Disease has begun to set in across the state as lots of crops come to harvest. More rain is forecast for this week, so now is the time to make sure you are current on your disease programs. Blueberries, blackberries, peaches, cucurbits, and potatoes are all being harvested now. See details below.
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Coastal Region
Anna Sara Hill
- It’s nice to see the sun today after the cloudy, rainy days of last week. Hopefully, fields will dry out enough for equipment to get in to spray fungicides before we get the next round of rain forecasted for the end of this week.
- Results from the cantaloupe samples sent off last week were positive for pythium root rot. Listen to Dr. Keinath’s report on the SC Grower Exchange Podcast this week to learn more information about Pythium Root Rot and treatment recommendations.
- There has been an uptick in foliar diseases in watermelon. I have seen several fields with gummy stem blight (GSB). The best fungicides for GSB are Miravis Prime rotated with Inspire Super plus Manzate. At this point in the season, check PHIs if the crops are getting close to harvest.
- Cucumber, squash, and zucchini production has been heavy this year and is rapidly drawing to a close.
- Cucumber vines have a good bit of downy mildew showing up on them, and I have seen powdery mildew on squash vines. It will help to reduce spread to other susceptible crops if these diseased vines are disked under as soon as possible after the last picking.
- White and red potatoes have started coming in, and it looks like it will be a good production year. The potatoes are large due to the rain, and many have swollen lenticels, which is not a disease.
First white potatoes of the season.
Anna Sara. Hill, ©2025, Clemson Extension
Zack Snipes
- We have finally started getting some consistent rain, which is welcomed. However, the diseases that the extra moisture helps to create are not so welcomed.
- We are seeing gummy stem blight in watermelon and, right on cue, downy mildew has shown up on cucumbers.
- Zinnias and other cut flowers are showing leaf spot symptoms.
- It is so important to identify the pathogen that is causing disease on our plants. Many fungicides, bactericides, and oomycete products can be extremely disease specific, so just choosing a random fungicide to spray with will oftentimes do nothing. Identify your disease and choose a targeted fungicide based on recommendations found in the vegetable crop handbook.
- We are seeing heavy volumes of all of our produce coming to market right now.
Bacterial leaf spot on zinnia. Using a “fungicide” on a bacterial disease won’t do much good.
Zack Snipes, ©2025, Clemson Extension
Downy mildew shows up on cucumbers within a few weeks’ window every year.
Zack Snipes, ©2025, Clemson Extension
Midlands Region
Phillip Carnley
- Things are looking up in the Midlands. Around the lake, we received some much-needed rain.
- Snap beans are being harvested with good quality and quantity, with little in the way of insect pressure or disease.
- Cowpeas are thriving currently with no sign of cowpea curculio. If your peas are just about to flower, it is time to do a perimeter treatment with a pyrethroid to halt migration into the field.
- Cucurbits are doing great with cucumbers vining nicely, squash flowering profusely, and watermelons sizing up and lapping the rows. With rain in the forecast, don’t neglect your fungicide applications.
- Tomatoes look great, but there have been some outbreaks of Sclerotinia and Agroathelia here and there. If these pathogens are present, control your bed moisture, plant resistant varieties, and a basal application of group 7 fungicides, like Fontelis, will help also.
- Sweetpotatoes are all but finished being planted and are vining nicely. Make sure to keep the deer out, if possible.
- Peaches are being picked, and the quality seems to be fair so far for early varieties. There is some residual fruit damage from hail earlier in the season.
- Muscadines are flowering and setting fruit at the moment. There have been some cases of herbicide drift, so make sure you know what and when your neighbors are spraying. 2,4-D seems to be the big culprit at the moment but the vines affected should be just fine.
Likely herbicide damage on new muscadine growth.
Phillip Carnley, ©2025, Clemson Extension
Muscadines are flowering and starting to develop fruit.
Phillip Carnley, ©2025, Clemson Extension
Peach picking is starting in the Orangeburg area.
Phillip Carnley, ©2025, Clemson Extension
Sarah Scott
- Continuous rain and poor field conditions have put an end to most strawberries in the area.
- Blackberries and blueberries are nearing mid-harvest and are both high-yielding this season.
- Peaches are still coming in heavy, and we are moving into our freestone varieties. So far, bacteriosis has been our main concern of the year, disease-wise. Thrips were an issue early in the year, and another flush is out now and the population is heavy. Silvering is showing up on fruit which, although cosmetic, can be worrisome as it means thrips can feed heavy enough to damage leaves. Curling and yellowing of the leaves can occur after heavy feeding, which will weaken the tree and reduce growing vigor if left unchecked.
There is a heavy thrips population this year. A tiny, tan, spindle-shaped thrips on this peach.
Sarah Scott, ©2025, Clemson Extension
Pee Dee Region
Brittney King
- The Pee Dee received some much-needed rain, with some areas receiving up to 2.5 inches last week. Overall, crops seem to really be taking advantage of the rain, and things seem to be progressing nicely.
- Cucurbits are progressing well, and cucumbers are being harvested. I have seen leaf spots consistent with gummy stem blight on watermelon. Symptoms seem to be concentrated on leaves at the crown of the plant/in the plant canopy and can be easily missed if you are just scouting from your truck. With the rain we received last week it is a great idea to get out in the fields and closely inspect for signs of pest issues.
- Tomatoes are loaded up and starting to turn color. Some varieties should be ready for harvest later this week/next week. Not seeing too many issues with tomatoes so far other than thrips feeding on flowers. Thrips can be a vector for different tomato viruses, so it is important to manage this insect if you have them in your field. Refer to pages 186-187 of the 2025 SE Vegetable Handbook for a list of recommended insecticides. Remember to rotate MOA to decrease the chance of resistance.
- Blueberries and blackberries are being harvested. The quality of both this year is excellent, and yields are pretty heavy right now.
Gummy stem blight lesion on a watermelon leaf. Lesions are typically concentrated on the leaf margins with gummy stem blight.
Brittney King, ©2025, Clemson Extension
Upstate Region
Andy Rollins
- We are picking multiple early peach varieties. We are having serious bacterial spot issues and treating for Japanese and June beetle infestations. We’re not seeing any plum curculio, although it is difficult to tell on certain farms where we had small hail damage previously. We have had frequent rains, and I have encouraged growers to continue using Captan instead of sulfur for cover sprays because of the weather. Growers need to be careful of herbicide drift issues going into June. It is common, especially along rights-of-way, for volatilization events from high temperature applications. Try to use low pressure. 20-30 PSI running pressure is plenty. Keep booms as close to the ground as possible. I like using XR TeeJet 11002 stainless steel nozzles, as they have a 110-degree spread rather than the typical 80-degree. This allows me to keep the herbicides on the ground where they belong, not up in our peach trees.
- We’re finding multiple insect pests in strawberries now. Scout closely and apply insecticides if needed. No one likes eating a corn earworm inside of a crab-claw berry.
Herbicide damage on peach trees following a right-of-way application.
Andy Rollins, ©2025, Clemson Extension
