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Pear Psylla (Cacopsylla pyricola)DamagePresence of honeydew and black sooty mold on fruit, leaves and bark, and brownish-black patches of dead tissue on leaves indicates pear psylla infestations. Sooty mold grows on the honeydew secreted by psylla nymphs. Heavy infestations can cause premature leaf drop, weaken fruit buds and reduce shoot growth. Honeydew causes enlargement and blackening of pores on the skin of the fruit and, along with the presence of sooty mold, results in downgrading of fruit.
IdentificationEggs - Oval, about 0.5 mm long; white when laid, gradually turning yellow.Nymphs - Five growth stages, the first three are yellow with red eyes and live within droplets of honeydew. Stage 4 is green with small wing pads and lives freely without honeydew droplets. The fifth stage (hard-shell) is brown to black with distinct wing pads. Adults - Summer adults are greenish to brown in colour with pale wings held roof-like over the 3mm-long body. Overwintering adults are larger and darker in colour.
Life HistoryPsylla overwinter as adults on trees and shrubs adjacent to pear orchards to which they return in early March to begin laying eggs on or near buds. In the summer, females lay eggs along the mid vein of leaves on new shoots and suckers, or on lower leaves when populations are very high. Three or four overlapping generations are produced each year with overwintering adults appearing in late summer.MonitoringIn the dormant period, use a limb tap sample of 25 limb taps/hectare of orchard. If a dormant treatment is applied, sample again 10 to14 days later to determine if a second dormant or a pink treatment is needed. In June collect 100 spur leaves and examine for eggs and nymphs. Repeat the procedure in July and August by collecting 100 terminal leaves for examination. Psylla predators (see biological control below) should also be monitored using limb taps at 3-4 week intervals.ControlCultural - Reduce excessive tree vigour by limiting nitrogen applications and summer pruning to reduce psylla numbers.Biological - Pear psylla is fed upon by many predatory insects such as the mullein bug (campylomma), pirate bugs (anthocorids), lacewings, ladybird beetles, earwigs and some species of ants. Preservation of these beneficial insects by avoiding use of certain chemicals (such as azinphos-methyl, diazinon, synthetic pyrethroids, endosulfan and formetanate hydrochloride) has proven to be effective in reducing psylla numbers.
ChemicalDormant to Pink Bud Stage - Apply a dormant or pink spray if 1 or more psylla adults are collected per limb tap in the spring.Dormant oil sprays (70 L/ha or 2 L/100L) applied in early March will inhibit psylla from laying eggs on pear trees for about 6 weeks until leaves emerge. The addition of Endosulfan or Thiodan or lime-sulphur to this early dormant oil treatment will improve control of adult psylla and also suppress pear rust mite and pearleaf blister mite. If the average number of psylla per limb tap remains at or above 1, apply a second oil plus endosulfan (see rates above) treatment using half rate of oil. Do not add endosulfan if predatory insects are present. Synthetic pyrethroid products (Ambush, Belmark, Cymbush, Decis, Pounce and Ripcord) are no longer recommended as pear psylla has developed resistance to these products in most areas. A new synthetic pyrethroid, cyhalothrin-lambda (Matador 120 EC) is now available for application no later than tight cluster. Application after tight cluster risks harming any pear psylla predators present at the time. At the pink bud stage apply Morestan to complete the prebloom control program for psylla. It will also control pear rust mite and powdery mildew and assist in control of European red mite. Summer - For summer control of pear psylla, apply Agri-Mek with oil, insecticidal soap, Mitac or Pyramite. Do not exceed 1500 mL Agri-Mek per ha per season. Agri-Mek plus oil may cause fruit injury to d’Anjou when temperatures exceed 30°C within 24 hours of application. Application of Agri-Mek will also control twospotted spider mite, European red mite, and pear rust mite. Use Agri-Mek in rotation with products with different modes of action to avoid development of pesticide resistance. An alternative to Agri-Mek is insecticidal soap. Soap sprays are very effective against nymphs, partially effective against adults and not effective against eggs. Spray volumes of 2000 L/ha or more must be used for soap sprays to be effective. Apply the first sprays when newly hatched nymphs appear on new growth. Repeat treatments at 10-14 day intervals as long as the nymphs are present so that they don’t develop to the hard-shell stage. Apply Mitac pre or post bloom for control of psylla adults and nymphs when daytime temperatures exceed 10°C. For pre-bloom control, apply just prior to egg laying or immediately after first generation eggs have hatched. Apply post bloom sprays when the majority of psylla are in adult or young nymphal stages. Do not apply more than 3.35 kg/ha, no more than twice per season nor more than 6.70 kg/ha per season. See label for instructions regarding protective clothing, re-entry and posting spray warnings. Mitac is toxic to predatory mites, moderately toxic to anthocorids (pirate bugs) and Deraeocoris, and slightly toxic to green lacewings, parasitic wasps, campylomma and ladybird beetles. Pesticide resistance management – Psylla can develop resistance to successively applied insecticides from the same chemical class or with the same mode of action. For example, psylla is resistant to pyrethroid products (Ambush, Cymbush, Decis, Matador and Pounce). Consult the Tree Fruit Production Guide for assistance in selecting products to use in a rotational program to prevent or minimize the risk of pesticide resistance. Integrated Control ProgramThe integrated control of pear psylla involves the combined use of cultural and biological control methods (see above) with the careful selection and application of chemical control products for psylla and other pests. It is important to monitor psylla and beneficials as well as to keep accurate records of monitoring results and spray treatments (see Grower’s Orchard Monitoring Record and Grower’s Spray Record) for the program to be most successful.Products recommended for psylla control are as listed above under Chemical Control. For other pests, apply only products that do not harm psylla predators. For leafrollers and bud moth, an effective spring control program is essential to minimize the need for summer control sprays (see discussion for leafroller control). Apply a Bacillus thuringiensis (Bt) product (Dipel, Foray or Bioprotec), Confirm or Success when larvae are actively feeding in the spring. These products will also control any fruitworm present. Ensure thorough coverage because leafroller larvae must eat these products to be most effective. Do not apply Confirm for control of leafroller populations tolerant to organophosphate products. Success can harm some beneficial insects exposed to direct sprays, however the threat is reduced once the residues dry. For codling moth, use pheromone traps to determine whether sprays are necessary. If they are, use Imidan, Zolone or Confirm rather than Guthion or Sniper. Imidan and Zolone provide less residual control (10-14 days) than Guthion or Sniper (3 weeks). To minimize or eliminate the need for cover sprays, use mating disruption for control of codling moth. Treat orchards requiring control of San Jose scale with dormant oil prebloom rather than with summer sprays of diazinon. For control of European red mite and McDaniel spider mite during the summer, use Kelthane or Apollo rather than Carzol which is disruptive to integrated control of psylla. Apollo is harmless to predatory mites. Apply Kelthane only once per season. Use Kumulus rather than Endosulfan or Thiodan for control of pear rust mite (except on Anjou pears). February 2004
Return to Tree Fruit Pests and Diseases
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