West central Michigan vegetable update – May 29, 2019
Asparagus harvest is heading into week two with sporadic but big pickings. Overall field work has continued but the abnormally cool, wet weather is impacting everybody.
Overall, the forecast suggests we will move into a drier and cooler weather pattern. We will see a system move through tonight, bringing chances for precipitation through Thursday morning, May 30. The best chances will appear across the far southern lower, with chances decreasing to the north. Overnight Friday into Saturday we will see a cold front move through, which will bring some light, scattered showers and cool weather. This front will cut off Gulf of Mexico moisture. As a result, the next chance for rain after Saturday morning will be the middle of next week.
In the medium term, both outlooks call for cool but drier than normal weather for June 3-11. This change will occur as a trough in the Jetstream is forecast to move over the Great Lakes region, bringing us into a cool northern airmass that is cut off from Gulf moisture.
Asparagus harvest has been ongoing, with marketing and pricing the biggest challenges.
Common asparagus beetle activity was detectable for the first time this past Friday in one out of three problem fields I've been monitoring. The weather was cool and rainy, so I did not detect beetles, but they had been active (likely during a brief warm spell), and eggs were present on two of 100 spears I checked along field edges. If you scout for beetles during cool weather, check for egglaying on spears along the worst edge of your hottest beetle field; beetles are easier to spot but aren't very active in cool, cloudy weather. If you detect eggs, consider applying insecticide after a picking on a warm, sunny day.
For celery, aster leafhopper samples taken on May 27 from Allegan and Van Buren counties had 0% infectivity.
Cole crop planting has continued in west Michigan. Imported cabbage worm caterpillars and diamondback moth adults have been present in brassica fields. Coragen is an effective product that helps conserve beneficials. Another option is to use a tray or transplant-hole drench of Verimark; this can protect against cabbage maggot and provide early season caterpillar control.
Ask you chemical dealer if Harvanta is available in the pipeline. It is in the same chemical class as Coragen and Verimark and is labeled for leafy brassicas for caterpillar control. Pyrethroids like Brigade and Baythroid are also effective, but will kill natural enemies that can help keep aphids and diamondback moth in check. There are other selective products available (e.g., Avaunt, Confirm, Intrepid), but I do not have experience with their efficacy. Bt products like Dipel remain good options for organic growers (and even conventional growers), but need to be applied when caterpillars are small and have a short residual activity.
Onions planted in early April are doing good, and there are some nice onion stands out there, but later planted onions have been slow to develop. Michigan State University Extension weeds specialist Bernard Zandstra recommends applying Goaltender at the one true leaf stage, which is especially important for smartweed control.