Weekly Field Update – 9/20/21

Coastal Region

Rob Last reports, “Fall cucurbit crops, including cantaloupes, and watermelons are ripening and approaching harvest. Disease pressure from powdery mildew and gummy stem blight have really increased significantly over the last week. Maintaining a tight spray program will be key to managing disease. As we look forward to strawberry planting land is being prepared. If you are planning to fumigate, make sure the plant back interval between fumigation application and planting is maintained. A good test can be to plant some lettuce seed in the treated area. When lettuce germinates, the risk of damage from fumigation is reduced. Finally, on any remaining fall plantings, consider using a labeled pre-emergent herbicide to help with weed management. Once the crop and weeds emerge, options are drastically reduced.

Zack Snipes reports, “Land is being prepared and fall crops are going in around the Lowcountry. Early fall crops look better with the slightly cooler temperatures and periodic rain. We are wet in some parts. I am seeing lots of bacterial spot in the fall tomato crop. We have good herbicide management plans for greens, but folks will need to take advantage of pre-emergents now.”

Bacterial spot is bad this fall due to the consistent rain. Photo from Zack Snipes.

Midlands

Justin Ballew reports, “This past week was fairly rainy. There are several fields that are pretty soft, even some sandy fields. Folks are still planting brassicas for the fall and they are looking really nice right now. Strawberry growers are also getting prepped to fumigate and lay plastic. We’ve been seeing a lot of damping off (Pythium) in young cucurbits and some brassicas lately. The wet weather is definitely creating the perfect conditions for this. A few things that can be done to help minimize damping off include planting on plastic beds, planting at the proper depth (just deep enough to cover the plug with native soil), rotating fields wisely (tomatoes are a host for Pythium), and using a fungicide at planting may also make sense when environmental conditions are right for Pythium development.”

When transplants are set deep like the one pictured here, the moisture in the soil creates favorable conditions for Pythium to develop all the way up the stem. Instead, set transplants just deep enough to cover the plug with native soil. Photo from Justin Ballew.

Phillip Carnley reports, “Cucumber production is in its final stages here in Orangeburg and Calhoun counties with most growers close to or in the process of harvesting. There is still a noticeable amount of cucurbit downy mildew, but due to the dryer weather it has been easier to keep in check. Sweetpotatoes are currently being dug with yields looking to be fairly good. There have been a few issues with wireworm damage in sweet potato fields with the majority of damage being seen on the lighter colored tubers. Diamondback caterpillar is ramping up in brassica crops, especially in collards. Make sure to scout early and treat in a timely fashion, if your insecticide program is not showing the desired level of control talk with your local agent about scheduling a bioassay to screen your population’s resistance to different insecticides. Also be on the look out for black rot and other fungal problems in early transplants.”

Holes bored into sweetpotato tubers by wireworms. Photo from Phillip Carnley.

Sarah Scott reports, “We received some heavy rain in areas throughout Edgefield and Aiken Counties last week, up to 2 inches in spots. In preparation for October planting, plastic has been laid in strawberry fields. Brassica crops are being planted as field conditions allow. Late summer plantings of broccoli are starting to get some good size on them. Pepper plants that were put out in August are setting fruit that is starting to size up nicely.”

Strawberry plastic laid and ready to go. Photo from Sarah Scott.
These broccoli plants were put out on September 2. Photo from Sarah Scott.
Fall peppers are sizing up nicely. Photo from Sarah Scott.

Weekly Field Update – 9/13/21

Coastal Region

Zack Snipes reports, “We had a heavy downpour of rain last week surpassing 2.5 inches in some spots. I am seeing downy mildew in cucumbers and lots of gummy stem blight in winter squash and pumpkins. The worm pressure has lessened in the past few weeks. I am seeing lots and lots of black rot in transplanted brassicas. Inspect your plants before planting them to make sure the disease is not coming from the nursery. Once a brassica is planted in the field, there is not much we can do to slow the spread except hope that environmental conditions (rain, humidity) are not conducive to spread the disease. I am also seeing lots of early weed pressure in fall planted crops on both bare-ground and plastic. We have some very good herbicide options to apply preplant. Once you plant the crop, we have very few herbicides that can be used over the top of the crop. Right now is the time to get down strawberry herbicides before the season starts. As the old proverb goes: an ounce of prevention is worth a pound of cure.”

