Insect Pests

Thrips
Thrips are often the most serious insect pest in greenhouses. They are very difficult to control once a population becomes well established. Thrips feed on leaves and flowers of a wide variety of host plants. The feeding injury can render a plant unmarketable and the act of feeding by the thrips can transmit viruses to a susceptible host plant. The thrips lifecycle begins as an egg is deposited in plant tissue. After the larvae emerge they begin feeding on the plant. Thrips pass through 2 larval and transformation stages before becoming an adult. Feeding injury is done by the larvae and adults but only the adults can transmit viruses. The lifecycle of a thrips is temperature dependant with development occurring between 50 – 90° F. The egg to adult cycle lasts between 10-38 days at these temperatures. At temperatures below 50° F thrips can survive but no development occurs.
Aphids
There are many species of aphids that can attack greenhouse plants but the two most common species are the green peach aphid (Myzus persicae) and the melon/cotton aphid (Aphis gossypii). Both of these species are green in color but it can vary from light to dark green for the melon aphid and from light green to nearly pink for the green peach aphid. Aphids have small soft bodies with piercing-sucking mouth parts which they use to insert into the phloem tissue of plants and remove fluid. Aphids cause problems from injury by feeding, the transmission of viruses and by spreading sticky honeydew over the surface of leaves and flowers. In the greenhouse most aphids are female and they produce live young called nymphs. An average female produces between 50 to 200 nymphs during her lifetime. The nymphs, which are all female, begin reproducing in 7-10 days. Adult aphids appear in 2 forms, winged and wingless, depending on population density and /or host plant conditions. Winged aphids are troublesome because they are able to disperse throughout the greenhouse and are also able to fly into the greenhouse from outdoors.
Fungus Gnats
The fungus gnat is a common pest of greenhouse plants. The adults are tiny, dark, slender, fragile looking flies. They have long antennae and legs and a small head in relation to their bodies. The lifecycle of the fungus gnat is completed in 25-30 days. The adults live about one week and lay up to 200 eggs. The eggs hatch in about 4 days into larvae. The fungus gnat larvae are white and translucent with shiny black heads. The larvae live in the soil for two weeks and feed on the roots of plants. The pupal stage lasts 3-4 days before the adults emerge. Extensive damage can result from larval feeding, resulting in plants that show signs of wilting. The adult fungus gnat is primarily a nuisance pest.
Spider Mites
Spider mites are a persistent pest problem in the greenhouse. Many species of spider mites are found in the greenhouse, but the most common is the two-spotted spider mite (Tetranychus urticae). Spider mites are very small arthropods that develop mostly on the undersides of leaves. Their lifecycle lasts between 7-14 days but varies considerably depending on temperature. An adult female spider mite can produce 100-200 eggs in her lifetime. The eggs hatch into tiny larvae in a few days. The larvae pass quickly through several nymph stages before becoming adults. Spider mites cause injury to plants while feeding. Using their piercing-sucking mouth parts, they extract plant fluids. Feeding injury often give the upper leaf surface a characteristic mottled or speckled appearance. Large numbers of spider mites produce a webbing that can completely cover leaves and flowers.
Whiteflies
Whiteflies are a very common pest in greenhouse production. The most common species are the greenhouse whitefly (Trialeurodes vaporariorum) and the silverleaf white fly (Bemisia arentifolii). The adult silverleaf whiteflies are smaller, more yellow and active than the greenhouse whiteflies. In the pupal state the silverfleaf whiteflies are flat without spines or fringes whereas the greenhouse whitefly pupae have vertical sides with spines. The adult whitefly lifecycle lasts from 21-36 days. Each female produces 60 to 100 eggs that hatch in 7-10 days. The newly emerged crawlers move for a short distance before settling down to feed. After molting 3 times the pupae emerge and in 6 days will grow into adults. During development whiteflies are usually found on the underside of leaves. The adult and immature stages of whiteflies use their piercing-sucking mouth parts to extract fluid from plant tissue. A few adult whiteflies on plants are a nuisance. However, feeding by a large number of adults and especially immatures can weaken or kill a plant. Whiteflies also produce a sticky honeydew that can be a growth medium for lack sooty fungus.
CHEMICAL INSECT CONTROLS
(all chemicals applied at an average rate of 200gal/A unless otherwise noted)

Acephate (Orthene)
Percent of total area treated: 60%
Target pests: Aphids, Thrips, Whiteflies
Average rate and frequency of application of most common formulations2)
Orthene TT&O – 11 oz/100 gal, twice
Application method: High Volume Spray
REI: 24 hours
Efficacy rating: Good

