Thrips are common greenhouse pests and challenging to control with chemicals. They are tiny (1-2mm) and hide in between leaves and flower bracts. They are easily overlooked until the telltale signs of feeding occur: discolored or distorted leaves, stipling, silvering and premature leaf drop. Using yellow sticky cards in the crop can alert you when they show up and trap them, decreasing the population.

Different species of thrips behave in different ways. Always try and ID any pest before you act. The Ontario Floriculture website has a comprehensive Thrips ID just for this purpose. Western Flower Thrips are a common greenhouse pest, but there are many other species that cause damage, as seen in the image below. 

It is vital to stop thrips early. Not only will they damage plants, but they can also vector deadly viruses throughout the greenhouse, such as tomato spotted wilt virus (TSWV) and impatiens necrotic spot virus (INSV).These viruses can infect a large variety of plants and significantly damage vegetable crops and ornamental crops.

Following is a simple and effective biocontrol plan to be equipped for thrips this season.

• Focus the biocontrols on the susceptible plants
• Start in propagation, it's less expensive and most effective
• Always dip incoming cuttings, plugs and liners in soaps, oils or microbial products. 
• Apply the predatory mite Amblyseius cucumeris weekly, for three weeks
• Release Dalotia the rove beetle once
• Weekly drench with nematodes like Steinernema feltiae
• Weekly spray with Botanigard or like product
• At spacing use one mini sachet of predatory mites (Cucumeris or swirskii) per pot or flat
• Use sticky cards to mass trap pests (every female caught removes 300 eggs from the system!)
• Introduce the minute pirate bug, Orius, for hot spots (as seen in the photo below)

Predatory mites are a substantial part of thrips control. Besides feeding, their general harassment will also reduce pest pressure. The statistics are compelling. Use of predatory mites reduces:

• Thrips feeding by 25%
• Thrips larval survival by 50%
• Thrips life span by 40%
• Thrips egg laying by 70%
• Thrips plant damage by 30% 

Preparing ahead will save you time, money and stress. There are three layers for Western Flower Thrips control: Stratiolaelaps and nematodes for soil, Amblyseius cucumeris or swirskii for young stages of thrips on leaves and Orius for all stages of thrips on the plant. Stay ahead of this perilous pest this season.

One of the best aphid predators for indoor and outdoor crops is the tiny parasitic wasp Aphidius colemani. These North American natives are produced in insectaries for the biocontrol industry, but they can be raised in any growing system with the right conditions. Growing banker plants to rear Aphidius colemani is like putting money in the bank. Instead of buying Aphidius on a regular basis, you can produce your own on barley or oat grasses that have been inoculated with cherry oat aphids. This establishes them in the greenhouse before aphids become a problem.

You may wonder, why would I ever bring aphids into my greenhouse? Cherry oat aphids (Rhopalosiphum padi) are pests of wheat, oats and barley (monocots) and will not survive on ornamental crops that aredicots. This allows them to exist in most greenhouses and provide habitat and food for the aphid parasite Aphidius colemani. As the Aphidius population grows, they spread throughout the greenhouse hunting down aphids, often finding them before you do. 

It's essential to produce fresh banker plants throughout the growing season, so a separate area is needed where the parasitic wasp is excluded while the grass and cherry oat aphids grow. This allows overlapping generations in the greenhouse. Start with 2 banker plants per greenhouse, adding fresh banker plants until July. The entire system takes 4-6 weeks to get started, so it’simportant to begin early in the season or as soon as crops are growing in the greenhouse. Banker plants can remain active for several months.

Why stop in July? There’s always a smaller bug and it’s called a hyperparasite. They show up in late summer and start laying their eggs inside of the aphids that have already been parasitized by Aphidius. You can tell if these hyperparasites are present by a jagged and uneven exit hole in the aphid mummy (Aphidus leaves a clean round exit hole). Hyperparasites can wipe out an Aphidius colemani population if allowed to reproduce. 

Try growing banker plants in 10 inch hanging baskets for easy placement around the greenhouse. Put them on a regular watering and fertilization schedule and try not to wet the foliage while watering. Adding dates to the pots can help for future reference. Once you get aphid banker plants in the bank, consider making future deposits for your growing system: pepper banker plants for Orius, Mullein banker plants for Dicyphus and Alyssum banker plants for numerous beneficial insects. Your savings will take you far.

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