BiologicallyBased, Insect Pest Management in Vegetables

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Biologically-Based, Insect Pest Management in
Vegetables
University of Wisconsins Pyle Center October 21,
2008
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Vegetable Production in Wisconsin

• Important production state nationally
• Good crop climate also limits pests
• Production linked
• historically to
• canning industry
• Recent increase in
• fresh market

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Wisconsin Vegetable Production Statistics (Wis.
Ag. Stats. 2007)
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Changing Economic Ground

• Fuel prices
• Changing consumer demand
• Major market makers redefining landscape
  (Wal-Mart)
• Current market makers rapidly adjusting (Whole
  Foods)
• New institutional buyers beginning to enter the
  market
• Public policy national, state local
  sustainability standards
• Environmental costs internalized
• Food security
• TIPPING POINTS???

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Scoping Partners for Regional Food Strategy
Project

• Blue Planet Partners
• Michael Fields Agricultural Institute
• Center for Integrated Agricultural Systems
• DATCP
• REAP
• UW Center for Cooperatives
• Common Wealth Development, Inc.
• UW College of Agriculture
• Other key food systems leaders (Keystone
  Leopold Groups)

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Goal of Regional Food Strategy Project

• Develop cohesive strategic framework for scaling
  up this regions sustainable food system (Madison
  Milwaukee Chicago)
• Strategies nesting both locally and regionally.
• Goal Increase consumption of sustainable,
  regionally produced and processed food from 2 to
  10 in 7 to 10 years.

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Scaling Up a Sustainable Food System

• Values (Sustainable)
• Local, organic, environmentally sound, life
  giving for communities, healthfulness, freshness,
  taste, etc.
• Economics (Profitability Sustainability)
• Financial viability

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Insect Management on Vegetables

• The problem
• Many Insects on Many Crops
• Some perspective on insects
• Why is it difficult to manage insects?
• Lots of insect species on the planet
• Over 1 million animal species
• ¾ are arthropods
• Remember only a few are actually pests
• Each species has lots of individuals
• Short life cycles
• High numbers of individuals
• Combination HIGH REPRODUCTIVE CAPABILITY

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Factors that regulate insect populations

• Physical Factors
• Environment
• Temperature, rainfall
• Pesticides
• Biological Factors
• ?Influence increases at higher populations?
• Competition
• Food availability
• Parasites, predators
• disease

Insect management seeks to blend various
biological and physical factors together to hold
pests at acceptable levels.
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Insect Management ? The 6-step Process

• Identify the key pests
• Look closely at
• Biology
• Ecology
• Behavior
• Impact on crop
• Identify weak links
• Develop management strategies to exploit
  weaknesses
• Tailor pest management to individual needs
• Fit sporadic pests into program

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IPM Integrated Pest Management

• IPM is a decision-making process considers and
  utilizes ALL available pest management options or
  strategies to prevent economically-damaging pest
  outbreaks below an acceptable, pre-determined
  injury level or action threshold while reducing
  risks to human health and the environment

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What IPM is NOT!

• IPM does NOT preclude the use of pesticides!
• IPM is NOT merely a biological or organic pest
  control program
• IPM is a decision-making process, NOT a stringent
  or rigid management regime

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Components of an IPM Program

• Monitoring and Sampling (inspect)
• Pest Identification (what pest)
• Decision-making (what action(s))
• Intervention (take action (s))
• Follow-up (re-inspect)
• Record-keeping (write it down, history)
• Education (learn)

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Insect Management Trends on Vegetables

• 1950s to 1980s

High value Low tolerance HIGH RELIANCE ON
INSECTICIDES
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Insect Management Trends on Vegetables

• 1980s to 1990s Problems

• Fewer insecticides
• Resistance in pests
• Label cancellations
• Reregistration
• FQPA
• Raw product residues
• Worker safety
• Environmental concerns
• Nontarget toxicity
• Groundwater

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Insect Management Trends on Vegetables
Targeted insecticide use
Integration of non-chemical alternatives
Present and Future
Reduced risk, ecologically-based IPM
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• Potato Production in Wisconsin
• 70,000 Acres, value 203 million, 3rd Nationally
• Most grown in Central Wisconsin
• Several varieties grown for seed, processing,
  and tablestock

