Notes on Stone Fruit Insects &
Mites
Pear psylla
Identification
Adults are small (2 mm), reddish-brown with four membranous wings. They
lay elongated white-yellow eggs. Nymphs are flattened and pass through
five instars before the adult stage. Youngest nymphs are yellow then green.
Older nymphs have sturdy wingpads and are black in colour. All stages
have mouthparts that pierce and suck and produce sticky honeydew as they
feed.
Period of activity
Pear psylla adults overwinter in cracks of tree bark or under debris.
Adults become active when temperatures reach 10°C. Mating and egg
laying occur prior to bud break. There are two to three generations per
year in Ontario.
Monitoring and thresholds
Examine samples of fruit spurs for eggs and adults in early March to
provide an indication of potential pest pressure. From mid-April through
to harvest examine spurs, new terminals and water sprouts weekly for eggs,
nymphs and adults. Tapping trays are useful for monitoring adults. Collect
at least 25 fruit spurs and terminals (1/tree) per orchard. Table 1. Thresholds
for Pear Psylla, provides thresholds for control. See OMAFRA Factsheet,
Pear Psylla in Ontario Pear Orchards, Order No. 90-101, for more information
on monitoring.
Table 1. Thresholds for Pear Psylla
| Stage of crop development |
Decision/threshold |
| Delayed dormant |
Depends on previous history, adults present, egg laying started |
| White bud stage |
10 eggs or more/spur with hatching started |
Immediately at petal fall
|
10 actives/spur and majority of eggs hatched |
| Emergency summer spray #1 |
5-10 actives/sucker |
| Emergency summer spray #2 |
20 actives/sucker with low predator population; stickiness and fruit
loss imminent |
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