Saginaw Bay area vegetable regional report – July 30, 2014

Cool wet weather may reduce pollination service from honey bees in some vine crops.

Please contact me at .(JavaScript must be enabled to view this email address) or 989-758-2500 ext. 202 to grab any suspected disease samples, or send the diseased plant parts to Michigan State University Diagnostic Services.

Consistent upper air troughs and cool weather patterns from the north have kept degree day accumulations lower than normal, but not as low as 1992. The rainfall and growing degree day (GDD) base 50 degrees Fahrenheit accumulations as of July 28, 2014 from MSU Enviro-weather stations at the Bay and Thumb area vegetable growing regions are as follows:

  • Romeo: 12.95 inches, 1458.3 GDD (+0.33 inches, and +128.1 GDD from last week).
  • Lapeer: 15.99 inches, 1397.6 GDD (+0.43 inches, and +109.2 GDD from last week).
  • Frankenmuth: 15.79 inches, 1410.1 GDD (+0.56 inches, and +116.4 GDD from last week).
  • Munger: 14.68 inches, 1424.6 GDD (+0.76 inches, and +117.8 GDD from last week).
  • Linwood: 14.82 inches, 1305.5 GDD (+0.92 inches, and +112.1 GDD from last week).

In my Michigan State University Extension visits to the major Macomb, Lapeer and Bay county vegetable areas, my best estimates of crop progress are below.

Sweet corn is being attacked by red winged black birds all over the Bay and Thumb. A combination and rotation of firecrackers, propane cannons, and visual scare tools have been successful for some growers. Other growers just have really good sweet corn.

Onions are sizing up, but are under heavy disease pressure in the Bay area. Bacterial leaf blight (P. agglomerans), purple blotch (Alterneria) and downy mildew (Peronospora) have been confirmed in the state, and should be managed with a rotation of fungicides. MSU recommends products like Bravo, Quadris, or Cabrio for purple blotch, and Ridomil, Revus, or Aliette for downy mildew. Mancozeb products work well on both diseases. Bacterial leaf blight may or may not respond to copper-based products, and water soaked leaves indicate that the disease has already commenced in breaking down the plant. Suppression is the best you will get.

Melons and watermelons are succumbing to root rots in some areas. There isn’t much you can do once the wet conditions favor root rots.

Summer squash and zucchini are being replanted for a second harvest.

Winter squash and pumpkin pollination may be impacted by this cool wet weather we’ve been having. These crops only bloom for about 6 hours, opening before dawn, and closing around noon. On cooler days they will stay open longer, but their nectar will evaporate and their pollen will become increasingly nonviable as the day progresses. Honey bees only pollinate well in dry weather above 65 F. However, in Saginaw temperatures remained below 65 F until 11:00 AM for the past two to seven days. Thus, on those days, pollination was minimized. This coming week may bring more moisture and cooler weather. In the future, make sure and place honey bee hives in view of the rising sun to enable them to warm up in the mornings. Consistent low temperatures also favor the production of female flowers, and this reduction of male flowers will also hinder pollen transfer for fruit.

Pickling cucumbers are being harvested, with 200 bu/A coming in from some fields. Defects haven’t been too different from past years, but pickles blooming this week may experience some pollination deficits due to the cool wet weather and cold nights keeping bees in their hives. Downy mildew has been confirmed in Tuscola County in a field that missed a preventative application due to rain. Some growers have been flying on fungicides in these events. Send any suspected downy mildew samples to the Hausbeck lab.

Tomatoes, peppers and eggplants are in various stages of growth and harvest. Various bacterial and fungal diseases are showing up in tomatoes, including bacterial speck and early blight.

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