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Common Pests and Problems for
July
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Continue to monitor for plant bugs on phlox and treat if required. Mildew is another common problem of phlox. Aster yellows is distinctive and can affect many different plants.
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Phlox Bugs
Phlox bug damage (Hemiptera) on phlox (Phlox)
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Aster Yellows
Extreme leafy growth from flower of black-eyed Susan (Rudbeckia) caused by aster yellows
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Reduce problems with weeds by keeping them from making seeds by cutting or pulling before they flower.
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Continue to monitor for black spot on roses and treat as required. Also continue to monitor lace bugs on azaleas. Treating this late in the season, however, may have little value. In following years learn how to detect them earlier and treat them.
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Black Spot of Rose
Yellowing rose (Rosa) leaves with black spots are characteristic of black spot of rose
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Lacebugs
White flecking on upper leaf surface on azalea (Rhododendron) caused by feeding of lace bugs (Hemiptera); heavy infestation
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Lacebugs
Adult oak lace bug (Hemiptera ) on underside of bur oak leaf (Quercus macrocarpa)
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Make your second treatment for peach tree borer. Monitor for leafhoppers.
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Leafhoppers and Planthoppers
The damage on this silver maple leaf (Acer saccharinum) is typical of feeding by leafhoppers (Hemiptera) but it could be caused by a true bug
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If you are treating grubs with Merit, do so early in the month as it takes several weeks to be effective. Many galls affect the leaves of trees and shrubs and do little if any damage.
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Grubs in Lawns
Grubs (Coleoptera) can be found when the dead grass is pulled back.
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Gall-forming Eriophyid Mites
Eriophyid mites (Acari) are responsible for many galls, like these galls on the males flowers of an ash (Fraxinus)
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Galls on Trees
This gall on an oak leaf (Quercus) looks like an oak flake gall caused by a wasp (Hymenoptera) but dissecting the gall is the only sure way to tell what caused the gall
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Blossom-end rot of tomatoes and vine crops is a common occurrence as summer gets into full swing. Control squash vine borers early before they do serious damage.
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Squash Vine Borer
The rotted crown of this summer squash plant (Cucurbita) was caused by squash vine borers (Lepidoptera)
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Other tomato problems to be aware of and treat if necessary are septoria leaf spot, early blight, and spider mites, which affect many plants.
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Spider Mites - Outdoors
The bleaching and discoloration of the leaves on this astilbe (Astilbe) was caused by spider mites (Acari)
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Mildew on lilacs is common but rarely requires treatment. Check iris for iris borers and perennials for southern blight.
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Iris Borer
Larva of iris borer (Lepidoptera) tunneling in iris rhizome (Iris)
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Very common problems of plants during the heat of the summer are drought, scorch, and heat stress. During dry spells water as needed. Plants that regularly scorch even when given ample water may benefit by being relocated to a more shaded location.
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Watch for signs of oak wilt and be prepared to remove roses that are affected by rose rosette. Apple scab is a common fungal diease of apples that results in yelllowing and dropping leaves.
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Oak Wilt
Oak (Quercus) dying from oak wilt
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Rose Rosette
Symptomatic thorns on rose (Rosa) caused by rose rosette
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Apple Scab
Yellowing leaves and spots caused by apple scab on crabapple (Malus)
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Common problems of cucumbers, melons, and other cucurbits this time of year include bacterial wilt, cucumber beetles, and pollination problems.
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Japanse beetles will continue to cause damage the first part of the month but will then taper off. Verticillium wilt is a destructive wilt that can quickly kill many tree, shrub, and herbaceous plant species.
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Japanese Beetle
Japanese beetles (Coleoptera) feed on over 300 species of plants
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Verticillium Wilt
Redbud (Cercis) wilted and died within a week from verticillium wilt
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Cicadas start appearing this month.
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Be alert to the flight of peachtree adults that are active from July - September. See August and May for control measures.
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© Missouri Botanical
Garden, 2001-2009
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