West central Michigan vegetable regional report - July 30, 2014
Cool weather has challenged crop development and favored some crop diseases not typically present at observed levels.
Symptoms of aster yellows and Cercospora continue to be present in West Michigan carrot fields.
An area scout reports spotty aster leafhopper captures this week. Scattered aphid colonies were also developing in area celery fields. Captures of variegated cutworm have also continued, and a local scout reports the first sighting of a celery leaftier larvae in a single West Michigan location.
Poor pollination weather has challenged area vine crops. As a result, female flowers without sufficient pollination produce fruit that drops off the plant or is misshapen. Symptoms of Phytophthora capsici were also present and severe in one West Michigan location this week. Areas that have continued to receive rainfall after this spring’s wet weather, and have a history of this disease, are at special risk. Foliar applications of fungicides can help protect fruit from further infection. Alternation of Presidio (a.i. fluopicolide; note the label requires a tank mix partner with a different mode of action) with Revus (a.i. mandipropamid) on a weekly basis, in this order, can help when used according to the label. Fungicide applications will be more effective if you limit further spread of inoculum within fields by disking under areas with affected fruit, including a disked up buffer zone around these hot spots. In addition, limit spread to other fields by making infested areas your last stop and power washing equipment afterwards. Cucurbit downy mildew has spread to a newly detected location in Tuscola County. Keep an eye out for this disease.
Mary Hausbeck of Michigan State University Extension has detected onion downy mildew earlier than normal this year, and cool weather continues to favor its development. As a result, this disease has the potential to wipe out fields quickly if it is present and a good fungicide program targeting this disease is not used. Fungicides for this group of pathogens—which includes late blight, cucurbit downy mildew, and other water molds—include products that are not typically used in onion fungicide programs, and that are different than those used for diseases such as botrytis. In other crops, the following fungicides have proved effective for water molds: Revus (a.i. mandipropamid), Forum (a.i. dimethomorph), and Zampro (a.i. ametoctradin/dimethomorph). Consider alternating mancozeb with one of these materials to bolster your defense against late-season losses to downy mildew.
According to forecast models, there is minimal risk of continued corn earworm migration this week, as the weather forecasts northwest to southeast airflow. For trap catches, one corn earworm moth and ten western bean cutworm moths were captured over the past seven days in an Ottawa County location.