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| Vegetable Crop Advisory Team Alert newsletter | ||||
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| Vol. 22, No. 13, July 25, 2007 |
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In this issue  European corn borer/ corn earworm update Aster leafhopper numbers increase Downy mildew update Pocket scouting guide for potato diseases available Regional reports Weather |
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| European corn borer/ corn earworm update Beth Bishop Entomology 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. You can find current degree-day accumulations for your area by consulting the degree-day table in this issue of the Vegetable CAT Alert, or by accessing the MSU Enviro-weather website at http://www.enviroweather.msu.edu. Select the nearest weather station from the pull-down list at the top of the page, then click on “vegetables”. The first selection, “Weather Summary” will generate a table that includes degree-day data. Look in the degree-day base 50 column to find DD50 accumulations by date. Corn earworm trap catches continue to be very low throughout Michigan Since corn earworm (unlike European corn borers) cannot survive the Michigan winter and must migrate into the state each year, precisely when they arrive each year and how many come is variable. Michigan corn earworm trap catch is now included on Penn State’s PESTWATCH sweet corn monitoring system’s website (http://www.pestwatch.psu.edu/sweetcorn/tool/tool.html). Growers can see the average daily trap catch for corn earworm at six or more Michigan locations and in neighboring states. This site will help us track the northern migration of corn earworm into Michigan each year. |
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| Aster leafhopper numbers increase Beth Bishop Entomology 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. At this infectivity level, celery fields should be treated for aster leafhoppers if five or more leafhoppers are found per 100 sweeps. However, the population level in this particular field/area appears to be lower than that; only 2.5 leafhoppers were caught in 100 sweeps. About two percent of aster leafhoppers collected from a carrot field in Mason County were infected with aster yellows. At this infectivity level, carrots should be treated if 25 or more aster leafhoppers are found per 100 sweeps. In this particular field, population levels were higher than the treatment threshold. The number of aster leafhoppers present in celery and carrot fields in Western Michigan has increased a bit over the past few weeks. However, the infectivity rate remains very low (no leafhoppers infected with aster yellows have been found in most samples tested by Diagnostic Services). We recommend a treatment threshold of between 25 and 35 aster leafhoppers per 100 sweeps for celery and 40 to 50 aster leafhoppers per 100 sweeps in carrots. Currently, pyrethroids remain the best choice for controlling aster leafhoppers in celery and carrots. See Bulletin E-312, 2007 Insect, disease and nematode control for commercial vegetables insecticides registered for carrots and celery. You can find this bulletin online at http://web4.msue.msu.edu/veginfo/E312. |
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Downy mildew update
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| Pocket scouting guide for potato diseases available Phillip Wharton and Willie Kirk Plant Pathology The new potato diseases scouting guide "A Pocket Guide to Disease Scouting in Michigan Potatoes" is now available for purchase from the MSU Extension Bulletin office. This is a comprehensive pocket reference text for use in disease scouting in Michigan potato fields. It provides information on the disease cycles and biology of common potato pathogens and on management options for their control. The guide may be used as a reference to help identify diseases while scouting and to guide timing of scouting activities. For more information, call MSU Extension Bulletin office at 517-353-6740. |
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| Regional reports 1 -- Southwest Ron Goldy Weather Temperatures during the week were generally below average (83oF) with highs of 73o to 85oF and lows from 51o to 65oF. The area received from 1.0 to 3.5 inches of much needed precipitation providing a brief slow down in irrigation activity with systems back to running full speed. Cooler temperatures have brought a much needed slow down for harvest activity. Crop reports Sweet corn harvest continues. European corn borer activity seems lower than normal this year. Tomato harvest from all types continues. Volume has increased as more fields come into production. Pepper harvest has slowed primarily due to current low prices. Some sunscald has shown up on harvested fields and some blossom end rot is also evident. Eggplant harvest should begin soon. Yellow squash, zucchini, cantaloupe and cucumber harvest continues with no problems. Early fields of cucumbers and squash are being removed and made ready for a second planting. Pumpkins are runnering, flowering and setting fruit, with some fruit soft-ball size. Watermelon is sizing well and harvest is expected to begin within two weeks. Squash vine borer trap counts have dropped to 4 per trap down from 24 last week. Virus levels remain low with only an occasional plant and fruit from the field being identified with symptoms. All stages of squash bugs can be found. |
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| 2 -- Grand Rapids Area Bill Steenwyk Weather Temperatures were a bit cooler this past week, but the unending dry spell continues. Parts of Van Buren County received a half to one inch of rain. Farther north, in central Allegan County, about a third of an inch fell, while Ottawa, Kent and Ionia counties had to settle for dampened pavement. Fields in central Ottawa County, similar to much of the region, have received a mere half inch of rain since July 1; 1.6 inches since May 28 and 3.3 inches since May 1. Place those numbers in the context of 15 inches of potential evapotranspiration loss since June 1, and the conclusion is obvious. Crop reports Insect and disease pressures in most crops are low. The main variables now are whether or not the fields are irrigated and how frequently. Fields receiving consistent irrigation are doing well. In non-irrigated fields, soil texture, structure and compaction dictates plant-available water and, accordingly, crop welfare. Despite the increased cost of supplying all that water, some farmers report that the reduced need for disease control measures more than offsets those costs. The occasional field has severe weed pressure. In this period of water deficit, competition from weeds is especially detrimental. On muck soils, celery is being harvested. Reported yields range from good to moderate. The last of the transplants are now, or will soon be in the fields. In some fields where the early crop was harvested, a second planting has been established. Aster leafhopper numbers remain low, with some reporting populations somewhat higher than before. Onion and leek appear to be doing well. Even the considerable acreage of non-irrigated onions continues their development. Some of the earliest plantings are lying down. Red beets are looking good, with harvest continuing. New radish plantings are growing where an earlier crop was harvested. On upland soils, cucumber harvest is underway. I found a few fields with small infestations of bacterial wilt. Melons, zucchini, and squash are developing well where irrigated. Large portions of non-irrigated fields show severe drought stress. Cabbage development continues well unless the grower hasn't been able to keep up with water needs. Tomatoes and peppers are developing normally. Sweet corn is perhaps, the most variable crop. Irrigated corn is developing normally and the early harvest is quite good. Some non-irrigated fields however are a complete failure. Other fields have poor tip fill or inconsistent maturity. Blackbird feeding is a major problem in some areas. |
