Oregon State University Extension Service encourages sustainable gardening practices. Always identify and monitor problems before acting. First, consider cultural controls; then physical, biological and chemical controls (which include insecticidal soaps, horticultural oils, botanical insecticides, organic and synthetic pesticides). Always consider the least-toxic approach first.
Recommendations in this calendar are applicable to Oregon’s Willamette Valley.
PLAN & PREPARE
Prepare and prime irrigation system for summer.
Place pheromone traps in apple trees to detect presence of codling moth. Plan a control program of sprays, baits, or predators if found.
If needed, fertilize rhododendrons and azaleas with acid-type fertilizer. If established and healthy, their nutrient needs should be minimal. Remove spent blossoms.
PLANT
Plant dahlias, gladioli, and tuberous begonias in mid-May.
Plant chrysanthemums for fall color. When selecting new roses, choose plants labeled for resistance to diseases. Fertilize roses and control rose diseases such as mildew with a registered fungicide.
Plant most vegetables now; check with local gardeners. Use a soil thermometer to help you know when to plant vegetables. Wait until the soil is consistently above 70 degrees F to plant tomatoes, squash, melons, peppers and eggplant.
Prevent root maggots when planting cole crops (cabbage, broccoli, collards and kale), by covering with row covers or screens, or by applying appropriate insecticides.
PUT PESTS OUT
Manage weeds while small and actively growing with light cultivation or herbicides. Once the weed has gone to bud, herbicides are less effective.
Trap moles and gophers as new mounds appear.
Leaf-rolling worms may affect apples and blueberries. Prune off and destroy affected leaves.
Monitor aphids on strawberries and ornamentals. If present, control options include washing off with water, hand removal, or using registered insecticides labeled for the problem plant. Follow all label directions. Promoting natural enemies (predators and parasitoids that eat or kill insects) is a longer-term solution for insect control in gardens.
Spittlebugs may appear on ornamental plants as foam on stems. In most cases, they don’t require management. If desired, wash off with water or use insecticidal soap as a contact spray. Read and follow label directions.
Control cabbageworms in cabbage and cauliflower, 12-spotted cucumber beetle in beans and lettuce, maggot in radishes. Control can involve hand removal, placing barrier screen over newly planted rows, or spraying or dusting with registered pesticides, labeled for use on the problem plant. Read and follow label directions when using insecticides.
Tiny holes in foliage and shiny, black beetles on tomato, beets, radishes, and potato indicate flea beetle attack. Treat with Neem, Bt-s, or use nematodes for larvae. Read and follow label directions when using insecticides.
Monitor rhododendrons, azaleas, primroses and other broadleaf ornamentals for adult root weevils. Look for fresh evidence of feeding (notching at leaf edges). Try sticky trap products on plant trunks to trap adult weevils. Protect against damaging the bark by applying the sticky material on a 4-inch wide band of poly sheeting or burlap wrapped around the trunk. Mark plants now and supply beneficial nematodes when soil temps are above 55 degrees F. If root weevils are a consistent problem, consider removing plants and choosing weevil-resistant varieties.
Control slugs with bait or traps and by removing or mowing vegetation near garden plots.
