Plant Doctor Archive

Whitefly infestation

HOW do you get rid of whitefly? We seem to get it on everything in the summer. I spray with neem oil, but that only shifts it from one plant to the other.

WHITEFLY can be tricky to control, especially in warm weather when they breed rapidly. Adult whiteflies can simply fly away to avoid being hit with contact action sprays. And in the height of summer, even if you manage to knock down the adults with a contact spray, you need to spray again around five days later to get the next generation that develops from the scale-like nymphs on the leaf undersides.

Keep your garden as weed-free as possible, especially from sow thistle (puha), which whitefly love. Regularly check plants that you know are susceptible.

As soon as you spot a few adults, spray - don't wait until mid-summer when there's a population explosion. Ideally, use a systemic spray such as Target, Confidor or Rogor which not only knocks down adults but travels through the leaf to get to the nymphs below. Spray three times at five to seven day intervals and take note of the withholding period on the label before eating any sprayed vegetables or fruit.

If you want to use organic sprays such as Nature's Way Insect Spray or neem, make sure to get good spray coverage on the undersides of the leaves to get the nymphs as well as above for the adults. Spray in the cool temperature of early morning or evening when the adult whiteflies are least active. Then, for the rest of the season, keep a careful watch for reinfestation and repeat the three sprays again if and when necessary.

Reproduced with permission from the former Weekend Gardener magazine. The views expressed here are not necessarily those of the RNZIH.