Know Your Bugs: Cucumeris

Neoseiulus cucumeris (formerly known as Ambylseius cucumeris) is used primarily for the control of thrips – mainly Western Flower Thrips and Onion Thrips. However, as a generalist predatory mite it is known to be effective in controlling spider mites, whitefly eggs, cyclamen, broad and russet mites. 

Besides the fact that it performs (when healthy and fresh) like a typical predatory mite, it’s great benefit to the user is that Cucumeris is inexpensive and therefore the number of predatory mites on a plant can be relatively high. And that is the single most important factor is thrips control.

Thrips are a major problem in ornamental crops where their damage is foliar, quick to develop and immediately reduces the value of the crop. But lately, with almost total chemical resistance, thrips like the Western Flower Thrips has become a problem in most crops. 

Thrips populations can remain in a greenhouse with minimal issues and being mostly controlled by some established or voluntary predators. However, when conditions are right, thrips populations will explode. Similarly, an outdoor crop may see little thrips pressure all year only to find a devastating infestation the next day. 

Cucumeris eating a juvenile thrips

Outdoors the immediate population growth is almost entirely due to the weather and adjacent host crops. Thrips, while winged, do not really fly. Instead, they flutter or tumble, and their feathery wings allow them to levitate due to electro-magnetic atmospheric changes. Seriously. You may find that weird, but it is not entirely uncommon for insects. So what farmers usually find is a day of wind and atmospheric convection (think thunderstorms or at least large cumulous clouds), is the day a swarm of thrips are blown into their crop from adjacent crops and farms. The only bio-control agent suitable for a massive release to match the massive inundation of thrips is Neoseiulus cucumeris. And there are two reasons:

Thrips wings are not for pushing air, but rather, for maintaining electro-static levitation

First: Cucumeris will be applied to crops at a rate of 10 to 100 mites per plant (sometimes more). If they have been provided fresh from a producer they will immediately begin feeding and laying eggs. The freshness is essential because thrips will lay eggs immediately in the crop. The eggs are laid inside the leaf tissue, protecting it from predation. 2-3 days later the eggs hatch and after a quick feed the thrips larva begin to emerge from the plant tissue. It is at this point that the cucumeris will feed on the thrips – literally biting their heads off when they poke out of the leaf. They will continue to feed on thrips in the thrips’ larval stages but once a thrips becomes an adult it is too good at defence for most predators. So this inundation of cucumeris to be applied when thrips arrive is essential because it promises to prevent the second generation of thrips. Without the timely intervention the 10,000 thrips that landed on your crop become 1,000,000 three days later. And don’t you dare wait another three days!

Second: Cucumeris are cheep. Consider this: Neoseiulus fallacis will eat thrips, and very effectively. However, 1,000 true, and fresh fallacis will set you back up to $80, whereas the same number of cucumeris will cost you $1. If you were to apply the amount of fallacis needed to thwart a thrips invasion if would be cheeper just to destroy the crop – every time. 

At this point you may wonder about Fallacis as a thrips preventative, since it never leaves your crop once it’s applied at its wonderfully low rate of 2 mites per square meter. Well, again, it is the thrips that have the upper hand: Even with the preventative application of fallacis and lots of available food for them, the fallacis population with have slight increases but never reach a level as high as you can achieve by applying cucumeris straight from a producer. So, fallacis is great to have (and you should have it), but when that wind blows in the thrips, you simply can’t afford not to respond with cucumeris. And the best part: the two don’t effect each other beyond reducing the available food.

    Of course, fallacis has a strange “staying power.” They eat so much, that few adults can survive, so their population remains small. This allows them to survive on a crop permanently, as there is always enough wind-blown pollen or small, soft-bodied pests to survive on. Cucumeris is different in that they are comfortable in large populations and will wipe out food supplies quickly and then leave. We’re not entirely sure where they go, but the average time cucumeris will spend on a crop is 4 weeks unless the pest is persisting, where the available food maintains the cucumeris population. But even then, fallacis will eventually win-out and be the last standing.

