HortFACT
Identification
The adult codling moth is easily distinguished from related species by its colour. The forewings are grey crossed with fine brown bands, the tips have dark brown oval areas with brilliant bronze markings. The hindwings are a more uniform pale satin brown. The wing span is 15-20 mm. The moths are active around sunset, resting by day on the trunk or branches of the host tree.
Eggs about I mm in diameter are laid, usually singly, on leaves near the fruit or on the fruit itself. Where there is one generation per year [univoltine] the egg-laying period extends throughout the summer (see chart), in contrast to the short egg-laying period often found in univoltine populabons overseas.
The larvae [caterpillar] after hatching is about 1.4 mm long and grows through five instars (four moults) to about-20 mm long. The head and prothoracic plate [plate behind the head] are black in early instars, but in the final (fifth) stage the head is brown. At this stage the prothoracic plate is pale and the remainder of the body may be pink after leaving the fruit, instead of the usual White.
Cocoons containing diapausing (dormant) caterpillars are usually constructed in crevices and under the bark of the trunk or branches of the tree but may be found in other places, such as box stacks, buildings, and wood piles, near where apples are grown or stored. Subsequently they may be transported out of the vicinity of fruit. In these circumstances the close woven, dense cocoon, 15-20 mm long, is a help in identification.
Larvae of the genus Carposina sometimes damage fruit in a similar manner to the early stages of codling moth, but can be distinguished by the last three segments of the abdomen, which taper abruptly and are modified to form a shallow basin.
Host plants
Pome fruits [pip fruits, such as apples and pears] are the main hosts. Other plants less frequently but consistently attacked are walnuts and plums. Other known hosts include peaches, nectarines and apricots.
Damage
Important damage is caused by the larvae only and is confined to fruits. The larva enters the fruit at any point on its surface, though more often through the exposed side. It tunnels to the seeds, which are eaten, and extensive damage is done in and around the core. The tunnels usually contain frass [faecal pellets], though some frass is removed to the outside where it protrudes from the entry hole. Often the larva dies shortly after entry, and its damage is characterised by a small spiral gallery just below the fruit surface. A "sting" occurs on the fruit when a larva bites the surface but fails to enter. The larva may die or fail to enter fruit both through natural causes and from insecticides, the insecticides currently used prevent damage almost entirely.
Distribution
The codling moth occurs throughout New Zealand wherever pome fruits are grown. It is commonly found attacking isolated apple trees alongside road and rail routes, even in remote areas.
Life cycle
| Egg |  |
| Larvae | |
| Pupae | |
| Adult | |
| Month | |
| Note: Coloured bars indicate periods of peak activity in each of the life cycle stages | |
The illustration shows a typical life cycle in areas, such as Nelson, where there is one generation per year. In these areas there is a partial second generation in some years, as is often found in Canterbury and southern parts of the North Island. In the Auckland area two generations and a partial third are normal, with some overlap between them. In all cases the diapausing fifth instar larvae overwinter in cocoons under the bark and in holes in the wood of host trees. These larvae change to pupae in the spring.
C.H. WEARING