Spinosad (Conserve)
Percent of total area treated: 56%
Target pests: Thrips
Average rate and frequency of application of most common formulations: (2)
Conserve SC – 6 oz/100 gal, twice
Application method: High Volume Spray
REI: 4 hours
Efficacy rating: Very Good

Bifenthrin (Talstar)
Percent of total area treated: 53%
Target pests: Thrips, Aphids, and Whiteflies
Average rate and frequency of application of most common formulations: (2)
Talstar F – 20 oz/100 gal, twice
Application method: High Volume Spray
REI: 12 hours
Efficacy rating: Good

Chlorpyrifos (DuraGuard)
Percent of total area treated: 53%
Target pests: Thrips, Aphids, Whiteflies and Fungus Gnats
Average rate and frequency of application of most common formulations: (2)
DuraGuard ME – 39 oz/100 gal, twice
Application method: High Volume Spray
REI: 12 hours
Efficacy rating: Good

Abamectin (Avid)
Percent of total area treated: 52%
Target pests: Thrips, Aphids, and Mites
Average rate and frequency of application of most common formulations: (2)
Avid 0.15 EC – 8 oz/100 gal, 3 times
Application method: High Volume Spray or Fogger
REI: 12 hours
Efficacy rating: Good to Very Good

Fenpropathrin (Tame)
Percent of total area treated: 48%
Target pests: Thrips, Aphids and Whiteflies
Average rate and frequency of application of most common formulations: (2)
Tame 2.4 EC – 9 oz/100 gal, 2-3 times
Application method: High Volume Spray
REI: 24 hrs.
Efficacy rating: Good
Used with Orthene TT&O for best results.

Fluvalinate (Mavrik Aquaflow)
Percent of total area treated: 36%
Target pests: Aphids, Thrips, and Whiteflies
Average rate and frequency of application of most common formulations:
Mavrik Aquaflow – 9 oz/100 gal, twice
Application method: High Volume and Low Volume Spray
REI: 12 hours
Efficacy rating: Good to Very Good

S-Kinoprene (Enstar)
Percent of total area treated: 24%
Target pests: Thrips, Whiteflies, Aphids
Average rate and frequency of application of most common formulations: (2)
Enstar II – 7 oz/100 gal, twice
Application method: High Volume spray
REI: 4 hours
Efficacy rating: Good to Very Good

Azadirachtin (Azatin)
Percent of total area treated: 22%
Target pests: Thrips, Whiteflies and Fungus Gnats
Average rate and frequency of application of most common formulations: (2)
Azatin XL – 12 oz/100 gal, twice
Application method: High Volume Spray or Fogger
REI: 12 hours
Efficacy rating: Good to Very Good

Methiocarb (Mesurol)
Percent of total area treated: 16%
Target pests: Throps
Average rate and frequency of application of most common formulations: (2)
Mesurol 75W – 2lb/A in 50 gals, twice
Application method: High Volume Spray
REI: 24 hours
Efficacy rating: Very Good

Fenoxycarb (Precision)
Percent of total area treated: 14%
Target pests: Thrips
Average rate and frequency of application of most common formulations: (2)
Precision – 4 oz/100 gal, twice
Application method: High Volume Spray
REI: 12 hours
Efficacy rating: Good to Very Good

Formentanate Hydrochloride (Carzol)
Percent of total area treated: 13%
Target pests: Thrips
Average rate and frequency of application of most common formulations: (2)
Carzol – 16 oz/A, once
Application method:
REI:
Efficacy rating: Good

Endosulfan (Thiodan)
Percent of total area treated: 12%
Target pests: Thrips, Aphids and Whiteflies
Average rate and frequency of application of most common formulations: (2)
Thiodan 50 WP – 16 oz/100 gal, twice
Thiodan 3EC – 48 oz/A, twice
Application method: High Volume Spray
REI: 24 hours
Efficacy rating: Good to Very Good

Beauveria bassiana (Naturalis-O)
Percent of total area treated: 3%
Target pests: Aphids, Thrips and Whiteflies
Average rate and frequency of application of most common formulations: (2)
Naturalis-O – 31 oz/100 gal, twice
Application method: High Volume Spray
REI: 4 hours
Efficacy rating: Good
Imidacloprid (Marathon)
Percent of total area treated: 2%
Target pests: Aphids and White Flies
Average rate and frequency of application of most common formulations: (2)
Marathon 1% - ½ tsp (2 grams)/10 inch pot, once
Application method: top dress for 1% and drench for 60 WSP
REI: 12 hours
Efficacy rating: Very Good