Plant Health Problems

See Apple for a discussion of problems that may occur on quince.

Diseases caused by Fungi:

Black spot, Fabraea maculata.
This common disease of quince can cause severe injury if not controlled. On the leaves the disease shows as small circular spots, reddish-brown on the periphery, with black centers. In the centers, numerous minute black spore-bearing pustules can be seen. A heavy infection will cause extensive defoliation. The fruit infections appear as irregular sunken black spots scattered at random over the surface. The spots may become confluent and cause cracking of the fruit. The causal fungus overwinters on the old leaves, producing two types of spores in early summer. These start new infections on the foliage and young fruit.

Control can also be achieved with the use of fungicide sprays. Among the compounds registered for use in Connecticut is mancozeb. Consult the label for dosage rates and safety precautions. It is interesting that Thaxter conducted perhaps the first successful control experiments at this Station in 1890.

Rust, Gymnosporangium clavipes.
This rust occurs on the leaves, stems, and fruit. On the leaves it produces small orange-colored spots, on the stems it causes swollen gall-like growths, and on the fruit it appears as circular orange-colored areas which may comprise half the surface area. On all infected parts of the plant the brilliant orange spores are borne in very small, white, toothed cups. See Apple for a more detailed discussion of this disease.

Fruit speck, Mycosphaerella pomi.
Not common on quince but is mentioned because of a slight similarity to black spot. See Apple for a more detailed discussion of this disease.

Black rot.
See Apple for a more detailed discussion of this disease.

Diseases caused by Bacteria:

Fire blight, Erwinia amylovora.
Fire blight is more common and serious on quince than on apple, but not as destructive as on pear. See Pear for a more detailed discussion of this disease.

Insect Problems

Apple aphid, Aphis pomi.
Nymphs and adults of apple aphid, Aphis pomi, the apple grain aphid, Rophalosiphum fitchii, and the woolly apple aphid, Eriosoma lanigerum, can injure quince trees. Aphids damage leaves on water sprouts and rapidly growing terminal shoots. Young quinces may be deformed when infestations are severe. In the fall, females lay elongate shiny, black eggs on the bark. The nymphs hatch from eggs in the spring. Both the nymphs and adults of this small green aphid pierce quince tissue to suck the sap in stems, foliage, and fruit. During the growing season, apple aphids have many generations, during which young are produced asexually. In the fall, sexual forms appear, and after mating, the females lay the eggs that will overwinter. Heavy fertilization with nitrates may increase aphid infestations. Materials registered in Connecticut to control aphids on quince include horticultural oil, malathion, diazinon, azadirachtin, ryania, and insecticidal soap. Dormant sprays of horticultural oil have been marginally effective because of later migration. Sprays of malathion and diazinon control aphids but are detrimental to natural enemies. Azadirachtin, ryania, and insecticidal soap are alternative sprays for aphid control. If using insecticides, follow the label instructions and where applicable, observe preharvest intervals. Natural enemies, such as syrphid flies, ladybird beetles, and lacewings, sometimes adequately control apple aphids.

Codling moth, Cydia pomonella
Caterpillars of the codling moth damage the quince. This moth is one of the three most destructive apple insects that feed directly on quince. Pinkish caterpillars that have overwintered under bark or debris form pupae in spring. Females emerge around bloom to lay eggs on fruit. The grayish adults are slightly more than 1/4" long, with wavy lines and a dark band at the tips of the wings. Caterpillars of the first of the two generations enter the fruit shortly after the blossoms fall. Those of the second generation injure fruit in August and September. The amount of damage varies greatly from year to year. Caterpillars of the codling moth are distinguished from those of other boring caterpillars by having a dark brown anal comb at the rear of the body and by tunneling directly to the core of the fruit. Pheromone traps may be used to monitor adult flights. Applications of carbaryl, phosmet, or ryania, which are among the compounds registered for use against this pest in Connecticut, about 21 days after full bloom control the caterpillars. Consult the labels for dosage rates, safety precautions and where applicable, preharvest intervals.

