Saginaw Bay area vegetable regional report – August 6, 2014

Disease pressure in vegetable crops continues as we head into August.

Advanced stages of downy mildew on cucumbers.
Advanced stages of downy mildew on cucumbers.

Rainfall and growing degree day (GDD) base 50 degrees Fahrenheit accumulations as of August 6, 2014 from Michigan State University Enviro-weather stations at the following Bay and Thumb area vegetable growing regions are as follows:

  • Romeo: 14.15 inches, 1604.2 GDD (+1.2 inches, and +145.9 GDD from last week).
  • Lapeer: 16.82 inches, 1532 GDD (+0.83 inches, and +134.4 GDD from last week).
  • Frankenmuth: 17.17 inches, 1543.4 GDD (+1.38 inches, and +133.3 GDD from last week).
  • Munger: 15.42 inches, 1567 GDD (+0.74 inches, and +142.4 GDD from last week).
  • Linwood: 17.66 inches, 1438.6 GDD (+2.84 inches, and +133.3 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 sequentially harvested, with some growers going through early day varieties so fast that they have to shut down for ripening.

Onions are laying down in some places. Downy mildew and bacterial pressure continues.

Melons and watermelons are getting powdery mildew, and downy mildew was spotted on the muskmelon sentinel plot at the Saginaw Valley Research and Extension Center yesterday, Aug. 5. Fusarium wilt has been diagnosed across the state and is best prevented with resistant varieties. (See page 97 of the Midwest Vegetable Production Guide for Commercial Growers.)

Summer squash, zucchini, winter squash and pumpkins are getting powdery mildew across the region. If left untreated, leaves will die and the lack of shade cover will harm the fruit. Quintec and Torino work well on powdery mildew. Squash bugs have been found in low numbers. Aphids have been spotted in the southern tier of the state, and in the southwest, cucumber mosaic and zucchini yellow mosaic virus have been diagnosed.

Downy mildew is in many pickling cucumber fields that are close to harvest, but in low numbers. However, stay on top of things because outbreaks can happen rapidly, especially in mixed veggie fields. Send any suspected downy mildew samples to the Hausbeck lab.

Field-planted tomatoes, peppers and eggplants are starting harvest. Various bacterial and fungal diseases are showing up in tomatoes, including bacterial speck and early blight. Remember, streptomycin cannot be used on field tomatoes. Some bacterial resistance to streptomycin and copper has been observed. If you think your copper applications are not working, please contact an MSU Extension educator to collect or ship these to campus for analysis.

Phytophthora late blight has been found in greenhouse tomatoes and can be identified by hard brown lesions on green fruit and by large amorphous stem lesions. It can be controlled relatively well with the same chemicals used to prevent Alterneria early blight and Septoria leaf spot.

Please contact me at or 989-758-2500 ext. 202 to grab any suspected disease samples, or send the diseased plant parts to MSU Diagnostic Services. If you’ve missed out on the recent rains, disease will still be spreading during nighttime and morning dew periods. 

Did you find this article useful?