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Tomato gardeners, know your enemy: A guide to whiteflies, hornworms and bagrada bugs

How to grow 2-pound tomatoes

Pete Frichette of Sacramento shows how he grows 2-pound Aussie heirloom tomatoes with less water during the California drought.
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Pete Frichette of Sacramento shows how he grows 2-pound Aussie heirloom tomatoes with less water during the California drought.

Nearly every avid gardener finds a spot in their garden for at least one tomato plant. And just as certain, even one lonely plant will attract three common pest insects. Whiteflies, tomato hornworms and bagrada bugs will hatch, increase and infest or feed on tomato plants as our normal hot summer weather settles in.

Here’s a closer look at the three pests:

Whiteflies – Early detection for whiteflies is important for good control since without preventative measures their populations increase rapidly making it difficult to keep populations down. Whiteflies are tiny and generally only seen in the air when the plants they’re nesting in are disturbed. They are a sap-sucking pest that attacks many species of plants. Heavy infestations can seriously weaken plants; whiteflies can also carry viral diseases.


Begin control by practicing good sanitation in the garden. Remove all leaf litter, weeds and crop debris, especially debris from plants that previously had whitefly infestations. Sticky yellow traps placed at the edges of the vegetable garden will catch whiteflies. Replace the traps when they are full. Spray neem oil or insecticidal soaps to drench the underside of leaves and wash dust off plants. Dust coatings will hinder beneficial predator insects from feeding on whitefly nymphs and adults. The application of broad spectrum insecticides to control for whiteflies will also kill the beneficials which provide major control for whiteflies.


Tomato hornworms – You might have a hard time seeing tomato hornworms since they hide during the day and feed at night, but you can’t miss their damage. Tomato hornworms hatch from pupae in the soil as temperatures warm and can defoliate an entire tomato plant overnight, devouring leaves, stems and flowers. Keep a sharp eye out for irregular holes in leaves and for black frass or droppings on leaves or the soil surface underneath plants.

Handpick hornworms (big, bright green with white stripes) at dusk or dawn; they look scary, but they don’t bite. Or cut them with pruning shears, or spray Bt (Bacillus thuringiensis) to coat leaves. Bt kills all caterpillars by disrupting their digestive process and is non-toxic to birds, pets, humans and other types of insects.

Bagrada bugs – It’s a stink bug and a fairly recent invader into the Central Valley. It’s only about a quarter-inch long and has black and orange markings. Bagradas feast on the cool-season mustard family and Brassica genus including broccoli, cabbage and arugula. When temperatures are above 85 degrees, populations of bagrada bugs increase and the adults begin to fly to feed on other crops including tomatoes, bell peppers and melons. The damage caused by their feeding is often the first sign of their presence in the garden. They suck juices from leaves, stems, flowers and fruit by inserting their sharp mouthpieces into plant tissue and injecting digestive enzymes. Look for stippling and light-green, star-shaped lesions on leaves and fruit.

Place tunnel-type row covers or screening materials over valuable crops before the bagrada population explodes in warmer weather. Remove weeds and any members of the mustard family that might serve as host plants for the stink bug. Sweet alyssum and arugula, commonly found in summer gardens, attract Bagrada bugs and should be removed.

Pesticides are not very effective since bagrada bugs can fly away from the chemicals. Adult bugs have few natural enemies since they emit a stink when attacked.

Elinor Teague: etgrow@comcast.net