Hawthorn lacebug, Corythucha cydoniae.
These small sucking insects with large lacy wings feed on the under surfaces of the leaves. The adults spend the winter under leaves on the ground. Among the products registered for use against this pest on ornamental quince in Connecticut are horticultural oil, insecticidal soap and imidacloprid. Consult the labels for dosage rates, safety precautions and timing.

Oriental fruit moth, Grapholita molesta
Caterpillars of this moth are among the most destructive pests of quince in Connecticut. The principal damage is "wormy" fruit, but shoots may also be killed. Mature caterpillars overwinter in impervious silk cases on the bark of the trunk or upon debris in orchards. These caterpillars are pink and about 1/2" long. In spring, they form pupae in the cases, and the mostly gray adults emerge in May, starting when peaches bloom. The moths have wingspan of just less than 1/2". The females lay eggs upon the undersides of the leaves and, in some cases, on the twigs. The caterpillars of the first generation tunnel into the tender shoots early in the season, and later they leave the twigs to enter the fruit. As twig borers, the caterpillars kill the tips of shoots and cause the shoots to branch. The caterpillars of later generations go directly into the fruit after hatching. In peach orchards in Connecticut, the oriental fruit moth has three generations and sometimes a partial fourth generation. They may infest fruit until late September. Insecticidal applications of phosmet or diazinon, which are among the compounds registered for use against this pest in Connecticut, from petal fall until four weeks before harvest control this pest. Consult the labels for dosage rates, safety precautions and where applicable, preharvest intervals. Use of pheromone traps will assist in timing the sprays.

Quince curculio, Conotrachelus crataegi
In Connecticut, this beetle is one of the most destructive pests of quince fruit. After spending the winter in the soil, the larvae form pupae in spring. The adults appear in midsummer, usually about the middle of July. These brownish gray beetles are about 1/4" in long. Females lay eggs singly in fruit. After the eggs hatch 7-10 days later, the larvae tunnel into the flesh of the fruits, rarely reaching the core. The flesh-colored larvae are grub-like and without distinct legs. In about one month, usually in August, the mature larvae leave the fruit to make cells 2-3" deep in the soil where they remain until the next year. Adult curculios can be controlled on quince fruit trees by applying phosmet, which is among the compounds registered for use against this pest in Connecticut, at petal fall and again about 10 days later. Consult the label for dosage rates, safety precautions and preharvest intervals.

Resplendent shield bearer, Coptodisca splendoriferella
The caterpillars of this moth cause minor foliar damage to quince and apple. In May, the tiny adults emerge from pupae that have overwintered in cases on the tree. The forewings of these moths are lead gray on the basal half and golden with streaks of dark brown and silver at the tip. The females lay eggs on the leaves. After hatching, the caterpillars form tiny blotch mines as they feed on leaves. When the caterpillars are mature, they cut out shield-shaped portions of the leaf for cases and fasten them to the bark. They have at least two generations, with pupae of the last remaining the leaf cases until May of the following spring. Sprays applied for other foliar pests have controlled this pest.

San Jose scale, Quadraspidiotus perniciosus.
San Jose scales commonly infest quince. Large infestations of the San Jose scale can cause branch and even shrub death. Partially-grown scales overwinter under their circular gray covering or scale on the twigs and the branches of trees. They begin to feed as the sap starts to flow. When apple trees bloom, the males emerge from under their scales to mate with the immobile females. Females are circular and cone-shaped, and their circular scales are about 1/16" in diameter, with a raised center or nipple. The males are smaller and elongate, with the nipple not centered on the scale. Females give live birth to tiny bright yellow crawlers in June. The young crawlers quickly settle, insert their long mouthparts into the twigs, and then suck sap from branches. As they grow, the crawlers secrete a waxy filament that becomes their scale or covering. Overlapping generations are present from June through September. Scales may be controlled by applying horticultural oil at a dormant timing or in June when crawlers are active. Diazinon, which is among the compounds registered for control of this pest in Connecticut, can also be applied against the crawlers in June. Consult the labels for dosage rates, safety precautions and where applicable, preharvest intervals. To detect the yellow crawlers, wrap black tape coated with Vaseline around small branches. Adult flights may be detected with pheromone traps.