Zucchini Problem - Pest?

Asked July 14, 2014, 1:11 PM EDT

I'm seeing an issue with my zucchini plants that I've not seen in all the years I've grown them. This year I have two plants which are three feet in diameter; I planted them with a little Nutrimulch. As shown in the first picture, they are adjacent to each other a few feet apart. We have been getting good zucchini from both plants for the last 2&1/2 - 3 weeks. Both get the same amount of water and sun. Seemingly overnight, the plant on the left in the first picture seems to have wilted and mostly died. (It is hard to see, but a few leaves on the back side still look healthy, and there is a small, but healthy zucchini fruit still on there). About a week before this occurred, I noticed several fruit on the plant on the right (the healthy-looking plant) that look like the close-up in the second picture. Is this some kind of insect or other pest? Or is it a symptom of some other problem? Thank you!

Utah County Utah vegetables zucchini

1 Response

I'm located in Oregon and the recommendation for chemicals my be different in Utah

PNW Plant Disease Management Handbook
Printed page URL: pnwhandbooks.org/plantdisease/node/3953

Squash (Cucurbita spp.)-Sclerotinia Stem Rot

Cause The fungus, Sclerotinia sclerotiorum, has been observed frequently in Oregon, particularly on zucchini and kubocha squash. This fungus overwinters in soil as sclerotia or on old infected plant material. The greatest losses are in pumpkins or squash piled in the open, or in storage, following preharvest infection. In storage, the disease is called watery soft rot.

Symptoms Plants wilt, and affected tissue near the soil line becomes water soaked. A profuse, cottony white growth may be on rapidly spreading lesions. Black fruiting bodies (sclerotia) are produced later in the lesions.

Cultural control

  • Avoid overhead irrigation or excessive watering through a drip line.
  • Deeply plow under plant debris soon after harvest if possible.
  • Space plants and rows to promote fast drying.
  • Rotate crops, but avoid potatoes in the rotation.

Chemical control

  • Carboxamide (Group 7) formulations are registered for use in squash. Do not make more than two (2) sequential applications before alternating to a labeled fungicide with a different mode of action.
  • Endura at 6.5 oz/A on 7- to 14-day intervals is labeled for other diseases in squash. Preharvest interval is 0 days. 12-hr reentry.
  • Fontelis at 16 fl oz/A on 7- to 14-day intervals. Preharvest interval is 1 day. 12-hr reentry.
  • Topsin M 70 WP at 0.5 lb/A on 7- to 14-day intervals is labeled for gummy stem blight and will give good control of Sclerotinia. May be applied through sprinkler irrigation lines according to label directions. 12-hr reentry.

Pscheidt, J.W., and Ocamb, C.M. (Senior Eds.). 2014. Pacific Northwest Plant Disease Management Handbook.
© Oregon State University.

Use pesticides safely!

  • Wear protective clothing and safety devices as recommended on the label. Bathe or shower after each use.
  • Read the pesticide label—even if you’ve used the pesticide before. Follow closely the instructions on the label (and any other directions you have).
  • Be cautious when you apply pesticides. Know your legal responsibility as a pesticide applicator. You may be liable for injury or damage resulting from pesticide use.

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H - Homeowner packaging commonly available. O - Acceptable in organic production.