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Information about PESTS OF FIELD CROPS 2006

Published on January 22, 2008

Author: Stefanie


Slide1:  Alex Latchininsky Assistant Professor / Extension Entomologist Dept. of Renewable Resources January 2006 PESTICIDE SAFETY AND APPLICATION PLNT 1150 Slide2:  DISCLAIMER Trade or brand names used in this presentation are used only for educational purposes The information given herein is supplied with the understanding that no discrimination is intended, and no endorsement information of products is implied Slide3:  I. PRINCIPLES OF FIELD CROP INSECT CONTROL You must know… Basics of insect classification and biology Crop value Preventive measures What’s new? Slide4:  II. WHAT CAUSES INSECT OUTBREAK? It can be weather, but… Slide5:  … Frequently it’s our own fault … Large-scale monocultures Poor cultural practices Overuse of insecticides (killing natural enemies) Pest introduction in the new environment Disruption of a natural equilibrium Slide6:  III. TYPES OF CONTROL 1. Biological Introduction of exotic species of parasites and predators Conservation of parasites and predators Augmentation of parasites and predators Microbiological control (pathogens) Drawbacks: may be costly; often slow and weather-dependent Slide7:  Ladybird beetle larva and adult Pathogens Biocontrol agents Slide8:  TYPES OF CONTROL 2. Mechanical Hand picking Trapping Using devices like screens and barriers Drawbacks: time- and labor-consuming, slow, often impractical at large-scale Slide9:  TYPES OF CONTROL 3. Cultural Crop rotation – good for insects with long life cycles (e.g., corn rootworms) Trap crops – attracts pests; then the trap crop is destroyed or treated with insecticide Tillage – good for soil-inhabiting insects Clean culture – removal of crop residues Timing of planting and harvesting Resistant plant varieties, including genetically modified cultivars Slide10:  Cultural control: advantages Normal farming practices, making environments unfavorable for pests Preventive strategy Economical Good for low-unit-value crops Cultural control: drawbacks Will not work in an outbreak situation when pest infestation is heavy Slide11:  TYPES OF CONTROL 4. Chemical Reduction of insect populations or prevention of insect injury by the use of materials to poison them, attract them to other devices, or repel them from specific areas Still our first line of defense despite adverse publicity Slide12:  Chemical control: advantages Efficient Economical Fast-acting Easy to use Generally safe Slide13:  Chemical control: drawbacks Temporary relief May cause resistance Residues in harvest Environment: side-effects to non-targets Some insecticides have direct hazards Slide14:  TYPES OF CONTROL 5. Integrated (IPM) Management of insect populations by the utilization of all suitable techniques in a compatible manner so that damage is kept below economic levels Ecological approach to avoid economic losses and to minimize adverse effects Slide15:  IV. MAJOR FIELD CROP PESTS Slide16:  Western Corn Rootworm Northern Corn Rootworm Southern Corn Rootworm Spider (Banks grass) mites Slide17:  Western Corn Rootworm The larvae attack the roots, causing the plants to fall over and become goose-necked. The adults feed on the silks and, at times, become so numerous that pollination cannot occur. Overwinter as eggs in the soil. One generation per year. Diabrotica virgifera - beetle larva adult Slide18:  Western Corn Rootworm Control The most effective means of control is by crop rotation. Corn grown year after year on heavy soil is the most seriously damaged. Pesticides: do not use when rotating crops. If necessary, apply granules in a 6-7 inch bank over the row at planting time or as a cultivation treatment. Do not apply sprays for adults unless pollination is threatened. Heavy root damage Slide19:  Adults are found on the silks of corn. Like the western corn rootworm, this species overwinter as eggs, which are deposited in cornfields. The adults are common on goldenrod flowers. Control: Similar to Western corn rootworm. Northern Corn Rootworm Diabrotica barberi - beetle Yellowish-green 3/16 to 1/4 inch (5 to 6 mm) long, slightly smaller than the western and southern corn rootworms. There are no markings on the elytra. Slide20:  Southern Corn Rootworm Pale greenish-yellow beetle with six black spots on each wing cover. Slightly bigger than WCRW and NCRW. Occurs commonly on cucumber, melon vines, corn silk, weeds, and in alfalfa fields. Overwinter as adults. May