Squash Summer Pests
Squash bugs and aphids sure can suck the joy out of your summer garden — especially if you love zucchini.
Both these pests feed on the tender growth, leaves and flowers of zucchini, crookneck, and other members of the Cucurbit genus, including summer and winter squash, pumpkins, melons, and cucumbers. The best strategy to protect your crop is through prevention.
Let nature help. By supporting beneficial insects that feed on other bugs, gardeners can deter pests such as squash bugs and aphids.
“Our goal every year, first and foremost, is to support our native ecology and build up native predators,” says Alfred Melbourne, founder of Three Sisters Gardens, which has four farms in West Sacramento. “To fight aphids, we create habitats for ladybugs to thrive. We use bugs to combat other pests.”
Melbourne plants mint next to his squash as a habitat for ladybugs (also known as lady beetles). “Mint is really conducive to attracting ladybugs; they like it. Then when we plant the squash, they go to work [and eat any aphids].”
Similarly, the folks at Three Sisters use hedgerows — two-foot-wide strips of insect-friendly native plants — around the perimeters of its vegetable plots. Made up of mixed shrubs and perennials, the hedgerows provide winter shelter for beneficial insects.
“It allows the beneficial bugs to build up their numbers and get established,” Melbourne explains.
To tackle spot infestations of aphids, Melbourne recommends neem oil or bug soap: “Two tablespoons of dish soap mixed with one quart water. But you have to be really thorough [in spraying foliage],” he says.
Insecticidal soap, available in nurseries, offers similar results; it coats the foliage with a soapy film that aphids don’t like. Or just use a strong jet of water from the hose to knock aphids off plants; they won’t survive the blast. No matter your choice, spray in the morning, not during hot afternoon sun!
What about pesticide sprays? Broad-spectrum foliar insecticides (such as pyrethroids) kill aphids on contact, but they also kill all the ladybugs, bees, and beneficial insects. And only those aphids directly sprayed will die; these sprays have no lingering protection. Aphids then quickly rebuild their numbers without any natural predators.
Unfortunately, although it may work on aphids, bug soap — or most any spray, including pesticides — is not effective against squash bugs. Few beneficial insects or birds like to eat squash bugs either, which complicates matters. Often mistaken for stink bugs, squash bugs taste bad and release awful-smelling chemicals when disturbed.
Gail Pothour, Sacramento County master gardener, has plenty of experience fighting pests on squash and other crops at the Fair Oaks Horticulture Center in Fair Oaks Park.
“Squash bugs are common pests in vegetable gardens, although our experience in the Fair Oaks Horticulture Center vegetable demonstration garden is that they are more of a problem in some years and not in others,” Pothour says. “They feed on foliage of plants in the Cucurbit genus. Leaves develop small specks that turn yellow and later brown.”
Heavy infestations cause plants to wilt and can kill new transplants. After eating the leaves, squash bugs will start on the developing squash. Squash bugs can be plucked off plants (with gloves) and squished; the young nymphs can’t fly and are easier to catch. Or knock them off the plant into a bucket of soapy water; they can’t swim.
Squash bugs tend to love some squash more than others, Pothour notes. “Zucchini seems to be a favorite, as are many winter squash varieties; however, we have never found any on butternut squash.”
Before squash bug populations can build up, Melbourne puts out simple traps: double-sided sticky cards with an attractant (such as squash bug pheromone), which is available at nurseries.
“We place them at lower levels of the plants,” he says. “It’s worked for us.”
Squash bugs tend to overwinter where they feasted the summer before. Crop rotation — not planting squash in the same spot year after year — can break the squash bug cycle; any bugs that hatch in spring have no squash plants to eat.
“We do a lot of diversity in our planting,” Melbourne says. “Crop rotation confuses them.”
Best wishes for a pest-free garden this summer!
RESOURCES
Looking for more advice from master gardeners about these pesky pests? The University of California’s Statewide Integrated Pest Management (IPM) Program is a great resource.
Squash bugs: Ipm.ucanr.edu/pmg/garden/veges/pests/squashbug.html