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| 3 -- Oceana County Norm Myers Weather Drought has returned to our area with only a couple of hundredths of an inch of rain in the last ten days. Irrigation is once more running flat out where it is available. Crop reports This year’s crop of asparagus fern does not look that good, with generally small size and relatively few stalks per crown even after the rains we received on or before July 4. Tom-Cast sensors in full-season fields are now mostly at or near the 15 disease severity value trigger for the first purple spot spray. Rust and common asparagus beetle are also still active. In carrots, Disease Severity Values have also jumped greatly. While there is probably some alternaria blight active, Mary Hausbeck’s technician Brian Cortright did identify some of the disease symptoms we are seeing as bacterial blight. Carrots are wilting badly where irrigation is not available. Zucchini harvest continues for processing, but prices for fresh zucchini are so poor that most of that is being diverted to processing. I have seen no viruses yet, and with the dry weather phytophthora is also not an issue. In winter squash and pumpkins, scouts report some alternaria lesions, but no signs of any other diseases including powdery mildew yet. In sweet corn, I caught no corn earworm or European corn borer moths in my traps for the second week in a row. Snap beans’ late planting is now emerged and looks good so far. |
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| 4 -- Mason-Newaygo counties Jim Breinling Weather |
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| 5 -- Macomb, St. Clair and Lapeer counties Hannah Stevens Weather and crop conditions Much cooler temperatures over the past two weeks (a high of 85oF and lows ranging from 51-60oF) has felt more comfortable, but in Macomb County crops are suffering from the extended dryness. In central Macomb, less than 0.1 of an inch of rain has been recorded this month, less than 0.3 of an inch since June 6. Some areas in St. Clair and Macomb have received more, with isolated thunderstorms accounting for much of this. Crop reports Harvest of early sweet corn is beginning this week bringing with it the opening of farm markets for produce. The quality is variable but, by and large, clean and excellent considering the dry conditions. European corn borer trap catches for the past two weeks remain about the same as they have been in Central Macomb at an average of five per trap per week. At this location, it looks as if we may not get much of a break this year. No corn earworms have appeared in the traps this week. Many growers are now reporting some heavy losses due to Stewart’s wilt on some varieties in some locations. Summer squash harvest continues. Incidents of virus are few so far this season. Muskmelon harvest is beginning this week. Watermelon harvest will begin in a few days. Tomato picking is beginning. While I would expect to see more blossom end rot on the first fruits, it seems to be limited. Growers must be doing an excellent job with consistent irrigation. Fall crops such as broccoli transplants continue to be set. Miscellaneous Pollinators are more abundant than I have ever seen them in any and all flowering plants, cultivated and wild. Their humming may be heard from a distance in floriferous crops such as soybeans, and this morning five to six could be seen in each male pumpkin blossom. |
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| 6 -- Monroe County Paul Marks Weather Warm and very dry weather this last week has increased the stress on most crops and increased the cost of production on irrigated crops. The saving grace has been the cooler temperatures, especially the nights in the very low 50’s. For the month of July, according to the MSU MAWN station in Petersburg near the center of Monroe County, the total estimated evapotranspiration is now just over six inches. This is an average of 0.25 per day, during a period of 24 days, when precipitation has totaled just 0.56 inch of water. Crop reports Sweet corn harvest is now in full swing with growers packing a nice crop from fields that have been irrigated, and lower quality from non-irrigated fields. Corn borer and corn earworm activity has been very low. Tomatoes for fresh market are just getting started with good quality fruits being packed. Disease pressure is low from fungal pathogens, but bacterial diseases have marked some fruits. Processing tomatoes for early harvest appear to have good fruit loads, but vines are much smaller than in recent years. Some blossom end rot is evident. Later maturing varieties are now just beginning to show fruit. Vine crops have tolerated the dry conditions well, but are now showing stress in lower fruit numbers and size. Pumpkins are just beginning to set fruits. Downy mildew in our area is still limited to cucumbers, with the exception of one home garden of melons. Pollination has not been a problem as the bees, perhaps lower in numbers this year, have been able to work every day and all day with no rain to slow them down. Peppers are being harvested for fresh market with nice size and quality bells now being marketed. Banana peppers for processing are just beginning to be harvested this week. Plant sizes in both crops appear to be smaller than normal. Potatoes for fresh market are being harvested and packed, although still quite green. Tuber size is good from irrigated fields, but will be smaller from fields that lack irrigation, where vines are now maturing due to lack of moisture. Leafhopper numbers have been very low the last several weeks. |
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| Weather news Jeff Andresen Agricultural Meteorology Geography An upper air ridging feature anchored across the Great Plains region led to yet another abnormally dry week last week across most of Michigan and the Great Lakes Region (some lucky areas did receive significant rainfall, but were the exception rather than the rule). Since the end of the first week in June, precipitation deficits have grown in many areas to the two to four plus inch range, which unfortunately has also coincided with periods of greatest seasonal plant water needs. The lack of plant available water is currently most acute across southern and interior sections of northern Lower Michigan, and across western and central sections of the Upper Peninsula. |
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