Occurrence Characteristics and Control Methods of Pear Orchard Armored Scale

Pear orchard armored scale belongs to the order Homoptera, family Diaspididae, and is a pest that is relatively difficult to control on pear trees. In recent years, through observation, we have basically grasped the occurrence pattern of pear orchard armored scale in the Korla region, and through several years of control trials, we have developed a set of effective control methods.

I. Damage Characteristics

Pear orchard armored scale mainly damages fruit trees and forest trees. Among fruit trees, it mainly damages the branches, fruits and leaves of pear, apple, jujube, grape, apricot, plum, etc. Branches are often densely covered with many scale insects, and the damaged areas show red round spots; in severe cases, the cortex splits and even dies. After fruits are damaged, a ring of red halo appears around the insect body; when there are many insects, a patch of red appears, and in severe cases the fruit surface cracks, reducing its commercial value. On red fruits, the fruit surface beneath the insect body cannot color; after wiping off the insect body, many small spots appear on the fruit surface, causing the fruit to lose its commercial value.

II. Morphological Characteristics

1. Adult

The female adult is entirely covered by a waxy scale; the body is slightly round, orange-yellow, 0.9-1.2 mm long and 0.8-1.2 mm wide. The mouthparts are thread-like, located at the center of the ventral surface; the antennae are wart-like, and the eyes and legs are degenerated. The body scale is round and gray, with concentric rings on the surface, slightly raised in the center; the scale point is yellow or reddish-brown, located at the center of the body scale. The male adult is 0.6 mm long, with white semi-transparent wings, degenerated wing veins, and a wingspan of 1.2 mm; the body is orange-yellow, the head and thorax are darker, the eyes are dark purple, and the mouthparts are degenerated.

2. Nymph

The first-instar nymph is 0.2 mm long, oval, orange-yellow, with relatively well-developed antennae, mouthparts and 3 pairs of legs. The mouthparts are 2 times the body length, curved beneath the abdomen, and there are 2 long hairs at the tail end. The first-instar nymph molts into the second-instar nymph, at which point males and females can be distinguished. In females, the antennae, legs and eyes disappear, and the scale is round; the male scale is shield-shaped, and pupation occurs beneath the scale.

3. Pupa

The pupa is 0.6 mm long, pale yellow, conical, with antennae, legs and wings colorless.

III. Occurrence Pattern

It occurs 2-3 generations per year, overwintering as 1st-2nd instar nymphs on branches and trunks. In the following spring, when sap flows, it continues to cause damage. Generally, in early April the overwintering insects begin activity and molting; in late April the female body begins to swell and the male pupates. The first adult emergence period is in early to mid-May; the second male emergence is in mid-July, with late July being the end period. From late May to early June, the first generation nymphs are produced by viviparity; second generation nymphs appear in late July to early August, and third generation nymphs appear from late September to early October. The newly born nymphs of pear orchard armored scale produced by viviparity are bright yellow; after staying inside the scale for a period, they crawl out of the scale. At that time they are very active and crawl rapidly; after selecting a suitable site on branches or fruits, they insert their mouthparts into the plant tissue to feed on nutrients, then become fixed and motionless. After 1-2 days, white wax is secreted on the body and gradually forms a scale, which gradually turns grayish-yellow. After 10-12 days, they molt, and the antennae, legs, eyes, etc. disappear, and male and female differentiation occurs. The male pupates after molting 3 times, then emerges as an adult. The female becomes an adult after molting 2 times, and produces offspring after mating. Females prefer the sunny side of branches and trunks. The summer generation mostly parasitizes the underside of leaves and fruits. Males mostly parasitize along the main vein on the sunny side of leaves. Nymphs produced by the last generation at the end of August molt after 10 days into second-instar nymphs and overwinter on branches.

IV. Integrated Control Methods

1. Strict quarantine

Quarantine work must be carefully carried out when transporting nursery stock, branches, scions, fruits, etc., to prevent spread and diffusion.

2. Manual removal of insects

In combination with winter pruning, cut off infested branch sections; at the same time, they can be brushed off with a scouring ball or copper wire brush. Although labor-intensive, this is relatively effective.

3. Protect natural enemies

The natural enemies of pear orchard armored scale include ladybugs, lacewings, parasitic wasps, etc. As long as natural enemies are well maintained, pear orchard armored scale generally will not cause huge losses to production. If insecticides are used improperly and kill large numbers of natural enemies, it can cause major outbreaks and bring huge losses to fruit tree production.

4. Chemical control

Because the generations of pear orchard armored scale are not uniform and overlap seriously, several key control periods should be grasped: ① Before bud break in late March, when overwintering nymphs are feeding and causing damage, spray 5-6 degrees Baume lime sulfur mixture. Applying pesticide at this stage on bare pear branches is very effective for killing nymphs. ② During the growing season, in early to mid-June and early to mid-August, choose 40% Supracide 1000x solution, Guosheng 500-1000x solution, or 48% Lorsban 1000x solution for spraying; where infestation is severe, spray again after 7-10 days. ③ From late September to early October after fruit harvest, choose 40% dimethoate 1000x solution + 80% dichlorvos 1000x solution for spraying, which can reduce the base population of the pest.