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Friday, March 1, 2024
March 1, 2024

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Gardening with Allen: Keep aphids, mites at bay in garden


My tree is dripping sap. When I looked at the leaves, they had little green bugs and ants. The leaves on my marigolds are turning yellow. What do you suggest?

The sticky sap is produced by the little green bugs called aphids when they suck the sap out of the leaves. The ants are there because they eat the sticky sap. Aphids are also commonly found on new rose growth.

The most likely cause of yellow leaves on marigolds or other flowers is either fertilizer shortage or mites. Apply fertilizer if you did not when you planted the marigolds. You can check for mites by holding a white sheet of paper under the edge of the plant and shaking the plant. Tiny moving spots would be mites.

Light aphid populations are often naturally controlled by ladybugs. Heavier infestations may require spraying.

Both aphids and mites can be washed off plants. A strong stream of water will wash some of them off. You can purchase insecticidal soap or you can make your own by placing a teaspoon of dish detergent in a hose attachment sprayer. Once the aphids or mites are washed off the plants onto the ground, they cannot find their way back up onto the plants.

Neem oil is an organic pesticide that is also effective against aphids and beetles, as well as leaf diseases such as mildew and rust. Chemical pesticides include malathion, carbaryl (Sevin) and acephate. You will need to look at the list of ingredients on pesticides to find many of these generic insecticide names.

Other summer insects include slugs, snails, thrips, earwigs and borers. Slugs and snails must be treated regularly or they eat holes in leaves of annual and perennial flowers and vegetables. They only feed at night so you seldom see any signs except holes and their slimy trails. Snail and slug bait lasts about a week and then must be reapplied. The most common slug baits contain Mesurol. However, baits with iron phosphate are safer for use around pets and wildlife.

Thrips are tiny insects that live inside flower buds. If you have flower buds that fail to open properly, shake a bud over white paper to reveal these long bodied insects. They are hard to reach with a spray. Spinosad is an organic systemic insecticide that will control them.

Earwigs also feed at night. Two of their favorite foods are flowers and corn silks. Earwigs are best controlled by earwig and cutworm bait.

Dead twigs and branches in woody plants may indicate borer damage. Borers eat the tissue under the bark. Cutting through the bark may reveal tiny tunnels. Spinosad also controls borers.