2 Lifestages of the Codling Moth
Most of this paper concerns the codling moth (Cydia pomonella) specifically, and the goal is to explain how to use high technology, which is within the reach of the backyard orchardist, to control this pest, but the technology can be directed toward other pests, of course, and some gestures are made in that direction, describing the software (below).
First, though, it is important to identify the pest(s) of concern and confirm that it is C. pomonella.
Codling moth has a 0.5 to 0.75 inch wingspan. The tip of each forewing has a coppery-tinged, dark brown band that distinguishes codling moth from other moths found in apple orchards. Females lay eggs singly on leaves and sometimes on fruit later in the season. The eggs are smaller than a pinhead, disk-shaped, and opaque white when first laid. Just before hatching the black head of the larvae becomes visible. Newly hatched larvae are white with black heads. Mature larvae are 0.5 to 0.75 inch long, pinkish white, with mottled brown heads.
Codling moth ... causes two types of fruit damage: stings and deep entries. Stings are entries where larvae bore into the flesh a short distance before dying. Deep entries occur when larvae penetrate the fruit skin, bore to the core, and feed in the seed cavity. Larvae may enter through the sides, stem end, or calyx end of the fruit. One or more holes plugged with frass on the fruit's surface are a characteristic sign of codling moth infestation. Calyx entries are difficult to detect without cutting the fruit (UCANR, "Management Guidelines").
In most contries of the world you can rely on a network of quasi-governmental agencies for help identifying pests and recommending control measures appropriate to your crop, location, and circumstances. There are, after all, local regulations concerning chemical applications that you should be aware of and abide by, and this paper by itself is not an adequate guide. In the United States, please contact the County Cooperative Extension Agent of your state Land-Grant College.
There are several control methods used to attack codling moth, but each is effective during only one or another of the developmental phases of the pest. A prerequisite to itemizing these methods of attack is to list the lifestages of the codling moth.
The life span of codling moth is short, and there can be at least two generations (flights) during a growing season. Synchronization of lifestages insures that most adults will be present together at the same time to mate.
At all lifestages, codling moth development proceeds most rapidly during ideal temperatures. Cooler or warmer temperatures slow development.
Adults lay eggs individually on fruit or on the undersides of leaves. These hatch in one or two weeks.
The larvae locate fruit and burrow in. They remain in the fruit for three or four weeks.
While they are inside, the larvae are invulnerable to any kind of attack (except long-term cold storage) that does not also destroy the fruit. Of course, they leave traces. One may notice the frass at the entry hole although it is possible to overlook it when the entry is at the calyx.
The larvae leave the fruit to find a place to spin a cocoon.
Cocoons of the offspring of the first flight are usually discovered in crevices in the bark of the tree, but may be in ground litter. Those of subsequent flights may even be found on other timber and perhaps in orchard equipment, depending on where infested fruit has been stored.
The larvae remain in their cocoons until ready to pupate. Pupation, which takes place inside the cocoon, lasts two to three weeks.
In early summer, most larvae of the first flight pupate immediately. The adults that emerge make up the second flight. There are a handful of larvae of the first flight, however, that enter diapause in their cocoons and do not pupate until the following spring. In most years in most temperate locations, most of the larvae of the second flight remain in their cocoons over winter, and the third flight is insignificant, but, in some locations and under favorable conditions, a substantial third flight or even a fourth is possible. The larvae of the third or fourth flight may still be inside the fruit when the harvest is brought in and, thus, will not contribute to the next spring's population.
In the spring, the pupation of all the larvae that overwintered in their cocoons is synchronized.
Pupae then emerge as adults, which mate and lay eggs.
By trapping adult males, the time of the first flight can be observed, and, by recording daily maximum and minimum temperatures from then on, the arrival of subsequent lifestages can be predicted. In fact, pupation in preparation for the first flight can be predicted based on cumulative degree-days.