Russet Burbank
Yukon Gold
Atlantic
Dark Red Norland
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Insect Management in Potatoes - Key Pests -
Green peach aphid
Colorado potato beetle
Potato leafhopper
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Colorado potato beetle adult
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• Overwintering site
• Close to last crop
• Adults 6 to 12 deep
• Protected by mulch

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• Adults walk to crop
• Damage depends on temperature
• May - June

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• Adults lay eggs on underside of leaves
• Yellow / orange
• 20-40 eggs/mass

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• Larvae hatch 5-7 days
• 1st instar move to plant terminals
• Little damage

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• Small larvae feed in terminals
• 4 instars, 5-7 days/stage
• Large larvae (34) feed extensively

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• 4th instar larva

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• Larval feeding
• 4th instars leave plant and pupate
• in soil

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• Pupae in soil
• 2-3 weeks
• Summer adults emerge (July)

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• Summer adults emerge in July
• Very active
• Very hungry

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• Rapid defoliation
• Partial second generation
• Adults leave to overwinter or
• Can be partial 3rd gen.

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Managing outside crop

• Rotate crop to avoid adults
• Trap adults moving into crop in spring
• - spring trap crops
• - trenching
• - border sprays
• Trap adults moving out of crop in fall

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Colorado Potato Beetle Dispersal / Crop
Colonization
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Crop Rotation avoid planting adjacent to
previous potato
Sexson and Wyman (2005)

• Rotate gt 400 m (¼mile)
• Delays infestation
• Reduces infestation size
• effect increased if small grain separates field
  from source of overwintered beetles
• Causes infestation to proceed from field edge
• facilitates scouting
• allows spot or perimeter applications of
  insecticide

Adult CPB / 10 plants
Distance (m)
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Perimeter Insecticide / Edge Treatments
Apr 25
May 2
May 9
May 16
Larval CPB
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Trap adults moving into crop
Walking Beetles
Beetle Trench
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Biological Controls

• Predators, parasites exist but rarely effective

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Chemical Control

• Must control overwintered generation in June
• Ignore overwintered adults unless severe feeding
• Target young larvae, 1st and 2nd instar
• Look for egg hatch
• 5 to 10 days, depending on temperature

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Chemical Control
Problem beetle has developed resistance
to many insecticides e.g.
carbamates, organophosphates,
Tools available Biological (specific)

• Bacillus thuringiensis var tenebrionis
• Target 1st, 2nd instar
• Multiple applications
• Good coverage needed
• Spinosad (Entrustorganic)
• Target 1st, 2nd generations
• 1-2 applications only

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Potato leafhopper

• Appearance
• Adults, small (1/8) wedge-shaped, bright green
• Rapid movement
• Nymphs, yellow-green, lack wings

• Occurrence
• Does not overwinter in Wisconsin
• Adults migrate from gulf states
• Arrive June, 2-3 generations/year
• Very broad host range includes potatoes, beans,
  alfalfa
• Can infest quickly

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Potato leafhopper damage in snap beans

• Both adults and nymphs feed
• Sucking mouthparts
• Saliva clogs plant, causes yellowing, leaf
  necrosis
• Can kill young plants quickly
• May only cause stunting

Untreated
Treated with insecticides
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Potato Leafhopper damage in potato
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PLH hopperburn
First signs of hopperburn
Later stages of hopperburn
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PLH Management
Cultural Biological - Plant early to avoid
- No effective biologicals
Chemical - Monitor often (June 1) - Treat only
when threshold exceeded (1/sweep) - Do not let
nymphs build up - Control is effective if
needed pyrethrins Evergreen, Pyganic
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Cole Crop Insect Control
Many crops with same insect pest complex
Head crops
Cabbage
Cauliflower
Broccoli
Also Brussels sprouts, Kale, Kohlrabi, Collards,
Mustard greens, Chinese cabbage, etc.
Root crops Turnips, Radish, Rutabaga, etc.
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Insect Pest Complex
Key Pests - Lepidoptera
Diamond back moth
Imported cabbage worm
Cabbage looper
Sporadic Pests
Cabbage maggot
Flea beetle
Cabbage aphid
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Managing Insects on Cole Crops

