West central Michigan vegetables regional report for July 24, 2013
Growers should keep on top of fungicide spray programs as 2013 weather has been more conducive to disease development than last year.
Spray programs for asparagus diseases are now the major focus in west central Michigan. Growers with center pivots irrigated last week given recent hot weather.
Celery scouts report that captures of variegated cutworm adults have increased to high levels across the celery-growing region. Be on the lookout for egg masses and caterpillars. Aster leafhopper numbers have also started to increase in some locations.
In cucurbits, summer squash and zucchini harvest is ongoing in Ottawa County, and either has started or should start soon in Oceana County. Powdery mildew has been detected in Oceana County. Given weather conditions this Monday and Tuesday (July 22-23), cucurbit downy mildew, which has been detected in Allegan, Monroe, Lenawee and Tuscola counties, may have spread to new locations within the southern half of the Lower Peninsula. If you suspect this disease is present, please contact your Michigan State University Extension county educator. Reporting its presence will improve our ability to notify others with at-risk crops.
There have been more reports of symptoms of Phytophthora capsici in cucurbits. Note, in cucumbers symptoms are primarily found on the fruit, while other cucurbits may display vine-wilt or fruit symptoms. Growers using surface water for irrigation, or with plantings in fields with a history of this disease, should especially be on the lookout for symptoms.
Squash vine borer eggs that I detected on July 11 in Muskegon County are now in the larval stage and have been feeding for the past week or so. Feeding activity is evidenced by frass (insect excrement) that they push out of their entrance hole in the vines as they feed.
Entrance hole made by a squash vine borer caterpillar feeding in
a squash vine. Note sawdust-like frass outside the hole.
Photo credit: Ben Werling, MSU Extension
Initial symptoms of bacterial rot have been detected in a high percentage of the onion fields scouted by researchers in the Hausbeck lab at Michigan State University. Pictures of two types of symptoms are below; either one or both of these symptoms can be found in the same plant. The first set of symptoms includes the presence of water-soaked lesions on outer leaves, followed by leaf death. The second set includes death of the inner leaves of the onion plant. Other diseases, including botrytis leaf spot and anthracnose, have also been observed in onions; cool, wet weather earlier this year was favorable for these diseases.
An onion plant with its outer leaves dying; prior to death, leaves
may initially have water-soaked lesions. This symptom can occur
independent of, or along with, symptoms pictured below.
Photo credit: Hausbeck Lab, MSU
An onion plant with a dead inner-leaf. This symptom can occur
on plants with bacterial rot either independent of, or along with,
symptoms pictured above. Photo credit: Hausbeck Lab, MSU
Regarding potatoes and tomatoes, weather has been such that disease severity values, which are weather-based numbers used for predicting late blight risk, have been very high in west central Michigan. No new outbreaks of late blight have been confirmed since its initial detection in Allegan County. Toxic seed piece syndrome has been observed in some potato plantings due to recent weather conditions. Tomato diseases, including early blight, septoria leaf spot and anthracnose, have been much more prevalent this year than last year. Growers should maintain a regular spray program to control these diseases.
In sweet corn, over the period July 11-18, I captured eight corn earworm moths in one trap in Hart Township, Oceana County; zero European corn borer adults in three traps in Hart Township; and two western bean cutworm adults in one trap in Hart Township and 16 in a second trap in Weare Township in Oceana County. I detected no western bean cutworm egg masses on 100 plants yesterday (July 24) in a sweet corn field just starting to tassel in Ottawa County. To our east, larger western bean cutworm captures have occurred (100-plus moths per trap) with some egg masses detected in field corn. Sweet corn harvest has now started in at least one location in Ottawa County.