Introduction to High Tunnel Insect Pests and Natural Enemies
Christopher PhilipsAssistant ProfessorFruit and Vegetable EntomologistUniversity of MinnesotaDepartment of EntomologyNorth Central Research & Outreach Center (NCROC)
High Tunnel IPM
To reduce pests below damaging levels while maintaining economic profits, environmental quality and safety.
IPM Implementation
• Step 1 – Identify the pest.
• Step 2 – Evaluate the pest infestation level
• (sampling, monitoring, amount of injury).
• Step 3 – Assess the tolerance level of the commodity to injury.
• Step 4 – Take an action (or no action!).
Insect identification
• Why do I need to identify it anyway?• Determines your management strategy
• Different problems require different solutions
• NOT ALL INSECTS ARE BAD
Spotted wing Drosophila (SWD)
• Drosophila suzukii
• native to Asia
• lays eggs into healthy, ripening soft fruits, using a saw-like ovipositor
SWD non-SWD Photo credits: N. Gompel (top); M. Hauser (bottom)
What are my management options?
1) Biological
2) Genetic
3) Cultural
4) Mechanical
5)…Chemical…
(last option, only when necessary)
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TSSM GPA Melon GH WF BW-WF Silverleaf onion thrips WFT
Resistance to Insecticides
Thrips
(A) Flower thrips, Frankliniella tritici
(B) Western flower thrips, Frankliniella occidentalis
(C) Tobacco thrips, Frankliniella fusca
(D) Soybean thrips, Neohydatothrips variabilis
Scale bars represent 0.5 mm.
Onion thrips, Thrips tabaci
Thrips>7,000 species described worldwide
most are not pests
Biologymigrate into MN
FrequencyA recent survey of Midwest greenhouse operators identified WFT as the most difficult greenhouse pest to manage
20°C, ~ 19 days. 25°C, ~ 13 days.
Damagehave piercing-sucking, multi-purpose mouthparts.
The mouthparts are used to pierce leaves, flowers, seeds, pollen grains, and fruit, as well as to drink open liquids such as nectar, water, or insect secretions;
transmit pathogens
ThripsHosts and Damage
Extremely wide host range
Thrips feeding damage on cucumber fruit.
Thrips feeding damage on cucumber leaves
Thrips Damage
Oviposition scars and feeding damage on sweet pepper.
Thrips egg-laying scars on tomato
Thrips feeding damage on pepper leaves.
A very important aspect of thrips is the transmission of virus diseases.
Tomato spotted wilt virus, transmitted by the • western flower thrips, • tobacco thrips, and • onion thrips.
Sanitation • Remove weeds that act as a thrips (virus) refuge. • Remove and destroy crop residues and affected
plants after harvest.• Pasteurize soil to kill immature thrips.• Pruning
Thrips Cultural and Mechanical
ThripsBiological Control
Amblyseius cucumeris• Amblyseius cucumeris prefers a diet of thrips but is
considered a generalist because it can survive on pollenand spider mites in the absence of thrips.
A. cucumeris will work best at a temperature of 70˚F or aboveand RH > 65%.
Orius insidiosus• Minute pirate bug is a common generalist predator found naturally
in many field-grown crops.• It preys on thrips, whiteflies, spider mites, aphids and many other
pests. It can survive on pollen in the absence of prey.
Intrinsic capacity of Oriusinsidiosus to reduce flower
thrips populations
Predator-Prey Ratios1 : 217 = population suppression
1 : 51 = rapid local extinction
From: Sabelis & Van Rijn (1997) Thrips as Crop Pests. (Lewis, ed.) CAB International, UK
Thrips Predation
Photo Joe Funderburk
Whiteflies
Silverleaf and sweetpotato whiteflies(Bemisia argentifolii and B. tabaci)
Greenhouse whitefly(Trialeurodes vaporariorum)
Bandedwinged whitefly(Trialeurodes abutilonea)
BiologyDo not overwinter in MNcontinue from year to year in greenhouses
FrequencyCommon pest in MN
ControlThere is really no easy way to control whiteflies
Whiteflies
Aphids
Melon/cotton aphid, Aphis gossypiiGreen peach aphid, Myzus persicae
BiologyOverwinter and migrate into MN
FrequencyCommon pest in MN
ControlUsually not necessary; biological control
Aphids and WhitefliesHosts and Damage Numerous Host
Damage• Piercing/sucking mouthparts,
• plant distortion and discoloration, • leaf chlorosis, • leaf withering and premature leaf drop plant• death;
• Excrete honeydew, promotes the growth of sooty mold
Aphids and Whiteflies Damage
Tomato yellow leaf curl virus
Vector taxa Vector group Total plant viruses
Hemiptera Aphids 197
Whiteflies 128
Melon aphids are known to transmit 44 plant viruses, while green peach aphids are known to transmit more than 100 plant viruses
Aphid and Whitefly Management
• Prevent outbreaks of aphids by scouting weekly and releasing natural enemies at the first sign of damage.
