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New pests facing growers and how to deal with them

Plants can be exposed to numerous dangerous pests; keeping on top of your integrated pest management system is crucial to survival. Photo: NAD.

Learn about the biggest pests affecting growers today as well as the best natural and chemical way to deal with them.



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31 July 2018

Neil Helyer of National Agrochemical Distributors and Fargo provided an introduction to the main pest species of commercial note in Irish horticultural crops; primarily with a focus on nursery, bedding, and pot plants, at GLAS 2018. Check out his presentation below.

Common pests targetting the commercial sector.

Thrips setosus: Japanese or Eastern Flower Thrips

  • Polyphagous: very similar host range to WFT.
  • Dark brown to black, similar to cereal thrips.
  • Virus transmission: TSWV (same as WFT).
  • Similar life cycle to WFT: eggs laid in leaves, first and second instar larvae feed in patches on the underside of leaves causing characteristic silvering with minute black faecal pellets.
  • Does not feed on pollen but will damage flowers.


Rose thrips: Thrips fuscipennis; new pest of strawberry

  • Bronzing on green and red fruit.
  • Overwinter in tree bark, weeds such as Rosebay willow, Shepherds Purse and bindweed appear to be favoured host plants.
  • Not easily controlled by A. cucumeris.
  • Orius laevigatus works well but requires min 18 C.


Spider Mite – Tetranychus urticae

  • Red or two spotted spider mite.
  • Can bleach leaves completely.

Lewis Mite – Eotetranychus lewisi

  • Targets major host plants (all protected crops)
    • Capsicum
    • Carica papaya
    • Cucumis sativus
    • Euphorbia pulcherrima
    • Solanum
    • Citrus

Spider mite control with predators


Phytoseiulus persimilis

  • 1 : 5 – 20 pest day, average 2 eggs laid / day.
  • In use over 50 years, on many crops.
  • Optimum 22C and 75% Rh.
  • Less efficient at low Rh and above 35C.
  • Susceptible to many pesticides.

Amblyseius californicus

  • Licensed for crops in permanent protection
  • 1 : 2 to 10 pest per day, average 1 to 2 eggs laid per day.
  • Desert origin, good at high temps and low humidity.
  • General scavenger able to survive in absence of prey.
  • Reasonable pesticide tolerance.
  • Lose carrier and sachets.

Amblyseius andersoni

  • UK origin, found in most of Europe.
  • Wide host plant range: vines, orchard fruit, coniferous and deciduous trees and shrubs, herbaceous plants, soft fruit etc.
  • TSSM, FTSM, CSM, Eotetranychus species, pollen, thrips, rust mites, gall mites, tarsonemid mites etc.
  • Most beneficials are sensitive to environmental conditions: food source, temperature and humidity are the most important factors.


Andersoni – main crop uses

  • Raspberry – Phytoseiulus persimilis not always effective on true raspberry mite, Eeotetranychus rubi.
  • Hardy ornamentals: all mite species – Choysia, Skimia, (for citrus and other mites).
  • Roses – replace Amblyseius californicus.
  • Protected crops – aubergine, cucumber, pepper, tomatoes.
  • Outdoor soft and top fruit- Apples, grapes, hops, pears, strawberry etc.

How predators are used

  • As a preventative to control early spidermite outbreaks (they survive well without spidermites).
  • As an early spring treatment for spidermites, tolerates high summer temperatures but very low Rh can limit development.
  • As a cold-resistant predator, suitable for outdoor crops.
  • Survives starvation and lack of water by taking from leaf glands and pollen.
  • Less than half the cost of A. californicus.


Read all about FLiPPER from NAD and discover a powerful bioinsecticide  broad-spectrum contact insecticide/acaricide to control whitefly, aphids, and spider mites on protected crops of tomatoes, cucumbers, and strawberries.

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