Black rot on collard transplant (V-shaped lesion on the margin) just waiting for the right environmental conditions to decimate your yields. Photo from Zack Snipes.
A healthy stand of sunnhemp shades out most, if not all, summer weeds reducing the weed seed bank. Photo from Zack Snipes.

Midlands

Justin Ballew reports, “We received about an inch of rain (at my house), which we really needed. The temperatures over the last week have been very mild and it has started to feel like fall. Fall crops are doing well. We’re still planting brassicas and keeping an eye on caterpillars. Muscadines are being harvested now. Growers are reporting good fruit quality, but lower yields than last year. This is most likely due to the late cold weather that affected muscadine growers across the state. On pecans, black aphid populations and scab incidence are both high. It appears both of these pests are going to significantly reduce yield on sensitive varieties if growers didn’t stay on top of sprays.”

Pecan scab is severe this year. This disease can cause the tree to abort infected nuts. Photo from Justin Ballew
Black aphids are very small, but their damage is easy to see on the leaves. Photo from Justin Ballew

EPA Revokes Chlorpyrifos Tolerances

The Environmental Protection Agency (EPA) issued a ruling in August to revoke all tolerances for chlorpyrifos, the active ingredient in Lorsban, following a lengthy review and legal battle.

The summary of the ruling states, “On April 29, 2021, the United States Court of Appeals for the Ninth Circuit ordered EPA to issue a final rule concerning the chlorpyrifos tolerances by August 20, 2021. Based on the currently available data and taking into consideration the currently registered uses for chlorpyrifos, EPA is unable to conclude that the risk from aggregate exposure from the use of chlorpyrifos meets the safety standard of the Federal Food, Drug, and Cosmetic Act (FFDCA). Accordingly, EPA is revoking all tolerances for chlorpyrifos.”

Chloripyrifos has been used to manage insect pests in fruit and vegetable crops since the 1960s. This ruling is bringing its use to an end. According to the ruling, “This final rule is effective October 29, 2021. The tolerances for all commodities expire on February 28, 2022.”

We are still learning how this will affect the fruit and vegetable industry, but as of right now it appears growers will be able to use existing stock through the 2021 season.

Weekly Field Update – 9/7/21

If you haven’t already done so, please take a few minutes to fill out a survey to share your thoughts with us on Extension meetings. We’ll be using the information collected to help plan meetings over the next year. It will take less than 10 minutes and is anonymous. Click here to get started. Thanks!

Midlands

Justin Ballew reports, “We’re getting a little dry here in the midlands and folks have been running irrigation a lot. We got a shower last night (9/6) at my house, but it didn’t amount to much. Our fall crops are looking really good right now. The dry weather is holding down disease though we are still seeing some insects, mainly caterpillars. Squash, zucchini, cucumbers, peppers, tomatoes, turnips, and other brassicas are all growing pretty well.”

Fall zucchini ready to be picked. Photo from Justin Ballew.

Phillip Carnley reports, “Muscadine production is in its final stages here in Orangeburg and Calhoun counties with most growers preparing to harvest or in the process of harvesting. There is still a noticeable amount of angular leaf spot on many vines, but this late in the season, it is not much of an issue. Continue to keep an eye on the population of grape vine borer with the use of traps. Also keep an eye on water, as it is needed for nice plump fruit.

Small amounts of foliar diseases are present in muscadines. Photo from Philip Carnley.
Growers are preparing to harvest muscadines in Orangeburg and Calhoun counties. Photo from Philip Carnley.

