Controlling Thrips with Beneficial Mites

In some areas, thrips begin to appear in early spring. Most of us become aware of thrips during a large influx late in the spring and throughout the summer. Thrips don’t fly, rather, they tumble and in days of atmospheric convection, they (like many mites) use the electro-static conditions to levitate and travel large distances. It’s for those reasons that thrips nearly all arrive seemingly ‘at once.’ Most thrips can be controlled with traditional chemicals, but the cryptic nature of the pepper thrips and the complete resistance to chemicals of the Western Flower Thrips make them prime candidates for using beneficial mites or insects. Unfortunately, Western Flower Thrips and Onion Thrips are nearly identical and most are very similar.

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Thrips are primarily a cosmetic pest – damaging and distorting leaf and flower tissue. The cosmetic damage in the ornamental industry is significant, but so too in the production of fruit and vegetables. Thrips damaging flowers result in deformed fruit, often resulting in asymmetrical growth or a mottled or bleached look. When a cucumber curls, that is from thrips damaging the flower several weeks prior.

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Several weeks prior,” is a phrase to focus on:

Thrips damage actually occurs several weeks prior to the presentation of damage.

Thrips are relatively long-lived as adults (over 30 days), and are most vulnerable several weeks prior, when they are newly hatched.

The most efficient thrips predator, amblyseius (neoseiulus) Cucumeris, is best applied several weeks prior to ensure it is established before eggs are hatched. 

 

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Here’s how to control Thrips in your yard or greenhouse.

Step 1: Establish Stratiolaelaps Scimitus or Gaeolaelaps Gillespie in your soil.

Both of these are in-soil predatory mites that will prevent the cycling of thrips in your area by eating the thrips when the adults pupate in the soil. You will have the added benefit of controlling all fungus gnats, overwintering spidermite, black vine root weevil, and controlling or helping to control all sorts of nuisance pests or damaging pest in the soil. Both are cheep and in some cases need only be applied once for the life of the potted plant or garden. Apply both at a rate of 25 per square foot.

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Step 2: Establish Amblyseius Cucumeris on plants that frequently get thrips damage. Early in the spring I put Cucumeris on my strawberries and roses at a rate of 50/square feet. (if plants are large I do about 500 per cubic foot. I eventually establish Cucumeris throughout my gardens, and reapply every 4 weeks. Adult thrips will come into your yard or greenhouse and cause damage. Cucumeris will eat the newly hatched and few-day-old larva preventing more adults from causing problems. The added benefit is that Cucumeris can survive on pollen and will also consume cyclamen mites, russet mites, and broad mites. It will also eat spider mite eggs and whitefly scale.

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Step 3: Trap incoming adults and monitor their arrival. Try yellow sticky cards in your greenhouse or near popular thrips hang-outs in your yard. Also, try this effective trap: Get a bucket with a lid. Drill holes around the top half of the bucket. Fill the bottom half with soapy water and add a few drops of a floral extract. It could be vanilla, peppermint, almond, any culinary herb or even most regular perfumes. Place the lid back on and check daily. Thrips will enter the bucket and drown in the soapy water. You’ll be trapping them, but also monitoring. If suddenly you get a huge amount, it’s time to increase your Cucumeris to ensure they don’t cycle. Only use the soapy water for a few days, then empty, refill and use a different extract, rotating though different smells.

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There are other mites and insects available for thrips management, but some are more expensive or don’t work well with others, or have some negative feature:

Orius: Orius is the pirate bug. It is an excellent thrips predator, and maybe even the best. It’s draw-backs are that it has an obligatory diapause – meaning it will hibernate for half the year (but usually the time of year thrips are not a concern). Also, buying it can be expensive, but attracting native ones is as easy as letting dandelions flower, or planting alyssum. Also, being a true bug, it could damage your flowers as well. If you’re keen on biocontrol, I would buy these, or plant to attract them.

Swirskii: known as a predatory mite that eats thrips and whitefly. But, they are just a generalist, and most of these predatory mites do the same. Swirskii is likely the most aggresive predatory mite for thrips on the market, but it also eats the eggs of other beneficial mites and insects, which might cause a failure in your managment of other pests. Also, it needs supplements for best results. It is therefore more expensive and much less efficient than just using higher-numbers of cucumeris. If you don’t have other pests historically, you may want to give Swirskii a try. 

Where can you get Cucumeris, stratiolaelaps or gaeolaelaps (Canada only)

https://www.evergreengrowers.com (Western US)

https://www.naturalinsectcontrol.com (Eastern Canada)

https://www.ipmlabs.com (Eastern US)

https://www.thebuglady.ca (Western Canada)

For more information visit www.appliedbio-nomics.com and get info right from the source.

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