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Red spider mite
High temperatures and low relative humidity favour the development of this mite of the Panonychus ulmi species. The red spider mite life cycle is divided into: eggs, larvae, nymphs and adults. In winter, eggs hibernate at the bottom of the stalks, near the buds and on the trunk. The eggs hatch in spring, giving birth to the first generation of the year (in Portugal, it is believed to occur between six and ten generations each year). The larvae, nymphs and adults colonise the leaves from which they actively feed on. According to the temperature and relative humidity, it takes between 6 and 30 days for the mite to develop to the adult stage.
Leaves:
- Necrotic spots surrounded by a more or less intense discolouring. In the most serious cases, these spots can reach a significant part of the blade
- After budding: necrotic spots, necroses at the leaves’ edges, chloroses and deformations on the leaves
- Slightly copper coloured and “bronzed” in the most advanced stage.
Biological control:
If the vine has phytoseiid populations, the treatment programme should be adapted to use pesticides not very toxic to predators. When the vine does not have predators, one can carry out inoculative releases of populations collected from other vines.
Chemical control:
Winter Treatment:
- Summer Oil
- malathion + Summer Oil
Spring / Summer Treatment:
- cyhexatin
- dicofol
- fenpyroximate
- summer oil
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Português