Pee Dee

Bruce McLean reports, “Soils are getting pretty dry in many locations. Even though dry weather would greatly benefit the muscadine growers, we could use a little rain. Vegetable crops are looking pretty good. Spider mite activity has increased over the last couple of weeks, especially on tomatoes. Bedding and fumigation (for strawberries) is getting ready to begin. Wine and juice muscadine harvest is upon us. Muscadine harvest is going to be a bit tricky this year. In many locations, half the crop is ready to pick and half the crop needs a little additional time, especially Carlos and Doreen cultivars. This is likely due to the late spring freeze that we experienced this year. Primary growth (that recovered from the freeze) is giving us a timely crop. Secondary growth (growth from secondary buds) is a little delayed. Watch harvesting too much under-ripe fruit. Under-ripe fruit does not contain the sugars or the juice, and will reduce your overall juice yield and total sugars.”

“Skirting the vines” is a common practice where the grower removes (by shearing) the excessive vegetative growth to allow the fruit to be more easily shaken from the vines during harvest. Photo from Bruce McLean.

Upstate

Kerrie Roach reports, “Things have significantly slowed down in the Upstate with the Labor day weekend signaling the true end of summer. The growers who are doing fall vegetable production are in the thick of things with insect and disease monitoring of utmost importance. I would typically be posting about apples and the harvest for this season, but the late cold event from April 22, 2021 has put a significant damper on local orchards. Growers have apples available, but u-pick operations are very limited, if not cancelled for this season. Orchard management is imperative even when the trees are not producing, and can be a good opportunity to get weed control and pest management under control.”

Weekly Field Update – 8/30/21

Don’t forget to sign up for the Virtual Strawberry Production Meeting we will have this Thursday (9/2) at 6 PM. We will have speakers from Clemson, UGA, and NC State and we expect it to be a great program. Visit the Upcoming Events page to see a list of topics and click here to register.

Also, if you haven’t already done so, please take a few minutes to fill out a survey to share your thoughts with us on Extension meetings. We’ll be using the information collected to help plan meetings over the next year. It will take less than 10 minutes and is anonymous. Click here to get started. Thanks!

Midlands

Justin Ballew reports, “We had a chance to dry out some this past week, though it really doesn’t take long with our sandy soil. Fields are still being prepped and planted for fall crops and what has been planted is doing well. We’ve been getting reports of high armyworm counts in pastures and row crops and we’ve been seeing some in vegetables also. Stay vigilant.”

Fall tomatoes are doing well in the midlands. Photo from Justin Ballew.
Armyworms, like this Southern Armyworm, have been showing up in pastures, row crops, and vegetable crops. Stay on top of scouting! Photo from Justin Ballew.

Pee Dee

Bruce McLean reports, “It’s getting into a transitional period for vegetable production. Cool season crops are starting to be planted (in volume), and warm season crops, like squash, zucchini, okra and peas, are still being harvested in some good volume. Fumigation for strawberries is getting ready to get started. Blueberry propagation (green-tip, semi-hardwood cuttings) is going on. Fresh market muscadines are busy being harvested. Wine and juice varieties of muscadines are getting close to harvest. Carlos and Noble are really coloring quickly. Doreen is just starting to color. Testing for sugar content (Brix) will begin this week to identify the correct harvest date for wine and juice muscadines.”

Nobel muscadines are coloring well.
Grape Root Borer on Carlos muscadine.

Upstate

Kerrie Roach reports, “Dry weather this last week was much needed after the significant rains from the week before. As many other areas across the state, armyworms reports and calls are coming in more and more each day. Stay vigilant with your scouting. As with many of our tree fruit and nut crops, the pecan harvest is looking to be pretty slim after the April 22nd cold event that affected many areas of the Upstate. Continue to monitor and treat for disease and insect populations so that next year the are not even more problematic. For bearing trees, now is the time to be monitoring and treating pecan weevil populations. Several specialists have also recommended monitoring and potentially treating non-bearing trees as well, if populations detected are high. While ideally, no pecans means the life-cycle for the pecan weevils would be incomplete, there are most likely enough pecans present in the tree to support some of the population. Check out the Pecan Management Guide for more information.”

