By Ruth Ann Hales, Colorado State University Cooperative Extension, horticulture
We start the gardening season with the best of intentions to reduce pesticide useage during the summer months.
Our resolutions, however, can change when plants start to discolor, wilt or become infested with insects. Then, the use of pesticide sprays seems like a better idea.
Gardeners can avoid the schizophrenia about spraying pesticides, however, by planning ahead. Look for trees and shrubs that resist diseases and insects. Plants are very much like people when it comes to resistance. Some contain more genes for resisting disease than others. Smart gardeners plant these resistant varieties.
When planting fruit trees in the metro area beware of a disease known as fireblight. Apple varieties such as Red Delicious, Winesap, Duchess, King David, Turley and Haralson are more resistant to fireblight than other varieties. Pear varieties, such as Magnes, Moonglowe and Starkly, and Crabapple varieties, such as Vanguard, Dolgo and Redvein Russian, also are more resistant to fireblight.
When selecting shade trees choose Hackberry, Western Catalpa or Burr Oak. These trees have fewer disease problems and require fewer pesticides than trees such as Aspen or Green Ash. Over planting of the latter two trees has caused outbreaks in pests and diseases of both trees.
Aspen trees are subject to the Poplar Twig Gall Fly, borers, aphids and diseases such as cytospora canker and marsonninia leafspot. Green Ash can be invaded by the ash sawfly and a leafspot disease called anthracnose.
When selecting shrubs try Potentilla fruticosa, Shepherdia, argentea (Buffaloberry) instead of disease-ridden honeysuckle bushes. For shady locations, Japanese barberry is a good choice.
If you are interested in reducing pesticide inputs to your turf grass, consider these two noteworthy disease-free grasses. Try turf type tall fescues that combine the look of Kentucky Bluegrass with the ability to withstand insect infestations. Suggested turf type fescue varieties include Arid, Mesa, Tital and Tribute. For gardeners desiring a more native looking grass, try planting Buffalo grass.
Photo of Dolgo crabapple: Judy Sedbrook
© CSU/Denver County Extension Master Gardener 2010
888 E. Iliff Avenue, Denver, CO 80210
Date last revised: 01/05/2010