The most harmful caterpillars that occur in the greenhouse belong to the Noctuidae, which is the largest of all the lepidopteran families. Their forewings are mostly shades of brown and grey, whilst the hindwings can be highly coloured. Important species include tomato looper (Chysodexis chalcites) and silver Y moth (Autographa gamma).
The Tortricidae are another group of caterpillars that affect greenhouse crops. The term ‘leafroller’ refers to the fact that the caterpillars can often live in rolled up leaves, although some species live between leaves, or flowers, that have been spun together, in holes in stems, flowers, or fruit, or in the bark of trees. Important species include light brown apple moth (Epiphyas postvittana) and carnation tortrix moth (Cacoecimorpha pronubana).
Lepidopteran biology is largely comparable. Females lay eggs on leaves either in groups or individually. After leaving the egg, caterpillars then feed and moult. Once fully-grown, caterpillars cease to feed, and then pupate. Eventually the moth or butterfly emerges from the pupa.
Pheromone traps are available for monitoring adults of several species. Installing a range of different traps in problem areas at the beginning of the season can help with identification, and effective spray applications.
Controlling weeds is also important, as these can act as alternative hosts for caterpillars. Important species include charlock, creeping thistle, dandelion and docks. Bioinsecticides including Dipel (Bacillus thuringiensis var. kurstaki) can be used to control small, immature caterpillars. Dimilin flow (diflubenzuron) can be applied at egg hatch as a moulting accelerator insecticide, to control the larvae of codling, tortrix and winter moths. For more extensive outbreaks of larger caterpillars, the insecticides Runner (methoxyfenozide) or Tracer (spinosad) can be used.
Use plant protection products safely.
Always read the label and product information before use.
Pay attention to the risk indications and follow the safety precautions on the label.