Now is the time to monitor and tree pecan weevil populations.

Andy Rollins reports, “Bigred peaches are in the upstate and quality is amazing.  Use of pheremone ties Isomate OFM to exclude males from being able to find mates has been a huge success for late season peach.  Insecticides alone previous years even with adequate rotation did not prove successful. We have fall collard, broccoli and other brassicas being planted. Both hot and other peppers are being harvested in quantity despite excessive rains earlier in the year.  Squash and zucchini production is slowing with only limited late season plantings.  Nematode survey work is being done this week.”

Herbicide injury to peach trees.  Look out for your investments.  In this case a local cable company had spread a granular herbicide on the ground directly onto the rootzone of several peach trees adjacent to a power pole and a above ground cable box.  Check all of your borders of your plants regularly, especially where they meet up with a right-of-way or a neighbor.  This is normally not done intensionally but it does cause an economic impact larger than what you probably realize.  Clemson’s Department of Pesticide Regulation can help with these cases.

Not Planting to Manage Phytophthora Blight by Reducing Disease Risk

From Clemson Plant Pathologist Anthony Keinath and Clemson Agricultural Economist Felipe Silva.

After an absence of several years, Phytophthora blight reappeared in South Carolina in July 2021 on three farms. As expected, the outbreaks were on two of the three most susceptible vegetable crops: 2 cases on pepper and 1 case on pumpkin. (Summer squash is the other very susceptible crop.)

A white powdery layer of Phytophthora capsici spores covers this pumpkin fruit. A watery rot will soon follow. Photo from Dr. Mary Hausbeck, Michigan State University

Five management options are listed in Land-Grant Press 1014: Managing Phytophthora capsici Diseases on Vegetables. One of the recommendations under Soil Management is to not plant low areas in an infested field, because that is where the Phytophthora blight pathogen, Phytophthora capsici, will first become active. Rain or overhead irrigation will spread the pathogen to the rest of the field. Remember that once a field is infested with Phytophthora capsici, The. Field. Remains. Infested. Period.

Based on the calculations shown in Table 1, a grower that considers the likelihood of disease outbreaks and plants only the well-drained 4.5 acres in a 5-acre infested field would earn an expected average of $1,600 per 5 acres per year. A grower who does not consider the disease occurrence pattern and plants all 5 acres can expect an average loss of over $2,600 per year (see the column labeled “Avg. Net Return”). These estimates consider the likelihood of disease occurrence based on the different planting sizes and areas.

The difference between planting 5.0 vs. 4.5 acres in an infested pumpkin field totals a positive net return of $4,300 per 5 acres. Why does not planting—and forfeiting yield—make more money? Assume that an outbreak of Phytophthora blight reduces the entire farm yield by 50%. Not planting the low area of the field, where disease is likely to start, will cut the number of outbreaks of Phytophthora blight in half (see the column labeled “Disease likelihood”), decreasing the chances of an outbreak from 60% to 30%. This estimate comes from vegetable pathology colleagues in other states who have worked on Phytophthora blight for many years.

Even in an infested field, by reducing the disease risk, the expected net return increases by more than $4,000. Note that over half of the gain in profit comes from reducing input costs by not planting the 10% of the field that probably will not yield anything. Although this example is calculated for pumpkin, the risk of the pathogen spreading from diseased peppers in a low spot in the field is just as likely or greater, because the pathogen produces spores readily on the fruit. Reducing disease risk is the key to increasing profits.

Weekly Field Update – 8/23/21

If you haven’t already done so, please take a few minutes to fill out a survey share your thoughts with us on Extension meetings. We’ll be using the information collected to help plan meetings over the next year. It will take less than 10 minutes and is anonymous. Click here to get started. Thanks!

