Gardening with Allen

Warm Weather Brings Pests

I am seeing holes in some of my plant leaves. I also notice a little green bug on some tree leaves. What do you recommend that is safe to use to control these pests?

Insects multiply much faster in warm weather. Aphids and mites are two pests to watch for as the weather warms. Aphids (often called plant lice) are small soft bodied sucking insects usually concentrated on new growth. They are usually green, but can also be pink or black. Aphids exude a sweet juice which drips on the ground. Ants are often associated with aphids because they use the juice for food. Mites are tiny eight legged pests which suck juices almost entirely on the underside of leaves. They are especially bad on needle-leaf evergreens. Yellow and brown mottling on leaves or needles is the most common symptom. Hold a white piece of paper under affected growth and shake. You will see tiny specks which move.

Both aphids and mites can be washed off plants. A strong stream of water will wash most of them off. However, soap or detergent will do a more thorough job of removing them. You can make your own mixture using dish wash detergent or insecticidal soap. A “Syphonex” works very well for this purpose. It is an inexpensive connector placed between two hoses or between the faucet and hose. It has a rubber tube which is placed in a bucket of strong soapy water. The soapy water is siphoned into water running through the hose. With a nozzle on the end of the hose you can wash these two pests off onto the ground and they will not find their way back up onto the plants.

Holes chewed in leaves is often caused by a flying beetle which flies in, eats for a while and then moves on to your neighbor’s plants.

Two natural pesticides that are effective in controlling aphids, mites, and many other pests are neem oil and spinosad. Chemical pesticides include malathion, carbaryl (sevin), and acephate. Kelthane is specifically for mite control.

Slugs and snails are another pest which must be re-treated regularly or they eat holes in leaves of annual and perennial flowers and vegetables. They only feed at night or in high moisture conditions, so you seldom see any signs except holes and their slimy trails. Snail and slug bait lasts about 2 weeks and then must be re-applied. The most common slug baits contain mesurol. However, baits with iron phosphate are safer for use around pets and wildlife.

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. Cyfruthrin, and spinosad are two systemic chemicals which can be used to get inside tissue and kill borers. Spinosad is a natural organic.

Be sure to read and follow all precautions when using pesticides, even natural ones. For example timing may be important to avoid harming beneficial insects such as honey bees.

 

Allen Wilson

Allen has been writing about gardening for over 30 years. He is a retired professor of Horticulture. Additional gardening information is available on his web site: naturalpruningnw.com under "how to guide". A monthly email garden newsletter can also be signed up for on this site or by sending a request to allenw98663@yahoo.com.

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