• ??Excellent example of potential for biological
  control ??
• (Mahr et. al. NCR Regional pub. 471)
• History of problem
• Direct damage to marketable product by key pests
• Worms on heads
• Maggots on roots
• Multiple insecticide applications used
• Resistance developed as threat to production
• Solution
• IPM implementation based on biological control of
  key pests
• Pesticides switched to specific, soft materials
  to preserve natural control

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Key Pests of Cole Crops

• Complex of 3 lepidopteran species
• All feed on marketed crop
• Need to identify species but can treat as a
  complex

Imported cabbage worm
Cabbage looper
Diamondback moth
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Diamondback moth life cycle

• Adult
• Small night flyer, short fast flights
• ½, wings have diamond pattern
• Can monitor with pheromone trap
• Eggs
• Small, hard to see
• Laid close to veins
• Larvae
• 4-5 instars up to ¾ long
• 2-3 weeks
• Cigar shaped, pointed at ends
• wiggle when touched
• Spin thread and hang
• Pupa
• Usually on underside of leaves
• Neatly spun pupal case

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Diamondback moth

• Occurrence
• Does not overwinter in Wisconsin
• Blown in on wind or imported on plants
• 4-8 generations per year
• Damage
• Window pane feeding, may also deform heads
• 1st instar mine in leaf
• Damage usually early-mid season (June/July)
• Resistance to many insecticides
• Major problem worldwide

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Imported Cabbage Worm life cycle

• Adult
• White, day flying butterfly
• Eggs
• Laid single on undersurface
• White, turning yellow at hatch
• Cigar shaped
• Larvae
• 5 instars 3-4 weeks
• Velvety green with yellow dorsal line
• Slow moving
• Up to 1 ½ inches in length
• Pupa
• Distinctive angular shape
• Usually on plant debris/old leaves

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Imported Cabbage Worm

• Occurrence
• Overwinters as pupae in Wisconsin
• 3 generations per year, 1st on weeds
• Damage
• Usually most damaging species in Wisconsin
• Large holes in leaves and heads
• Often extensive frass
• Peak damage mid-season (June/July)

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Cabbage Looper life cycle

• Adult
• Large, night flying moth
• Hour glass marks
• Eggs
• Laid singly on undersurface
• White, turning tan at hatch
• round shaped
• Larvae
• 5 instars 4-5 weeks
• Green with white stripe
• Loop when moving
• Up to 2 inches in length
• Pupa
• Roughly spun silk cocoon
• Underside of old leaves or on debris

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Cabbage Looper

• Occurrence
• Does not overwinter, adults blow in (June/July)
• 2 generations per year, persisting in late season
• Damage
• Damage usually late season
• Extensive leaf holes and head damage

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Managing the Lep. Complex

• Cultural
• Use clean transplants
• Biological
• Good complex of parasites
• Diamondback moth 70-90 parasitized
• Imported Cabbage worm 30-60
• Cabbage looper 10-30
• Multiple species

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Managing the Lep. Complex

• Chemical
• Pest Specific
• Bacillus thuringiensis (Kurstaki Btk, or Azaiwi
  Bta)
• Many materials registered
• e.g. Dipel, Thuricide, Biobit, Cutlass, etc.
• Short persistence ? timing critical
• Stomach poison ? coverage important
• Weak on looper
• Spinosad Entrust
• Broad Spectrum
• Pyrethroids
• Multiple applications
• Resistance can be a problem
• Eliminate biological controls

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Key Pest of Root Crops
Cabbage Maggot Life Cycle

• Adult
• Small grey/black fly
• Similar to housefly
• Eggs
• Small, white
• Laid in soil at base of plants
• Larvae
• White, legless maggots
• 4 instars up to 1/4
• 3-4 weeks per generation
• 3 generations per year
• Pupa
• Brown, oval shaped
• In or close to the roots

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Cabbage Maggot Life Cycle

• Occurrence
• Overwinters in soil as pupa
• Adults emerge in spring
• 3 flight peaks
• First peak is most serious and occurs at 300 heat
  units or when lilacs bloom (May)
• Damage
• Larvae tunnel on root surface
• May be secondary rot
• Major importance on root crops
• Causes wilting, death on head crops