have two or more annual generations. Other name: spotted cucumber beetle. Damage: The larvae damage roots of corn and winter rye, and adults eat holes in melon foliage. Adults spread bacterial wilt to cucumbers. Control: Similar to WCRW and NCRW. Diabrotica undecimpunctata - beetle Slide21:  Spider mites Twospotted spider mites Tetranychus urticae Banks grass mites Oligonychus pratensis Overwinter as adults in debris. Several generations per year. Damage: pierce plant cells and suck out liquid contents. Leaves develop chlorotic spots and may die back. Start feeding on the lower leaves and move upward. Hot, dry conditions are favorable. Control: systemic insecticides. Size: <1/32” 8 legs Slide22:  Alfalfa weevil Pea aphid Lygus bug Blister beetles Slide23:  Alfalfa weevil Hypera postica - beetle The color is brown with a darker brown stripe down the middle of the elytra. The pronotum has a dark brown stripe through which runs a pale line. Adult length is about 1/4 inch (6 mm). Slide24:  Larva is green or yellow with dark head. Damage: mostly by larvae. Skeletonize leaves. Feed on the foliage, especially terminal leaf buds, then drop to the ground and pupate in the litter. Adults overwinter. One generation per year. Alfalfa weevil Eggs Larvae Slide25:  Alfalfa weevil Cultural management: Early first harvest; fall grazing; spring burning; resistant cultivars. Chemical control: Mostly organophosphates, which are highly toxic for pollinators (bees) and other beneficials. Apply early in the morning or late in the evening. Leaf skeletonization by larvae Slide26:  Pea aphid Acyrthosiphon pisum Green, long-legged, about 1/6” long. Many generations per year. Overwinter as eggs or adult females. Slide27:  Pea aphid Damage: Suck the sap. Cause wilting and reduce quality and quantity of alfalfa hay. Control: preferably systemic insecticide sprays. Apply when T>50°F early in the morning or late in the evening to preserve the beneficials. Slide28:  Lygus bug Lygus lineolaris – true bug Adults: ¼” long, variable in color. Distinct “V” on the back. Piercing-sucking beak. Overwinter as adults. Three generations per year. Slide29:  Lygus bug Lygus bug larvae Damage: Most serious in seed production. Cause buds to die, flowers to drop, immature seeds to shrivel. Forage production and quality also affected. Control: Systemic insecticides and carbaryl. Non- targets (predators, parasites and pollinators) are a great concern. Timing of application is important. Slide30:  Blister beetles Toxic chemical cantharidin can make hay poisonous Slide31:  Mexican bean beetle Slide32:  Mexican bean beetle Epilachna varivestis – a ladybird beetle larva adult Adults are red with 16 black spots, ¼” long. Larvae are yellow with branched spines, up to ¼” long. Overwinter as adults in litter. One generation per year. Slide33:  Mexican bean beetle Damage: Both adults and especially larvae chew off portions of leaves. They usually feed by clinging to the under surface of the leaves and eating irregular sections of the lower leaf surface. The upper surface of leaves quickly dries out, giving a lace-like, skeletonized appearance. Slide34:  Mexican bean beetle Control: Cultural – burning or destruction of crop residues; Resistant varieties (e.g., Lima beans); Biological – several species of parasitoids available; Chemical – systemic and non-systemic insecticides, soil applications and foliar spray. Difficult to control because feed underneath the leaves. Slide35:  Sugar Beet Root Maggot Beet Leafhopper Slide36:  Sugar Beet Root Maggot adult fly larva (maggot) Tetanops myopaeformis – a true fly Overwinters as a larva (maggot) in the soil. Adult flies emerge in May. Females deposit eggs around the base of sugar beet plant. One generation per year. Slide37:  Sugar Beet Root Maggot Damage: maggots attack seedlings and cause loss of stand. Yields are reduced. Control: only larval control is recommended. Apply granules to the soil as a 4-6” band over the row. Granules must have moisture to be activated. Slide38:  Beet Leafhopper Circulifer tenellus adult nymph Overwinter as adults in weedy areas. Host plants include wild mustards, Russian thistle and other weeds. Eggs hatch and nymphs move into beet fields. One or more generations per year. Slide39:  Beet Leafhopper Damage: vector of the virus causing the disease curly top in sugar beets. Control: Cultural – Weed management. Resistant varieties. Chemical – granulated formulations to the soil. Moisture is necessary to activate the granules. Slide40:  