The first roses of the season are in bloom at least two weeks earlier than normal this wacky weather year and the first aphids of the season are also feeding on the roses earlier than normal. The majority of the pest insects we see in our Valley gardens are springtime pests. Aphids, whiteflies, mealybugs and cotton cushiony scale prefer to feed on very tender new growth. Hoplia beetles chew through new petals (generally on white or light-colored flowers) from late March until May. Snails and slugs proliferate in warm, wet spring conditions and also feed on tender, new growth. Our intense summer heat slows or stops new growth as well as pest insect feeding and reproductive activity.
We can expect an increase in pest insect problems on our water-stressed plants during this drought year. Stressed plants attract pest insects, but we should try to avoid increasing our use of broad spectum insecticides or systemic insecticides that would also kill pollinators and beneficial insects that prey on pest insects.
Here are few suggestions for less-toxic pest- insect-control methods.
Aphids are killed when blasted off plants with water from the hose because their sucking mouth parts are left behind when they fall. To conserve water, spray aphids with summer weight horticultural oils, neem oil or insecticidal soaps.
One of the best aphid controls is to include host plants that harbor beneficial, aphid-eating insects such as lady beetles in your garden. Artemesia, Queen Anne's lace and any plant that produces umbrella-shaped flowers (dill and carrots gone to seed for example) harbor both the larval (looks like a homely gray and orange tiny crocodile) and adult beetle stages.
This year, though, the aphids may be feeding well before host plants are in bloom, and the beetles can hatch. The timing may be off this year, and we'll need to step up our efforts to control aphid populations.
Mealybugs and cotton cushiony scale are smothered by summer-weight horticultural oils and killed by insecticidal soaps. Avoid spraying oils and soaps when bees and butterflies are flying. Whiteflies can be captured by yellow sticky traps, washed off the undersides of leaves or even vacuumed up in flight.
Handpicking snails and hoplia beetles is not for the squeamish, but it really is the most effective means of controlling their populations.
Follow the silvery slime snail trails back to their hiding spots and pick them out. I step on the snails (the big foot method) and leave the mess for the blue jays to clean up. The same method works well for hoplia beetles. You can also drop the snails and beetles into a jar of soapy water to kill them. If this method is too yucky for you, lay down an iron phosphate bait such as Escar-go or Slug-go. Unlike metaldehyde-based snail and slug flakes or pellets, iron phosphate baits are not toxic to children, pets, or the birds that eat the dead snails.