion planting in Newaygo County should be completed this week. First plantings are emerged and at flag stage. Carrot planting has been completed by most growers. There are some growers, however, that need to continue on a planting schedule into June. First plantings are emerged and at the cotyledon stage. Potato, parsnip, turnip, and spinach planting continues. First plantings of slicing cucumbers have been done. |
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5 -- Macomb, St. Clair and Lapeer counties There was scattered frost in the northern parts of the region on May 6 and 7, but mean air temperatures in central Macomb have ranged from the high 50’s to 65ºF this past week with a high approaching 85º F yesterday. Mean daily soil temperature on mineral soils have been no lower than 56º F. These numbers, as well as accumulated DD, are very similar to this period of time last spring, however, planting and crop development is behind this time last year. This week has been a tremendous one for seeding, transplanting and other field activities and the rainfall we are receiving now is timely for helping transplants getting established and bringing up seedings. Crop reports Potatoes are being planted. Early plantings of cabbage and other cole cropsare getting established. While some growers may have gotten an earlier start, I expect most early sweet corn on bare ground is just beginning to emerge. Tomatoes, peppers and vine crop transplants are hardening off, and planting is beginning. Onion, carrot, radish and lettuce planting on muck soil continue with early plantings completed. Winter spinach is being harvested for retail sales. |
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6 -- Monroe County Our area has been dry for the last 14 days. Many fields of newly set transplants could use a light rain to get them established. Yesterday’s high air temperature of mid to upper 80’s combined with nearly reaching 80 degree soil temperature for the first time this season, made a large difference in plant development and stress, as was the case for newly set transplants. For this last week, our daytime high in soil temperature has been in the low 70’s and the night time low has been in the low to mid 50’s. Crop reports Cabbage planted early has made good growth this last week. I have seen small diamondback moth larvae feeding in several fields with infestation levels just above 10 percent of the plants. Tomato planting has been at a rapid pace this last week for processing. Most early season fresh market tomatoes are planted. New growth is evident on these early market tomatoes that were planted seven to ten days ago. Pepper planting has begun this week. Sweet corn planted very early in April is now at the 3 to 4 leaf stage in open fields. I have not seen any signs of flea beetle feeding. Some vine crops have been planted this last week in open fields in an attempt to keep up with the growers who have crops in the fields under tunnels. Potato emergence has been slow in fields that were planted in early April, even though now they have been in the soil for more than five weeks. Later fields are now being planted. I have not seen any potato beetles yet this season. |
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Weather news On the morning of Wednesday, May 9, a weak frontal boundary stretched from Texas northeastward to Lower Michigan. This front is part of the same weather system associated with the major outbreak of severe weather across much of the central United States last weekend. Fortunately for us, this system is now much weaker than it was earlier and is expected to bring only the chance for showers and thunderstorms Wednesday into early Thursday. A second and stronger cool front is forecast to move through the state from northwest to southeast Thursday night and Friday, bringing the chance for a few isolated showers (most locations in the state will remain dry). Fair and dry weather is expected statewide Saturday and Sunday. Temperatures will fall back from daytime readings in the upper 70's and low 80's Thursday, to the upper 50's far north to the upper 60's to low 70's south by Saturday. Low temperatures will generally range from the low to mid 50's south Thursday morning, falling back to a range from the upper 30's north to the upper 40s south by Sunday. |
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