Field Update – 6/8/20 (Downy Mildew Arrives in SC)

Statewide

Downy mildew was found in Charleston, SC late last week on cucumbers. This is the first confirmed report of the 2020 season. If not already doing so, all cucumber and canteloupe growers should begin applying protective fungicides to help prevent or manage downy mildew. Ranman tank-mixed with a protectant such as chlorothalonil, mancozeb, or Zampro is a good option for protecting plants prior to symptom development. For more info, see Dr. Tony Keinath’s CDM Management publication.

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Downy mildew symptoms on the top side of a cucumber leaf. Note that the spots are angular in shape and are delineated by the veins in the leaf. Photo from Justin Ballew.

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Dark-colored downy mildew spores developing on the underside of a cucumber leaf. Photo from Justin Ballew.

Coastal

Zack Snipes reports, “It is a very busy time out in the fields. Every crop is coming in right now and folks are busting it to get crops out and keep the remaining crops healthy.  Keeping up with fertility, fungicide, insecticide, and herbicide programs can really help with the bottom line as now is when our crops need a little help. With the mild temperatures and cloudy, wet days last week, I saw some diseases appear and spread.  On tomato, I am finding increased bacterial spot that is starting to make plants turn yellow. This will cause a yield drag and the spots can be found on the fruit if the infection is not slowed down. Downy mildew was found in cucumber last week so be sure to be proactive and keep an eye out for that. I saw some other cucurbit diseases last week including gummy stem blight and Alternaria. The stink bug population has also increased in the past week or so with some damage showing up on tomato. Please refer to the 2020 Southeastern Crop Handbook for details on management programs for insects, diseases, and weeds.”

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Bacterial spot is increasing causing yellowing of the plants. Bacterial spot can reduce yields and develop spots on the fruit. Photo from Zack Snipes.

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Downy mildew found in cucumbers last week. Photo from Zack Snipes.

Midlands

Justin Ballew reports, “Last week was warmer and actually a little dry. Lots of irrigation has been running. Crops are progressing quickly. Strawberries are mostly done now. The silks on the earliest planted sweetcorn are browning and harvest isn’t far off. Tomatoes, peppers, eggplant, squash, beans, and cucumbers are also progressing well. Downy mildew has been found in the state, so be sure to start preventative fungicide sprays on cucumbers.  Let us know if you’d like help scouting fields for downy.  Collards, cabbage, and kale are still being harvested and are looking good.”

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Silks are turning brown on the earliest sweet corn plantings. Photo from Justin Ballew.

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Tomatoes are developing well. It won’t be long before harvest starts. Photo from Justin Ballew.

Lalo Toledo reports, “Downy Mildew has been diagnosed in Charleston County. However, Downy Mildew has not been found in Orangeburg county.  Please be advised that it is a matter of time before we start seeing symptoms. Please refer to the vegetable handbook regarding fungicide applications. It’s recommended to stay on a Fungicide schedule and to apply protectants even before we start seeing symptoms. Bacterial Wilt on tomatoes is present in many fields in Orangeburg county. Please contact your local extension office for proper recommendations.”

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It’s only a matter of time before downy mildew shows up in cucurbits in Orangeburg County. Photo form Lalo Toledo.

Pee Dee

Bruce McLean reports, “Field conditions really improved this past week. Cucumbers are being harvested in good volumes. Overall, quality is good. Downy mildew is starting to show up in cucumber fields that were affected by recent heavy rains. Squash and zucchini are beginning to be harvested, as well. Snap beans and southern peas are flowering heavily. Some acreage of snap beans were lost due to ponding caused by recent heavy rains. Many fields of sweet corn are tasseling well and beginning to silk. Watermelon, cantaloupe, and peppers are growing very well. Blueberry quality is beginning to improve. Much of the rain-damaged fruit has been removed. Currently, the blueberry crop looks good. Muscadine fruit set is good, but thrips and aphid activity is high, which could cause problems in yield. Scouting is necessary to determine pest presence and necessary insecticide application.”

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Downy mildew really showing up in rain-stressed fields. Photo from Bruce McLean.

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Snap beans affected by ponded water from recent heavy rains. Photo from Bruce McLean.

Tony Melton reports, “Some areas got 10 inches of rain in one day. Hundreds of acres of beans and cucumbers are drowned. Cucurbit downy mildew is here on cucumbers. Weeds are awful.”

Upstate

Kerrie Roach reports, “With heavy rains a few weeks ago, high humidity and heat this past week, we are seeing some disease problems pop up across the board… make sure you are following prevention practices that fit into your growing style. Conventional, organic, or somewhere in between, all growers should be managing disease through preventative measures. Crop rotation is arguably one of the most important strategies in an Integrated Pest Management (IPM) program. If you’re a grower that hasn’t moved crops around within your site in years, now is that time!”

