Family – Pseudococcidae

The grape mealybug has been a serious pest of pears in California for many years. In recent years, it has become a problem in the pear-growing areas of Washington and Oregon.

Nymph: The nymphs are pale yellow. Nymphs go through four to five instars, depending on the sex, with each instar larger than the one preceding it.

Adult: Males have one pair of wings. They have no mouthparts and die soon after emergence. Mature females are about 4.8 mm long.

Host Range
The grape mealybug has a wide range of hosts, including apple, pear, peach and grape. It is a common pest in all pear-growing regions of the West Coast and an occasional pest of pears in the midwestern and eastern United States and eastern Canada.

Factors Affecting Abundance
Grape mealybugs tend to build up in older orchards that provide better overwintering sites than younger pear orchards.

Life History
The grape mealybug overwinters as newly hatched first-instar nymphs in egg sacs composed of waxy filaments. These are located under bark scales on larger limbs or trunks or in trash at the cases of pear trees. Most crawlers will stay in the nest until the weather warms enough in the spring to make them active.

The crawlers begin migrating from the egg sacs to buds in April, as soon as the buds begin to swell. The first crawlers to emerge begin feeding at the bases of the buds. These are often located near water sprouts, so these areas should be inspected for early detection of this pest. When the buds open, the crawlers go directly to the new shoots and leaves. The nymphs will settle and feed in clusters at the bases of shoots or in leaf axils of the current season’s growth.

Shortly after feeding begins, crawlers begin to produce the wax that gives them their characteristic appearance and makes them more difficult to control with chemicals. The nymphs will go through four to five instars, depending on whether they are male or female. The adults begin to appear in late June, and the males appear about 10 days earlier than the females. The male adults have one pair of wings and are capable of flight.

The males possess no mouthparts and die shortly after mating. The females begin to emerge about mid-July. After they mate, they search for tough bark or older wood for egg-laying sites. Eggs are laid in late summer. Some eggs may hatch, but the majority remain in the egg sacs as first-instar larvae until the following spring.

Monitoring
In late summer, examine rough bark or older wood in pear trees for females and egg sacs. Infestations found at this time indicate that a problem exists and that treatment will be required the following year.

Control
Normally, mealybug populations will go undetected until late summer when females and egg sacs become visible. At this time it is generally too late for control measures. Identifying the infestation can alert you that a problem exists and that control measures should be applied the following year. The best control strategy is to control the migrating crawlers before they settle down and develop their protective covering. Early in the growing season when the crawlers are migrating, there is less foliage on the trees so that spray coverage of the bark on the trunks and limbs is more nearly complete. Control of the nymphs before they reproduce will reduce the damage from this pest.