300 DD
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Cabbage Maggot Management

• Cultural
• Rotate crop away from overwintering site (1/4-1/2
  mile)
• Prevent egg laying with barrier, row cover
• Predict egg laying with heat units (300 HU with
  43F base)
• Plant early or late to avoid eggs fly free
  periods
• Biological
• Some egg predation by beetles
• Chemical
• None currently available
• Experimental seed treatments in review (spinosad)

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Sporadic Pests of Cole Crops
Flea beetle (several species)

• Appearance
• Small, shiny black beetles
• Hind legs enlarged for jumping
• Overwinter as adults
• 2 generations per year
• Damage
• Adults chew small circular holes
• Can kill small plants
• Larvae in soil are not damaging

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Flea Beetle Management

• Cultural
• Exclude adults with row cover
• Attract adults to alternate trap crop (Indian
  mustard)
• Avoid early planting
• Biological
• No effective controls
• Chemical
• Repeat applications of natural pyrethrums
• DO NOT disrupt biological controls for lepidoptera

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Vine Crops Calendar of Insect Pests
April May June July
Aug Sept Oct
Cucumber Beetles
Aphids
April May June July
Aug Sept Oct
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Striped and Spotted Cucumber Beetles

• Lifecycle
• Adult beetles 8-10 mm length
• and 3-4 mm wide
• Striped cucumber beetle
• Acalymma vittatum
• Spotted cucumber beetle
• Diabrotica undecimpunctata
• Striped cucumber beetles overwinter in protected
  areas as adults and become active in mid-spring.
• Appear early, lay eggs at the base of cucurbits,
  and have 2 generations / year
• Striped is most severe

Striped cucumber beetle
Spotted cucumber beetle
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Striped cucumber beetle(Acalymma vittatum)
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Cucumber Beetles Damage
Pollination interference
Defoliation
Feeding scars
Rindworms
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Cucumber Beetles Bacterial Wilt

• Most damage is from bacterial wilt, Erwinia
  tracheiphila
• Closely associated with beetle, vectored via
  posterior-station
• No cure for bacteria, control through vector
• Susceptibility
• Melons (not watermelon) gt cucumbers gt
  butternut and Hubbard squash

• Causal agent Erwinia tracheiphila, transmitted
  by the cucumber beetle

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Management Bacterial Wilt

• Avoidance of bacterial wilt is accomplished
  through effective cucumber beetle control.
• Cucumber beetles are not always present
• Cucumber beetles are not efficient vectors of the
  bacterium
• Sampling can be accomplished with yellow sticky
  traps
• Established Thresholds (direct counts)
• 1 beetle / plant for melons, cucumbers, and
• young pumpkins
• 5 beetles / plant for watermelon, squash,
• and older pumpkins

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Cucumber beetles Management

• Cultural
• Later planting
• Eliminate weeds, weedy edges
• (sanitation)
• Row cover early
• Crop rotation
• Transplants
• Trap crops on plastic mulches
• Biological
• None effective
• Chemical
• Avoid flowering to protect bees (late afternoon
  sprays)
• At-plant systemic (nicotinyls) and foliar
  insecticides (pyrethroids, carbaryl)
• Attract-and-Kill, (Adios) discontinued

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Alternative Chemical Control

• Insecticide seed treatments (2008-09)
• Cucumber and squash seeds treated with spinosad
  Entrust
• Cucurbit seeds treated with thiamethoxam or
  clothianidin reduced cucumber beetle densities
  and damage in Ohio similar control as Admire and
  Platinum (Welty 2006, unpublished)

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Insects Impact Cucurbit Production
Pollinators
and Devastators
European honey bee
Striped cucumber beetle
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European honey bee (Apis mellifera)
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Can we rely on honey bees to pollinate cucurbit
crops?
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Factors Harming Honey Bee Populations

• Diseases (e.g., American foul brood)
• Parasitic mites (NRC 2006)

Tracheal mite (Acarapis woodi)
Varroa mite (Varroa destructor)
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Factors Harming Honey Bee Populations

