A common question we get during the springtime and sometimes throughout the year. Customers often say their knockout roses look beautiful and are blooming gorgeously and then all of the sudden the leaves start to turn white or brown. This phenomenon can often be attributed to what are commonly called “rose slugs”.
More About “Rose Slugs”!
First of all, a “rose slug” isn’t a slug. It’s a sawfly in on of it’s larval stages. They secrete a slimy substance over their bodies just like slugs do. Rose sawflies are yellow-green and grow to about 3/4ths of an inch long and they feed on the leaves of rose shrubs. Adult sawflies emerge in early spring and lay their eggs on the underside of host plant leaves. Larvae appear several weeks later, feed on soft leaf tissue for about a month, and then drop into the soil to pupate. Depending on the species of sawfly, they can produce 1-6 generations per year.
What To Look For
Rose sawfly larvae feed on a leaf’s soft tissue and leave behind a papery, translucent surface with veins. A light to moderate infestation is usually just cosmetic but a heavy infestation can stress and even kill rose shrubs. If you have a heavy infestation, the rose shrub will have a brown scorched appearance.
What To Do
- Early Detection – Start looking for sawfly larvae in mid-spring on both the upper and lower surfaces of the leaves on your rose shrubs. If you find infestation, remove the leaves and kill the larvae. A stiff spay of water is usually enough to kill and knock off the soft bodied larvae. Make sure to spay the leaves tops and bottoms.
- Low Pesticide Usage – If you need pesticide usage to a minimum, insects such as parasitic wasps, insectivorous birds, small mammals, predaceous beetles, as well as fungal and viral diseases all assist in keeping sawfly populations lower.
- Insecticide Usage – When necessary, use chemicals when larvae are found. Horticultural oil, insecticidal soaps, neem oil, bifenthrin, carbaryl, malathion, permethrin, cyfluthrin, imidacloprid, and acephate can all be used to control sawflies. Follow the directions completely. Bacillus thuringiensis (Bt), an insecticide that controls caterpillars, is NOT effective against sawfly larvae.
Burger Farm has an assortment of organic and synthetic insecticide options to control the rose slug. Come on out and see one of our specialist who can help you pick the product that works best for your style. For the gardener that doesn’t have time to continually reapply foliar organic or insecticide sprays every six weeks; Burger Farm and Garden suggest using a systemic insecticide that controls insects from inside the plant out. Apply Fertilome Tree and Shrub Systemic Insect Drench in early spring and your roses should be protected throughout the growing season.
Contact Us (513-561-8634) Today for More Information!
The Most Beautiful Yards in Cincinnati come from Burger Farm and Garden Center. Family owned and operated since 1904, we supply all of your landscape and gardening needs in one convenient spot. We provide our customers the freshest plants and best gardening accessories in the Greater Cincinnati area. Our full time staff has over 100 years of experience in the gardening business and are always ready to help. Throughout the year Burger Farms also transforms itself into holiday specific attractions for Halloween, Thanksgiving, and Christmas!
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