Which reminds me, Cucumeris is compatible with most other bio-control agents, but there are a few caveats: Because cucumeris will eat spider mite eggs, it is best to control spider mite hotspots with persimilis ahead of applying cucumeris. Persimilis prefer to eat spider mite eggs over the adults which also allows their population to increase at a faster rate. Give persimilis a head-start before applying cucumeris (Of course, if you have fallacis in there it’s not likely you have spider mites.) The reverse is true of Dalotia coriara, the rove beetle also known as Atheta. If you’re applying Dalotia it is important to give the cucumeris a head start, and to use the loose granular mixture as opposed to sachets designed for slow release or “breeding.” Dalotia eat. And they eat a lot. And that sachet on a stick just looks like a lollipop to the rove beetle which will happily feast inside. One or two days after cucumeris is applied they will have spread out and begun to lay eggs in protected places under leaves next to veins where they are somewhat protected. 

In green house crops you have a few more tools to work with. First, if thrips are an ongoing issue for you, invest in thrips screens for your vents. Then, remember that they are going to come in anyways, through doors and on workers. So set up your yellow sticky traps. But unlike a typical application of the yellow sticky trap, this time, set them up along the ground. Remember, thrips don’t fly – they tumble. Studies have shown more thrips per card the lower they are to the ground. Next, enhance the trapping by dipping cotton balls in plant-based flavour extracts (like peppermint, rosemary, vanilla..etc) and stick them to the middle of the cards. Thrips love flowers/pollen and those scents attract them. Some people have even used simple perfumes. The trick is to rotate the scent every few days. Also, consider shining cheap LED flashlights onto cards at night to further attract the thrips by visual cues. If that sounds labour intensive you can always do the “small greenhouse option:” Fill a bucket with a few inches of soapy water (dish soap is fine). Then add a few drops of the same flavoured extracts. Every few days, empty the bucket and fill again with a different extract. Keep this bucket near doors or below benches. In both these cases you develop an effective trapping system, but also a monitoring system. If every day you see one to two thrips, and then one day there are 30 – it’s time to dump in a large amount of cucumeris. In the meantime, small amounts of cucumeris, regularly, are the best way to keep ambient thrips populations down. 

Of course, if you’re a grower/gardener experienced with bio-control agents then there is no way you don’t have Stratiolaelaps scimitus or Gaeolaelaps gillespiei in your pots already. But if you need a refresher, remember that thrips larva need to drop to the ground and pupate in soil before emerging as adults. At this stage, the two soil mites (with particular emphasis on Gaeolaelaps) will feed on thrips pupa and prevent those “missed” larva from becoming new egg-laying adults. 

How and what to buy:

You can get cucumeris from a list of distributors, here: 

Sizes include:

1,000 mites in a small sachet. (Perfect for homeowners or to apply specifically to plants and avoid applying the carrier.

Slow Release Sachet. These are specifically formulated for the continual growth of cucumeris for 4 or more weeks. Adults slowly leave the bag as their population increases and when food becomes scarce. This is great for preventative approaches.

1 Litre, 5 Litre and 10 Litre bags. In each of these volumes one litre of media contains 50,000 mites. These are essential for broadcasting and large applications to react to thrips invasions. And there is no reason not to use this method for prevention, as well. 

The carrier is typically bran and peat. If broadcasting, take a moment the next day (or a few hours later) to blow or rinse the bran off if you’re worried about the cosmetics. Otherwise, broadcast to the base of plants; they’ll find their way up. 


    Cucumeris hatch and are nymphs that will not feed for two days. After that, they spend a week as a larva capable of feeding on thrips and then the next month as an adult. Adults are over 60% female and will lay 1-3 eggs per day for their entire life. 

Technical stuff:

    Cucumeris is a foliar mite. The reason for its low price is that it reproduces quickly on a fictitious diet and shows no difficulty resuming its natural diet. Sometimes feeding insects and mites non-natural diets makes them reproduce but they are genetically weakened or conditioned to the new food. The producers you want to work with (like me) painfully scrutinize these diets and rearing conditions to ensure the product is still going to do what we expect it to do in the crop. Fortunately cucumeris is one of the first, and one of the best examples of success rearing on a fictitious diet. 

