Finding that something has been eating your rose leaves is a frustrating experience, leaving you wondering just what it is that’s munching on your shrub. The rose genus (Rosa spp.) contains about 150 species of flowering shrubs that grow in U.S. Department of Agriculture plant hardiness zones 2 through 11. These elegant garden staples attract various insects to the area. Unfortunately, some of these visitors turn your roses into their own personal buffet. Correctly identifying the culprit will help you find the best course of action to killing the pests easting your rose leaves.
Caterpillars — which are the larvae of moths and butterflies — that feed on foliage create holes and ragged edges of the rose’s leaves. Tent caterpillars, loopers and leafrollers are a few foliage-feeding caterpillars that prey on roses. Their appearance and damage varies depending on the species of caterpillars. For example, leafrollers roll the rose foliage and secure it with webbing, while tent caterpillars construct a web encasing the leaves and branches of the plant. Unless their numbers are large, leaf-eating caterpillars typically won’t cause extensive damage to the plant. Excessive infestations can, however, lead to defoliation and loss of vigor. Killing the caterpillars requires mixing 4 tablespoons of Bacillus thuringiensis (Bt) concentrate — which is a safer alternative to chemical insecticides — with 1 gallon of water and spraying all leaf surface liberally with the Bt.
The fuller rose beetle is one insect that feeds on the leaves of roses causing them to have a ragged or notched appearance. This flightless pest is a snout beetle with a brown body and bulging eyes. Damage to established roses can usually be ignored unless the fuller rose beetle population is high, according to the University of California Statewide Integrated Pest Management Program. Picking beetles off the rose bush and disposing of them in a bucket of soapy water will kill the pests. To prevent a future infestation, attach a 6-inch sticky band around the trunk of the plant and trim any branches that reach out toward the rose bush that can act as a bridge for the beetle.
Sawflies are a wasplike insect with a flattened, dark-colored body that measures about 0.5 inches long. They lay their eggs on the underside of rose leaves. When the eggs hatch, the yellow- or green-colored slug-like larvae feed on the foliage. Their feeding can skeletonize rose leaves and — in high populations — defoliate the plant. Spraying the leaves of the infested rose bush with ready-to-use insecticidal soap will kill the sawfly larvae. Repeat treatments once a week may be needed to provide complete control over the pest. Furthermore, if heavy rain occurs within 24 hours after treatment, another application should be applied.
Leaf-cutting bees are plump bees measuring about 1/4 inch long that cut semicircular holes out of edge of leaves. These beneficial insects cause no real serious damage to roses and usually only affect the appearance of the plant. Since they are important pollinators, no control should be taken against leaf-cutting bees. You can however take steps to prevent the bees from damaging roses by covering the rose with loose netting in late summer when the bees are most active. Also, eliminate rotting wood near the rose that can act as a breeding site for leaf-cutting bees.
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