Leaf-feeding pests

Control of phytophagous mites, Aleyrodidae, Aphidadae, and Jassidae and some leaf feeding pests in cotton, various field and fruit crops, ornamentals, vegetables... 

Sap-feeding pests that move only when newly hatched, when they crawl around looking for a plant to feed on. They then settle to feed near the leaf veins... 

Symptoms Black or brown sootlike deposits on upper leaf surfaces and other plant parts. Plants may also be infested with sap-feeding pests such as aphids, whiteflies, scale, or mealybugs. 

Diafenthiuron is a thiourea compound. It is an insecticide and acaricide that kills the larval, nymphal, and adult stages of phytophagous mites and leaf-feeding insect pests by contact and stomach poison activity. Its oral LD50 in rats is 2068 mg/kg. 

SAFETY PROFILE Poison by ingestion and skin contact. An insecticide used against leaf-feeding larvae of cotton insect pests. When heated to decomposition it emits very toxic fumes of POx, SOx, and NOx. See also ESTERS. 

B.t. var. ismelensis (BTI) attacks larvae of blackflies, fungus gnats, and mosquitoes when applied to standing water where these pests reproduce. B.t. var. san diego (BTSD) controls certain leaf-feeding beetles, including black vine weevils, boll weevils, Colorado potato beetles, and elm leaf beetles. 

In Mexico there exist two major insect pests of corn, an armyworm Laphygma frugiperda (A. S.), which breeds and feeds in the leaf whorls of young corn, and the larvae of certain coleoptera which inhabit the soil and feed upon the roots of the corn plants. Of these two the armyworm is the most important. Its attack is particularly severe on corn grown during the summer but, as it is able to breed continuously, it is a problem in corn grown throughout the year in the tropics. 

Pests are often classified according to where and how they feed on the plant (see facing page). Although this is convenient, these categories are not mutually exclusive. Many leaf-feeders also feed on stems some sapsucking aphids also feed on roots and flowers. 

Symptoms Not a serious pest but the damage can be unsightly. Narrow, light green tunnels burrowed between the upper and lower leaf surface develop into blotches as the larvae continue feeding between leaf layers. 

The sunflower budworm or bud moth (Suleima helianthana Riley), considered a minor pest of the sunflower in which damage is sporadic, also feeds on the Jerusalem artichoke (Pedraza-Martinez, 1990 Rogers, 1979). In North America, the insect is found from Maryland to California and south to Mexico. Damage is caused by larval feeding, typically on the apical bud or axils of upper leaves, producing distorted, misshapen plants. Young larvae act as leaf miners or enter a leaf rib, while older larvae enter and feed on buds, leaf axils, stems, and bracts. 

Leaf surface compounds provide important information about host-plant acceptability to coleopteran insects. Although the tortoise beetle, Cassida canaliculata, is only weakly attracted to odors from host plants, it shows strong preferences for host plants when additional contact cues are provided.64 The cottonwood leaf beetle, Chrysomela scripta, which is a pest of cottonwood, poplar, and willow, is stimulated to feed by leaf surface chemicals produced by a beetle-preferred poplar clone 65 The feeding stimulants have been isolated and identified as 1-docosanol, 1-tetracosanol, 1-hexacosanol, 1-octacosanol, 1-triacontanol, and... 

Leaves stippled with yellow foliage webbed. Cause Spider mites. These tiny, spiderlike pests generally feed on the undersides of plant leaves. They suck sap from plant leaves, initially causing a yellow flecking on the upper leaf surfaces. Severe infestations can cause leaves to turn yellow or white damaged leaves will eventually turn brown and drop. Tiny webs may be evident on leaves and stem tips. 

Leaves with tan or brown blotches or serpentine tunnels. Cause Leafminers. These tiny pale green fly larvae feed between the upper and lower leaf surfaces. Prune off and destroy infested leaves. Remove debris in fall to destroy overwintering leafminers. Let parasitic wasps control these pests, or apply weekly insecticidal soap sprays starting when the first tunnel appears. 

New leaves twisted or curled and covered with a sticky coating. Cause Black cherry aphids. Look on leaf undersides for clusters of these tiny black insects. The sticky coating is honeydew secreted by these pests. Leaves also may be covered with a black fungus, called sooty mold, which feeds on honeydew. Aphids... 

Flowers deformed leaves and petals with white flecks. Cause Thrips. Gladiolus thrips are a very destructive common pest. These V25", yellow to black, flying insects feed by rasping petals and leaf surfaces, leaving silvery spots and streaks. They hide under leaf sheaths and inside flowers. Other symptoms are partial bloom, failure to bloom, and shriveling. Thrips wastes may appear as black spots on the undersides of leaves. Infested corms are dark, sticky, and rough. 

Cause Grape phylloxeras. Feeding of this aphidlike pest causes root tips to die, decompose also forms harmless leaf galls. 

Leaves covered with iacy brown patches. Cause Pear slugs. Pest feeds on upper, leaf surfaces,... 

Willow lace bug adults and larvae also feed on willow leaves, causing severe discoloration. These A - A" pests have distinctive lacy wings and commonly feed on the undersides of leaves. Control by spraying upper and lower leaf surfaces with insecticidal soap. 

Leaves rolled up. Cause Strawberry leaf rollers. These green or brown, k" caterpillars mine leaves in the early spring and later form webs and roll leaves as they feed. Leaves may brown and die fruit is deformed. For light infestations, destroy the rolled leaves along with the caterpillars inside. For a very heavy infestation, apply BTK. See the opposite page for an illustration of this pest. 

Leaves tunneled. Cause Leafminers. The larvae of some flies, moths, sawflies, and bee-iJcs feed in between upper and lower leaf surfaces these pests are collectively known s leafminers. I hey may cause narrow, curved I jnnels in the leaves or large, silvery brown r lotches. Severe infestations can cause leaves to brown and wilfor drop. The most effective control is handpicking and destroying infested leaves. Sprays and dusts are usually ineffective because the larvae are protected within the leaves for most of their lives. 

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