• Insecticides (Kevan et al. 1997)
• - Do not apply to crops in bloom
• - Application timing apply in the late
• afternoon or early evening
• - Choose short residual products
• - Adjust spray to weather conditions
• low temps extend residual
• protract foraging times
• - Application formulation (s)
• EC gt WP, WSP, D

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Factors Harming Honey Bee Populations

• Colony Collapse Disorder (CCD)
• caused by the Israeli Acute Paralysis Virus
  (IAPV) that weakens bees immune system (Stokstad
  2007)
• honey bee colonies lose all of their worker bees
• responsible for a loss of 50-90 of colonies in
  beekeeping operations across the U.S.

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Understanding Colony Collapse Disorder (CCD)

• Israeli Acute Paralysis Virus (IAPV)
• - May not be the sole cause (ESA 2007)
• Bee colony attrition may be linked to a
  combination of factors
• - Mites associated acaricides
• - Stress associated with production
• - Pesticides
• - IAPV

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Squash bug, Anasa tristis

• Occurrence
• Adults are large black bugs which aggregate on
  plants
• Round eggs are laid in neat rows
• Nymphs are white/grey
• Damage
• Phytotoxic saliva causes wilting
• Cucurbit yellow vine decline
• - Hubbard and winter squash more severely
  affected

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Squash bug - Management Thresholds

• Seedling Stage
• Treat if wilting and squash bugs are observed
• Flowering Stage
• Treat if gt 1 egg mass is
• found per plant
• Control
• pyrethrums
• Cultural
• - sanitation remove overwintering sites
• - destroy crop residue

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Two-spotted spider mites, Tetranychus urticae

• Occurrence
• Usually occur in hot dry conditions
• More severe in dusty, road side locations
• Multiple generations on undersurface of
• leaf

• Damage
• Adults feed in large numbers on leaf surface
  causing silvering
• Lower surface often covered with webbing
• Late season pest
• Can be flared by pyrethroids

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Spider mite, Management
Leptothrips

• Cultural
• Maintain good plant growth, irrigate
• Avoid dusty roads
• Biological
• Several effective predators
• Avoid broad-spectrum insecticides
• Chemical
• Unless necessary, do not use
• Hormoligosis boosts egg production
• Insecticidal soap, M-pede

Minute pirate bug
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Squash Vine Borer

• Occurrence
• Adults are diurnal, wasp-like moths
• Lay eggs singly on vines
• Larvae bore into plants and destroy
• vascular tissues wilting and death.
• Not a pest of watermelon,
• muskmelon, or cucumbers
• Emerging issue on winter
• squash (Hubbard) and pumpkin
• Occasional second generation

Adult moth
Larvae
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Squash Vine Borer Control

• Sampling
• Field history past problems future problems
• Often more serious in smaller plantings
• Pheromone traps
• Direct observation entrance holes frass
• Cultural
• Practice good field sanitation
• destroy residue
• Chemical (re-application)
• Natural pyrethins
• Bacillus thuringiensis var. kurstaki

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Cucurbit Virus Complex
Major Viruses Cucumber mosaic virus
(CMV) Watermelon mosaic virus-2 (WMV-2) Papaya
ringspot virus (PRV) (synonymous WMV-1) Squash
mosaic virus (SqMV)-cucumber beetle /
seed Zucchini Yellow Mosaic Virus (ZYMV) Minor
Viruses Tobacco ringspot virus
(TRV)-nematode Tomato ringspot (TmRSV)-nematode Cl
over yellow vein virus (ClYVV) Beet curly top
virus (BCTV) Beet pseudo-yellows virus (BpYV)
Papaya ringspot virus
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Cucumber mosaic virus

• Widely distributed
• Non-crop inoculum sources
• Stunting, leaf curl
• Elongate, shoestring leaf
• Color breaking

• Regularly encountered
• Leguminous plant hosts (e.g. clover)
• Mild mosaic
• Rugose leaf, cupping
• Fruit distortion and color breaking

Watermelon mosaic virus - 2
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New Pest
2005 Distribution
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AMV
CMV
Emerging bean viruses the problem
German et al. (2004)
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Non-Persistent Virus Transmission

