Presentation on theme: "Entomology 462 Ornamentals Pests: Intro & Foliage Eaters David J. Shetlar, Ph.D. The “BugDoc” The Ohio State University, OARDC & OSU Extension Columbus,"— Presentation transcript:
Insects and mites that attack ornamental plants are often grouped according to three basic plans: By taxonomic group (e.g., beetles, caterpillars, etc.). By plant and part of plant attacked (leaves, stems, roots). By feeding method (e.g., chewing, sucking, gall forming, etc.).
Woody Ornamental Insect and Mite Groups (by damage) Woody Ornamental Insect and Mite Groups (by damage) Chewing Pests - Foliage Feeders Chewing Pests - Leafminers Chewing Pests - Borers Chewing Pests - Root Feeders Sucking Pests Gall Making Pests Nuisance Pests
Woody Ornamental Insect and Mite Groups (by plant zone) Woody Ornamental Insect and Mite Groups (by plant zone) Foliage Feeding Pests chewing, sucking, leafmining, gall makers Stem, Branch & Trunk Pests borers, girdlers, miners, sucking, gall makers Root Feeding Pests chewing, sucking, gall makers Nuisance Pests
We will work through the groups using a hybrid of the “Mode of Attack” system (for chewing pests) and “Taxonomy” (for sucking pests). Insects that have chewing mouth parts usually attack in distinctively different ways or feed in or on different plant zones (e.g., foliage feeders, miners, borers, root feeders). While pests with sucking mouthparts attack similar plant zones, it is easier to group them according to taxonomic groups, mainly because their life cycles are similar and control approaches are similar. For diagnosis, knowing the damage symptoms caused by each pest group can make identification a simple task. In fact, I have often stated: “If I know the host plant species, the time of the year that the damage occurred and the damage symptoms, I can usually identify the pest! In short, I rarely need an actual specimen of the pest.” This is why our approach will be to learn the terms used when describing pest damage.
Woody Ornamental Pest Groups Chewing Pests - Foliage Feeders Woody Ornamental Pest Groups Chewing Pests - Foliage Feeders Defoliators and General Feeders Specialized Feeders Skeletonizers, Leaf notchers, Hole makers Nest Makers Bagworms, Casebearers, Tent caterpillars, Webworms, Leaftiers, Leafrollers
Defoliators and General Feeders are occasionally some of the more difficult to identify to species because they leave rather non-descriptive symptoms. The foliage is simply missing or badly chewed up! Many of these pests, usually caterpillars or sawflies, are what I call “hit artists”! The adult insect may locate a suitable host, lay dozens to hundreds of eggs in a single spot, and the young larvae may go undetected for some time. Once these larvae reach maturity, they “suddenly” strip off the remaining foliage. They then pupate and disappear “literally over night”! For many of these pests, they may damage a tree or shrub one season and be absent the next season. These pests are difficult to manage unless a regular surveying or scouting program is adopted. Even if these pests are missed, their damage is usually not critical to the long-term health and survival of the tree or shrub. Most plants can survive a defoliation event every few years. However, repeated defoliation (as with gypsy moth) may sufficiently weaken a plant that it dies from infection by diseases or attacks by other pests, such as borers.
Woody Ornamental Pest Groups Foliage Feeders - General Defoliators Woody Ornamental Pest Groups Foliage Feeders - General Defoliators Caterpillars - (moths & butterflies) 2-5 pairs of prolegs crochets (hooks) on prolegs Sawflies - (wasp-like insects) 6-9 pairs of prolegs no crochets on prolegs
Spiny elm caterpillar (mourning cloak butterfly) IO moth caterpillar Elm looper caterpillar
Oak sawfly larva Willow sawfly female laying eggs Darkheaded ash sawfly White pine sawfly pupa
Redheaded pine sawfly larvae pupal cases adult female
The next three groups of chewing pests are what I call “Specialized Feeders” because they produce very characteristic symptoms. Skeletonizers generally eat the tissues between leaf veins. Even skeletonization damage can be further characterized. There are crude skeletonizers, like Japanese beetles, that eat most of the leaf tissues and only leave behind larger veins. Others are very delicate skeletonizers, leaving behind all the veins and even the upper or lower epidermal layer. This is another clue as to the pest identity. Did they remove the upper leaf tissues or lower tissues? The oak slug skeletonizes from the lower leaf surface while the poplar leaf beetle larvae skeletonize from the upper leaf surface.
Woody Ornamental Pest Groups Foliage Feeders - Skeletonizers Woody Ornamental Pest Groups Foliage Feeders - Skeletonizers Beetles - Leaf Beetles - (elm, poplar) Scarabs - (Japanese beetle) Weevils - (yellow poplar weevil) Caterpillars - Sawflies - Slug sawflies
Japanese beetle adult, a crude skeletonizer. Note the old damage in the background (brown tissues) compared to recent feeding. These subtle symptoms can help the manager determine if activity is current and controls would be warranted and effective. These hollyhocks have been nearly completely skeletonized by the hollyhock sawfly, not Japanese beetles! Because the damage is similar, many people assume that Japanese beetles caused the damage.
Poplar leaf beetle larvae skeletonize from the top. Bristly roseslugs (a sawfly) skeletonize from the bottom.
