How to Control Whiteflies on Tomato This Summer

Whiteflies on the bottom of pomegranate leaf

Q. I am new to gardening in the desert and am surprised
at my success thus far!  That is, until
the white flies came.  They showed up on
the grapes and zucchini first, maybe in May or June.  Unfortunately, I didn’t think they would
become a problem. By August they had attacked everything! I pulled broccoli plants
and found I needed a mask to keep from inhaling them! What can I do this
season?

A. Whiteflies are a very tough to control once they get
established in the numbers you are talking about. They are much easier to
control if you’re diligent about controlling them when you first see them.

Females lay a couple hundred
eggs at a time and these become adults that can lay more eggs in about six
weeks. This means you can have exponential growth in their numbers if they are
left undisturbed in six weeks.

Whiteflies, like so many garden pests,
do not show themselves but remain hidden. Unless you stoop over and turn over
leaves and look at their undersides, you will not know they are there until you
see their telltale signs of plant damage. Signs of damage are yellowing and scorching
of older leaves, sticky residue on upper leaf surfaces of lower leaves and
ants.

Bottom leaves of sunflower yellowing and scorching due to past problems on the bottom side of the leaves. Photo courtesy Viragrow.

Ants love the sticky residue
that whiteflies and aphids produce. Ants climbing on plants in the garden or on
fruit trees is a very good sign you have a developing pest problem.

Backpack sprayer suitable for vegetable and Orchard spraying

If you buy transplants to put
the garden, spray the undersides of the leaves and the stems with insecticidal
soap, neem horticultural oil. Once the transplants have been placed in the
garden and they have grown a little bit, remove the bottom leaves of transplants
that are within a couple inches of the soil.

These bottom leaves are perfect hiding
and living quarters for many of the problem insects. They are so close to the
soil surface they can’t be sprayed effectively.

Stay away from conventional
garden insecticides unless this past really gets out of control. Whiteflies are
resistant to many conventional pesticides and these traditional pesticides can
knock out whitefly predators that help keep them under control.

Get yourself a decent compressed
air garden sprayer such as Solo or Chapin and use soap and oil sprays in
rotation with each other. Early in the season when it is still cool, check the
undersides of the leaves and look for critters.

Weekly applications are probably
enough during cool weather. When it starts to get warm, inspect the bottom
sides of the leaves and spray twice a week. Make sure you spray the undersides
of the leaves. That’s where these critters are!

Control ants that are getting
into the garden. They are buddy buddy with aphids and whiteflies. Ants come from
a nest in the ground. Follow their entourage back to the hole in the ground and
treat around the hole with a bait that they can carry back to the nest. These
are the most effective for ant control.

If you see bottom leaves that
are starting to get yellow, pinch or clip them off. If they started to turn
yellow they are contributing to the plant anymore. Look at the underside. There
are probably critters feeding away. Removing these leaves, removes pest
problems.