Mid-Atlantic Region CCA Exam

Authors:  Joanne Whalen, Christie Hurt, Marty Spellman

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Competency Area 3 – Management of Insects and Other Invertebrates

  • Major Insect Pests of Field Corn, Soybeans, Wheat and Alfalfa
  • Key Characters of Major Pests: life cycle; when damage occurs in season; damage symptoms; and alternative controls

Know factors that affect insect growth and development – e.g. crop growth; crop production practices; weather factors; natural controls


True Armyworm in Field Corn

Life Cycle

  • Moths emerge in April
  • Lay eggs on grasses
  • Larvae feed on small grains and field corn then pupate in soil or under debris
  • 3-4 generations/year
  • overwinter as partially grown larvae

Damage

  • Larvae feed in late spring-early summer on early mid-whorl stage corn
  • Attack small/seedling stage corn in no-till
  • Do not damage growing point

Alternative Controls

  • Avoid planting near small grains
  • Avoid planting into no-till small grain cover crop
  • Bt Corn – for small larvae only present at planting time/ not-till covers

Slugs in Corn

Life Cycle

  • Overwinter as egg, immature or adult
  • Feed on seedling corn leaves, young sprouts, and seeds

Damage

  • Feeding occurs in spring when cool and wet on young (spike-3 leaf stage) corn leaves, sprouts, seeds
  • Favored by no-till; surface residue; wet conditions;  poor seed furrow closer

Alternative Controls

  • Cultural practices
  • conventional tillage one season
  • min. tillage to reduce surface trash
  • starter fertilizer
  • trash cleaners

Stinkbugs in Field Corn  

Life Cycle   

  • Egg, nymph (immature), adult
  • Overwinters as adult in leaf litter or debris
  • Move to wheat in April, then to corn in late spring

Damage  

Alternative Controls

  • Plant early
  • Tillage to reduce harborage/overwinter sites
  • Good seed slot closure – prevent feeding below ground

Northern & Western Corn Rootworm

Life Cycle and Life History

  • Overwinter as egg
  • Larvae hatch mid-late May
  • Feed on roots 3-4 weeks
  • Pupate and males emerge first as early as late June
  • Adults emerge late summer and lay eggs at base of corn plants

Damage and Conditions Favoring Development

Alternative Controls

  • Crop rotation still works
  • No variants – beetles laying eggs in soybeans documented in our area
  • No extended diapausing beetles – stay in soil 2 years documented in our area

European Corn Borer in Field Corn (First Generation)

Life Cycle

  • Overwinter as larvae
  • Pupate in spring
  • Moths lay eggs on corn in whorls
  • Peak larval activity in mid-June
  • Second Generation: late corn and vegetables

Damage

  • Feeding by 1st generation peaks in mid-June-affects translocation of nutrients
  • Plants 18-24 inches in whorl stage most susceptible

Alternative Controls

  • Avoid early planting,
  • Genetically resistant varieties/ BT corn
  • Natural Controls: Nosema; fungal pathogens
  • Deep Plowing – must be done in an area
  • Released Parasites: Lydella thompsoni; Trichogramma

Black Cutworm in Field Corn

Life Cycle 

  • Overwinter as full grown larvae or pupae
  • Moths emerge in March
  • Lay eggs on weeds
  • Larvae hatch and feed on weeds then corn (1 generation/year)

Damage  

Alternative Controls

  • Avoid  by minimum or no-till plantings
  • Avoid late planting and poorly drained soils
  • Early heavy growth of broadleaf weeds favors moth egg laying – early burn down with herbicides
  • Limited activity with Bt corn – small larvae only

Seed Corn Maggot in Field Corn

Life Cycle

  • Overwinters in soil as pupae
  • Flies emerge as early as February
  • Prefer to lay eggs in moist, freshly plowed soil with decaying organic matter or manure
  • Eggs hatch in 1-9 days
  • Larvae active- as low as 40 degrees F

Damage

  • Feed on seed content
  • Death of seed or poor germination
  • Occurs with cool, wet seasons and in highly organic soils

Alternative Controls

  • Shallow planting in well-prepared seedbed to encourage quick germination
  • Fall plowing of manure
  • Early plowing of cover crops
  • Complete plowing of cover crops

Common Stalk Borer in Field Corn

Life Cycle 

  • Overwinter as eggs on weedy plants (esp ditch banks)
  • Larvae emerge in May, move to corn and move deep into whorls
  • Moths emerge late summer

Damage

  • Feeds from spike to 4 leaf
  • Larvae feed deep in whorl and then bore into stalks
  • Feed on the growing point eventually boring into stalk

Wireworms in Field Corn

Life Cycle 

  • Overwinter as larvae
  • Five year larval life cycle
  • Adults emerge in summer – click beetles
  • Very responsive to moisture gradients in soil

Damage

  • Feed on seeds as well as the growing point of young plants
  • Appears as missing plants in field/ wilting or death of terminal shoots
  • Problem in cool, wet springs;  fields that were grassy or weedy the previous year

Alternative Controls

  • Summer plowing of fallow fields
  • Crop rotation away from small grains
  • ?????

