Insects and Related Pests in the Greenhouse

Presented by Terry Ferriss, PhDUniversity of Wisconsin—River Falls

Common Pests in the Greenhouse

AphidsThripse

Fungus gnatsShore fliesWhiteflies

Red spider mitesCyclamen mites

LeafminerMealy bugs

Scales

Aphids Description: 1/8” in

size black to green in color winged and wingless “tail-pipes” “Y” shaped vein at wing

tip

Feeding: piercing - sucking mouth

Location on plant: Found on entire plant

(growing tips to roots) Primarily buds Underside of leaves Stems

Signs/Symptoms: Distorted new growth /

chlorosis Chlorotic pin-point spots

on older leaves Honeydew and sooty mold

Honeydew and Sooty Mold

Aphids & many other insects frequently excrete: Honeydew” --- shiny, sticky

Ants love to eat “honeydew”

Sooty mold grows vigorously on “honeydew”

Aphids (cont.)Reproduction: Female nymphs give birth to

other females without mating

Males and females appear outdoor as winter approaches – mate eggs overwinter

7 day life cycle possible !!!

Aphid’s Lifecycle

From: Nelson, Greenhouse Mgmt book

Aphid

From: Nelson, Greenhouse Mgmt book

Aphid damage to a chrysanthemum

Controlling Aphids Common crops:

impatiens, dahlia, cineraria , peppers, tomatoes Management:

Avoid high N fertilization wash aphids off plant Aphidied parasitic wasp Enstar (IGR) Horticultural Oil Orthene Others …..

Thrips Description: 1/32”-1/25”

2 pairs of wings dark brown / cigar shaped may be confused with a speck of dirt on sticky card

Feeding: Rasping - sucking mouth

Location on plant: in buds, in flowers, in leaf axils,

between bulb scales Signs/symptoms:

White to silver feeding scars/streaks on new growth (turn tan to brown)

Distorted or malformed foliage/flowers Stunted growth Carry virus (TSWV, INSV)

ThripsReproduction: Can complete in 2 weeks Warm or cool temps Pupates in soil

Thrips’s Lifecycle

From: Nelson, Greenhouse Mgmt book

Thrips

Thrips damage

Controlling Thrips Common crops:

geraniums, chrysanthemums, impatiens

Management: Build resistance to chemicals quickly Sugar bait to increase exposure CO2 = irritant and increases exposure Contact chemicals: deliver as small particle size to reach

thrips hidden in leaf axils and buds. (several including Marathon, Avid) Biological control

Is it a fungus gnat or a shore fly???

Fungus gnat Short fly

Resemblance Tiny mosquito Tiny fruit fly

Legs/antennae Long Short

Wings Clear w/ a distrinct Y shaped vein

Five light spots on each gray wing

Food source Plants, organic matter in soil, fungi

algae

Fungus gnat vs. Shore fly

From: Nelson, Greenhouse Mgmt book

Fungus gnats Description: 1/16”-1/8”

adult looks like a tiny mosquito larvae: worm-like white with black head (1/4 “)

Location : Larvae are in soil feeding on decaying OM Adults do not feed but fly around plants and lay eggs in soil

Signs/symptoms:

Larvae can injure roots if high populations Adults do not cause direct damage to the plant but can carry

fungal spores and are very undesirable. Possible lack of vigor, chlorosis

Common crops: any plant in high organic media

Fungus gnat lifecycle (20 – 30 days)

From: Nelson, Greenhouse Mgmt book

Fungus gnat

From: Nelson, Greenhouse Mgmt book

Controlling Fungus gnats

Management: Avoid algae in the area Keep floors as dry as possible Clean up spilled media Eliminate weeds BT (Bacillis thurengiensis) Chemical options

Shore Fly

From: Nelson, Greenhouse Mgmt book

Shore Flies Description: 1/8”

dark in color, looks like tiny fruit fly

Location on plant: Favor damp areas and algal growth

Signs/symptoms: No direct injury to plants, but shore flies may carry plant

pathogens

Common crops: Found on any crop around damp areas

Management: Keep algae growth down, watch fertilizer and water runoff,

chemical and biological control

Shore Fly’s Lifecycle

From: Nelson, Greenhouse Mgmt book

Whiteflies Description: 1/16”-1/8”

wings covered with white waxy powder yellow-orange body Breed in oxalis and other weeds Life cycle of 4-5 weeks

