A dreaded insect pest (also known as grape moth or vine moth) in viticulture, which belongs to the butterfly family. There are two species that can be distinguished visually, but whose way of life and damage pattern are almost identical. The single-banded grape berry moth (Eupoecilia ambiguella) with a black head capsule occurs mainly in northern areas. The name is derived from the broad band in the centre of the wing. The cross-banded grape berry moth (Lobesia botrana) with a honey-coloured head capsule occurs mainly in southern areas. Its cross-banding is strongly curved. Both species can be found in Central Europe. They have been known as a major vine pest since the Middle Ages. The caterpillars feed on flowers, fruit and leaves. They are characterised by the plant parts spun into a living tube.
Hayworm
Overwintering takes place as a spun-in pupa, with the pests favouring the cracks in the bark of the stems. The moths hatch in spring from the end of April to May. After mating, the females lay their eggs in the flower clusters. After hatching, the caterpillars gnaw the flower buds and spin the flower parts into large nests, in which the caterpillars later pupate. The caterpillar of the single-banded grape berry moth has a black head and is 10 to 12 millimetres in size. In contrast, the grey-green to green-brown coloured caterpillar of the crossbred grape berry moth has a yellowish to orange head and is somewhat smaller at only eight to ten millimetres. This first generation of caterpillars is therefore also known as the hayworm, as they appear during the hay harvest in May to June.
Sourworm and sweetworm
The second generation of moths hatch and fly in July to August. Now the females lay their eggs individually on the grapes. The hatched caterpillars eat their way into the berries and are called sour worms or vinegar worms at this stage. The berries show typical, small boreholes. Inside the grapes, they make webbed tubes in which they withdraw. The adult caterpillars usually rappel down to the stems to overwinter. A third generation can only occur in warm years and under favourable conditions in the case of the cross-bred grape berry moth. The caterpillars that hatch from the eggs laid on the berries are called sweetworms because they feed on the already ripe and sweet berries.
Damage & control
The most dangerous sour worm damages the unripe berries, allowing them to be attacked by Botrytis, other fungi or bacteria. As a result, the berries do not ripen and remain acid, from which the name sour worm is derived. If it occurs frequently, there can be a considerable reduction in yield and quality. In the past, control was achieved by attaching corrugated paper trapping belts to the vine trunk in late summer. These sought out the pupating worms for overwintering. In spring, the pests were destroyed by burning the trapping belts. The pest is controlled biologically using Bacillus thuringiensis or insecticides. Another environmentally friendly and increasingly used option is to prevent fertilisation of the females using the confusion method (pheromone trap). An effective form of control is the "Méthode Raclet" (scalding the larvae with hot water) developed by the winegrower Benoît Raclet (1780-1844). See also under vine enemies.
Pictures: P. P. Kohlhaas / AGES Vienna
