Weekly Field Update – 7/6/21

Statewide

Dr. Tony Keinath reports, “Basil downy mildew was found in mid-June in Charleston. Symptoms start as faint yellowing of leaves, which eventually show brown spots surrounded by yellow areas. To see the spores, look on the bottom of a symptomatic leaf. Sometimes it helps to hold the leaf up to a light source (but don’t look directly into the sun). Seeing spores is useful to rule out nutrient deficiency or sunburn on leaves. Growers who use conventional fungicides should rotate two of these three labeled fungicides: Revus, Presidio, or Ranman. See page 203 of the 2021 Southeastern U.S. Vegetable Crop Handbook. Potassium phosphite products can be used as a preventative and by home gardeners. I do not know of any cultivars that truly are resistant or any organic biopesticides that are effective. Once downy mildew spores arrive in South Carolina, the disease will be present until frost kills the basil host.”

Basil downy mildew symptoms on the upper side of the leaves. Photo from Dr. Tony Keinath.
Basil downy mildew spores developing on the underside of a leaf. Photo from Dr. Tony Keinath.

Coastal

Zack Snipes reports, “Crops are still looking good coming off. Typically July 4th week is our busiest week in the field. One thing I saw this past week in some melon fields was crown decline. Crown decline is characterized by a yellowing of the crown leaves which makes the plant look weak overall. The disease can be mistaken for a nutrient deficiency. This disease is important to diagnose because yields can be reduced and fruit quality can be impaired at the middle to end of the season which can impact your bottom line. Read up on this disease and management options here. I am seeing some gummy stem blight and anthracnose in watermelon right now as well. Get your fungicides out before the tropical storm this week.

Crown decline appears late in the season and can be confused with a nutrient deficiency. Photo from Zack Snipes.

Midlands

Justin Ballew reports, “Things are progressing well in the midlands. Temperatures have been pretty mild and we saw about half an inch of rain at my house Thursday afternoon. It looks like Tropical Storm Elsa will be coming through Thursday, so plant diseases will continue to be our major issue for at least a little while longer. I’ve been seeing plenty of downy mildew, powdery mildew, anthracnose, and bacterial spot over the last week. Japanese beetle numbers are pretty high right now also.”

Japanese beetles feeding on developing muscadines. Photo from Justin Ballew.

Pee Dee

Tony Melton reports, “Sweetpotato vines are covering the beds. We’re starting to harvest processing tomatoes. We’re planting fall butterbeans and peas and picking processing peppers for the second time.”