HortFACT
Larvae [caterpillars] are not easily distinguished from the larvae of other leafrollers, i.e. the greenheaded leafroller Planotortrix excessana (Walker), the brownheaded leafroller Ctenopseustis obliquana (Walker), and Merophyas leucaniana (Walker), when occurring together in the same habitat.
The first larval instar [stage] has a dark brown head; all other instars have a light fawn head and prothoracic plate [plate behind the head]. Overwintering larvae are darker. First instar larvae are approximately 1.6 mm long, and final instar larvae range from 10 to 18 mm in length. The body of a mature larva is medium green with a darker green central stripe and two side stripes.
Pupae are at first green, but become medium brown after rapidly hardening.
Host plants
The range of hosts is extremely large. The more common hosts are: apples, pears, grapes, citrus varieties, black and red currants, kiwifruit, hops, red and white Covers, lucerne, lupin, tree lupin, plantain and other weed species, tutu, gorse, chrysanthemum, michaelmas daisy and other flowering plants, various shrubs (especially acacias), and conifers in the young stages of growth.
Damage
The larvae cause damage to foliage and fruit. Early instars feed on tissue beneath the upper epidermis [surface layer] of leaves, while protected under self-constructed silken webs on the undersurface of leaves. Larger larvae migrate from these positions to construct feeding niches between adjacent leaves, between a leaf and a fruit, in the developing bud, or on a single leaf, where the "topical" leaf roll develops. The late stage larvae feed on all leaf tissue except main veins.
Superficial fruit damage is common in apple varieties which form compact fruit clusters. Leaves are webbed to the fruit and feeding injury takes place under the protection of the leaf; or larvae spin up between fruits of a cluster. Internal damage to apple, pear, and citrus fruits is less common, but a young larva may enter the interior of an apple or pear fruit through the calyx or beneath the stem of a citrus fruit. Excreta are usually ejected on to the outside of the fruit; this does not happen with the codling moth.
Distribution
Within New Zealand, this Australian migrant occurs throughout the cultivated lowland areas, being especially troublesome where pip-fruit growing is concentrated and, along with other species, in citrus orchards and young exotic forest stands.
Life cycle
| Egg |  |
| Larvae | |
| Pupae | |
| Adult | |
| Month | |
| Note: Coloured bars indicate periods of peak activity in each of the life cycle stages | |
Lightbrown apple moth passes through three generations annually in the central New Zealand region, with a partial fourth generation in some years, and has no winter resting stage. There is considerable overlap in the generations.
In Auckland and northwards four generations are completed annually, with major flight periods occurring during September-October, December-January, February-March, and April-May. In Southland the number of complete generations may be reduced to two during prevailing inclement climatic conditions.
Eggs are laid in clusters of 3-150 on leaves or fruit. Adults produced by the overwintering larval generation emerge during October and November. These give rise to the first summer generation, in which final instar larvae mature between January and mid February. Second generation larvae reach maturity during March and April, and the adults from this generation provide third generation eggs. Normally, the rate of larval development is slowed considerably during the winter; thus the majority of larvae over-winter in the prolonged early juvenile phases of the second third, and fourth instars. During this period they normally feed on herbacious plants. Re-invasion of apple trees takes place during October-December, when moths of the third generation start laying eggs again on the apple leaves.
W.P. THOMAS