Andy Rollins reports finding black knot of plum. “Prune out these galled up branches as quickly as possible before they begin to sporulate. I also recommend sterilizing or at least sanitizing the pruners as much as is possible between cuts.  Treat with 2 lbs of Captan foliarly as soon as possible after pruning to try and keep those wounds free from other problems.  This problem can come in on the purchased trees, but can also come in from wild cherry trees or wild plum surrounding the orchard.  It is always a good thing to kill any and all wild cherry and plum trees directly adjacent to a commercial orchard.  Penn State has some good information here.”

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Black knot on plum branches should be pruned out before sporulation begins. Photo from Andy Rollins.

Field Update – 5/18/20

Statewide

Dr. Tony Keinath reports, “With the cooler-than-normal spring weather, two cool-season pathogens also may be active longer than normal. Downy mildew on brassicas, especially kale and collard, mainly affects the lower leaves. Sometimes it will move up onto the larger leaves in the middle of the plant. With a hand lens, you can see white mildew growth in lesions on the bottom of the leaves. In my spring 2020 trial, Presidio, potassium phosphite, and Zampro rotated with potassium phosphite worked well. Organic growers can use Badge X2 copper, which also performed well.

Fusarium oxysporum f. sp. niveum, the soilborne fungus that attacks watermelon, infects roots when soil temperatures are below 82F. At Coastal REC, I am still seeing new plants showing wilt symptoms. Remember that all control measures, and I want to stress all of them, must be applied before or at transplanting. There is nothing that can be done at this stage of crop growth. It is too late to apply fungicides, which will be a waste of money.”

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Tiny dark flecks of downy mildew on the bottom of ‘Blue Dwarf’ kale. Photo from Dr. Tony Keinath.

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Sporulation of downy mildew on the underside of ‘Tiger’ collard. Photo from Dr. Tony Keinath.

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Wilting and yellowing of lower leaves due to Fusarium wilt on watermelon 6 weeks after transplanting. Photo from Dr. Tony Keinath.

Coastal

Zack Snipes reports, “Things are coming along in the Lowcountry.  It has been very windy and I’ve had several farmers tell me that crops are using more water now because of the wind than if it were hot and humid.  Squash, zucchini, cukes, potatoes, and greens are coming off in good volume right now. Tomatoes are just a few weeks away and are in the sizing up stages right now. I have not seen any major pests or diseases as of late.  The conditions are ripe for the development of Powdery Mildew so be on the lookout when scouting watermelon, squash, brassica, and tomato.”

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Tomatoes are looking good and are just a few short weeks away. Photo from Zack Snipes.

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Powdery mildew on the shaded side of a collard leaf. Photo from Zack Snipes.

Midlands

Justin Ballew reports, “It’s dry in the midlands. It’s been great because we haven’t seen much disease lately (especially on strawberries), but we need some rain. The forecast looks like we may get some this week. Strawberries are still yielding fairly well, though we’re starting to see fewer blooms. Fruit size is getting smaller, but taste has still been great. The first few plantings of sweet corn are tasseling now. Brassicas are still growing well, though there is some black rot out there.  Tomatoes, peppers, and cucurbits have been growing fast the last few days also.”

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The earliest plantings of sweet corn are tasseling. Photo from Justin Ballew.

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Black rot symptoms on the margins of cabbage leaves. Photo from Justin Ballew.

Sarah Scott reports, “Peach season is here! Picking several early varieties now and running packing lines. The crop looks good for this season. Bacteriosis started to show up on leaves and fruit in fields. Still picking strawberries. Summer crops like bell pepper and squash are progressing nicely.”

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Phomopsis or twig blight in a peach orchard. Lesions on twigs cause dieback, gumosis and curling at tips. Remove damaged wood and burn. Photo from Sarah Scott.

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Twig dieback from Phomopsis twig blight. Photo from Sarah Scott.

Lalo Toledo reports, “Cool temperatures have slowed down the growth of many vegetables, but most vegetable plants are looking great. Please be aware of possible diseases coming in this week. Wet and hot conditions will be conducive for pests and diseases. Please spray accordingly and scout every two days, if possible.”

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Grasshopper damage on eggplant. Photo from Lalo Toledo.

