These are not insects but arachnids since they have eight legs whereas insects have six. Yellow and red mites belong to the Tetranychidae (spider mite) family and are classified as secondary vineyard pests.
Phytophagous mites should not be confused with typhlodromes which are predatory mites that play a major role in the regulation of phytophagous mites that are harmful to vines.
| | Panonychus ulmi | Eotetranychus carpini |
|---|---|---|
| Spring | Larvae stings on young shoots leading to necrosis and and wrinkling of the leaves. These stings can also reduce overall growth and even destroy partially or totally the early grape clusters. | When the population is abundant, developing clusters are affected and shoot growth is slowed or stopped. |
| Summer | Population predominantly on the underside of the leaves. A severe outbreak leads to a foliage color change which takes on a " lead-like " appearance. The crop quality is affected. | Population solely on the underside of the leaves, along the veins. Their stings cause red or yellow spots depending on the grape variety which can reduce the potential. |
Panonychus ulmi: The female is dark red, with a globular body measuring approximately 0.5 mm, and a highly domed back decorated with setae from a tubercle. The male is smaller and more slender (0.3 mm). Its body tapers at the rear and is orange to light red. The onion-shaped egg has numerous striations and a tapered pedicel at the upper pole. The winter egg is a brighter red than the summer one.
Panonychus ulmi (Source: Vigne Vin Occitanie)
Eotetranychus carpini: The female is 0.35 mm long, while the male is smaller with a conical posterior. The large body is slightly longer than it is wide, yellow with a pair of red eye spots at the front, and seven rows of long dorsal setae and dark spots on the sides. The diverticula become coloured after a meal. The egg is spherical and translucent.
Eotetranychus carpini (Source: Vigne Vin Occitanie)
Panonychus ulmi: The winter eggs hatch at budburst and the larvae invade the young shoots. Development to the adult form involves three active larval stages, and lasts about 20 days in spring and 8 days in summer. Males live for 10 days while females live for 12 to 18 days. Eggs are deposited on the undersides of leaves from the end of April. The fecundity of females decreases gradually with each generation (from 26 eggs for the first generation to 14 eggs for the 3rd). The duration of the evolutionary cycle is closely dependent on climatic conditions (optimum of 20 to 25°C with 70 % humidity). The number of generations per year varies from five to seven.
Eotetranychus carpini: The females overwinter in the trunks and become active in the spring. Each female lays about 30 eggs on the undersides of leaves. Incubation takes 8 to 15 days depending on temperature. The life cycle lasts about 25 days and five to six generations.
By encouraging Typhlodromus pyri: typhlodromes are the main predators of mites, well ahead of ladybirds, bugs and thrips. One mobile form per leaf is necessary to avoid an acaricide treatment. In order to favour the development or a re-establishment of auxiliary fauna, it is necessary to eliminate any products that may be toxic to typhlodromes from the treatment programme. Products classified as neutral or low toxicity may be used.
Sulphur-based preventive treatments can also be effective against spider mites.
Extract from Vigne Vin Occitanie.