• Inspect the upper and lower surfaces of plant leaves
• If you disturb the plant foliage, whitefly adults will fly up and be easier to spot.
• Use a hand lens
• Also check for evidence of natural enemies such as lady beetles, lacewings, syrphid fly larvae and the mummified skins of parasitized aphids. Look for disease-killed aphids as well:
• They may appear off-color, bloated or flattened.
Sanitation
• Remove weeds in and around high tunnels
Limit the use of quick-release fertilizer
Aphid and WhiteflyCultural and Mechanical
Photo credit: Galen Weston,
Biological control of Aphids: Parastitoids
Aphidius colemaniWorks best at a temperature of 50 to 76˚F and tolerates cool temperatures.
Aphidius erviThis small, black wasp parasitizes all types of large aphids. It prefers an air temperature of 86˚F.
Biological Control of Whiteflies: Parasitoids
Encarsia formosa
(Hymenoptera: Aphelinidae)
8-10 eggs per day
Primary Prey: whiteflies and aphids
Key Characters: parasitized hosts turn black
Vegetable crops: release needed
Eretmocerus eremicusE. formosa prefers an average temperature above 64˚F, and RH >70%
Parasitoids
Insect which lives in or on another insect during its immature stages. Differs from parasitism in that:
1. only larval stages are parasitic, adults are typically free flying
2. larvae eventually kill their host
Feed on over 180 host plants, including over 100 cultivated species
Damage• Spider mites injure leaves by piercing cells
and sucking out cell contents. • This injury produces white or yellow spots
or "stippling" that is heaviest on the underside of the leaves
• As mite numbers increase, these white speckles will increase in number, the leaf will take on a bleached appearance and die.
Two-spotted Spider MiteHost and Damage
• Chemical control of spider mites generally involves pesticides that are specifically developed for spider mite control
• Few insecticides are effective for spider mites and many even aggravate problems.
• Furthermore, strains of spider mites resistant to pesticides frequently develop, making control difficult.
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TSSM
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Two-spotted Spider MiteManagement
Two-spotted Spider Mite Cultural and Mechanical
Sanitation • remove alternative hosts could reduce infestation of plants
nearby• disposing of old or infested plant material
Inspections
Avoid over-fertilization • promotes succulent new growth which is more susceptible
to two-spotted mites.
Use of high-pressure water spray or overhead irrigation to dislodge spider mites
Predators are very important in regulating spider mite populations and should be protected whenever possible.
Important predators include:
the predatory mites,• Phytoseiulus persimilis,• Mesoseiulus longipes,• Neoseiulus californicus,• Neoseiulus fallicus• Galendromus occidentalis
The lady beetle, Stethorus;
The minute pirate bugs, Orius;
Two-spotted Spider Mite Biological control
Predatory MitesAcari: Phytoseiidae
67 genera, 2,000 species
Primary Prey: spider mites, thrips; fungus gnats
Predatory Stage: nymphs and adults
Key Characters: teardrop shape; fast moving
Vegetable crops: most greenhouse crops
Amblyseius fallacis
Galendromus occidentalisMesoseiulus longipes
Phytoseiulus persimilis
Neoseiulus californicus
Anatomy Body structure, mouthparts
ReproductionParthenogenic, haplodiploidy, polyembryony
OntogenyGrowth rate, metamorphosis, pest stage
Insect EcologyEnvironmental interactions
Why Do Insect Pest Problems Occur?
