Weekly Field Update
Clemson Extension agents provide updates in The South Carolina Grower this week about the status of various crops being produced throughout the state.
Tom Bilbo reports, “When scouting strawberry fields for spider mites, also keep an eye out for naturally occurring predatory mites, such as the [potentially] highly effective specialist predator Phytoseilus persimilis. Sampling conducted in spring 2022 across Lowcountry strawberry farms detected this predator in all six fields sampled. However, in most cases, they appeared ‘too little, too late,’ to suppress spider mites in a timely matter. Purchasing and releasing predatory mites can be a very effective approach, but most research to date has been conducted in the large strawberry systems of California and Florida. This spring, I am initiating research on how to release predators in South Carolina strawberry fields to determine an approach that is both effective and economical. Whether predatory mites are naturally occurring and/or released into fields, the single most important factor in their success is the use of compatible insecticides. Pyrethroid insecticides (IRAC group 3) are highly toxic to predatory mites and are virtually guaranteed to kill them in your field. If needed, apply instead any number of the much more selective acaricides available that have been shown to be compatible with predatory mites. These include the active ingredients bifenazate (Acramite), cyflumetofen (Nealta) and abamectin (Agri-Mek). Once the research is conducted for South Carolina strawberries, I will write a separate post outlining specifically how to utilize predatory mites. Until then, you can find more information on predatory mites here from my research in North Carolina tomatoes.
Matt Cutulle reports, “It is Valentine’s Day week, which to a weed scientist means crabgrass is going to germinate in the Lowcountry and Midlands. This is a good time to get out your burn down herbicides and conduct the stale seed bed technique.”
Rob Last reports, “The Lowcountry has had another warm week with some additional rainfall. Foliar diseases are evident in strawberries with low insect pressure. As we move further into February, our thoughts are turning to fertigation. When we start fertigating, we are approximately six weeks away from the harvestable crop. Typically, 5.25 pounds of nitrogen and potassium should be applied when fertilization begins in the first week. Further refinements can be made following the results from tissue sampling to dial in the required nutrient levels. If you are unsure how much fertilizer to apply, check out the Clemson drip fertigation calculator. The calculator is a great tool to help accurately apply fertilizer. Now is also an excellent time to apply boron to strawberry crops. We are looking to apply 1/8 pounds (2 oz) of actual boron per acre, which equates to using 11 oz per acre of a 20.5% Boron product. This will help to prevent bullnose fruit.”
Zack Snipes reports, “It’s wet. Strawberries are coming along, and some growers are starting to protect blooms. Remember that once we cover plants, we are making a commitment to begin the season. That might mean many nights of putting row covers on and then taking them off. One grower estimates that putting covers on and taking them off costs about $400 each time this happens. This also means we must stay on top of keeping plants healthy by sanitizing dead or diseased tissue and preventively spraying our fungicides. The time it takes from a flower to fruit is about 35 days. I am getting a lot of questions about covering or not covering. Ask yourself, do you want to be open and picking berries 35 days from now? Another chore we should be doing as fields dry out is putting out an application of boron to help flowers develop properly and prevent ugly-looking fruit.”
Justin Ballew reports, “We got around 2.5 inches of rain around the Midlands over the weekend. According to our weather station in Lexington, we’ve already received almost 12 inches of rain in 2023. We’ve had a few frosts in low lying areas, but for the most part the weather has been mild. I’m predicting we will be picking a few strawberries by the second to third weeks of March. We’re still seeing a fair amount of leaf spot on some farms. Be sure to send samples to the disease lab so we can see if it is Gnomonia leaf spot or the newer Neopestalotiopsis. Sanitizing these diseased leaves will be important as we move into bloom.”
Sarah Scott reports, “The Ridge area received, on average, between 2 and 2.5 inches of rainfall last week. Field conditions are still pretty muddy, which makes work a bit slower. Peach trees are still being planted, and pruning continues. We are a little behind this year’s chill hour accumulation, not at 800. Trees with an 800 chill requirement and above could have a reduced crop. One thing growers can do is put off pruning these varieties as long as possible, especially inner portions of the tree that would be more protected in a late freeze event. If we wait to prune, we can get a better idea of crop size and avoid pruning off potential fruit buds. Warm temperatures in the forecast are going to really encourage movement on the buds, and we are likely done accumulating any chill this season.”
Bruce McLean reports, “Wet… that is my comment today for the conditions around the Pee Dee. The region got a good soaking this weekend, with some areas getting over 3 inches of rain. This, combined with pretty moist soil conditions from recent rains, has caused some water to pond in some fields. If you have water standing, do what you can to move the water off of your fields and keep a close eye on your crop. Excess moisture can lead to root rot issues. Corrective measures to treat root rot may be necessary. Heavy rainfall can also create erosion issues or soil crusting issues (when the soil begins to dry out). Light cultivation may be needed to re-bed rows and break up surface crusting, but be sure to wait until the soil dries enough to be able to run a tractor back through the field. Working the soil while it is still wet can cause more problems than it’s worth. Strawberries are showing a good bit of fungal leaf spot as of late. Be sure to step up your fungicide spray program during periods of favorable (disease) weather… like we are having (rainy, moist, mild conditions). If you see anything that looks unusual or something that doesn’t look like it is responding well to your fungicide applications, be sure to reach out to your local Extension agent. Also, if you haven’t already, go ahead and try to secure your seed for this year. It sounds like seed quantities are low on certain crops and varieties. Right now, fertilizer availability is good, and prices may be a little less than last year.”
Andy Rollins reports, “In the upstate, we are seeing some movement in peach varieties. This marks the beginning of bloom, and caution for oil use is recommended. For this reason, we need to consider reducing our mineral oil percentages from 2% to 4% for dormant trees to 1% to 1.5% for partially dormant trees (SE Peach Spray Guide). Even before bloom, if varieties have buds that have swollen, you need to reduce those concentrations. Diazinon is one example of an insecticide that can be mixed with oil, but several others exist. Diazinon is an organophosphate similar to Lorsban, which is no longer available. Some labeled versions only go up to 1.5 pints per acre rate.”