Cucurbit Downy Mildew Found In SC

Cucurbit downy mildew was found in SC this week in Bamberg, Barnwell, and Calhoun Counties. In each case it was found on cucumbers and for now severity seems low. This is about two weeks earlier than in the past couple years.

Downy mildew symptoms on cucumber. Lesions are often limited by the veins in the leaves.
Dark-colored downy mildew spores developing on the underside of cucumber leaves.

If not already doing so, all cucumber and cantaloupe growers in SC should begin applying protective fungicides to help prevent or manage downy mildew. Ranman tank-mixed with a protectant, such as chlorothalonil or mancozeb, or applications of Zampro are good options for protecting plants prior to symptom development. For more info, see Dr. Tony Keinath’s CDM Management publication.

Weekly Field Update – 4/26/21

Join us this Wednesday (3/24/21) at 12:30 pm for an update from the tomato fields with Zack Snipes. It will be a relatively short meeting, lasting 30-45 minutes, so tune in while you eat your lunch. Click here to register.

Coastal

Rob Last reports, “Crops in the area continue to develop well, and I expect this to continue after some welcome rainfall over the weekend.  Following the rain over the weekend and returning to warm temperatures, keep scouting for diseases in crops and ensure fungicide applications are made promptly. Spider mites show activity in a range of crops from strawberries to peppers, tomatoes, and blackberries. Always remember to use a specific miticide for spider mite control to avoid flaring populations. Cucumber beetles are beginning to be found in sticky traps. Currently, no damage is being seen to crops. Treatment options include neonicotinoid insecticides applied as a foliar spray or through the drip system.  When treatments are made, it is possible feeding damage will be seen as the pests need to ingest the pesticide.”

Zack Snipes reports, “We finally got some rain last week that I think will benefit all of our crops. Spider mites were the talk of the community last week. I saw high populations on strawberries as well as blackberries. On farms with mixed produce, you will want to scout all crops, even if they are at a stage where they normally wouldn’t have mites. I found mites on tomatoes last week because they were adjacent to a strawberry crop. We need to get on top of this pest before its too late. There are plenty of IPM techniques and strategies for this pest. Also, if you have sprayed a product in strawberry and are considering treating other crops nearby, you may want to rotate products/chemistries from what you sprayed on strawberry. Chances are those are the same genetically similar spider mites so if you had any resistance in strawberry, or another crop, then you may see it on tomato or watermelon.”

Taking good photos of spider mites is tough but on this leaf you can see several two-spotted spider mites. Don’t wait until you see symptomatic damage to manage this pest.    

Midlands

Justin Ballew reports, “We had a cold event in the midlands that seems like it got around 5 degrees colder in most areas than what the forecast called for. It got to 35 at my house Wednesday night/Thursday morning. South of Columbia and Lake Murray, I only heard a couple reports of light frost, but north of Columbia, I heard reports of the temperatures reaching 31. We’re certainly going to see some damage in those areas to spring crops that weren’t covered. On another note, strawberries are yielding really well right now. Growers are reporting that yields are at times outpacing sales. We finally got some rain this weekend (just under an inch at my house), so we’re going to see some water-damaged berries and the moisture will give grey mold an opportunity to increase. The rain was good news for spider mite management, as their populations had been thriving in the dry conditions. Diamondback moth populations are increasing in brassicas, so keep up with scouting.”

Strawberries have been yielding well and berry size has been quite large on some cultivars. Photo from Justin Ballew
We haven’t seen much grey mold lately, but the rain we had over the weekend may allow it to make a comeback. Photo from Justin Ballew

Pee Dee

Bruce McLean reports, “Last week’s brief kiss of frost doesn’t appear to have caused any significant problems on the crops. But, it is starting to get a bit dry. Sweet corn and pea emergence has been looking good, with most locations having an excellent stand. Cucurbit crops are starting to emerge, as well. Transplant tomatoes are looking very good. Everyone is taking advantage of this beautiful weather to plant vegetable crops and blueberries… just don’t forget to irrigate. Strawberry harvest is peaking right now and the fruit looks really good. Disease pressure is pretty low, but spider mite activity is high in many locations. In blueberries, much of the damaged fruit (from the Easter freeze) is beginning to shed off of the plant. Hopefully, this will continue… so lingering damaged fruit will not slow down harvest (starting in a few weeks). Muscadines are starting to show some early flower bud development.”

