Insect of the Month - Greenhouse Whiteflies

 
  Hort Snacks - January 2019
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 Causal Organism: Trialeurodes vaporariorum (greenhouse whitefly – GFW)); Bemisia tabaci (sweetpotato whitefly); Bemisia argentifolia (silverleaf whitefly)
  • The specific species present may vary by region
Crops Affected: Wide host range (250+ species) – a range of greenhouse vegetable crops (e.g. tomatoes, cucumbers), as well as ornamentals (poinsettia, cut flowers, bedding plants, house plants, etc.)

Life Cycle:
  • True bugs – feed on plant sap by piercing and sucking
  • May cause a reduction in plant vigour and some secondary sooty moulds (due to sticky honeydew)
  • Life stages include eggs, nymphs (crawlers), pupae, adults
  • Life cycle is affected by temperatures, with shorter times at warmer temperatures
  • Sensitive to cold temperatures
  • Adults
    • Small (1.5-2mm), powdery white winged insects
      • GWF has the wings held flat and parallel to the resting surface, and the overall body shape is triangular
      • B have the wings in a tented fashion above the body, and the overall body shape is more linear
    • Difficult to see with the naked eye
    • Adults lay 100-300 eggs (over a 3-5 week lifetime) along the undersides of younger leaves
  • Eggs are sometimes laid in circular “fairy-ring” patterns
    • Eggs start off a creamy-white, darkening within a day or so
  • Nymphs
    • Eggs hatch in 5-10 days to produce a flat, scale-like, largely immobile nymphal stage, referred to as “crawlers”
    • Nymphs pass through 3 instars before pupation
  • Pupae
    • Pupation lasts about 1 week, with no feeding taking place
      • GWF pupae are somewhat raised off of the surfaces of the leaves, and may be surrounded by a fringe of hairs
      • B pupae sit flat on the leaf surface and have no hairy fringe
Multiple life stages of Greenhouse Whitefly
(
Trialeurodes vaporariorum)
Adult Silverleaf Whitefly (Bemisia argentifolia)
Photo by Whitney Cranshaw, Colorado State University, Bugwood.org
Photo by Scott Bauer, USDA Agricultural Research Service, Bugwood.org

Symptoms:
  • A decline in plant vigour
  • Stunting, yellowing of leaves and premature leaf drop
  • The observation of the insects stages may be indicative of presence
  • Some species transmit plant viruses, which produce other symptoms
Management:
  • Monitor / inspect plants regularly for pests
    • Quarantine new plants to ensure they are not bringing in a problem
  • Use pest-attractive plants as trap or monitoring sites (e.g. eggplants)
  • Apply controls quickly to prevent populations from increasing rapidly
  • Control alternative hosts (e.g. weeds) in adjacent areas
  • Use clean, virus-free plants (to avoid virus transmission)
  • Biological controls can be effective at managing populations of whitefly, including specific parasitic wasps, ladybeetles, predatory bugs and a couple of different fungal biocontrol products.
  • Yellow sticky traps or yellow sticky tape can be used broadly and/or in population hotspots to draw whiteflies
    (and other insects) out of the crop
  • Vacuuming adults from hotspots can work to quickly bring a population in one area down, however this is not effective in larger areas
  • Install fine-meshed screens over vents and doorways, to prevent entry and movement between areas, and from outside to inside a greenhouse
  • Registered chemical controls may be applied at specific stages to reduce populations
    • Use these with care to prevent the development of resistance
    • Certain products are more effective on certain life stages (e.g. horticultural oils are best for immobile, immature stages
 
 
 
 
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For more information about the content of this document, contact Robert Spencer.
This information published to the web on December 12, 2018.