Central Michigan vegetable update – August 8, 2018
These small frequent rain showers are keeping leaf surfaces wet for longer periods and are a concern from a plant disease standpoint.
We’ve had predominantly moderate temperatures for the first week of August, with highs in the 80s and lows in 50s and 60s. Small amounts of rain have been received in most areas over the past week with a few locations getting an inch or more. The brief rain showers have given some relief from the predominantly dry weather, however, many are feeling the effects, and especially small-scale market gardens that rely on surface water as many of those sources are drying up. These small frequent rain showers are keeping leaf surfaces wet for longer periods and are a concern from a plant disease standpoint.
The first chip potatoes of the season have been desiccated and will be harvested soon for direct shipment to the processor. We are still at least a month away from harvesting potatoes for storage, however, direct shipments will pickup from this point to the end of fall. Michigan State University Extension documents no reports of late blight in Michigan as of this writing. Growers are advised to be vigilant and continue preventative spray applications on schedule. It is also advised to monitor volunteer potatoes and control them if not done previously.
For pickles, I do not have any confirmed reports of downy mildew in this part of Michigan yet, however, growers are advised to continue downy mildew fungicide spray programs. The disease has been confirmed in Michigan. See confirmed downy mildew reports in Michigan from the Hausbeck Lab at MSU.
Harvest of summer squash continues with powdery mildew becoming more prevalent.
Sweet corn harvest continues. See insect comments below
Table beets are sizing well and harvest is occurring for the fresh market. Cercospora leaf spot is a concern going into August and should be monitored for.
Japanese beetle adults continue to feed on various crops including asparagus fern and sweet corn silks. Defoliation can be severe and treatable but usually in small areas where the beetle is congregating. It is important to remember that silk feeding in sweet corn becomes no more than an aesthetic issue after pollination has occurred.
Western bean cutworm flight has all but ended. Larvae range from first to third instar and can occasionally be found in corn silks and if you are patient you can find them in dry beans and snap beans. Scouting in sweet corn was addressed in this article: Scout sweet corn for western bean cutworms, and you can find more information about scouting in dry beans in this article: Western bean cutworm flight in central Michigan is up from recent seasons.
Black light traps are indicating European corn borer second generation flight is underway. This is a pest that is making something of a comeback as some corn grain producers have opted to grow conventional non transgenic corn in the past few seasons or have cut cost by purchasing corn hybrids without Bt traits.