West central Michigan vegetable update – May 31, 2017
Asparagus quality is excellent, early-season insect pests are being detected in vegetables.
For growers using compost, remember that compost piles that are not managed properly may not produce enough heat to kill weed seeds. Talk with your compost supplier to see if they are following best practices and see “Compost Production and Use” from the Michigan State University Department of Horticulture.
You can also spread compost in a flat in the greenhouse and water it to see if any weeds germinate. Be aware if you do this in spring, winter annuals that require high temperatures to break dormancy may not germinate. It is also possible for weed seeds to disperse from other parts of your farm to your compost pile, so keep in mind your pile’s history when considering where weeds are coming from.
Asparagus harvest is continuing with excellent tip quality due to cooler weather. Seedling pigweed was readily observable in a research plot I visited yesterday, May 30. If you have a field with a carpet of pigweed seedlings, this is an ideal stage for applying Sandea (active ingredient halosulfuron, one day pre-harvest interval).
Experience suggest that efficacy of this product for pigweed control declined over time, making it even more important to target small seedlings, and suggests in-season pigweed control can help growers avoid having a field of pigweed that is hard to pick through at the end of the harvest season.
Some growers have observed slight crooking of spears. In plots at the research farm, most of these crooks were facing west. When it is cold, the morning sun can warm the east side of growing shoots while the west side remains cool. This can cause slight crooking resulting in spears “watching the sunset” as the east side grows faster than the west side of the shoot.
For carrots, aster yellows was detected in a small sample of aster leafhoppers collected in Mason County on May 25.
An aster leafhopper sample submitted May 25 from Allegan County showed zero percent were carrying aster yellows on celery.
For cucurbits, one early season pest of note is seedcorn maggot. Research with cantaloupe at Purdue University showed soil temperature can have a significant effect on the risk of damage due to that pest. Specifically, the risk of seedcorn maggot damage declines greatly once maximum daily soil temperatures at 4 inches deep consistently reach 70 degrees Fahrenheit.
You can check soil temperatures with MSU Enviroweather. Look at the “max soil temp at 4 inches” column under the “soil conditions” link on a station’s webpage. For example, this is the data for the Elbridge/Hart station. Direct sowing of zucchini has commenced in Oceana County.
For leafy cole crops, diamondback moth larvae were observed in brassicas in southeast Michigan. Caterpillars of this pest are easy to identify as they wiggle when you poke them. Thresholds for control are in the Midwest Vegetable Production guide. Early in the season, Bt products can be an effective tool to control caterpillars while conserving beneficials that can keep populations in check later on.
Early plantings of chip potatoes in Montcalm County were 5-6 inches tall and the first hilling, cultivation and sidedressing were upcoming.
True armyworm larvae, hatched from eggs laid by flights of moths in late April, could be feeding on leaf edges of sweet corn right now. Spotty damage has been detected in east and southeast Michigan sweet corn. The best time to scout for this pest is early in the morning because it hides during the day. You can target high-risk fields for scouting, which includes those planted into a heavy rye cover.
Overall, damage from this pest is very spotty, so scouting can help you detect those fields where there might be a problem. This pest is easy to control with pyrethroid insecticides if problems are spotted before they become severe.