In the UK Codling moth — Cydia pomonella — is a widespread pest of apples and occasionally pears. Damage is caused by the caterpillar burrowing into developing fruit and is more prevalent in the southern half of England than elsewhere.
The most serious infestations normally occur during long, hot summers. The surface of the apple often only has a small entry hole visible, normally covered with dry frass, but significant burrowing may have taken place within the fruit. If effective control regimes have been adopted, populations are normally very small in commercial apple orchards.
There is one complete generation of Codling moth each year, but in warm summers the earliest emerging caterpillars can produce a second generation of adults in August and September. Normally, the first moths emerge at the end of May or beginning of June, with the bulk of emergence taking place between late June and the middle of July.
Fully grown Codling moths reach 8mm in length and have grey-brown forewings with a copper patch near the tip. They fly and mate on warm, still evenings for as long as the temperature exceeds 13°C. Evening temperatures above 15.5°C are most conducive to egg laying, resulting in eggs being laid singly on leaf or fruit surfaces. Eggs are round, with a diameter of approximately 1mm, flat and translucent, sometimes giving the impression of scales.
Young caterpillars hatch after 10 – 14 days and immediately attack fruit by burrowing in and producing a cavity just beneath the surface. Newly emerged caterpillars are white with a black head, turning pink with a brown head at maturity. Codling moth caterpillars have five pairs of abdominal legs. As the caterpillar matures it burrows through the flesh to the core, sometimes attacking a second fruit before full maturity is reached. After about four weeks feeding the caterpillar leaves the fruit to form a cocoon. Second generation moths only appear if the first generation is able to spin a cocoon before the end of July. The winter is spent as a fully fed caterpillar in a cocoon.
Tracer* (active ingredient spinosad) has full approval for control of Codling moth in apples and pears. Tracer enters target insects primarily through contact and ingestion. Contact occurs by direct application or by insect movement on treated surfaces. Ingestion occurs from feeding on treated surfaces. Following entry, Tracer acts on a unique neuro-receptor site of the insect. Symptoms appear almost immediately and complete mortality occurs within a few hours. Tracer is not systemic but does show translaminar movement.
To avoid variable performance with Tracer, timing of application should be optimised and good coverage of the foliage must be achieved. Optimal timing for post-blossom applications of Tracer for the control of caterpillars is when first egg hatch is predicted, based on threshold counts in pheromone traps being reached or exceeded. It is important when making all applications to apples and pears to use sufficient water volume to achieve effective cover and penetration of the foliage.
Applications of Lorsban* WG (active ingredient chlorpyrifos) in the second half of June will control infestations of Codling moth very successfully. Applications are timed most accurately when pheromone traps are used as part of an integrated management approach. The use of pheromone traps improves spray timing and can sometimes lead to a decrease in the number of sprays required. In some seasons a repeat application of Lorsban WG will need to be made after 14 days and again if necessary. Do not apply to crops in flower or to those in which bees are actively foraging. Do not make applications when flowering weeds are present.
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