The organic spray program is designed to prevent most if not all of the pest insects and diseases listed below. If you choose not to follow the spray program, you may find that your pear crop is blemished in various ways. You will still get edible pears, but they won’t look pretty and parts will need to be cut out before they are eaten. Pear trees share many of its more unique problems with apple trees.
|Pear Tree Problems|
|Pears Have Worms||Apple Maggots|
|Tunnels in Pears||Codling Moth|
|Leaves Yellow and May Drop||Pear Pyslla|
|Small Misshapen Pears||Cherry Fruit Fly|
|Black Spots and Pitting||Tarnished Plant Bug|
|Discolored Leaves, Scarred Fruit||Thrips|
|Withered and Dead Blossoms||Fire Blight|
|Foliage Curls, Puckers, Turns Yellow||Aphids|
|Pears Fall, Have Cuts in Skin||Plum Curculio|
|Defoliated Tree||Gypsy moth caterpillar|
|Leaves Stippled Yellow||Mites|
|Leaf Buds and Early Bark Eaten||Weevils|
|Twig Dieback; Foliage Loss||Scale|
|Velvety Olive-Green Spots on Pears; Fruit distorted and drops early||Pear scab|
Pears Have Worms
Apple Maggots - Although they are hard to detect on the outside, sometimes white worms eat the flesh inside maturing pears, digging tunnels into the flesh. These are apple maggots, the larvae of the apple maggot fly. They are white or yellowish and measure 1/4 inch long. The adult fly is also 1/4 inch long. It is black with yellow legs, yellow markings across the abdomen, and bands that zigzag across the wings. These flies lay eggs in punctures in pear or apple skin. The best way to control apple maggots is to prevent the adult fly from laying eggs. Trap them with a commercial trap made from a red ball and/or a yellow rectangle covered with sticky material. Hang these traps in trees in late June and remove them after harvest. Use two traps per tree for dwarf and semi-dwarf pear trees and four traps for standard trees. Keep them clear of surrounding branches. Clean up all fallen fruit immediately.
Tunnels in Pears
Codling Moths - A codling moth larva is 1 inch long and pink with a brown head. The adult is a grayish brown moth with lacy brown lines on its forewings and pale, fringed hind wings. It has a 3/4-inch wingspan. The larvae of codling moths tunnel their way through pears, eating as they go. Their presence is signalled by visible cocoons in the bark crevices. Adult moths lay white, flat eggs singly on leaves, twigs, or fruit buds. To control these pests, spray dormant oil on trees prior to leaf budding in late winter or early spring to suffocate the eggs. As the pear blossoms are just beginning to show pink and open up (open cluster), set out commercial sticky traps with pheremone lures to catch the moths. If there are more than 10 moths caught in a single trap during the 10 to 14 days after bloom time use ryania in a spray as the blossom petals begin to fall. Spray BT and light horticultural oils every 7 to 10 days later in the season to kill newly hatched larvae. Plant butterfly weed (Asclepias tuberosa) nearby because it hosts parasites of codling moths.
Leaves Yellow and May Drop
Pear Psylla - Psyllids are jumping insects that produce a honeydew, inviting infections of fungal molds harmful to pear trees. The insects attack the blossoms and prevent fruit set. Adult psyllids are reddish brown and emerge in spring and mate. Females then lay their yellow eggs on twigs. Both the immature insects and adults feed by sucking out the tree’s juices. Leaf yellowing and a general decline in vigor may indicate that your trees have pear psyllids. Severely infected trees may (drop)their leaves. The best preventive measure is a thorough dormant-oil spray in the early spring before the leaves come out.
Small Misshapen Pears
Cherry Fruit Fly - Adult cherry fruit flies resemble small houseflies with bars on their wings. They are about 1/5 inch long. Adults emerge in late spring or early summer. The females lay eggs inside the developing fruit. The maggots that hatch out are yellowish white and legless, with two dark mouth hooks. If your pears are small and misshapen, and have maggots feeding on rotten flesh in the fruit, cherry fruit flies have infested your trees. The pears may (drop)prematurely. To control cherry fruit flies, it is essential to control the adults before the eggs are laid. Set out red spherical sticky traps to catch the flies and signal their arrival; then spray the trees with rotenone. Continue to spray at 7 to 10 day intervals until traps show no more adults.
Black Spots and Pitting
Tarnished Plant Bug - The adult tarnished plant bug is a 1/4-inch-long, oval, flat, brownish insect, mottled with yellow and black. It sucks on plant parts. The tarnished plant bug’s eggs are long and curved, and can be found inserted in stems, tips, and leaves. The nymphs are pale yellow. Black spots and pitting can be seen on the stem tips, buds, and fruit of infested pear trees when these pests are present. Tarnished plant bugs are highly mobile. They deform roots, blacken terminal shoots, and ruin flowers. Only buds that escape feeding will set fruit. Use sprays early in the morning when bugs are least active.
Discolored Leaves, Scarred Fruit
Thrips - Thrips are only 1/25 inch long, virtually invisible. What is visible are their dark fecal pellets on the undersides of infested leaves. Thrips puncture leaves to suck the sap, causing considerable discoloration and distortion. Leaves may become bleached and wilted. For detailed info on solutions go to the Controlling Thrips file in Yardener’s Helper.
Withered and Dead Blossoms
Fire Blight - Fire blight fungus is one of the most serious pests of pear trees. Very few trees are completely resistant and those that are usually produce poorer fruit. While it is a major problem, it is a disease that can be controlled with correct fertilization and pruning.
Shoots infected with fire blight turn brown or black and have a scorched appearance. The blossoms wither and die. Reddish water-soaked bark lesions appear, and on warm days they ooze an orange-brown liquid. Later they become brown and dry. The best defense against fireblight is diligent pruning. In the winter, look for affected branches with visible cankers, and prune them off just a few inches below the cankers. On limbs too large to remove, pare away diseased tissues, sealing the wounds with tree paint. In the summer, watch for blackened leaves, stems, or fruits, and cut them off 12 inches below the sign of disease. Also snap off vigorous suckers thrown up along branches and from the rootstock; these are very prone to fireblight. IMPORTANT - Disinfect your pruning tool in a bleach solution (one part household bleach to four parts water) AFTER EACH CUT! Hold the shears in the solution for at least 2 seconds.
Varieties of pear trees resistant to fir blight: Asian varieties and Comice, Dawn, Douglas, Duchess d’Angouleme, El Dorado, Fan-stil, Harvest Queen, Lincoln, Luscious, Mac, Magness, Maxine, Moonglow, Orient, Seckel, Starking Delicious, Sugar, Sure Crop, Waite, and Winter Nelis. Disease-resistant rootstocks: Kieffer, Moonglow, Old Home, Oriental (Pyrus bitulafolis), Oriental (Pyrus communis), Oriental harbin pear (Pyrus ussuriensis), Seedling, Stark Honeysweet, and Starking Delicious.