Pee Dee

Tony Melton reports, “Hail has destroyed at least 10 A squash, 200 A peaches, 30 A strawberries, 8 A blackberries, many acres of field corn, tobacco, rye, and wheat.  Damaged another 35 A strawberries, 300 A peaches.  Thank goodness that the wind has let up for a while and temperatures have risen on tomatoes, peppers, peas, beans, and sweet potatoes.  Thrips have been awful and imidacloprid is only partially controlling them. If labeled use dimethoate, acephate, etc.   More herbicide damage than usual this year because of cool temperatures and wind, even on labeled crops and drift to non-labeled crops has been awful.”

Upstate

Kerrie Roach reports, “With a week of good growing conditions, things are looking great in the Upstate for fruit & vegetable producers. In higher elevations, there were some losses of young tender plants during isolated frost events early last week. With rains expected most of this coming week, things should start to really push for our market vegetable growers. Peaches and apples are on track for a good season.

Field Update – 6/10/19

Statewide

Dr. Tony Keinath reported downy mildew being found on cucumbers in Bamberg County this past week. He cautioned all cucumber, cantaloupe, and watermelon growers to begin preventative sprays, if they are not already doing so. Refer back to this post for more info.

Downy mildew on cucumber leaves.

Coastal Region

Zack Snipes reports, “We finally got some much needed rain in the Lowcountry. I expect to see some disease to show up this week. Growers should be scouting all crops and spraying when needed. Downy mildew was found on cucurbits this week so be aware that you may see it in your fields as well. We had a great field day this week at the Coastal Research and Education Center.”

Clemson Plant Pathologist Tony Keinath discussing watermelon diseases at the Coastal REC Field Day. 6/5/19. Photo from Zack Snipes.

Midlands

Justin Ballew reports, “We had thunderstorms come through late in the week and it’s rained every day since. We needed it badly. Sweet corn and tomato picking has begun and they are looking good. We’re seeing a few stink bugs in sweet corn, but nothing severe. Powdery mildew is showing up on some cucurbits now that moisture has returned. Downy mildew could show up at any time here, so keep an eye out for that and stay on a good preventative spray schedule.

Sweetcorn ready for harvest. Photo from Justin Ballew
These tomatoes will be harvested soon. Photo from Justin Ballew

Sarah Scott reports, “Rain fall amounts range from 1 inch to over 5 throughout Aiken,Saluda and Edgefield Counties which will give irrigation systems a much needed break. Flea beetles are showing up on peppers.”

– Adult flea beetle and damage to pepper plant. Photos from Sarah Scott

Pee Dee Region

Tony Melton reports, “Pythium has been awful with all the heat.  Bad on snapbeans, cucumbers, etc.  Southern stem blight has been awful on tomatoes and peppers with the heat.  Black rot has taken over some kale, cabbage, collard fields.  Sensation strawberry has had very poor yields this spring but is still bearing in the heat.  Pickleworm is hear and is worse in yellow squash, then cucumbers, and then zucchini.  The heat caused the flowers to fall on the early planted butterbeans causing all the early plantings to come together with the later planting then with the rain and cooler temperatures all plantings are setting now.  It appears we may have butterbeans but all plantings will come in at the same time causing problems with marketing.”

Field Update – 5/13/19

Coastal: Zack Snipes reports, “Another great week of weather has things right on track. For the most part we are finished with strawberries and have maybe one more cutting of broccoli left in the field. We are in the middle of squash and zucchini harvest. The tomato crop looks great as plants have small green fruit with little to no disease. The blackberry crop is loading up. Diamondback moths continue to be an issue on late planted greens. Watch out for spider mites on tomato, melon, and blackberry crops this week.”

Blackberries are loading up in the Coastal Region. Photo From Zack Snipes
Diamondback moth caterpillar populations remain high on the Coast. Photo from Zack Snipes

Midlands: Justin Ballew reports,”We had great weather last week. A storm came through Saturday evening and brought around an inch of rain. Strawberries are decreasing in size and we probably only have a couple weeks of harvest left. Once again, the rain caused a lot of damage to developing fruit. First planted sweet corn is now tasseling and is looking great. Tomatoes are blooming and fruit is starting to develop. Most other crops are doing well.”

Sweet corn is starting to tassel in the Midlands. Photo from Justin Ballew
Tomatoes are blooming and starting to develop fruit in the Midlands. Photo from Justin Ballew

Upstate: Kerrie Roach reports,”Things are coming along well in the Upstate with market producers just starting to see the beginning fruits of their labor. We should be ready to roll into farmers markets for Memorial Day weekend! Peach growers are finishing up hand thinning. Overall, they are a few weeks out still and have about 40% overall loss on some varieties from freeze damage. Early apple varieties such as the goldens and galas are showing about 25% loss, but later varieties like Mutsu, Pink Lady, and Arkansas Black look to be a full crop load!


This is from a recent research project looking at the value added potential in bottling mature fruit. Photo from Kerrie Roach