Integrated Pest Management: Tips for April

Check hemlocks weekly for woolly adelgid hatchlings. To spot the small insects, tap a branch sharply over a piece of white paper. You will see the small, brown, oval adelgids moving slowly on the paper if they are present. Chart the number of crawlers you see each week and spray infested trees with horticultural oil when numbers level off, a sure sign that most of the eggs have hatched. While it is difficult to successfully treat eggs since they are well protected under the waxy wool produced by adult females, the unprotected hatchlings are vulnerable to the horticultural oil. Spray infested trees thoroughly since the horticultural oil must contact the adelgid to kill it. Concentrate your efforts on the lower branches where most of the adelgids are found.

Don’t work your soil when it’s wet. Tilling wet soil may ruin the soil structure by turning small aggregates of soil particles into large brick-like clods. Soil is also more easily compacted when it’s wet, so avoid mowing, weeding, and other prolonged garden chores when the ground is saturated.

Delay moving houseplants outdoors until night temperatures stay above 50°F. Many tropical plants turn brown or black when they experience low temperatures even if freezing never takes place. Acclimate houseplants to brighter light found outdoors by placing them under a tree or in another shady spot and gradually moving them into a sunnier location.

Aphids multiply rapidly on succulent spring growth. They are easily removed by washing them off with a strong stream of water from the hose. A wide variety of naturally occurring beneficial insects including ladybird beetles, hover flies, and parasitic wasps control aphids very effectively. All of these insects appear only when the population of aphids is quite large. You may see as many as twenty aphids per shoot before their natural enemies appear; so resist the temptation to spray an insecticide when only a small number of aphids are present. It is seldom necessary to treat aphids with an insecticide unless cool weather has delayed the appearance of the beneficial insects that feed on them. Avoid frequent watering and excessive fertilizing since they often result in succulent, rank growth that aphids love.

Check bearded iris frequently for signs of iris borers. The borers are caterpillars that begin feeding in the fan of growing leaves in the spring, quickly tunneling down to the rhizome. Injured rhizomes are often colonized by bacteria that turn them to mush. Check plants carefully for leaves that look wilted or water-soaked; spread the fan of leaves apart to find the caterpillar and remove it. You can also treat iris with insect-eating nematodes if your planting is too large to remove all the borers by hand. Avoid covering rhizomes with soil or mulch since iris borers prefer to attack plants that are planted too deeply or mulched heavily.

Decrease the amount of herbicides you use on your lawn: Think of how you use your lawn. Your front lawn might function as staging for the rest of your landscape while your back yard may be used primarily as a play area for children. You would want to concentrate your weed control efforts in the front lawn if this is the case.

Spot treat weeds instead of applying pesticides to the whole lawn. You can use herbicidal soap or another nonselective herbicide applied carefully to the weeds from a small squirt bottle. You will use much less pesticide than if you treated the whole lawn with a broadleaf herbicide.

Tolerate some weeds. A diversity of plants in your lawn limits the impact of diseases and insects. Clover fixes nitrogen and can help reduce the amount of fertilizer you need.

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