Greenhouse Whitefly

Latest Update 2nd August 2017.

Greenhouse Whitefly. 

Details.
  • Binomial name                                            Trialeurodes Vaporariorum.
  • Family:                                                       Aleyrodidae
Why Greenhouse Whitefly are a Pest.
  • In small numbers they don't have much effect on plants, but they multiply quickly and in large numbers can cause a lot of damage.  They exude honeydew, attract ants and the adults can transmit viral and fungal pests which can kill plants very quickly.
  • After living in greenhouses and feeding off the sappy green foliage of greenhouse vegetables for decades, greenhouse whitefly have built up resistance to chemical pesticides, and have carried that resistance with them to the backyard garden.
  • I have always had a few whitefly in my garden, but in recent years they have become a serious pest.  They are difficult to control, especially if allowed to become established in spring, and I believe the only way to control them in a suburban environment without spending lots of time or using expensive organic pesticides is to use natural predators.  To do this you need to create a natural environment with lots of insect attracting plants in your garden. 
Pest Control.
  • Grow lots of flowering plants especially herbs to attract natural predators like hoverflies, lacewing, ladybirds and praying mantis.  This is the best way to control chewing insect pests, but while your predators are getting established you may need to use other measures.
  • Start looking for signs of whitefly in winter, especially on brassicas, and remove them early by hand so they don't become established later in the season.
  • They will appear on the undersides of mature leaves on brassicas in my garden as a smudge of protective fine webbing covering the larva as it pupates and then hatches into the fly.  Just rub them out with your finger. 
  • A monthly foliar spray of aerated compost tea provides plant foliage with some resistance to whitefly by toughening the cellular structure of the target plant.
  • To control a substantial whitefly attack that has evaded defensive measures, I use full organic cows milk diluted to a 10% concentration in rainwater.  It smothers them in the nymph and adult stages of their life cycle.  I follow up in a day or two to ensure whitefly hatchlings are killed as they emerge from their protected pupa stage.
  • Take care to target only the whitefly and avoid collateral damage among beneficial insects.