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

Aphids

Whiteflies

Spider mites

Thrips

Common Pests

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

Two-spotted Spider Mite

BiologyOverwinters in MN

FrequencyCommon pest in MN

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

Arthropod Predators

True Bugs

Beetles

Flies

Others

• lacewings

• Spiders

• Mites

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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Questions?

What are my management options?

1) Biological

2) Genetic

3) Cultural

4) Mechanical

5)…Chemical…

(last option, only when necessary)

Types of Natural Enemies

Generalists and Specialists

Predators and Parasitoids

Pathogens

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

Predatory Flies

Hover Flies

Predatory Midge

Predators – Beetles

Lady Beetles

Rove Beetles

Soldier Beetles

Ground Beetles

Other Predators

Spiders

Praying Mantids

Mites

Lacewings

LacewingsNeuroptera: Chrysopidae/Hemerobiidae

Primary Prey: aphids and other pests

Predatory Stage: larvae

Key Characters: green or brown adults; net-veined wings; alligator-like larvae with sickel-shaped jaws

Vegetable crops: most