Downy mildew was found yesterday, June 17, 2020, in one watermelon field in Bamberg County, South Carolina. All growers should immediately spray watermelon with Ranman, Revus, or Gavel to protect their crops from downy mildew. In addition to direct yield loss, loss of vine cover can expose fruit to sunburn (when the sun comes out again). Growers who find downy mildew in a field should apply Orondis Ultra or Orondis Opti in a weekly rotation with Ranman or Gavel. For more information on downy mildew, see the updated Cucurbit Downy Mildew Management for 2020.
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.
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.”
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.”
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.”
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.”
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.”
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.”
Zack Snipes reports, “Finally we have a break from the rain! I lost count of how many inches of rain we had. In fields with clean ditches and water furrows, water drained off pretty quickly, however, some fields suffered from all the rain. If your fields are wet, try to stay out of them until they dry. One of the worst things that can happen is when fields are entered when wet and soggy, causing compaction issues in the soil. I am seeing lots and lots of disease in strawberry and blueberry. The cold weather a few weeks ago killed many developing fruit and blossoms leaving them vulnerable to fungal infection. With over a week of consistent rain/cloudy weather and mild temperatures, the fungal pathogens have exploded. If you can get into your fruit fields then both protectant and systemic fungicides should be applied.
Justin Ballew reports, “We had lots of rain last week, but a very nice weekend and I saw the first bit of pollen on my windshield Saturday afternoon. Despite the rain, spider mites are starting to build up in strawberries in several places, requiring treatment. This is probably a result of having the row covers on for so long. Conditions are still perfect for disease development and we are seeing lots of Botrytis as well as some anthracnose fruit rot. More rain is coming this week, so be timely with fungicide applications and be sure to sanitize dead leaves, flowers, and fruit from the plants. These become sources of inoculum as disease develops, so get that material out of the field.
Tony Melton reports, “Fields are rapidly drying – hopefully, it doesn’t rain until later this week so we can finally get some greens planted. We have got some acres planted but there are thousands left to be planted. Peaches are still up in the air. Some varieties are totally lost but others are fine. Growers are running wind machines and burning hay bales most nights to protect blooms from the cold. Covering and watering to protect strawberries and some growers have been picking for weeks, though others want to wait until they have enough fruit to open. With all the rain, Botrytis is tough on strawberries. Some growers are spraying twice a week, while others are letting it go and will pick-off bad fruit with the good fruit and sell what they can.
Kerrie Roach reports, “Last week was the annual ‘Upstate Fruit Grower Meeting’ in Oconee County. Extension Agent, Kerrie Roach, along with Extension specialists from Clemson and NC State presented on topics to more than 30 attendees. Topics covered included apple diseases, PGRs, peach disease management, insect & disease ID, fungicide resistance, blackberry PGR research, the MyIPM app. along with much more. Lots of great networking and conversations were had over lunch and continued after the meeting. The Upstate is looking forward to a great growing season!”
Zack Snipes reports, “The horticulture team got the opportunity to tour some really nice greenhouse/transplant providers last week. One point I’d like to bring up is transplant quality. Yes, quality transplants cost more upfront but healthy, quick-growing plants will help you recoup your investment. I see lots and lots of subpar transplants going into fields that come from transplant providers with disease and insect issues from the start. The plants will require more attention and cost more to fertilize and spray than healthy plants from the start. We also got to see some grafted tomato and melon plants. If you have been having trouble with a particular disease, cultivar, or area within your farm then grafted transplants may be an option for you. I have seen several farms in the past few years switch to using grafted plants and they are loving the results. Again they cost more but they are less likely to die with a full fruit load in late May.”
Justin Ballew reports, “We had a little break in the rain over the weekend. Hopefully, strawberry growers have taken advantage of that to sanitize the fields and get a fungicide application out. Conditions have been perfect for Botrytis development (lots of moisture and temps in the 60’s) and we are seeing a ton of it. The MyIPM app is a great resource for determining which fungicides to include in your rotation. There are a few fruit out there that are ripening up, but they’re ugly and don’t taste great yet. This will improve with time as long as pollination is good and we get some sunny days. Keep in mind it’s still very early in the season. Start taking tissue samples now to make sure we get the fertigation right.”
Sarah Scott reports, “Recent rains have caused a lot of erosion issues in orchards, especially those with trees planted on berms. With more heavy rain in this week’s forecast, farmers should focus on problem areas and consider erosion control methods such as coconut coir logs to help slow the movement of water through the orchard. Peach trees are progressing quickly but it is still too early to make predictions about this year’s crop.”
Tony Melton reports, “Farmers are hurrying to get greens/cabbage/collards planted before the rain this week. Also, getting sweet potato beds in for transplant production. Growers are fumigating fields for tomatoes, peppers, and other summer vegetables.”
Kerrie Roach reports, “Last week several S.C. agents toured two different grafting/vegetable transplant production operations in WNC. Grafting can translate some great resistance/tolerance traits to otherwise susceptible varieties of tomatoes we commonly plant in small scale production. Check with your agent to see if grafted tomato plants might benefit your operation. Meanwhile, in the upstate, it didn’t rain for a few days and growers have finally been able to get into the field to prep and plant some early crops. Temperatures have been typical for this time of the year. Hang tight because more rain is forecasted for this week!