Fall Armyworm in Field Corn

Life Cycle  

  • Migratory pest, moths found in our area in June
  • Moths lay eggs on later planted corn
  • Larvae feed in the whorl of pretassel stage corn in August
  • Larvae most active early morning and late evening

Damage

  • Numerous ragged holes
  • May prevent formation of normal ears
  • General a problem in silage corn

Grasshoppers in Soybeans

Life Cycle

  • Egg, nymph, adult
  • Overwinter as eggs/nymphs
  • 3-4 generations per year
  • Move out of ditch banks into fields

Damage

  • Defoliates plants as seedlings or later in season
  • Can feed on pods
  • Dry weather favors grasshoppers
  • High populations: field edges; no-till plantings behind small grains

Green Cloverworm in Soybeans

Life Cycle

  • Egg, larvae, pupae, adult
  • Moths lay eggs on underside of leaves starting in late June
  • Larvae first detected in July and peak mid-Aug

Damage

Alternative  Controls

  • Fungal pathogens play major role in control
  • Natural Enemies

Spider Mites in Soybeans

Life Cycle 

  • Egg, larvae, nymph, adult
  • Adults overwinter in weedy and non-crop areas
  • Move into crops as temperatures increase
  • Development favored by hot,dry weather
  • Populations generally explode during bloom

Damage

Alternative  Controls

  • Natural Predators
  • Weather Conditions favoring pathogenic fungi

Mexican Bean Beetle in Soybeans

Life Cycle

  • Overwinters as adult
  • Adults lay eggs in early planted fields
  • Larvae feed, then pupate on plants  (3 generations/year)

Damage

  • Larvae defoliate early planted full season and double crop beans
  • Hot dry weather reduces populations

Alternative Controls


Corn Earworm in Soybeans

Life Cycle

  • Overwinters as pupae (in soil)
  • Moths migrate from south, lay eggs on corn
  • Larvae feed, pupate
  • Moths emerge and move to soybeans in August

Damage

  • Young larvae feed on terminal leaves, flowers, pods
  • Older larvae feed on pods and developing seeds
  • Mainly a pod feeder

Alternative Controls

  • Mostly a problem in late-planted, open canopy fields
  • Natural fungal pathogens – wet and humid conditions
  • Natural Enemies- no released parasites

 


Stinkbugs in Soybeans

Life Cycle

  • Overwinter as adults and become active in spring on wild hosts
  • Lay eggs in fields in late June but generally a problem late in the season

Damage

  • Mechanical injury to seed
  • Can transmit a disease organism
  • You seed damage = greater yield loss; late season infestations reduce oil content and germination of seeds

Bean Leaf Beetle in Soybeans

Life Cycle

  • Overwinters as an adult beetle
  • Active in April-early May
  • Larvae feed at base of stem or on roots
  • Adults present again in late July-August

Damage

  • Prefer young plant tissue
  • Pod damage – rarely on developing bean
  • Generally problem on early planted beans; defoliation and reduced stands

Alfalfa Weevil in Alfalfa

Life Cycle

  • Overwinters as adult and egg
  • Larvae feed on leaves 3-4 weeks
  • Pupate on plant or on ground (1 generation/ year)

Damage

  • Larvae feed on leaves in late March-early April
  • Pest of 1st cutting and sometimes regrowth for second cutting

Alternative Controls

  • Resistant varieties
  • Early cutting
  • Biocontrol: natural enemies/diseases
  • Winter grazing
  • Flaming

Potato Leafhopper in Alfalfa

Life Cycle

  • Egg, nymph, adult
  • Adults migrate by wind arriving in late April
  • Develop from egg to adult in 3 weeks when conditions favorable

Damage

  • Nymphs and adult feed on 2nd and 3rd cutting alfalfa
  • Severe damage also done to spring seeded alfalfa
  • Pest during hot,dry seasons

