MSU Extension Floriculture & Greenhouse Crop Production

Orius insidious, commonly known as the minute pirate bug, is a species of predatory insect used extensively in greenhouse biological control programs. Orius are highly mobile and aggressive predators that actively search for prey, typically killing far more pests than they consume. Although they are frequently used to control thrips, they will happily feed on a wide-range of soft-bodied insects as well as pollen and nectar. The ability to feed on alternative food sources is important because it allows minute pirate bugs to survive and reproduce even when pest populations are low. There are two common ways in which Orius are utilized as biological control agents. The most direct way is to apply them to the foliage or the substrate at various locations throughout the crop. Many growers, however, prefer to implement a banker plant system. Banker plants are secondary plants added to a cropping system that are used to support and sustain populations of beneficial insects. The primary purpose of a banker plant is to provide biological control agents with a safe place to eat, mate, and reproduce. We've been using banker plants now for on and off for the probably started after year two, so 10 years now. We use the banker plant for Orius and Orius alone. JJ Klimp is the owner of Hidden Leaf Greenhouse in Kalamazoo, Michigan and has been using biological control for over a decade. The Orius will eat up to 50, 50 adult thrips a day. In fact, they're pretty angry. They'll just sometimes kill some and just go out you know and kill some thrips. So I like having my banker plant system to just create control on the whole life cycle of my target pest, which is the western flower thrips. Selecting suitable banker plants for Orius insidiosus involves choosing plant species that provide abundant nectar and pollen over an extended period. Plants that are attractive to thrips are especially helpful because it provides Orius with prey. So when we make our banker plants, there's a few factors you need to look at. You need pollen. The Orius needs pollen. You can buy pollen and apply it. I tried a little bit. It was too time consuming just to be attempting to feed. If you're down with that and you you know go for it. So my banker plant, your banker plant, any banker plant is for Orius is going to need a pollen source. So we all drifted into purple flash ornamental pepper. The purple flash is very slow to berry, so it just puts out tons of flowers. So that's what we use predominantly. Research has shown that the presence of pollen and prey increase both the longevity and reproductive rate of Orius females as well as as well as the survival rate of their offspring. The last few years, the whole market has been looking at alyssum. So we plant alyssum with our peppers. It gives us a bigger, stronger, and we all know alyssum. Thrips love the things. You can't keep them off them. So it works perfect. You've now created a sustainable system where they will breed and fly around and kill their 50 thrips a day and come back to the plant and keep your adult population to a certain degree in check. It's not an end all, but you're controlling that one life stage and that's what we want to get to when we use these banker plants. We find that the pots planted by every post works great. Now we do have to re-up the Orius. So each week, just like my Aphidius mix wasps, we just switch sections of the greenhouse. So I kind of take every acre of greenhouse. Each week I buy enough Orius to treat that acre, and I want to return after three weeks. So I'll apply here this week. I'm going to apply there next week. I'm going to apply over there the following week, and then I'm going to need to purchase more to apply here. So I give it two weeks off, one week on, just add some new population so that I can keep those breeder banker plants. I can keep them breeding and helping out with the program. Banker plants allow growers to establish populations of predators or parasitoids that continuously mate and reproduce, creating an army of natural enemies that disperse throughout the greenhouse to feed on target pests. So the important part when doing a banker plant program with Orius is to make sure that you have pollen readily available for them to start and to keep their breeding going. Lots of the plants, these pepper plants, need long days. The Orius also need long days. So if you're lighting, you can start your program earlier. If you’re not lighting, you’re limited to wait until after the Spring Equinox. So this time we are going to be doing two pepper plants in the center. Plant them up like you normally would. We're all greenhouse people. Don't bury the crown of the plant. These pepper plants were started in December. You can kind of fudge it with some alyssum and some marigolds to wait for the peppers to flower up. But we like to aim it so the pepper plants have flowers when we're starting our program. The marigolds and the alyssum, it's not crazy important how many you put. You just put it depending on how big of a pot you're using or how many you want. Like I mentioned earlier, if you don't remove them, certain varieties of ornamental peppers will stop producing flowers and just show off their awesome peppers. So what we like to do when we're going through the greenhouse later in the season is when you apply the Orius, you clean the peppers, the mature peppers off the plant, and that way it will keep putting out peppers all season long. So, once we get to summer, we'll come through and just rip out the alyssum and just go with a big, huge, beautiful pepper plant. When you're doing Orius bankers and you receive your Orius, one of the first things you need to do is open the box that they came in, and before application, well, when you open the box, you want to check for a vitality of the insects. So one way we can do this is by pouring it on a white sheet of paper. And you can see that all of my Orius are alive and well. Depending on the size of your container and depending on the amount of pots you have to apply to, you'll get used to it after the first few weeks, whether it's a tablespoon or more or even a teaspoon. But you want to hit every single pot that you have to keep that natural cycle still going to reapply. I wouldn't recommend dumping it directly on the plants because you could rot some of the plants off with the vermiculite inside. So just dump it off to a nice dry spot of dirt off to the side. One super important thing to remember is when you're using banker plants, if you ever do any hotspot sprays or spray biorationals, you need to make sure that you remove or put your plants where they will not contact the sprays. When you apply your Orius to your banker plants, it's a great opportunity to check to see if it's working. Takes about three weeks to a month, all depending, and you'll start seeing immatures. So you want to look inside of the flowers. You want to look in all the little nooks and crannies of the branches. And sometimes you'll find some thrips. Lots of times you'll start seeing the orius. Now they're going to be yellow, orange, or brown, and they don't fly, but then you know your banker system's working. Using a banker plant system can be an effective strategy for maintaining a reproducing population of natural enemies that provide long term pest suppression within the greenhouse. More information on banker plants, biological control, and many other topics in floriculture production can be found online at the MSU Extension floriculture website.