Most summertime pests can really bug us, but there are many fairly easy ways to control them.
Aphids, whiteflies, mealybugs, red spider mites and caterpillars can be washed off plants or smothered or killed by applications of lesser toxic pesticides such as neem or jojoba oil, Bacillus thuringiensis or Bt, and insecticidal soaps.
But there are two pest insects of summer crops that are less easily controlled: the Bagrada bug (a stink bug) and the leaffooted bug (closely related to stink bugs).
Invasive Bagrada bugs arrived in Fresno County in 2013. You may not have seen the bug yet, but their populations are increasing rapidly. They’re small, about a quarter of an inch long, shield-shaped with black, white and orange markings. Their small, barrel-shaped eggs are laid in the soil under host plants or sometimes on stems and leaves. Several generations can overlap in the garden in summer. Primary host plants include members of the mustard and cole crop family (broccoli, cauliflower, kale, turnip and mustard greens as well as radishes and arugula), most of which are cool-season crops in our climate. However, Bagrada bugs also lay eggs on and feed on weeds and ornamental flowering perennials and annuals, especially sweet alyssum which is often in bloom in summer here. When their cool-season food sources dry up, Bagrada bugs will feed on ripening tomatoes, bell peppers, melons and the leaves and flowers of corn, sunflowers and snap beans.
Bagrada bugs use needle-like mouthpieces to suck out plant juices and insert digestive enzymes. Feeding damage causes light-green starburst lesions on stems, leaves and fruit, stippling on leaves, stunting, and may kill seedlings and small plants.
It’s hard to see Bagrada bugs, so look for signs of feeding damage. Row covers to protect plants must be set up before the bugs arrive. Pyramid traps used to trap stink bugs can be baited with crushed sweet alyssum to attract Bagrada bugs. They have few natural enemies (they’re stinky – birds and beneficial insects won’t feed on them), and they can fly away from pesticides. For now, control entails removing host plants and weeds from the garden.
Leaffooted bugs are much easier to spot and to identify. They’re about 1 inch long, narrow and brown, with unusual leafy-looking hind legs. Their eggs are laid end-to-end in strings or strands on leaf stems or midribs on host plants; they have a wide range of host plants but tend to prefer desert plants (yucca, palm trees). Leaffooted bugs feed on seeds and ripening fruit with their piercing-sucking mouths. They are most often seen on tomatoes and pomegranates, but feeding damage is usually cosmetic. Leaffooted bugs overwinter as adults and fly into gardens in April. All life stages of leaffooted bugs can be in the garden during summer.
Birds, spiders and assassin bugs prey on leaffooted bugs and tiny parasitic wasps also kill the eggs. Control includes avoiding the use of broad spectrum pesticides that kill beneficial predators, row covers and removal/cleaning of winter hiding places (protected woodpiles, barns, palm fronds). Leaffooted bugs can be shaken off plants and stepped on (quickly, they’re fast fliers).
Correction: In the column printed June 1, I mentioned Monterey Lawn and Garden Products “Caterpillar Clobber” as an example of a Bacillus thuringiensis or Bt product name. A rep from Monterey contacted me to tell me that “Caterpillar Clobber‘ has not been sold for 10 years. Their current product is called “Monterey Bt.”
Send Elinor Teague plant questions at firstname.lastname@example.org.