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Brownheaded leafrollers - Reproduction |
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The two pest species of brownheaded leafrollers produce
distinct female sex pheromones for long range communication with
males seeking a mate. Pheromone traps
exploit this by being baited with the distinct pheromone of each
species; this enables each species to be monitored separately.
The main pheromone components are:
Ctenopseustis obliquana:
(Z)-8-tetradecenyl acetate, (Z)-5-tetradecenyl acetate
Ctenopseustis herana:
(Z)-5-tetradecenyl acetate
The ratios of Z5-14:OAc to Z8-14:OAc in C. obliquana vary
in different parts of the country. The pheromones are released in
the evening and night, but particularly around dusk, and attract
males over long distances. Females are normally mated once,
although both sexes are capable of mating more often. The male
passes sperm to the female in a sac (spermatophore) which the
female stores in the bursa copulatrix. Most mating occurs 1-4
days after adult emergence.
The female lays a series of egg batches, averaging on apples in the field about 56 per batch (range 2 - 216), almost exclusively on the upper leaf surface. Fecundity is highly variable between individual females and in one study averaged from 58 to 429 eggs/female when larvae were fed on freeze-dried apple foliage. Higher average fecundities were obtained at 11.5oC than at 18 or 22.5oC. Egg infertility in New Zealand under natural conditions is rare at <1%. Egg mortality from other causes is also low with inviability (failure to hatch) averaging only 2% of eggs. New Zealand lacks many of the predators which feed on leafroller eggs overseas. High mortality of (neonate) caterpillars occurs when they disperse after hatching from their egg batch.