    However, this comes with one issue: It still wants to be on a plant, so it is difficult to keep it alive in the carrier. So, when you buy cucumeris, look for producers like us, who don’t warehouse, or cold-store or are not located across an ocean. When you order cucumeris from us, we put it in a bag, close it, but it in a box and ship it within a hour. This is important because stressed cultures can quickly become ineffective. Most mites will begin to consume the males or reabsorb their eggs when food becomes scarce or when populations are uncomfortably dense. Also, plants are the perfect environment: In humid conditions the tops of the plants/leaves provide the best conditions, and when dry, next to veins under leaves is always a more humid spot. In any packaging, humidity can peak and mites will begin to suffer. Worse yet, the mites and their food mites are living and generating heat, so sealed cultures can become overheated and high in CO2 if not properly vented.

    Avoid purchasing when there is long-shipping times, cold-storage or warehousing. And always put out the products immediately. 

Thrips in dandelion

   We got called to a grower in the Eastern US when he wanted to switch to us as a supplier of beneficials. When there, he asked what we could do for thrips and when we told him it would be cucumeris he got mad and said “cucumeris is shit. I have some right now, and I won’t even spend the labour to put it out.” We asked to see the cucumeris he had. It was from a large company that produces it over seas. It was in buckets, shrink-wrapped and palletized. It was more than the grower needed (over sold) and thus a large task for his workers to put it into the crop. I don’t remember exactly, but I believe the process would take a couple days. Brian, our President, removed the shrink wrap and opened a bucket. He poured some on a table and looked for mobile adults. There were none. Then he removed more buckets from the pallet and grabbed one from the middle and handed it to the grower. “Here’s the problem,” he said. The bucket was hot to the touch. “There won’t be a single living mite in this bucket.” So this poor grower was about to send his crew of several workers on a two or more day task of spreading dead cucumeris on his flowers. No wonder he thought Cucumeris is “shit.”

    Most bio-controls (cucumeris included) perform poorly in cannabis. It has nothing to do with the plants but everything to do with the growing environment. When conditions are too dry, most predatory eggs won’t survive. When fans are constantly blowing, most insects and mites with “hunker-down” waiting (in nature) for the storm to pass. And when plants are pumped full of nutrients it favour sucking insects to a point where many bio-controls simply can’t keep-up. If you’re thinking of a bio-control program for cannabis, please consult my other posts and speak to us directly. It’s a steep learning curve. But consider this principal: always grow first for plant health, then grow for product. It will always be easier and it will usually be less expensive. 

Special Mention

   Every day people call or email and ask about our products. In many cases they are asking to control a pest outside of the focus of most beneficial insect companies who tend to specialize on common greenhouse pests. But, nevertheless we try to help as best we can.

    Whenever the target pest is small and especially when it is a mite, there is a very good chance that we can control it if we are able to apply cucumeris or fallacis at a vulnerable life stage. For example, this coming spring I hope to trial both mites against the Pear Leaf Blister Mite. However, in the winter, the Blister mite is already safe within next year’s buds. Shortly after the seasonal growth begins the mites will be mobile and head towards new growing tips. In the fall, they will move towards the nodes that will become next years buds. So we have an opportunity to see if we can apply predatory mites during those mobile stages to reduce the blister mite (and…fingers-crossed…control it.) 

    In most cases like this, I recommend either mite, but then say “always try cucumeris first. It is a fraction of the price and if it works: perfect.”

    So my “special mention” is that cucumeris is such an excellent generalist mite and so inexpensive that it falls into the category of “why not?” I’d never say that to a commercial grower who needs it to work and will be spending a lot of money on it. But for an unknown mite on a plant in your garden, for the cost of a couple bucks, why not?


    If you have thrips right now but large amounts of cucumeris. 10-100 adults per plant is a general place to start. If thrips pressure is high, this amount will need to be applied weekly. 

    If you do not have thrips yet, apply cucumeris at 10-25 adults per plant once, early in the season. 

    For whitefly control. Ensure you have proper whitefly predators established first (Encarsia or Delphastus), then apply cucumeris at the lowest rate.

    Other mites: use the thrips release rates. And always try cucumeris before fallacis. 

    Like all foliar predatory mites, they prefer humidity of 70% or higher. And remember that inside a plant canopy during low air movement, the ideal humidity will be easy to find for the mites. 

    Chemicals, soaps, acids/bases, and detergents hurt the plant and predators more than the pests. Use only as a last resort. 

    All beneficial insects and mites need to be applied as soon as you receive them.

    Always source out the freshest, proven products. 

Want more: Click HERE for the free biocontrol handbook!

photos by David Spencer and David Gillespie

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