Midlands

Justin Ballew reports, “Last week was warm and humid again. Some of our sandier fields got dry enough early in the week that crops were wilting in between waterings. We got a bunch of rain over the weekend, though (a little over 2 and a half inches at my house). Overall, fall planted crops are coming along nicely. Some of the earliest planted fall squash and zucchini is being picked now. We’re still seeing the same disease problems that have plagued us all summer, though growers seem to be managing them fairly well. As far as caterpillars go, I’m seeing mostly diamondback moth and armyworms with a few loopers here and there. Get ready. This could be a high pressure fall for caterpillars.”

Even though we’ve had lots of recent rain, it doesn’t take long for the sandy soil in Lexington to dry out and let the plants wilt. Photo from Justin Ballew.

Phillip Carnley reports, “Not much has changed here in Orangeburg or Calhoun Counties. Its been hot and humid and we’ve had a few untimely showers delaying cucumber harvests. There is still plenty of downy mildew to go around. We are seeing loopers on pickling cucumbers that are ready for harvest. At that stage the loopers should be treated prior to harvest with Coragen, Harvanta, or Radiant. Fall brassica, peas, and tomatoes are just now being planted.  We are seeing increased amounts of scab in pecans this year, due to the rain and humid weather. For insect and disease management in pecans, have a look at the UGA Commercial Pecan Spray Guide.”

Caterpillar damage to fall cucumbers. Photo from Phillip Carnley
Loopers are causing some damage to fall cucumbers in the Orangeburg area. Photo from Phillip Carnley.

Upstate

Andy Rollins reports, “Excessive rains have caused cracking of fruit at several upstate muscadine farms. Powdery mildew is also present but I’m not sure how much of a role it is playing on the cracking part. The powdery is damaging the skin of the fruit. Topsin M is labeled and recommended with Captan but have to wait 7 days to pick so have to watch your PHIs. Also finding some insect pests in peach. Oriental fruit moth and sap beetles have been found last week but only a small amount of affected production. Herbicide control has been difficult this year because all the rain has caused excessive grass growth, especially in new orchards.”

Seeing some cracking of the skins in muscadines in the upstate. Photo from Andy Rollins.
This new grower has done a good job of keeping his understory clean. This will pay off for him in the spring of next year if he can keep up the diligent work. Photo from Andy Rollins.

Input Wanted for Fruit and Vegetable Meeting Planning

Clemson Extension has created a short, anonymous survey to help plan for future commercial fruit and vegetable meetings. The survey will take less than 10 minutes to complete and no personal or identifying information will be collected. Your responses will be used to make Extension meetings more useful and enjoyable for those who attend. Please take a few minutes to share your opinions with us.

Click here to complete the survey.

Weekly Field Update – 8/16/21

Coastal Region

Zack Snipes reports, “Its hot and humid in the Lowcountry. Fall tomato and watermelons are in the ground and enjoyed a week of mostly dry weather. Okra and sunchokes, aka Jerusalem artichokes, are loving this heat. With the exception of those crops, there aren’t too many crops in the ground right now.  I am seeing lots of summer cover crops. I love the idea of using a mixed species of cover crop. One reason is, it spreads out the risk that one of the species in the mix won’t germinate or will be eaten by deer. So by using multiple species, you can almost guarantee that something will be there covering the soil. Multi-species mixes also provide different benefits to the farm. Cowpeas may fix nitrogen while sorghum X Sudan hybrids may be a deer deterrent and shade out weeds.”

A beautiful mixed-species stand of cowpeas and sorghum X Sudan hybrid (sudex). Photo form Zack Snipes.
Buckweat is one of my personal favorites because of its ability to attract beneficial insects and mine potassium from the soil. Photo from Zack Snipes.

Midlands

Justin Ballew reports, “Not much has changed here in the midlands over the last week. Its been warm and humid and we got a little rain a couple times throughout the week. Recently planted fall brassica and cucurbit crops have gotten off to a good start. We are seeing some caterpillar activity already. We are seeing increased amounts of scab in pecans this year, thanks to the rain and humid weather. I’m seeing some black pecan aphids causing damage as well. For insect and disease management in pecans, take a look at the UGA Commercial Pecan Spray Guide.”

