spider mites in Roses
Asked July 7, 2018, 11:42 AM EDT
What is the best way to control spider mites in knock out roses. The leaves are yellow to bronze around the edges. Yamhill county.
Marion County Oregon
Spider mites often attack during hot, dry weather (such as our recent heat waves) when plants are stressed. Make certain the shrub has sufficient water. And add a 2-inch deep mulch of bark dust or bark chips to help retain the moisture.
"Conserving natural enemies, providing sufficient irrigation, and reducing dust may all help control mites. Overhead irrigation or periodic washing of leaves with water -- [a harsh water spray] -- can be very effective in reducing mite numbers. Releases of predator mites have been used in some situations [but seldom works in home gardens].. . . If treatment is necessary, spider mites can be controlled with insecticidal soap, horticultural oil, or neem oil. . . " ("Roses: Insect and Mite Pests and Beneficials" - http://ipm.ucanr.edu/PMG/PESTNOTES/pn7466.html)
A caution: If you apply any pesticide other than plain water when the temperature is, or will be, greater than 80F, you risk damaging the rose bush. And with water, it's wise to spray early in the day so that the leaves can dry as rapidly as possible.