Horticulture Hints Summer 2014
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Horticulture Hints Summer 2014 Landscape Gardening and Ornamentals Crape Myrtle Part Of Southern Landscape; Try These Tips For Caring For Yours Although native to the Far East, mold), powdery mildew and Cercospora leaf spot. Caterpillars are an occa- crape myrtles are almost indispens- sional problem. able in the Southern landscape. You can control aphids by spraying the tree with any commercially available Their vibrantly colored flowers in insecticide labeled to control aphids, such as permethrin. Imidacloprid is a sys- shades of pink, purple, red and white temic insecticide applied as a drench to the roots and also will control aphids. from May to September virtually It is better to apply a systemic insecticide early in the season, around April or define the summer season here. The May, but June is not too late. relatively small size of crape myrtle Cercospora leaf spot is a fungal disease that occurs more in mid- to late trees and long, colorful blooming summer, particularly when weather is rainy. Leaves develop dark spots, change season make them useful in a variety color and drop from the tree. This disease is not life threatening and does not of landscape situations. significantly affect the overall long-term health of the trees. It is not practical to A common problem is damage spray, and there is no need to do so. to the trunk caused by the careless Common reasons for lack of blooms are young trees, trees getting too use of mowers and string trimmers much shade, trees that are sickly or low in vigor and heavy insect or disease around the base of these thin-barked problems. Given time, good care and proper growing conditions, crape myrtle trees. To prevent this type of damage, flowers are as certain as summer. do not allow grass to grow within a foot of the trunk. Keep the area The amount of flowers young trees produce generally increases with time mulched with about 4 inches of pine and age. straw pulled back slightly from the trunk. Once a crape myrtle tree gets older, it regularly sheds its outer layer of bark. There’s no need for concern. Simply gather up the bark it sheds to keep things looking neat. Remove suckers regularly – as soon as they appear. When prun- ing suckers, do not leave a stub, or several suckers will appear for every one you cut off. To prevent suckers from growing back so quickly, treat the freshly cut spots with a product such as Mon- terey Sucker Stopper or Ferti-lome Sprout Inhibitor. (Some local nurser- ies may carry these, or you can order online.) A few insects and diseases attack crape myrtles, but they gener- ally don’t cause significant damage. Common problems are crape myrtle aphids (which also cause black sooty 1 Summer 2014 Horticulture Hints Caterpillars Common Summer Pests Caterpillars of various types are common pests in flower beds, trees, shrubs and even lawns during the summer season. Basically, caterpillars are baby moths or butterflies. Moths and butterflies pass through four distinct phases in their lives: egg, larva (caterpillar), pupa (cocoon or chrysalis) and adult (moth or butterfly). If you wonder where the caterpillars on your plants came from, an adult moth or butterfly flew to the plant, laid the eggs and flew off. When moths or butterflies are in the egg, pupa and adult stages, they pose no direct threat to our plants. But the caterpillar stage is another matter. The caterpillar phase basically is the stage when the insect eats large amounts of food to grow and develop. Caterpillars have chewing mouthparts. They bite into tissue and swallow it. Caterpillars of various types feed on virtually every part of the plant. They bore into stems and trunks, they eat fruit and they can chew on flow- ers. But, by far, the caterpillars we most often have problems with are those Buck Moth that feed on the foliage. adult and larva Caterpillars that feed on foliage of trees and shrubs are not life threaten- ing to the plants they infest. They could eat every leaf, and the tree or shrub would recover by sending out new growth. It would not be good for the tree or shrub, but it would not kill it. The visual effects on the beauty of the tree or shrub, however, may make control efforts worthwhile. Eating the foliage of flowering perennials and bedding plants is more serious. Significant damage can occur that will weaken the plant greatly. Where control is practical and desirable, there are things you can do. Insecticides containing Bt (Bacillus thuringiensis) and spinosad are the least toxic insecticides available for caterpillar control. Chemical controls include carbaryl and pyrethroids such as bifenthrin, cyfluthrin and permethrin. Stinging caterpillars also are out during summer. The saddleback cat- erpillar, puss moth caterpillar and IO moth caterpillar all can be found on a variety of trees and shrubs through the summer. Children, in particular, should be shown what these caterpillars look like and cautioned about touching them. They can be controlled with the products already mentioned. For additional pictures of these stinging caterpillars, the LSU AgCenter has an excellent publication you can see online (do an Internet search using “LSU AgCenter stinging caterpillars” and click on the link). Or contact your local LSU AgCenter Extension office for a printed copy. IO Moth adult and larva Bark Lice Harmless Midsummer and into fall are the bark lice are in no way harmful to the times of year when silvery webbing trees. appears on the bark trees. These The insects feed on organic debris webs are caused by tiny insects lodged in the bark, such as molds, called bark lice, which are common pollen, fragments of dead insects and in Louisiana. similar materials. They will be active The small, soft bodied creatures until fall. They usually go away about are about 3 to 6 millimeters in October, if not before, and once the length, live under the webbing and bark lice begin to die, the webbing will may or may not have wings. The break up and disappear. They will not proper name for these insects is injure your trees, and no control is psocids. The webbing they produce necessary. on the trunk and branches is to If you can’t stand the appearance of protect themselves from environ- the webbing, you can sweep it off with mental conditions and predators. a broom or blast it off with water. Most The webbing looks alarming people just leave them alone, however, as it spreads on the tree from the and let them clean off the bark of the ground to the upper branches. But tree. 2 Summer 2014 Horticulture Hints Beware Of Summer Heat Working outside in especially hot weather places extra stress on the body. Take frequent breaks and try not to stay outside in the heat for extended periods. Gardeners working outside may lose up to 2 quarts of water each hour. To prevent dehydration, drink cold water before, during and after working outside. It is best to bring a container of cold water out with you and to keep it with you. You are more likely to stay properly hydrated if you have water with you and don’t have to stop what you are doing to go back into the house. Work in your garden in the early morning or late afternoon when it is cooler and stay in shady areas as much as possible. Follow the shade in your landscape as the sun moves across the sky. Leave areas as they become sunny and move into areas as they become more shaded. Since you’ll tend to work in the cooler early morning and evening hours this time of year, you also don’t want to forget to apply a mosquito repellent. West Nile virus is still a concern. Wear a hat that shades your ears and the back of your neck in addition to your face. Wear loose, comfortable clothing and use sunscreen. Tips For Selecting An Arborist With the start of hurricane season, you should care- • Ask for local references, and look at other jobs the fully evaluate your shade trees for problems. If works company has done. Check with the Better Business needs to be done, it’s best to hire a licensed arborist. Bureau. • Have more than one arborist look at the job and Here are some things to consider when hiring give you estimates to ensure you get a fair price. an arborist: This also allows you to get other opinions on what work needs to be done. But don’t expect • The Louisiana Department of Agriculture and one arborist to lower his bid to match another Forestry website lists the licensed arborists in arborist’s estimate. Louisiana by parish. Do an Internet search using “LDAF licensed arborists” and click on the link. • A good arborist will never recommend or agree to “topping a tree” except under rare circumstances • Beware of door-knockers. This is especially common (such as to save the tree after severe physical after storms, when nonprofessionals see a chance to damage to the crown). earn some quick money. • Unless you simply need a tree removed, choose a • Never let yourself be rushed by bargains such as, “If company that offers a wide range of services (such you sign an agreement today, I can take 10 percent off as pruning, fertilizing, cabling/bracing, pest control, the price.” etc.). • Ask to see the state arborist license. All practicing • Do not allow an arborist to use climbing spikes to arborists must be licensed by the Louisiana climb a tree unless the tree is being removed.