Butterflies and moths

Introduction

Caterpillars of several butterfly and moth species cause damage to a variety of crops. The most important species occurring in glasshouses are the tomato looper (Chrysodeixis chalcites), the tomato moth (Lacanobia oleracea), the cabbage moth (Mamestra brassicae), the beet armyworm (Spodoptera exigua) and the silver-y moth (Autographa gamma).

Biology

The life-cycle of butterflies consists of four stages, namely egg, caterpillar, pupa and butterfly. The eggs are often laid in groups on the leaf or glasshouse structures. The larva of a butterfly is a caterpillar and has a well-developed head and strong jaws. Caterpillars eat almost continuously, except when they are moulting. The species listed do not generally fly during the daytime, unless they are disturbed.

Damage symptoms

• Small caterpillars mainly feed on the undersides of the leaves. The upper layer (epidermis) remains undamaged. If caterpillars mature, they disperse on the plant. Initially they cause small, later also bigger holes in the leaves.
• The large amount of excrements of the caterpillars soils the crop.