Leaf Feeders
damage and larva images: Whitney Cranshaw, Colorado State University, Bugwood.org
Roseslugs are caterpillar-like insects that are actually the larval form of stingless wasps called sawflies. When trying to differentiate between caterpillars and sawfly larvae, count the number of "pro-legs" on the back of the insect. There will be six true legs on the thorax and then there will be six or more prolegs on sawfly larvae versus five or fewer prolegs on caterpillars. Roseslug larvae are lime green, with an orange-red head capsule and they can be up to a half inch long. When they are small, they create windowpane damage on leaves but as they grow they can chew all the way though a leaf leading to holes/skeletonization. Most of the damage will occur between May and June.
damage: Kimberly Steinmann, University of California, Bugwood.org;
adult (inset): Johnny N. Dell, Bugwood.org
Adult female Leafcutter bees use their mandibles to cut semi-circular leaf discs from the leaves of plants. These leaf pieces are then folded into a cell, filled with food and an egg, then inserted into hollow plant stems, twigs, or other tubular structures as a series of nests for the bee's larvae. The damage is usually not serious enough to warrant treatment but is noticeable and odd.
Brian Kunkel, University of Delaware, Bugwood.org
Redheaded flea beetle adults are 1/4 inch long with a black body and red head (but it can be difficult to see). They have large femurs on their back legs that allow them to hop, as the name implies. Larvae are soil-based, have a creamy color and can be up to 1/2 inch long. This pest overwinters as eggs in the soil, and larvae hatch out to feed in the root zone, before pupating to emerge as adults. In Delaware and Maryland this first group of adults emerges when Southern magnolia is in bloom. A second generation occurs later in the summer. Adults feed on leaves causing extensive shot-hole damage.
University of Georgia , University of Georgia, Bugwood.org
Two-banded Japanese weevil adults are about 1/4 inch long and pear shaped. Unlike other weevils, which have long snouts, this weevil has a stout, short snout. Adults have a mottled appearance, with grey and brown blotches giving them an almost camouflage-like appearance. There are two distinct bands that form across the back of the elytra. Larvae look like other weevils -- small, white, and legless. The adults feed along the edges of leaves, making notches at first, then tattered edges. In heavy infestations, whole leaves may be consumed. They overwinter as eggs, larvae, and adults. Overwintering adults resume feeding in May and produce the next generation with new adults emerging in June-July.
Lee Townsend, University of Kentucky
Japanese beetles can feed on about 300 species of plants ranging from roses to poison ivy but basswood is one of their favorites. They usually feed in groups, starting at the top of the tree and working downward, and prefer plants that are exposed to direct sunlight. A single beetle does not eat much; it is group feeding by many beetles that causes severe damage. Adults feed on the upper surface of foliage, chewing out tissue between the veins. This gives the leaf a characteristic skeletonized appearance. For more information, see Entfact 451.
David Cappaert, Bugwood.org
European earwigs are flat, red-brown insects that are about 5/8 inch long. They are notable for their cerci -- long pincer-like structures at the tail end of their body. Males have larger cerci that are curved, while females have thinner cerci which are straight. Earwigs are usually found under objects or in natural settings, under bark. They are nocturnal scavengers but will attack some plant species by chewing irregularly shaped holes in the petals and leaves. This injury can look similar to slug damage but will lack the tell-tale shiny slug trails.
Alton N. Sparks, Jr., University of Georgia, Bugwood.org
Thrips are very small, elongate insects that feed by puncturing the outer skin of the leaf and sucking out the fleshy leaf tissue. Their feeding causes off-colored foliage and stunted growth.
Sap Feeders
damage and nymph images: Whitney Cranshaw, Colorado State University, Bugwood.org
Rose leafhoppers can be white, gray, yellow, or green. They look like tiny cicadas, only a quarter to half inch long. Damage can occur from feeding by nymphs and adults. They attack the undersides of leaves and their needle-like mouthparts cause stippling and ultimately lead drop. There is also damage from female egg laying activity. In the fall, females insert their eggs under the skin of rose canes inducing small, purple spots and nymphal emergence in the spring leaves small holes pathogens may utilize to infect the plant.
David Cappaert, Bugwood.org
Twospotted spider mites are tiny (1/50 inch) arthropods with a dark spot on each side of the oval, light green to yellow body. They live on the underside of leaves and use needle-like mouthparts to remove the contents of individual cells. This produces tiny white to yellow spots on leaves, sometimes called flecking or bronzing. These mites produce fine silk-like webbing that often covers infested plants. Infestations are usually most serious during hot, dry periods.
University of Georgia Plant Pathology, University of Georgia, Bugwood.org
The European red mite female is brick red, while the male is a pale yellow-green. They are small and globular. Some individuals may "balloon" to new locations, creating new infestations. They can feed on many different species of plants and cause leaves to become pale and eventually bronze. There can be 6-8 generations per year depending on the weather and they overwinter as eggs that are laid in the bark and near buds (red spheres in image at left). For more information, see Entfact 205.
John A. Weidhass, Virginia Polytechnic Institute and State University, Bugwood.org
Aphids are soft-bodied insects that use their piercing sucking mouthparts to feed on plant sap. They usually occur in colonies on the undersides of tender terminal growth in the spring. Heavily-infested leaves can wilt or turn yellow and senesce prematurely because of excessive sap removal. While the plant may look bad, aphid feeding generally will not seriously harm healthy, established trees. Some plants are very sensitive to feeding by certain aphid species. Saliva injected into plants by these aphids may cause leaves to pucker or to become severely distorted, even if only a few aphids are present.
Also, aphid feeding on flower buds and fruit can cause malformed flowers or fruit. Aphids produce large amounts of a sugary liquid waste called "honeydew". The honeydew that drops from these insects can spot the windows and finish of cars parked under infested trees. A fungus called sooty mold can grow on honeydew deposits that accumulate on leaves and branches, turning them black. The appearance of sooty mold on plants may be the first time that an aphid infestation is noticed. The drops can attract other insects such as ants, flies, and wasps that will feed on the sticky deposits. For more information, see Entfact 103.
Please see ID-118 for more information on roses and the problems that may affect them, particularly for information on the many caterpillar issues that can arise.