Insect Growth and Development
Affected by two major factors, time and temperature
The amount of heat required by an organism to complete its development is known as physiological time.
• Minimum or lower developmental threshold is the temperature below which insect development is negligible.
• Maximum or upper developmental threshold is the temperature at which insect growth stops.
Why Do Insect Pest Problems Occur?
• Almost unlimited food and improved environmental conditions
• Multiple generations - up to 12-15 / year
• Limited natural enemies to reduce populations
• Some life stages are not susceptible to treatment
• Major insecticide and miticide resistance
Biological control
• “the enemy of my enemy is my friend”
• e.g., predators, parasitoids, pathogens
• Biological control is a method of controlling pests using other living organisms.
Types of Biological Control
Classical
Augmentation
inundative releases and
inoculative releases
Conservation
Getting Started
• Start small and start early
• Pesticide Residues and when needed use soft pesticides
• Good Sanitation
• Weed management is critical
• Clean Transplants
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What are my management options?
1) Biological
2) Genetic
3) Cultural
4) Mechanical
5)…Chemical…
(last option, only when necessary)
Nymphs and adult stage
Primary Prey: whiteflies, thrips, aphids
Predatory Stage: nymphs and adults
Key Characters: very small, black and white coloration
Vegetable crops: most
Minute Pirate BugsHemiptera: Anthocoridae
Intrinsic capacity of Oriusinsidiosus to reduce flower
thrips populations
Predator-Prey Ratios1 : 217 = population suppression
1 : 51 = rapid local extinction
From: Sabelis & Van Rijn (1997) Thrips as Crop Pests. (Lewis, ed.) CAB International, UK
Thrips Predation
Photo Joe Funderburk
Big-eyed bugsHemiptera: Goecoridae
Geocoris punctipesBig-eyed bug
Primary Prey: insect eggs, small insects and larvae
Predatory Stage: nymphs and adults
Key Characters: small black, gray or tan with large
eyes
Vegetable crops: most
Damsel bugsHemiptera: Nabidae Nabis spp.
Primary Prey: insect eggs, small insects and larvae
Predatory Stage: nymphs and adults
Key Characters: slender yellowish-brown with narrow head, prominent eyes and long antennae
Vegetable crops: most
Primary Prey: aphids and whiteflies
Predatory Stage: larvae
Key Characters: Mosquito-like adults; small orange maggots
Vegetable crops: most attacked by aphids
Predatory MidgeDiptera: Cecidomyiidae
Predatory Midge: Feltiella acarisuga
Hover FliesDiptera: Syrphidae
Primary Prey: aphids and small caterpillars
Predatory Stage: larvae
Key Characters: adults resemble bees, maggots are tapered near head, green or pinkish, near aphids
Vegetable crops: most attacked by aphids
Primary Prey: aphids, mites, small insects, eggs
Predatory Stage: larvae and adults
Key Characters: alligator-like larvae; red or orange adults with black markings
Vegetable crops: most
Lady BeetlesColeoptera: Coccinellidae
Coleomegilla maculata
Larva
C. septempunctata
Delphastus pusillusDelphastus catalinae Stethorus punctum
Harmonia axyridis450 species of lady bugs in NA
Rove BeetlesColeoptera: Staphylinidae
Primary Prey: root maggot eggs, other soft bodied insects
Predatory Stage: larvae and adults
Key Characters: slender, short forwings
Vegetable crops: cole crops, onions, corn, and
others
Ground BeetlesColeoptera: Carabidae
Many, many species - usually ground-dwelling generalist predators
Larva
Elaphrus
Clivina
Notiophilus
Lebia
Primary Prey: soil-dwelling eggs larvae and pupae
Predatory Stage: larvae and adults
Key Characters: dark, sometime metallic color; fast moving, ground dwelling, thread-like antennae
Vegetable crops: most
The True Bugs
Key Characteristics
Piercing-sucking mouthparts
Generalist feeding
Omnivorous
Stink bugs
Minute Pirate Bugs
Big-Eyed Bugs
Damsel Bugs
Assassin Bugs