Early flower bud development in Carlos muscadine. Photo from Bruce McLean.
Crimson clover cover crop in a muscadine vineyard is a beautiful sight to see. It serves as a great habitat for beneficial insects. Photo from Bruce McLean.
Blueberries planted on plastic mulch covered beds. The plastic reduces the development of weeds, thereby reducing competition for the newly planted blueberry plants. Photo from Bruce McLean.

Tony Melton reports, “Peppers, cucumber, and tomatoes are just sitting and not growing. Extra fertilizer will do little for growth in these cool conditions. Cabbage needs to be sprayed for thrips, sclerotinia, and caterpillars. Cabbage, collards, and greens are loving the cool weather and hauling butt, so side-dress to keep growing. Strawberries are loving these cool conditions and are really producing. We are having an overabundance of local strawberries making them hard to sell – many are being discarded. Just a small amount of wind damage. Tomatoes, peppers, and cucumber plants were not big enough to act like a sail and be blown (twisted-off) in the wind. Got just enough rain to start planting dryland peas. I know I will regret saying this – “but I hope it warms up soon.”

Upstate

Kerrie Roach reports, “Every day brings us a little closer to May in the Upstate, and with that brings a little less chance of a frost or freeze event. Last week Thursday brought on lows of 30-32 degrees F in many places causing damage to warm season crops as well as landscapes across the upstate. Strawberry growers have slowed since the cool weather, but production will start to pick back up with warmer days and nights this week.”

Weekly Field Update – 1/11/21

Coastal

Rob Last reports, “Vegetable crops are growing out of the impacts of frost well. There is active Alternaria in places on brassica crops. Insect activity in vegetable crops in the area remains low. Strawberry crops are moving well with a few spider mites and aphids being observed. Remember if mite treatment is needed use a specific miticide to target the pest to avoid flaring populations. If you need a second pair of eyes to help scout then please give me a shout.”

Zack Snipes reports, “I’ve been getting a good many calls about strawberries in recent weeks.  The warm weather has really pushed our berries, perhaps too far along for this time of year.  I know of a couple of farms that are already harvesting which I’m not sure is a great thing this early in the season.  Most fields look good with great growth but we only have a few crowns for each plant.  Hopefully some cool weather will come in and slow them down.  Make sure to sanitize the plants by removing all dead tissue and put out a preventative spray once you are done sanitizing.  Good preventative sanitization right now can do wonders for disease management later in the season.  Now is a good time to manage weeds before they get too large.  And while I am at it…now is the perfect time to get ready for the season by checking sprayers, getting fertigation systems set up and calibrated, and purchasing pesticides you know you will need for the season.” 

A sanitized plant and the dead and diseased tissue that came off of it. This needs to be taken out of the field and disposed of. Photo from Zack Snipes.
Corn spurry is a weed that needs to be managed now before its too late. Photo from Zack Snipes.

Midlands

Justin Ballew reports, “The weather has remained cool, so everything is growing pretty slowly. We had another very rainy day last week and we got a little over 2 inches at my house. That’s over 6 inches for me so far in 2021 and I’ve had some folks tell me they’ve gotten over 8. We are seeing some cold damage to strawberry foliage, but nothing to worry about long term. Just make sure to sanitize any dead leaves and flowers as the temperatures warm in the spring. I’ve already seen some Botrytis developing on dead flowers, so we definitely need to remove these sources of disease inoculum. I’m counting 2-3 crowns per plant right now. If you’re behind that, it may be helpful to put row covers on for a couple weeks. Just scout for spider mites carefully first.”

Cold damage around the margins of strawberry leaves from the hard freeze right after Christmas. It didn’t get cold enough to damage the crowns. Photo from Justin Ballew
This bloom was killed by cold weather. It’s difficult to see here, but there are already a few botrytis spores developing on the flower. If not sanitized, this could become a significant source of inoculum. Photo from Justin Ballew.

Pee Dee

Tony Melton reports, “Cold hurt green winter strawberries more than ripe ones due to increased sugar in ripe ones. Still got some squash producing in high tunnels if covered inside tunnel with row covers. We’re bedding green fields to allow weeds to germinate so they can be killed using stale-bed culture.”