• Non-circulative (CMV, WMV-2, PRV, ZYMV)
• often referred to as stylet-borne
• Non-propagative

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Non-Persistent Transmission Movement in Insects

• Food Ingestion
• Pathogen particles attach
• to maxillary lumen

• Egestion
• Pathogen particles released
• with saliva

Ingestion
Salivation
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Nonpersistent Transmission

• Acquisition time - time required to acquire
  pathogen
• Seconds
• Inoculation time - time required by infectious
  insect to inoculate a susceptible host
• Seconds
• Latent period - (minimum time between acquisition
  of a pathogen and ability to transmit)
• Zero
• Retention time - time after acquisition
• that a vector remains capable of
• transmitting the virus
• - Minutes to hours

Chemical controls no option!!
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Traps for Winged Aphids
water pan trap
sticky traps, green yellow
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Landing of Migrating Aphids

• Alighting aphids orient preferentially to plants
  showing a contrast against a bare soil background
• concentrates landing
• around field margins if field has a bare soil
  border
• on young plants before canopy closure
• Eliminating contrasting background reduces
  landing rates
• border planting inter-planting
• reflective mulches

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Reflective Mulch for Aphid/Virus Management

• Theory
• Repels winged aphids (reflected UV)
• Delays aphid colonization
• Delays virus infection
• Reduces virus symptoms

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Aphid Management

• Cultural
• Trap cropping
• Weed control
• Rouging
• Light mineral oils
• Resistant varieties
• Biological
• Effective predators
• Chemical
• Ineffective

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Resistance

• A genetically controlled decrease in
  susceptibility of a population to a control
  measure
• resistance to insecticides (IRAC 2006)
• 500 insect species resistant to 1 or more
  insecticides
• 1800 species/insecticide resistance combinations
• adaptation to pest resistant crop varieties
• adaptation to crop rotation

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Chronology of Insecticide Resistance in Colorado
Potato Beetle Long Island, NY
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Resistance Development

• Resistance genes occur naturally at low
  frequencies
• 10 -8 to 10 -12
• Proportionately more insects with R-genes survive
  and leave offspring when exposed to toxin than
  insects with only S-genes

SS
RR
RS
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Measuring Resistance

• LD50 (or LC50) dose (or concentration) that is
  lethal to 50 of the test population under
  defined conditions
• LD90 dose that is lethal to 90 of the test
  population

90
Percent mortality
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LD50
LD90
Dose
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Resistance Ratio

• Ratio of LC50 of test population to LC50 of
  reference population
• LC50(test) / LC50(reference)
• Resistance ratios of susceptible (controllable)
  populations can vary as much as 20-fold

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Wisconsin, 2007 Imidacloprid Bioassays

• Survey Sites
• Adams County (8)
• Langlade County (7)
• Oconto County (1)
• Portage County (8)
• Waushara County (11)
• Total (35)
• CPB Populations
• Over-wintered adult
• 2nd generation adult
• Adult Topical Bioassays

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Wisconsin, 2007 Imidacloprid Bioassays
Preliminary Assays(2007) 35 populations, LC50
range (0.021 1.355)
LD50 (µg/beetle)
30X
20X
10X Susceptible LD50
Location
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Insecticide Mixtures Strategy

• Apply tank mixture of insecticides A B
• individuals resistant to one compound in the
  mixture will be killed by the other
• Basic principle
• if resistance to each compound is independent (no
  cross resistance) and initially rare, individuals
  resistant to both compounds will be extremely
  rare
• Equal persistence of both compounds
• If A loses activity before B, all individuals
  resistant to B will not be killed by A
• a 5 difference in persistence of A B can
  completely negate advantages of mixture

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Rule Out Common Causes of Control Failures Other
Than Resistance

• Calibration error
• Mixing error
• Use of inappropriate product
• Use of out-dated product
• Re-infestation following application

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Impediments to Resistance Management

• Must be implemented before resistance problem
  exists
• Involves added costs and/or complexity
• Pesticide dealers may not always stock inventory
  for required rotations
• Sales incentives favor maximizing pesticide sales
  in short-term
• No positive feedback

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