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.
Guido Schnabel reports, “The new year started with a disappointment and scare for some strawberry growers; stunted plants, gaps in the strawberry rows and leaves dying. The extent of the damage is yet to be determined, but it will be substantial. Most of the affected growers received the plants from the same nursery source, and it is very likely the problem is nursery derived. After talking to growers, meeting up with agents, and collecting samples for problem ID at the Clemson University Plant and Pest Diagnostic Clinic, the verdict is out. Gnomonia leaf blotch (Gnomonia comari) was the main cause of older leaf decay stunting many plants. This fungus is not known to be an aggressive pathogen but can, in some instances, break out in nurseries and continue to do harm on transplants after planting. The disease should start to fade in the spring as the weather warms up, together with sanitation and regular fungicide applications. Some plants at the same location did test positive for Phytophthora and the relatively harmless Pestalotiopsis. By now, we all know there is a new aggressive species out there (Neopestalotiopsis spp) that can devastate production. We are lucky to have a diagnostic clinic that now offers a molecular test for distinguishing the mild from the aggressive Pestalotiopsis species. This molecular testing verified most farms do not have the aggressive species. We do have one Neopestalotiopsis-positive farm, however, and we must hope that sanitation, aggressive and strategic fungicide applications, and a dry spring/early summer will help to mitigate the damage.”
Rob Last reports, “Following another inch of rainfall, we are looking at a few days respite. Phytophthora root and crown rot are active in strawberries in the area. Typically, the worst affected plants are j-rooted. Given wet soils, keep scouting low spots in the field, because these may see increasing levels of Phytophthora. If you are seeing standing water around it would be beneficial to look at improving drainage. Sanitation and removal of dead plants, infected leaves and freeze-affected flowers will help reduce disease inoculum later in the season. With both strawberries and blueberries, consider making plans for freeze protection later in the year. If that’s an irrigation-based system, then make sure we have no residual damage from the Christmas freeze. If using row covers, then getting them into the fields now will make life easier in March and April.”
Zack Snipes reports, “While the weather station in Charleston only collected 1.32 inches of rain this past week, it sure felt like more than that. These very humid mornings and gray days have things very soggy in the Lowcountry. I don’t think much fieldwork happened last week due to the sloppiness. If you haven’t had a chance to check out the Clemson Weather Station Website, give it a look today. We have two new calculators for rainfall and chill hours. We are currently building more calculators that will give growers powerful tools to make management decisions. We had a great turnout for the 2023 Preplant Growers Meeting in Charleston (may have been due to all the rain). Dr. Bilbo talked about insect resistance and management, Dr. Keinath talked about black rot management in brassicas (how timely), Rob Last talked about calculating spray rates and I gave an Extension Update. Hopefully, things will dry out, and we can all get out in the field this week.
Sarah Scott reports, “Conditions are pretty muddy around the Ridge, but hopefully, we’ll get some dry days this week. Pruning continues as well as some later planting due to late shipments of peach and plum trees. Buds are beginning to move on early varieties of peaches. Growers are getting in their second oil applications. Strawberries were covered ahead of the cold weekend temperatures. We’ll be checking them to see how they fared today and throughout the week.”
Andy Rollins reports, “We are finding orange blotch on blackberry farms. Orange blotch is a type of algae that damages the blackberry canes and is very difficult to control. In the past, we have used copper, which is labeled for controlling algae, but it is not very effective. The main products recommended are “phosphites.” This would include products like Rampart and Prophyt, both of which are potassium phosphites. I recommended the farm use lime sulfur first, though, as dormancy looks to be ending very soon. The vegetative buds have begun moving in blackberry, and this application should come first. It can then be followed with the phosphite applications. I would prefer plants to be pruned before making either of these applications, as it will give much better coverage. We are still having deer problems in other crops.”