West Central Michigan vegetable regional report – May 7, 2014
Field operations have been slowed by cool weather, but there are still pests to be on the lookout for.
Watch tomatoes for tobacco mosaic virus if you grow vegetable transplants and ornamentals. Michigan State University Extension specialist Mary Hausbeck reported that some petunia stock has been identified as carrying tobacco mosaic virus into area greenhouses. This virus, unlike insect-carried ones, is spread mechanically: if you brush up against infected plants you can then carry it to uninfected ones. This means that it could be carried from bedding plants to your veggie transplants, especially solanaceous veggies like tomatoes, peppers and eggplant.
Weather is ripe for seed corn maggot. Seed corn maggot damage is worse in cool soils and occurs on young seedlings of sweet corn, snap beans, chenopods, onions and cucurbits. Currently, growing degree day models suggest the peak of adult egglaying is occurring now or will occur within the next week across the region. Once maximum soil temperatures at 4 inches are above 70 degrees Fahrenheit, the risk declines. Soil temperatures are well below this now, which means they are attractive to egglaying flies at a time when seedlings are emerging and susceptible. Over the next few weeks, look for wilting seedlings and dig them up to look for tiny, white larvae.
All management is preventive; once damage is done the only option is replanting. Seed treatments containing the a.i. thiomethoxam, spinosad and chlothianidin can protect young plants. Row covers can help protect early plantings of sweet corn and spinach, as long as there are few pupae in the soil, which could produce emerging flies within the low tunnel that lay eggs on young plants.
In Southwest Michigan, asparagus growers have commenced harvest and are on roughly their third picking, while major harvest is expected to commence next week in Oceana and Mason counties. Rye was dying in Oceana County fields as of Monday, May 5. In cool weather like this, rye can take five days to die after glyphosate application. Grass-herbicides including Select Max (a.i. clethodim), Fusilade (fluazipop-P) and Poast (sethoxydim) have a one-day preharvest interval (PHI), are safe for asparagus, and are available to use if rye is not dying and harvest is approaching.
Carrot planting was delayed in some Oceana County locations last week with wet weather. Planting had resumed as of Monday, May 5, and will continue pending rain delays.
Celery transplanting has continued in Ottawa and Kent counties. Note we will experience southerly winds in the next week, which could bring aster leafhoppers up from southern areas.
Cole crop transplanting has continued this week in Ottawa County. Cabbage maggot growing degree day models ran with data from the Hudsonville and Sparta Enviro-weather stations suggest flies will begin to be active over the next week, with peak egglaying still 300-plus degree days base 43 F away.
Onion seeding had been finished within the last few days in Kent County as of yesterday, May 6. Seedlings have yet to emerge. Keep an eye out for seed corn maggot damage this year. Soils are cool, seeded onions are either not emerged or very young and susceptible, and growing degree day models suggest flies are laying eggs. FarMore FI500 seed treatments contain thiomethoxam and should provide protection. For organic growers, FarMore OI100 (a.i. spinosad) is an effective seed treatment; ask your seed dealer.
Reports suggest potato planting has started over the past week to our east in Montcalm County. Given that soil cover insulated soils this winter, weather models predict there is a high risk for volunteer potato survival across southern Lower Michigan. The late blight pathogen can survive overwinter in volunteer potatoes and spread to other plants. If you are a small grower, you can rogue out these plants this spring to reduce risk of late blight.
Sweet corn planting has continued this week, with emergence of early plantings in Southwest Michigan. Black cutworm flights have been heavy to our south in Indiana. This migratory pest rides air currents from the South to the North each year. Females lay eggs on winter annual weeds. After eggs hatch, caterpillars feed on weeds, but will move to the main crop when weeds are killed and can cut off seedlings at their base. Keep an eye out for cutworm damage over the next few weeks. Pyrethroids provide effective control, but are wasted if this pest is not present, so scouting is important. No moths have been captured in traps in Montcalm County.