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.
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You mention on your site that you use Vege Net exclusion netting on your beds - are the hole sizes small enough to exclude whitefly
ReplyDeleteI believe they are, but the problem with netting is that you do have to get access to the bed for sowing seeds, planting seedlings, harvesting, removing spent crops, applying compost and mulch, and spraying with aerated compost tea. You only need a few to get in and they will multiply at a great rate.
ReplyDeleteHaving said that it only happens if there is a major infestation in the rest of the garden, and I find I can control outbreaks under the netting with Eco-neem or Eco-oil spray fairly easily.
There's been a lot of whitefly around Melbourne this year, but my Ecobed crops have been largely unaffected, and I have only needed to spray Eco pesticides on a couple of occasions.