Pecan scab is really showing up this year. If growing cultivars with poor scab resistance (Desireable, Pawnee, Kiowa, Oconee), stay on top of fungicide applications. Photo from Justin Ballew.
Black aphid damage on pecan foliage. Photo from Justin Ballew.

Phillip Carnley reports, “It’s that time of year to be on the look out for Southern stem blight (Athelia rolfsii) in hemp. To avoid possible infections of this pathogen, avoid planting in fields that have previously had tomatoes, peppers, eggplant, or peanuts. Crop rotation is your best avenue for mitigation as there are no fungicides labeled for control of Southern blight in hemp at this time. Also be on the lookout for plant stunting from girdling roots. For information on chemicals labeled for hemp checkout the EPA website.”

Southern blight mycelium (white fuzzy looking growth) and sclerotia (small, tan bb-shaped structures) developing around the base of a hemp plant. Photo from Phillip Carnley.
This hemp plant has wilted due to Southern blight cutting off its ability to transport water from the roots to the shoots. Photo from Phillip Carnley.

Upstate

Kerrie Roach reports, “Late summer season crops are still producing in the upstate, but many market producers are starting to lose the disease battle. When something is finished for the season, make sure to remove all parts of the crop. Do not leave diseased plant material in the field. Dispose of the diseased crop in an area far away from your fields or garden. Do not use diseased plant material for compost. Most home compost piles do not reach consistent and uniform temperatures at which pathogens will be killed. Dead plant material harbors insects and pathogens that can and will cause issues for fall season crops as well as next year’s crop.”

Accidentally Infesting Fields by Moving Soil on Equipment or How to Exclude Soil Pathogens from Fields

From Clemson Plant Pathologist Tony Keinath.

Most growers probably have heard that it’s possible to infest a “clean” (pathogen-free) field by moving soil on equipment. The question is how much infested soil is too much. The answer depends on the pathogen and where the soil is deposited.

Some pathogens are present in soil at very high numbers. One of the worst is the clubroot organism that infects all brassica vegetables. According to a new report from North Dakota, presented at the 2021 Plant Health meeting last week, there are enough spores in 1/8 teaspoon of moist soil to infect one plant. So, if all the soil stuck on a small dozer, like the one shown here, landed in one spot at the edge of the field, a patch of clubroot surely would develop there.

Soil caked up on cultivating implements, dozer tracks, and tractor tires can transfer soil borne pathogens and nematodes from infested fields to clean fields.

In addition to the clubroot organism, root-knot nematodes and the water mold that causes Phytophthora blight are pathogens at high risk of being spread in infested soil. They’re not as concentrated in soil as the clubroot organism, but moving as much soil as is on the dozer above is enough to create a patch of diseased plants. It takes only about 1/3 cup of soil with young nematodes in it to cause a gall on a susceptible crop.

On the other end of the spectrum, since 2005 I have had a field at Coastal REC infested with Fusarium oxysporum f. sp. niveum, the fungus that causes Fusarium wilt on watermelon. As far as I know, the pathogen has not spread, or has not spread enough, to other fields to cause Fusarium wilt, even though the equipment is not cleaned after it is used in the infested field. Even though Fusarium is present in the soil, it’s not at high enough levels to be spread easily.

It’s true that environmental conditions must favor the pathogen for disease to develop from the pathogen inoculum moved in soil on equipment. However, all four pathogens mentioned in this blog are long-term soil residents. They will simply wait in the new field until environmental conditions are right for them to infect a susceptible crop.

The bottom line is equipment, especially dozers that carry a lot of soil with them as they are moved from field to field, must be cleaned by power washing every time they are used in a different field. Power washing should be a standard practice, not just done when the equipment is used in a “known” infested field, because sometimes you don’t know if a field is infested until it’s too late to take precautions.