Alternative Controls

  • Early cutting
  • Fungal Pathogens
  • Resistant Varieties – Hoppergard

Blue Alfalfa Aphid

Life Cycle

  • Egg, nymph, adult
  • Occur in March-April – same time as pea aphid

Damage

  • Damage to 1st cutting alfalfa
  • Plants stunted
  • Associated with spring  black stem disease

Garden webworm in Alfalfa

Life Cycle

Damage

  • defoliation and webbing

Alternative Controls

  • cutting to reduce food supply and expose webs to natural predation

Aphids in Wheat

Life Cycle

  • Egg, nymph, adult
  • Overwinter as eggs or adult females
  • More of a problem in early plantings
  • Favored by mild winter and cool, dry spring

Damage

  • Damage in fall ( first 60 days after planting): vector BYDV, greenbug aphid  injects toxin and get dead plants
  • Damage in spring: Grain fill, dead plants, blasted heads

Alternative Controls

  • Natural parasites and predators
  • Fungal Pathogens

True Armyworm in Wheat

Life Cycle

  • Moths emerge in April
  • Lay eggs on grasses
  • Larvae feed then pupate in soil or under debris
  • 3-4 generations/year
  • Overwinter as partially grown larvae

Damage

  • Larvae feed on leaves in early May
  • Young larvae on upper leaf surface
  • Older larvae- leaf blades
  • Last instar does most of the feeding
  • Heads clipped when all leaves consumed

 

Cereal Leaf Beetle in Wheat

Life Cycle

  • Overwinter as adult
  • Emerge March, lay eggs for 2-3 weeks
  • Larvae feed for 3 weeks, pupate
  • Adults emerge and feed on corn

Damage

  • Larvae first feed on stem leaves
  • Reduce Photosynthesis
  • Move to  flag leaf in late April-early May
  • Most important defoliator

Alternative Controls

  • Early planting
  • Introduced parasites
  • Weather factors – late winter warm up followed by cool early spring

Grass Sawfly in Wheat

Life Cycle

  • Adults emerge in April
  • Lay eggs on leaf margins until early May
  • Larvae enter soil in mid-June for summer diapause (prepupal) stage

 


Factors Influencing Insect Population Growth,
Decline and Management Decisions

Cultural Practices

  • No-Till Favors: slugs, stinkbugs, cutworms, seed corn maggot and cutworms in corn; grasshoppers in soybeans
  • Planting Date: late planting favors stinkbugs, cutworms and fall armyworm in corn; late planted wheat more susceptible to cereal leaf beetle; late planted, open canopy soybeans more susceptible to corn earworm

Environmental Factors

  • Hot, Dry Weather: increases spider mites and grasshoppers in soybeans; decreases Mexican bean beetle in soybeans
  • Cool wet weather: increase slug and seed corn maggot in corn
  • High Humidity and Moisture: fungal pathogens of alfalfa weevil, green cloverworm and corn earworm

Crop Growth

  • Alfalfa less than 12 inches tall= more susceptible to weevil and leafhopper damage
  • Blooming Soybeans: spider mites
  • Open Canopy Soybeans: corn earworm

Importance of Beneficial Organisms

  • Alfalfa weevil: released parasites, fungal pathogens
  • Aphids in Wheat and Alfalfa: predators, parasites and fungal pathogens
  • Green Cloverworm and Corn Earworm: natural enemies and fungal pathogens
  • Mexican Bean Beetle: parasitic wasps and predacious stinkbugs

Beneficial Organisms

  • Predators: Feed directly on pest, consume prey
  • Parasites: lay eggs in pest, larvae develop in pest
  • Pathogens: fungi, bacteria and viruses

Mode of Action of Insecticides

  • Contact – enters body wall by direct treatment of insect or treated surfaces
  • Stomach – ingested and acts on digestive system
  • Fumigant – absorbed through tracheal system as a gas
  • Systemic – translocated through vascular system of plant, killing insect after feeding on host

Types of Pesticides

  • Organophosphates and Carbamates
  • Pyrethroids
  • Chloronicotinyls – imidiachlorprid
  • Naturallytes: Spintor
  • Insect Growth Regulators
  • Biopesticides:
    • Bts
    • insecticidal soaps
    • Neem tree extracts

 

Botanicals

Insecticide Resistance

  • Definition of Resistance: population no longer controlled with insecticides used at previously efficacious rates
  • Resistance is inheritable, genetically linked trait
  • Requires a lot of selection pressure
  • It is not induced by low dosage habituation during life of an insect

Factors Favoring Development of Resistance

  • Over dependence on insecticide
  • Continued use of a single insecticide
  • Continued use of insecticides with the same mode of action