Potato Psyllid Colorado Potato Beetle Potato Flea Beetle Slide41:  Potato Psyllid adult nymphs Bactericerca (=Paratrioza) cockerelli Related to aphids and leafhoppers. The adult has clear wings that rest rooflike over the body. Predominantly black, with white markings. Scale like flat nymphs. Psyllids jump quite readily when disturbed. Overwinter as eggs. Several generations per year. Slide42:  Potato Psyllid Damage: nymphs inject toxin when feed causing “psyllid yellows” and upward curling of leaves. Control: granular systemic insecticides at planting time. Foliar spray of synthetic pyrethroids. Slide43:  Colorado Potato Beetle Leptinotarsa decemlineata Slide44:  Colorado Potato Beetle adult and eggs larvae Overwinters as an adult buried in soil. Eggs hatch in the spring. Larvae feed on foliage. One or two generations per year. Slide45:  Colorado Potato Beetle Damage: both larvae and adults are voracious feeders. They often completely defoliate potato plants. Control: systemics in the soil at planting time. Foliar spray after egg hatch. Resistance may be an issue. Slide46:  Potato Flea Beetle Epitrix cucumeris Adult beetle is 1/16” long and black in color. Has enlarged hind legs and jumps vigorously when disturbed. Overwinters as an adult in soil litter. One or two generations per year. Slide47:  Potato Flea Beetle Damage: destroys foliage. Spreads a fungal disease - early potato blight. Control: Cultural – destruction of plant residues. Weed control. Late planting. Chemical – systemic insecticides to the soil at planting time. Foliar spray with contact insecticides against larvae. Slide48:  Pale Western Cutworm Western Curl Mite Russian Wheat Aphid Greenbugs Grasshoppers Slide49:  Pale Western Cutworm Agrotis orthogonia – “miller” moth adult larva Eggs are laid in the soil in the fall. Overwinter as eggs. Hatch very early in spring. One generation per year. Slide50:  Pale Western Cutworm Larvae feed mostly underground. Cause pruning of plants, loss of stand, and stunted and unthrifty plants. Slide51:  Wheat Curl Mite The mites are very tiny, white, spindle-shaped, with 4 legs near the anterior end. Reproduce parthenogenetically (without males). Overwinter on grasses or volunteer wheat. Eriophyes tulipae Slide52:  Wheat Curl Mite Damage: Transmits a viral disease called wheat streak mosaic. This virus can cause serious reductions in wheat crop yields. Although the mites feed on a variety of grasses, wheat is the preferred host and high populations can develop during the summer and fall on volunteer wheat. Control: Cultural - prevent the growth of volunteer wheat. Late planting. Resistant cultivars. Chemicals are rarely effective. Hail belt areas are in greatest need of protection. Slide53:  Russian Wheat Aphid Diuraphis noxia Native to southern Russia and the Mediterranean region. Introduced in the U.S. in 1986. Reproduces sexually or asexually. Several generations per year. Overwinter as immatures or adults in grasses. Slide54:  Russian Wheat Aphid Soybean Aphid Russian Wheat Aphid identification characteristics Elongated Short antennae No cornicles (“tail-pipes”) Forked (double) tail Slide55:  Russian Wheat Aphid Damage: RWA initiates feeding at the base of the leaves near the top of the plant. It injects a toxic saliva into the plant. The edges of the leaf curl inward protecting the pest. Plants become purplish and leaves develop longitudinal yellowish and whitish streaks. Tillers of heavily infested plants run parallel to the ground (a prostrate appearance). Heads are distorted. Slide56:  Russian Wheat Aphid Control: Cultural – control volunteer wheat; avoid early planting; use resistant varieties; maintain healthy stand. Biological – parasitic wasps, ladybird beetles. Chemical – foliar sprays with systemics. Slide57:  Greenbug aphids Inject toxin when feed. Cause “greenbug spots.” Control: systemic insecticides. Slide58:  Grasshoppers in the West economically important in 17 western states a dozen pest species (out of >450) annually remove 20-22% of rangeland vegetation estimated average loss $400 million per year forage losses in 2000 in Texas: $190 million Slide59:  2005 Rangeland Grasshopper Hazard Map Based on adult Survey 2004 Slide60:  Grasshoppers 112 species in Wyoming; only ~10 are serious pests Migratory Differential Twostriped  Twostriped  Slide62:  Mormon cricket Anabrus simplex is neither a grasshopper nor a cricket – it’s a katydid Slide63:  Grasshoppers in Wyoming require vast areas to be chemically treated (up to 20 million ac