US National Arboretum


Pest Management
Pest Management Tips: June

image of a ladybug Watch your azaleas and pieris for lacebug damage. Leaves turn light green and become speckled with yellow as these bugs suck sap from the underside of leaves. They are 1/8 inch long, whitish, with lacy wings. The wingless nymphs are darker. They also leave tarry excrement on the leaf undersides.  There are usually several generations per growing season, so check your plants often. Horticultural soap or oil will control this pest.

image of a ladybug Flea beetles will also attack and kill young transplants of tomatoes, potatoes, peppers, and especially eggplants. These tiny, shiny, dark beetles jump like fleas when disturbed. They feed on leaves, leaving pits or shot holes, and can also spread diseases from plant to plant. Flea beetles, as well as cutworm populations, can be reduced by cleaning up the garden area. Remove all weeds and left over garden debris where insects hide and live over the winter months. Try using row covers (a protective fabric available at nurseries) until the plants are larger.  For heavy infestations, pyrethrum has been an effective organic pesticide.

image of a ladybug Another pest of the garden is the harlequin bug, boldly colored with orange and black spots. This true bug can be a major pest on plants in the mustard/cabbage family including cauliflower, Brussels sprouts, collards and radish. They can also be found on tomatoes, potatoes, eggplants, beans and other vegetables and some fruit trees. In the flower garden, they feed on cleome, chrysanthemum, nasturtium and sunflower.

These insects suck out the contents of plant cells, which results in brown and distorted leaves and flower parts. Plants can wilt and die. Caution should be taken when small vegetable plants are set out, because the adults, which survive the cold winter months, can be present anytime.

Monitor carefully for adults, nymphs (which look like smaller versions of the adults, but without wings) and the barrel shaped eggs. Hand picking of adults and nymphs, and destroying the egg masses can help control these pests when the population is low.
image of Harlequin bug eggs
image of Harlequin bug nymphs
Photo of Harlequin bug eggs (upper) and nymphs (lower).

image of a ladybug Don’t be in a hurry to chemically treat aphids in the garden, particularly if they are not damaging or distorting the host plant. Beneficial insects need food to survive and multiply. Aphids provide an excellent source of nourishment for many beneficials, including lady beetles, green lacewings, and syrphid fly larvae. Many times, all life stages of a beneficial can be seen on an aphid infested branch. If chemical treatment is warranted, use an ultra fine oil or horticultural soap. Beneficial insects rebound quickly from these products due to their low toxicity. image of lady beetle eggs
Photo of lady beetle eggs.

image of a ladybug Many gardeners are transplanting young vegetable and flower seedlings into the garden in June. Check very carefully for insects that can severely damage or destroy these young plants. Cutworms, the larvae of some moths, chew off the stems of these transplants, near ground level. They feed at night; gardeners can find dozens of plants destroyed the next morning. Placing a “collar” fashioned from a paper or foam cup or a tin can with both ends removed around each seedling will protect them.

image of a ladybug

image of rose with botrytis

Photo of a rose with botrytis, or grey mold.

Botrytis or grey mold is a common disease seen on many flowers and fruit. It usually begins on old flower petals or spent fruit and then spreads to flower buds and young fruit. Petals become soft and brown and are then covered with a grey felt-like growth of mold. Spores can be splashed around by water or blown to a new host by the wind. Therefore, it is important to remove any infected flowers or fruit before the disease can spread to healthy tissue. Try to make a habit of removing old flowers from roses on a regular basis to avoid infecting new rose buds. Destroy any strawberry fruit that show signs of rot. Water early in the day, so leaves, buds, and fruit have time to dry completely before nightfall.

image of a ladybug In the eastern United States, bagworms can be a real nuisance on many trees, especially conifers like junipers, arborvitae, and Leyland cypress. A heavy infestation can defoliate a tree and eventually lead to death. Young caterpillars are found in June, weaving a small silky bag with leaf and stick pieces attached, which eventually reaches two inches long. They are easy to control now with Bacillus thuringiensis (Bt) when the bag is less than 1/2 inch. If the bags have grown larger than this before you notice them, you can treat them with a spray containing spinosad. If left to mature, male moths emerge from the bag later in the season, mating with females who never leave their bag. Each female can lay up to a thousand eggs, which remain in the bag until they hatch in the spring. It is a very good idea to remove and destroy bags any time of the year.

Pest Management Tips Home

The best way to manage pests is to use a combination of chemical and non-chemical control. Only take action when the problem is serious enough to damage the plant. If we all use Integrated Pest Management (IPM), we can control pests in an environmentally conscious manner.

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Last Updated   June 17, 2010 3:52 PM