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Spring brings pests to landscapes

News Release Distributed 03/07/14

By Allen Owings

LSU AgCenter horticulturist

HAMMOND, La. – Spring is near. We have many wonderful plants coming into flower and foliage this time of year, but our landscapes also have diseases, insects and weeds that need to be monitored and dealt with when appropriate.

Lace bugs are a problem on azaleas each year in Louisiana. These little pests are now beginning to emerge from the eggs laid in leaf tissue last year. Azaleas that receive radiated heat from nearby buildings are the first to show injury.

Lace bug adults and nymphs feed with piercing, sucking mouthparts, and this injury to leaf cells causes the upper surface of the foliage to appear stippled and gray in color. This damage makes the azaleas look bad, and the leaves will appear this way all season. Three to four generations of lace bugs appear throughout the year, with the first emerging just after the plants begin to bloom and the last in the early fall.

To examine plants for lace bugs, knock the azalea leaves against a piece of white paper. If they are present, lace bugs will fall on the paper and be easily seen. If you find the bugs, you can use several materials to manage them. The insecticides acephate, malathion, Bayer Advanced Garden with imidaclorpid, summer horticultural oil and spinosad are all effective materials for managing this pest.

Another species of lace bug is infesting lantanas in Louisiana this year – their damage is more common in summer and fall.

Entomosporium leaf spot is a common disease of various woody ornamentals in the rose family. In Louisiana landscapes, however, it is most commonly a problem on Indian hawthorn and red tip photinia.

Initial symptoms include the appearance of circular, reddish to reddish-purple spots on the new foliage that quickly develop light-gray to dark-gray centers. Defoliation of severely diseased leaves often follows. The pathogen survives in infected leaves on the plant or on the soil beneath the plant, and spores are dispersed by splashing water from rainfall or irrigation.

Pruning to allow more air circulation, spraying with fungicides, keeping leaf litter picked up in beds and selecting resistant varieties are keys to managing this disease.

Fire ants currently are becoming a problem, with mounds visible in area landscapes. Worker ants are building mounds high above ground to avoid saturated soil. Many fire ant baits on the market work great. Broadcast baits across your lawn and landscape each March and September for a couple years, and you can remove almost all fire ants from your property. Also treat individual mounds for quick results.

One of the best defenses against pest problems is keeping your plants in tiptop condition through good culture. This includes proper plant spacing and planting the right plant in the right location where it receives the proper soil, drainage, water, light and nutrients.

An excellent way to avoid insect and disease problems is through plant selection. Choose plants that are well adapted to our climate – those that have been bred and selected for insect and disease resistance and those that are simply not prone to major problems.

If you have a plant or plants that constantly seem to have something attacking them despite your best efforts, consider removing them and replacing them with plants you have found to require less care.

In vegetable gardens and annual flower beds that are replanted from season to season, crop rotation is important. Planting the same type of plants in the same bed year after year can lead to a buildup of disease organisms in the soil that use the plants as a host. If possible, plant different things in your garden in different places every year.

Proper sanitation is another important factor in controlling insect, weed and disease problems. Always keep your yard, gardens and adjacent areas as weed free as possible. Fruits and fallen leaves infected with disease should be raked up, bagged and thrown away.

Cool-season weeds are abundant right now, and warm-season weeds have germinated and are growing. Mulches are the best way to save work and reduce the use of herbicides to control weeds in beds.

Weeds certainly are a leading garden pest. Weed control, by whatever method you use, is always more effective when done regularly and before problems become major issues. Apply herbicides for lawn weeds in February and apply fertilizer to your lawn in April. Avoid use of weed and feed products early in the season.

You can see more about work being done in landscape horticulture by visiting the LSU AgCenter Hammond Research Station website. Also, like us on Facebook. You can find an abundance of landscape information for both home gardeners and industry professionals at both sites.

Rick Bogren

Last Updated: 3/7/2014 1:54:17 PM

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