per year during outbreaks) 400,000 acres protected in 2003 in Wyoming (Niobrara, Goshen, Platte and other counties) Reduced Agent and Area Treatments - RAATs Slide64:  Grasshopper Outbreak Frequency 1944-1996 Slide65:  2005 Rangeland Grasshopper Wyoming Hazard Map Based on adult Survey 2004 Slide66:  I II III IV V LIFE CYCLE 1st instar - critical stage for GH survival (up to >90% mortality) Duration of nymphal period: ~ 30-40 d Slide67:  Grasshopper Treatment Application Strategies Conventional/Blanket RAATs Slide68:  THE RAATs CONCEPT Hoppers killed directly in the treated swaths More predacious insects and parasitoids survive treatment Hoppers move into treated strips and die Birds continue to feed on hoppers Less disruption to bio-control agents of weeds (APHIS data on Aphthona spp. beetles on leafy spurge in Montana) Slide69:  ATV- RAATs Slide70:  Boom Buster nozzles Slide71:  S.S. Co. ¼-KLC- 5 Fieldjet nozzles Half rate of “Boomless” type @ 2 Qt/min Low cost and simplicity 17-21 ft swath Slide72:  RAATs Aerial ATV treated untreated 100 ft 100 ft Slide73:  Malathion (Fyfanon®) PROS: Low cost/unit ULV logistics Reliable results Familiar product (since 1965) CONS: Hot weather; rain Low residual (no RAATs) Non-target effects Harm to people and planes Organophosphates – phasing out Organophosphate; neurotoxin (AcChE inhibitor) Slide74:  Carbaryl (Sevin® XLR Plus) PROS: Temperature Range Some Residual (RAATs) Reliable Results Easy Handling (water based) Familiar product (since 1979) CONS: Higher Volume Non-target effects Harm to people Carbamate; neurotoxin (AcChE inhibitor) Slide75:  Diflubenzuron (Dimilin® 2L) PROS: Safety (bees, people, etc.) Residual (RAATs) Reliable Results Temperature Range CONS: Timing!!! (IGR = nymphs) Less Familiar (since …) High Cost/unit Harm to aquatic invertebrates – R.U.P. Benzoyl-Urea; IGR (chitin synthesis inhibitor) Slide76:  MOLT Insects are killed when they grow to a next developmental stage Slide77:  I II III IV V recommended TIMING is critical when applying Dimilin not recommended ineffective Slide78:  Risks for Different Groups of Non-target Organisms Source: Food and Agriculture Organization of the UN, 2003 Slide79:  Environmental Profile Carbaryl Malathion Diflubenzuron CAR OP BU (IGR) Human toxicity (WHO/EPA class) II (Moder.) III (Low) Unlikely to be toxic Fish toxicity Moderate Low Low Aquatic invertebrate toxicity Low Moderate High Mammalian toxicity Moderate Low Low Toxicity for birds and reptiles Low Moderate Low Toxicity for honey bee High High Low Toxicity for other non-target arthr. High Moderate Moderate Slide80:  RAATs vs. Standard: Efficacy Control is 5 to 15% lower than conventional blanket methods (usually about 80% kill) It costs a lot to kill them all. Surviving grasshoppers provide a prey base for the predators. We haven’t observed any resurgence the following year in treated areas. Slide81:  RAATs COSTS 50-60% less than the standard treatment about $1.50 / acre protected Slide82:  Other Options Carbaryl bran baits Pros: Target specificity Operator safety Enhanced formulations Cons: Application logistics and cost Species constraints (not all species take them) Adverse conditions Systemics applied in the furrow at planting Slide83:  RAATs – the preferred option for USDA grasshopper treatments in recent EIS Slide84:  CARMA can be downloaded from Grasshoppers of Wyoming and the West at: or request a free CD-ROM Grasshoppers: Their Biology, Identification and Management from: Decision-Support software 2005: Crop protection module added Slide85:  Pest Control in Wyoming: Slide86:  Fine trophies guaranteed! Slide87:  Come catch the Entomology Short Course, 2006 February 1-3, 2006 What will be covered? General Entomology, Insect Identification, Arachnids, Grasshopper Management, Biological Control, Mosquitoes, RS-GIS and more. When is it? February 1st, 2nd, and 3rd, 2006. We will begin at 1 PM on the first day, go from 8 to 5 the second day and release you at noon on the third day. Where is it? College of Agriculture Building, 13th & Lewis St., University of Wyoming, Laramie, WY. Who teaches it? Dr. Alex Latchininsky & Scott Schell, UW-CES Extension Entomologists. Plus guest lectures by other experts in their fields. You will get two books, a course packet, and 2 hours of college credit for as little as a $100 (maybe less) Slide88:  Questions? Contact Alex Latchininsky or Scott Schell, Uwyo Extension Entomologists Phone 766-2298 or 766-2508 Email: or

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