All varieties of pear trees have problems with insects and diseases. Pear trees need to be watched during the growing season, as well as in the winter when they are dormant in order to head off problems that may cost the crop, or even the life of the tree.
Apple maggots don't just attack apple trees, they go after pear trees as well. They are the larvae of the apple maggot fly and eat the inside of the fruit. The larvae can be white or yellow and about 1/4-inch long. The adult is about the same size, but is black with yellow legs, yellow markings on the abdomen and yellow bands across the wings. The best control is prevention by trapping the adults in a trap built just for the purpose. Place the traps in the trees in late June and remove after harvest is over. Clean up any damaged fruit as soon as it falls off.
Pear psylla are jumping insects that deposit a substance called honeydew on the leaves. Any fungus spores that are airborne can fall on the honeydew, stick and grow. The insects themselves can do a great deal of damage by attacking the flowers and preventing the fruit from even getting started. The adults are a reddish brown and appear in the spring when the females lay their eggs on the twigs of the pear tree. Both the adults and the larvae feed on the tree itself, sucking out the juices. The leaves will turn yellow and severely infected trees will lose leaves. The insects can be prevented by using a dormant-oil spray early, before the leaves start to appear.
Fire blight is a serious fungal infection. Shoots will turn brown or black and look like they have been scorched in a fire. It will produce reddish water-soaked lesions on the bark that will ooze an orange/brown liquid when they first form and turn hard as they age. The blossoms will wither away and die, not giving the fruit a chance to get started. The tree needs to be inspected in the winter and any branches that have cankers need to be pruned away just below the cankers. If the branches are too large to cut off, pare away the diseased parts and seal the wounds with tree paint. The tree needs to be watched in the summer as well. Keep an eye out for blackened leaves, stems or fruit. Cut them 12 inches below where they appear. Cut away any suckers the tree sends out both on the branches and from the roots. It is very important to de-infest the pruning sheers in a solution of 1 part bleach to 4 parts water after each cut or you risk spreading the disease to other parts of the tree or to the next tree you prune.