August yard and garden tips from Clemson Extension

The Clemson University Cooperative Extension Service has released its August yard and garden calendar, offering Upstate homeowners and gardeners a guide to seasonal pests, diseases and planting windows.

Lawns

Warm season lawns need attention on several fronts this month. Homeowners should continue watching for brown patch and dollar spot, particularly in lawns that had trouble with either disease last year, and should also inspect for chinch bugs, spittlebugs and mole crickets. Eliminating mole crickets takes consistent effort through June, July and early August. Spittlebugs turn up on hollies as well as in turf.

Bacillus thuringiensis works well on Japanese beetle grubs, though it takes time to build up in the soil and does not control other grub species. A complete fertilizer should be applied to warm season lawns this month. Anyone who has not yet broadcast fire ant bait can apply a first treatment any time in August, using fresh bait and applying when ground temperatures fall between 70 and 95 degrees Fahrenheit, the range in which fire ants actively forage.

Fall is a good time to aerate cool season lawns such as fescue, while warm season lawns including centipede, zoysia, Bermuda and St. Augustine should be aerated in spring and summer. Irrigation remains important. Extension recommends about one inch of water per week for most lawns and vegetables, including rainfall, with sweet corn and yellow squash sometimes requiring up to two inches depending on growth stage. Applications should be adjusted as plants and seasons change.

Trees and shrubs

Bagworms can kill a heavily infested tree and should be watched for on juniper, arborvitae and pine, as well as broadleaf species such as rose, sycamore, maple, elm and black locust. Hand-picking handles light infestations, and Bacillus thuringiensis takes care of heavier ones.

Oakworms can strip the leaves from a five foot oak in two to three days. Carbaryl in liquid spray form works quickly, and Bacillus thuringiensis is an alternative that spares predatory insects. Fall webworms should begin appearing in pecan trees in mid to late August. Treating the bottom third of the tree is effective even when upper branches cannot be reached.

Pecan weevil treatment should begin the first week of August and continue weekly for six weeks, using five ounces of liquid carbaryl in 10 gallons or more of water sprayed from trunk to dripline. Because the weevils have a two year lifecycle, the program must be repeated a second year. All label precautions on mixing and use should be observed, and dusts should be avoided in favor of liquid formulations.

August is also a good time to prune most trees and shrubs, including azalea, dogwood, forsythia, redbud and rhododendron, which should be pruned after they bloom but before bloom set in the fall. Oakleaf hydrangea and late-flowering azalea cultivars may be considered now as well. Pruning in spring and fall should be avoided when possible. Homeowners planning to add trees or shrubs this year should start deciding on varieties and locating retailers that carry them.

Fruits

Fruit trees should continue on a fungicide program such as Captan every seven to 10 days. Insecticides should be held until fewer than 10 percent of blooms remain, protecting bee pollinators, with malathion added after the blooms have fallen. Fungicides do not affect pollinators.

Vegetables

Gardeners should keep an eye out for cucumber beetle and squash vine borer. Blossom end rot on developing tomatoes usually signals a calcium deficiency. A handful of gypsum placed in the soil beside the plant at planting time, or later, helps prevent it, and foliar sprays are available. Affected fruit cannot be salvaged and should be removed and discarded.

Sanitation accounts for roughly half the tomato disease battle. As plants finish producing, they should be pulled and taken to a landfill rather than composted, since many diseases overwinter on old leaves and stems. The same practice applies to any plant that had disease problems this season. Gardeners are also encouraged to sketch out where each vegetable was planted, which makes crop rotation easier next spring.

August planting windows include collards through Aug. 30, snap beans and half-runners from Aug. 1 to 15, and lettuce from Aug. 15 to 25.

Publications referenced in the monthly calendar are available at clemson.edu/hgic. Additional local information is available through the county Extension office.