Roseslug sawfly skeletonizing rose leafRoseslug adult Thorn & apple skeletonizer, a caterpillar
Many caterpillars and some sawfly larvae skeletonize the foliage of their host plants when early instar larvae. As the larvae get larger, they eventually eat large sections of leaf and finally whole leaves – defoliators. Many of these defoliators also have similar larval behavior. They are gregarious as skeletonizers and young larvae, but as they reach maturity, they often feed separately in the host foliage. The first few leaves that are skeletonized often appear white or yellow and stand out against the background of green foliage. By learning to watch for this symptom, control can be simply achieved by removing the clustered larvae that remain on a few leaves. By disposing by crushing or dropping into soapy water, extensive insecticide applications can be avoided.
Yellowneck caterpillar egg mass1 st instar larvae skeletonizing leaf Medium size larvae are orange & yellow Large larvae are black & yellow & defoliate host plants
Woody Ornamental Pest Groups Foliage Feeders - Notchers Woody Ornamental Pest Groups Foliage Feeders - Notchers Weevil Adults - Black vine, rough strawberry root, & strawberry root weevils Asiatic weevils Leafcutter bees -
Most notchers in landscapes are weevils, but several caterpillars and sawfly larvae also occasionally make notches in the margins of leaves. The types of plants attacked and size of the notches can often give clues as to which pest may be present. Black vine weevils produce relatively large notches, while Asiatic weevils make small and irregular notches. Privet leaves severely notched by black vine weevil, strawberry root weevil and rough strawberry root weevil adults. Distinctive notches made by leafcutter bee collecting leaf pieces for their nest building.
Black vine weevil adult. Note notching on taxus needles. Leafcutter bee adults carry pollen on their abdomens, not the legs. Leafcutter bee brood chambers in rose cane. Note leaf linings.
Woody Ornamental Pest Groups Foliage Feeders - Hole Makers Woody Ornamental Pest Groups Foliage Feeders - Hole Makers Shot Holes - (1-3 mm) Flea Beetles Flea Weevils Yellow Poplar Weevil - (bean shaped) Shothole Leafminer (a fly) Larger Holes - (>3mm, irregular) May/June Beetles Shothole Leafminer Adults
Flea beetles and flea weevils make small round or oval holes in the foliage of host plants. Some call their style of feeding “pit feeding” because the adults usually remove the epidermal layer and underlying tissues, but the lower epidermal layer is left intact. If pit feeding is done on young plants, the remaining epidermis dies and drops out. This results in a larger, usually teardrop-shaped hole. The shothole leafminer is a small fly that punctures oak leaves as they begin to expand. These punctures are made with the ovipositor but the fly sucks out sap from the damaged areas. As the leaves expand, the pin-pricks turn into small holes. Several beetles (especially May/June beetles), small caterpillars and other insects chew irregular holes in leaves. If these holes are made when the leaf is small, the holes get larger as the leaf expands and matures. You can usually tell if damage is old or recent by seeing if the edge of the holes have healed over and there will usually be a yellow or brown margin.
Flea weevil and typical shotholes made through pit feeding. Striped flea beetle feeding on spinach leaf with other characteristic holes.
Gypsy moth third instar larva and characteristic irregular holes. Larger larvae eventually eat the entire leaf – defoliation. Willow flea beetle and characteristic shot holes in leaf.
Woody Ornamental Pest Groups Foliage Feeders - Nest Makers Woody Ornamental Pest Groups Foliage Feeders - Nest Makers Using Plant Materials - Casebearers – caterpillars Bagworms - caterpillars Leafrollers - caterpillars & weevils Leaftiers - caterpillars Leaffolders - caterpillars Using Mainly Silk - Tent Caterpillars - caterpillars Webworms - caterpillars & sawflies
Case bearers are usually small insects that use small pieces of leaf to construct a pouch in which the larva hides, only poking its head out to feed on foliage. The bagworms actually make single bags or sacs of silk on which bits and pieces of plant foliage are attached. These insects increase the bag size as they grow. Leafrollers, leaffolders and leaftiers make nests by rolling up a single leaf, folding over the edge of a leaf or tying together two overlapping leaves. Most of these are caterpillars that skeletonize the foliage within the protection of their nests. Most are solitary, but several leaftiers live in small groups. The tent caterpillars are generally represented by one species, the eastern tent caterpillar. Tent caterpillars build silk nests in the crotch of a tree. The caterpillars hide within the nest except when they emerge to feed on the foliage. Webworms are caterpillars or sawfly larvae that live in groups which web over or encase foliage in their silken nests. The larvae feed on this enclosed foliage and they expand the nests as they grow.
Larch casebearer bag on needle. Adult larch casebearer (a moth) and needles damaged by the larvae.
Elm casebearer adult, a moth. Elm casebearer larval bag. Note that the bag is made from a piece of elm leaf. The larvae actually mine small patches in elm leaves.
Bagworms on spruce. Bagworm larva extending from bag. Male bagworm adult. Female bagworms remain in the bag as a pupa that contains the fertilized eggs.
Oak leafroller damage.Pine tube moth. Oak leaftier damage.Oak leaftier larvae and frass.