Location on plant: Underside of leaves (10 young lvs) fly when disturbed

Feeding: Piercing-sucking mouth part

Signs/symptoms: Chlorosis may leave honeydew

Whitefly’s Life cycle

From: Nelson, Greenhouse Mgmt book

Whitefly

From: Nelson, Greenhouse Mgmt book

Whiteflies (cont.) Sweet potato WF Sweet potato WF vs Poinsettia WFPoinsettia WF

SPWFSPWF: moves slower / larger enstar / flies further / grayer

PWFPWF: reproduces 30% faster

Common crops: poinsettia, geranium, tomato, pepper, fuschia

Controlling Whiteflies Management:

Weed control Enstar (IGR) Encarsia formosa Horticultural oil Chemical control (in nymph or adult

stage) Marathon Pyrethrum others

Red Spider Mite(2 –spotted red spider mite)

Description: .007”-.015” Red or orange in color

Location on plant: Underside of leaves and on flowers

Favorable conditions: Low relative humidity and high temperatures

Signs/symptoms: Chlorotic stippling on upper leaf surface Yellow / bronzing of foliage – dry lvs If severe will see webbing

cthr.hawaii.edu

Red Spider Mite Lifecycle

From: Nelson, Greenhouse Mgmt book

Red spider mite

Photo: NCSU

gardenscure.com

Photo: mumsanddahlias.com

Controlling Red Spider Mites

Common crops: English ivy, marigold, foliage plants, ivy

geranium Management:

Wash underside of leaves Humidity / temp control Parasitic mites Biological sprays Miticides effective only on adults

kenyon.edu

Cyclamen Mite Description: .007”-.015” Location on plant:

Growing tips

Signs/symptoms: Distorted or stunted new growth, blackened shoot tips

Common crops: African violet, new guinea impatients, ivy, clematis

Management: Rouge out infested plants, chemical control

Cyclamen Mite

From: Nelson, Greenhouse Mgmt book

Leafminer Description: 1/16”,

stout bodied flies that are black and may have a bright yellow thorax

Location on plant: Leaves

Favorable conditions: High nitrogen levels

Signs/symptoms: Punctured leaves where

females lay eggs “Mines” through leaves

after eggs hatch

Common crops: marigold, chrysanthemum,

petunia

Management: Resistant varieties,

chemical/biological controls

Leafminer’s Lifecycle

From: Nelson, Greenhouse Mgmt book

Leafminer

Leafminer damage

From: Nelson, Greenhouse Mgmt book

Mealybug Description: 1/8”-1/4”

soft-bodied insect covered in a white, waxy secretion

Location on plant: Leaf axils, leaf midribs, underside of leaves

Signs/symptoms: Honeydew on leaves, leaf yellowing and leaf drop, cottony white masses in leaf axils and underside of leaves, new growth is distorted

Mealybug Common crops:

Foliage plants

Signs / symptoms: “spitballs” in leaf axils and

along veins Stunted growth Chlorosis of adjacent plant

parts

Feeding: Piercing-sucking mouth

part

Management: Rouge out infested plants, wash off plants, chemical control (nymphs

are most susceptible), biological control

Mealybug Lifecycle

Mealybug

From: Nelson, Greenhouse Mgmt book

Scales Description: 2-5mm

soft and white to hard and dark bodied

Feeding: piercing sucking mouth

Location on plant: Stem, flowers, fruits, roots,

crown

Signs/symptoms: Silver streaking honeydew on

plant, Chlorosis

Common crops: woody interiorscape plants,

amaranthus

Management: Destroy infested plants chemical and biological

controls

Scales’s Lifecycle

From: Nelson, Greenhouse Mgmt book

Scales

University of Wisconsin—River Falls

Thank you

Terry Ferriss, PhD