Weekly Field Update – 7/5/22 – The South Carolina Grower

Be sure to scroll all the way to the bottom to see this week’s Question of the Week and check back on Thursday for the answer!

Coastal Region

Rob Last reports, “Disease pressure is likely to continue to increase given the recent welcome rainfall. Gummy stem blight can be found in cucurbit fields along with downy mildew in cucumbers and watermelons. Maintain vigilance and regular applications to manage these diseases. Tomatoes, peppers, and eggplant all look good with evidence of sunscald in most crops. Again, bacterial spot and fungal diseases are likely to increase in these crops too.”

Zack Snipes reports, “We finally got some rain. Our weather stations collected 4 inches in Beaufort County, 5.5 in Charleston, and 11 inches on John’s Island. While this certainly helps refill our ponds, some of our fields are holding water and are currently unworkable and unpickable. We are in the thick of things as far as harvest goes, but that should wind down here very shortly. Before the rain, I was seeing incredibly high numbers of spider mites in all crops (tomato, watermelon, cukes, blackberry). The rain should slow them down. I am also finding very high levels of bacterial wilt AND southern blight in our tomato crop. This past week I found bacterial wilt and Southern blight on the same tomato plant. Make sure you correctly identify the pathogen or pathogens causing your plants to die. I can almost promise you if we don’t take preventative measures then the problem will be much worse next season.”

Wilted and dead tomato plants that had both bacterial wilt and southern blight. (Z. Snipes)

Spider mite numbers were insane before the rains. (Z. Snipes)

Midlands

Justin Ballew reports, “We finally got some good rain last week. We had multiple rain events that totaled between 2 and 3.5 inches depending on location. It has been fairly humid since the rain started and diseases are already starting to take advantage of it. Cucurbit downy mildew finally showed up last week on cucumbers. I’m also seeing powdery mildew on cucurbits, black rot and Alternaria leaf spot in brassicas, and bacterial spot on tomatoes. If it stays wet, we are going to see a disease explosion this week. Folks are still harvesting squash, zucchini, cucumbers, sweet corn, collards, beets, and tomatoes. Now that the 4th of July has passed, growers are making some field preparations for fall crops.”

Early symptoms of downy mildew show up as yellow, angular spots on the leaves of cucumber and cantaloupe. (J. Ballew)

Phillip Carnley reports, “Here in Orangeburg and Calhoun Counties, there has been a great distribution of rain, much like the rest of the state. With this much-needed rain, I expect the disease pressure to increase in cucurbits specifically cucurbit downy mildew (CDM). For the most up-to-date information on CDM management please see this land grant press article. Last week growers in my area finished the last harvest of their first planting of cucumbers and now are prepping and planting the second crop. There has also been an increased occurrence of squash bugs. Corn smut is also making an appearance. Just like last week, cowpea curculio is still an issue we are facing in butterbean and cowpea production. At this stage, it is critical that you treat in a timely fashion with follow-up applications through PHI /harvest. The translucent egg of the curculio can be seen below. Once the curculio has deposited the egg there is almost nothing you can do other than hand-harvest the pods that have been pierced and discard them.”