Cydia pomonella This worm, the larva of a small (1/2 inch) gray-brown moth, attacks apples, quinces, and several other fruit and nut trees in addition to pears. The moths appear in the spring and lay their eggs on the leaves, twigs, and developing fruit, flying at sunset when temperatures are above 65°F. The eggs hatch in about a week, and the larvae that emerge tunnel into the fruit. They feed for several weeks, then emerge from the pears, often leaving a mass of dark excrement on the skin and inside the fruit. After pupating in sheltered locations on or around the tree, another generation of moths emerges in midsummer. Pears may be damaged by worms continuously throughout the summer. In fall the mature larvae spin cocoons in protected places, such as under loose bark or in tree crevices. They spend the winter in these cocoons and, with the warming temperatures of spring, pupate and emerge as moths.
You can''t kill the worms inside the pears. Remove and destroy all fallen pears and clean up debris around the trees. Apply an insecticide labeled for this pest, following the label directions.
This plant disease, also known as pear-leaf blight, is caused by a fungus (Fabraea maculata) that attacks pears and quinces. The fungus spends the winter in twig cankers and leaf debris. In the spring, spores are splashed to the leaves, shoots, and young fruit. Spots develop where the fungus penetrates the plant tissue. Infection may continue throughout the growing season. The premature death of the infected foliage greatly reduces the amount of food the tree can make and store. This results in weakened trees and poor-quality, lower yields of fruit.
Remove and destroy all leaf debris around the trees. Apply a fungicide label for this disease, following label directions.
This plant disease is caused by a bacterium (Erwinia amylovora) that is very severe on pears and also affects apples and several ornamental plants in the rose family. The bacteria spend the winter in cankers on the branches and twigs. In the spring the bacteria ooze out of the cankers and are carried by insects to the pear blossoms. Once a few of the blossoms have been contaminated, splashing rain, honeybees, and other insects continue to spread the bacteria to healthy blossoms. The bacteria spread down through the flowers into the twigs and branches, where cankers develop. Often developing cankers encircle a shoot or branch by midsummer, causing conspicuous branch and twig dieback. Although fire blight is spread primarily through flower infection, leaves and twigs damaged by hail or wounded in some other manner are also susceptible to infection, as are tender, succulent shoots and sprouts. Although severely diseased trees may be killed, more commonly only the fruiting stems (spurs) are killed, resulting in greatly reduced fruit yields. Fire blight is most severe during warm (65° to 85°F), wet weather.
In the fall, prune out and destroy infected twigs and branches at least 12 inches beyond visible decay. Disinfect pruning shears after each cut. To prevent excess growth of shoots and suckers, avoid fertilizing with high-nitrogen fertilizers. Plant varieties that are less susceptible to fire blight.
Psylla pyricola This insect is related to the aphid. Adults overwinter in crevices in the tree trunks, in groundcover, or in other protected places. Females lay eggs in the late winter or early spring on the bark and later on the emerging foliage. The young psyllas feed on the leaves and developing pears, causing damage by sucking the plant sap. The psyllas are unable to digest fully all the sugar in the plant sap, and they excrete the excess in a fluid called honeydew, which drops onto the leaves and fruit. A sooty mold fungus may develop on the honeydew, causing the pear leaves and fruit to appear black and dirty. Psylla damage may occur throughout the growing season.
These pests are often very hard to kill during the growing season. Apply an insecticide labeled for this pest, following label directions.
Phytoptus pyri These microscopic mites are related to spiders. They attack pears, apples, and several ornamental trees and shrubs. The mites spend the winter under leaf and flower bud scales. They lay eggs in the spring when the buds begin to swell. The young mites that hatch from these eggs burrow into the emerging leaves, causing blisters to form. Blister mite damage may continue throughout the growing season. With the onset of cold weather, adult mites move back under the bud scales.
Damage on the fruit cannot be controlled in the present year. To control future infestations, apply an insecticide labeled for this pest, following label directions.
Conotrachelus nenuphar These insects commonly attack stone fruits, apples, and pears. The adult insects are brown beetles with long, curved snouts. They hibernate in debris and other protected places during the winter. The beetles emerge in the spring when new growth starts and begin feeding on young leaves, blossoms, and developing fruit. After 5 to 6 weeks, the female beetles start to lay eggs in the young fruit. During this process they cut distinctive, crescent-shape slits into the pears. The grubs that hatch from the eggs feed for several weeks in the fruit. Usually the infested pears drop to the ground. The grubs eventually leave the fruit and bore into the soil, where they pupate. The emerging beetles feed on fruit for a few weeks, then hibernate. Or, in the South, they lay eggs, producing a second generation of grubs in the late summer.
You can''t kill the grubs inside the fruit. Protect the rest of the tree by applying an insecticide labeled for this pest, following label directions. Pick up and destroy all fallen fruit.