Integrated Pest Management: Tips for July

Hawthorn lace bugs plague many plants in the rose family including hawthorn, apple, cotoneaster, and firethorn. Adults have partially transparent wings with an intricate lacy pattern and opaque areas. Look for a whitish speckled appearance on the tops of leaves. The lower surfaces of the leaves are often discolored with excrement and cast skins of the developing nymphs. Use horticultural oil or a pesticide containing acephate and be sure to spray thoroughly on the underside of the leaves if large numbers of lace bugs are present.

During periods of dry weather, allow your lawn to go dormant to avoid turf diseases and to discourage weeds. If a green lawn is a must, water early in the morning and adjust your mowing height above two and a half inches.

Adult Japanese beetles feed on the foliage and flowers of over 300 different plants during the hot, summer weeks of July. These beetles have a metallic green body with reddish-bronze wing covers and are the size of a coffee bean. After mating, adult females lay eggs in turf. Dry soil conditions kill many of the eggs, so avoid watering lawns in July and August. To prevent serious damage, handpick the beetles daily in the early morning when they are less active and drop them into a bucket of soapy water.

Powdery mildew, a fungal disease that attacks the leaf surfaces of many flowers, shrubs, and trees, is a growing problem for dogwoods. Look for white powdery patches on the upper surface of new growth. This disease can cause the new growth to be curled and deformed, and often reduces the growth of very small trees. Loss of photosynthesis can also weaken the trees making them more susceptible to dogwood borers and canker diseases. To prevent powdery mildew, avoid heavy doses of nitrogen fertilizer, overhead watering, and excessive pruning. These practices can force tender new growth that is more susceptible to the fungus. Provide your trees with good air circulation, prune out dead wood, and place a thin layer of mulch over the root system. There are disease-resistant flowering dogwood cultivars available also such as ‘Cherokee Brave’ and ‘Sweetwater’.

Monitor your boxwoods for boxwood mites. These spider relatives are small, red, and slow moving. Yellowish stippling in a linear pattern appears on old foliage when mite populations are high. Beat test by tapping a stem onto a piece of white paper. Consider spraying with horticultural oil when the count exceeds twenty or more mites per beat. Do not spray if faster moving predatory spider mites, or small, jet-black mite destroyer ladybugs are present.

Monitor your plants for thrips. These very small insects may be found in the flowers and leaves of many plants. Thrips are orange to brown in color and they scrape leaves and petals with their mouthparts. Look for white streaks, curled leaves, and stunted growth. Find thrips by using the beat test. Gently tap a branch of the plant onto a piece of white paper and look for the thrips on the paper. If you count more than five thrips and the foliage shows signs of damage, you may want to consider spraying with a pesticide labeled for thrips. Before spraying, look for minute pirate bugs, small black insects that feed on thrips. They also feed on pollen, so look for them on the flowers. Refrain from spraying if these predators are present.

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