What is a spider mite on currants? - briefly
Spider mites are minute arachnids of the family Tetranychidae that colonize currant bushes, extracting sap from leaf cells. Their feeding produces stippled discoloration and may cause premature leaf drop when infestations intensify.
What is a spider mite on currants? - in detail
Spider mites that infest currant shrubs belong to the family Tetranychidae, microscopic arachnids with eight legs. Adult females are typically 0.2–0.5 mm long, oval‑shaped, and pale yellow to reddish. Their bodies are covered with fine hairs, giving a fuzzy appearance. Males are smaller and less conspicuous. Mites reproduce rapidly; a single female can lay up to 100 eggs over a two‑week period. Eggs are deposited on the underside of leaves, hatch in 3–5 days, and progress through larval and nymphal stages before reaching adulthood. Under warm, dry conditions the life cycle may be completed in less than a week, allowing populations to increase exponentially.
Feeding damage appears as stippling or a fine, silvery webbing on foliage. Mites pierce plant cells with stylet mouthparts, extracting sap and disrupting photosynthesis. Early infestations cause yellowing of leaf margins; severe attacks lead to leaf bronzing, premature leaf drop, and reduced fruit set. Webbing, especially visible on the undersides of leaves and on young shoots, provides a protective matrix for the colony.
Identification relies on visual inspection with a magnifying lens or hand lens. Key diagnostic features include:
- Small, oval bodies with elongated setae
- Presence of fine silk webbing on leaf undersides
- Distinctive stippled discoloration of leaf tissue
Effective management integrates cultural, biological, and, when necessary, chemical measures.
Cultural tactics:
- Maintain adequate plant spacing to improve air circulation
- Provide regular irrigation to reduce leaf surface dryness
- Remove and destroy heavily infested shoots during pruning
Biological control agents:
- Predatory mites such as Phytoseiulus persimilis and Neoseiulus californicus
- Lady beetle larvae (Stethorus spp.) that feed on spider mites
- Entomopathogenic fungi (e.g., Beauveria bassiana)
Chemical options, applied as a last resort, include oil‑based miticides (horticultural oil, neem oil) and acaricides with low toxicity to beneficial insects (e.g., spirodiclofen). Rotating products with different modes of action helps prevent resistance development.
Monitoring involves weekly scouting during the growing season, especially after periods of high temperature and low humidity. Early detection enables prompt intervention, limiting population growth and preserving fruit quality.