Civil Rights Information

Authors:  Joanne Whalen, Christie Hurt, Marty Spellman

(Click on blue hyperlinks to view photos - this will direct you to another web site and you will need to use the back button on your browser to return to this page)

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  

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  

• Feeds on seedling plants
• Inserts mouthpart into stalk and growing point
• Causes deformed, twisted plants, wilting of new leaves and elongated feeding holes
• Most susceptible at spike to 4-leaf stage and corn no-tilled into wheat
  

Alternative Controls 

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

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  

• Damage by larvae feeding on roots in late May-early June
• Favored by continuous corn
• Favored by heavy soils
  

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  

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  

• Damage in late spring on spike to 5 leaf corn
• Leaf feeding/ Shredding
• Cut plants
• Feeds on growing point
  

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  

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     

• Window Boxes - for small larvae
• Irregular Holes between main veins - larger larvae

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  

• Yellow discoloration
• Stunted Plants
• Feed on cell contents
• First detected on field edges but can balloon into fields
  

Alternative  Controls  

• Natural Predators
• Weather Conditions favoring pathogenic fungi

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

• Trap crops
• Parasitic wasps
• Predaceous stink bugs
• Weather factors  

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

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   

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

• Egg, larva, adult

• Overwinter as pupae, moths emerge in spring feed and larvae attack alfalfa in August
     

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