Pests

As the tender leaves emerge in the spring on many of our popular landscape plants, the Leafminor gears up for a feast.  They begin their assault on Birches, Holly, Arborvitae, Boxwood, Pine, and others at this time of year while the tissue is soft.  These chewing insects feed between the upper and lower leaf surfaces, leaving a brown or discolored patch that when held up to the light will usually reveal the culprit.  Although most damage is just cosmetic, repeated infestations can severely weaken the plant and even cause death.  Our native white barked birches suffer heavily from leafminer, and many landscapers now plant the River Birch, as it is resistant.  Control of leafminers is difficult, as timing to life cycle is crucial to success. Systemic controls are best, and your local extension service can give detailed information for controlling the specific leafminer causing the damage.  Some are safe to use near food crops and others are not, so read and follow all package directions.

Ants

For the most part, having ants in lawns and gardens is not anything to be worried about; however some stinging orbiting ants are probably not welcome.  Ants actually feed on aphids and scale insects, which is a good thing, but they tend to spread them around in the garden on the way to their nests.  Ant colonies in lawns can kill grass roots nearby, but are mostly harmless.  Use granular or liquid based products to control ants.  Just be sure that it is ants that you have and not termites, which look similar but are much more reason for concern.

Whitefly

Mid- to late summer is high season for whitefly infestations, seen mostly on annuals, vegetables, and fruit crops.  If you brush by a plant and see puffs of small white flying insects hovering in the area, its whitefly.  These sap sucking insects cause leaves to shrivel and die. Due to rapid reproduction, they severely threaten the life of the host plant.  Whiteflies are most obvious in mid- to late summer, when flying adults are most prevalent.  Yellowing leaves in early spring should alert you to the problem, and early treatment can prevent big problems.  Insecticides easily control whiteflies, but only in adults and nymphs phases, so spraying at four to six day intervals will complete the treatment.

Grasshoppers

Of the more than 600 species of grasshoppers, only five are of any threat to landscape plants. Serious infestations occur infrequently.  These daytime feeders hatch from the ground in late spring with large outbreaks occurring only after unusually warm winters or drought spring conditions.  Adult grasshoppers are migratory insects that can travel up to 50 miles per day on warm summer breezes.  Adults feed continuously on any leaves available, but prefer weeds and then move onto nearby vegetable and ornamental plants.  During severe outbreaks, grasshoppers can strip a tree or bush of leaves and then attack shoots and bark.  By late August and September, adult females begin to lay eggs in the soil for the following spring hatch, and continue eating foliage until cold weather kills them.  Control grasshoppers during warm weather adult stages, before they lay eggs.  Most commercial insecticides for fruit and vegetable crops will work on grasshoppers.