This section is from the book "Commercial Gardening Vol3", by John Weathers (the Editor). Also available from Amazon: Commercial Gardening, A Practical & Scientific Treatise For Market Gardeners.
The so-called Codlin Maggot is the larva of the moth known as Carpocapsa pomonella.. It often causes endless damage in Apple orchards all over the world, but seems to be now on the decline in Britain. The moth appears in June and July. In wing expanse it measures about 3/4 in.; the fore wings are grey, with darker transverse wavy lines, and a bright metallic spot at the anal corner; the hind wings are uniformly grey. The female lays her eggs on the side of the fruitlets. The ova are small flat bodies with reticulate shell, and are very transparent. They are seen with difficulty. The small larva coining from the egg crawls up the side of the fruit and gets into the eye, where it feeds for a short time, and then it enters the apple, making its way to the core, which it enters, and destroys the pips. It then makes an opening to the outside, and eventually escapes from the damaged fruit. The larva, or so-called maggot, is creamy grey to dusky pink, and reaches about 3/4 in. in length. It has six jointed legs in front, four pairs of prolegs, and an anal pair. It can thus easily be told from the Apple Sawfly larva. When it leaves the apple and falls to the ground it soon reascends the tree, and upon coming to any shelter, such as rough bark, moss or lichen, sacking or string, it at once spins a cocoon, and remains in this as a larva until the spring, when it changes to a brown pupa, from which the moth emerges soon after the blossom has fallen. Now and again the larvae pupate at once, and a second brood of moths appear in August. The larvae of this second brood pass the winter in exactly similar manner.
Fig. 343. - Lackey Moth (Clisiocampa neustria) 1, Eggs. 2, Catterpillar. 3, Moth.
Banding trees with manure sacking, so as to catch the ascending maggots, is an excellent plan. The sacking should be placed close to the ground and double folded. These traps should be taken off in the winter and burnt. Spraying with arsenate of lead within ten days after the blossom has fallen will also do good, as it poisons the small larva before it enters the apple by its eating the arsenic lodged in the eye or calyx cup.