Dr. Tony Keinath reports, “Growers who have “slacked off” on fungicide applications during the dry spell should resume biweekly or weekly fungicide sprays in areas that are or have received rain. For most fungal diseases, the amount of rain determines how severe the disease becomes. The more rain, the more fungicide sprays are needed. Note that many fungicide labels now state that the product may only be applied once every 7 days; 5-day spray schedules are going away.
Zack Snipes reports, “Another hot and dry week in the Lowcountry. Non irrigated crops are really starting to suffer. Many farms are waiting on rain to plant fall crops. We are beginning to prepare for strawberry season but dry conditions are making it hard to lay plastic. Festivals, corn mazes, pumpkins, and haunted trails are in full gear in the Lowcountry.”
Justin Ballew reports, “Last week was hot, but temperatures finally dropped over the weekend. It finally feels like fall. Dry weather remains, though. A few areas got some light showers, but it didn’t amount to much. Growers have laid their plastic for strawberries and planting is approaching quickly. Caterpillars are still very active in brassica crops and we are seeing some whiteflies as well. Keep scouting and stay on top of the insects.”
Sarah Scott reports, “We have had spotty rain throughout the Ridge but conditions are still very dry. Cooler night temperatures are bringing some relief. Field preparation for new peach tree plantings are underway including soil fumigation. With the recent discovery of the root knot nematode, Meloidogyne floridensis, in fields in Edgefield County, growers can request a PCR test if nematode samples test positive for root knot nematodes.
Lalo Toledo reports, “Phytophthora blight on bell peppers has been found in Clarendon and Orangeburg County. Phytophthora blight on peppers is extremely damaging and can result in total loss of the crop prior to the first harvest. Proper fungicide applications and resistant cultivars can be used to suppress this disease. Sweet potatoes are being harvested, as well as eggplants. White-fly populations have been found in broccoli and mustard.
Dr. Tony Keinath reports, “Phytophthora crown rot was observed on bronze fennel in a home landscape (mine) in Charleston. Fennel apparently is a new host for Phytophthora (species not identified). Foliar symptoms include a progressive yellowing, starting with the older leaves. Symptoms on the lower stem and leaf sheath are a water-soaked, “greasy” rot. It is very likely that Florence (green, edible) fennel also is susceptible. Potassium phosphite products are the only fungicides registered for post-transplant applications on the leafy vegetables crop group that includes fennel.”
Justin Ballew reports, “We got some much-needed rain over most of the midlands this week and temperatures have been a little cooler over the last few days. Planting continues with fall brassicas and diamond back moth caterpillars are showing up already. We need to be scouting weekly for those and using the treatment threshold of 5 worms per 10 plants at this stage of the season. The recent moisture is causing an increase in disease pressure, so stay on your regular spray schedules.”
Sarah Scott reports, “Peaches are wrapping up around the ridge. Broccoli plants are still going in for fall harvest. We have had rain in the last week which has been a nice break on irrigation systems.”
Pee Dee Region
Tony Melton reports, “Last of pickling cucumbers have been planted. Collard, kale, turnips, mustard, etc. planting in full swing with both transplants and direct seeding. Bed prep for strawberries has begun. Getting late to order strawberry plants. Fall blackberry harvest is continuing. Sweet potato harvest will begin soon. Double cropped processing peas are starting to flower. Butterbeans planted for fall production are starting to flower.”
Kerrie Roach reports, “The last few peaches are being picked this week in Oconee County. The apple harvest is coming along nicely, ‘Early Fuji’ and ‘Golden Delicious’ apples will start to be picked this week. A spotty hail storm in Long Creek last week has caused some damage across the orchards, but is very localized. Summer market vegetable growers are wrapping things up with some of the Farmers Markets closing at the end of August. With rain & cooler weather forecasted, disease and weed management will be a continued battle for growers.”
From Clemson Extension Plant Pathologist Tony Keinath.
During the 2019 Cantaloupe Disease Survey, Alternaria leaf blight has been found in several fields. It was more common in fields that had not been sprayed recently than in fields sprayed on a regular schedule. It also was found in a field rotated only one year out of cantaloupe.
The FRAC Group 11 fungicides (Cabrio, Quadris, Flint) are the recommended fungicides. Although the gummy stem blight fungus is resistant to this group of fungicides, they still are very effective against Alternaria leaf blight on cantaloupe and anthracnose on watermelon.
From Clemson Plant Pathologist Dr. Tony Keinath:
The first SC report of cucurbit downy mildew this year came on June 6 from a crop consultant, who found it on cucumbers in Bamberg County. Growers should spray all cucumber and cantaloupe crops to prevent or manage downy mildew. The cheapest downy mildew fungicide is Ranman. It can be tank-mixed with chlorothalonil, mancozeb, or tebuconazole to add protection against fungal leaf spots, like gummy stem blight and anthracnose, that will start to spread with the rain. Another option is Orondis Opti, a pre-mix of Orondis and Bravo (chlorothalonil). Watermelon growers should be spraying with protectants, as downy mildew has been spotted on watermelon in south Georgia.
For more info on downy mildew management in cucurbit crops, refer to this fact sheet.