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Since beneficial insects can cannibalize each other, Suzanne Wainwright-Evans, owner of Buglady Consulting, says they are not usually suited for long-term storage. However, immediate application is not always possible.

Once, she was visiting a grower in Texas that was experiencing a water issue and couldn’t release beneficial insects. “We were sitting in the office and their main water supply going to the roof of their building exploded,” she says. “It just started raining through the ceiling, so nothing was happening that day with bug stuff, I'll tell you that.”

To determine if and for how long beneficial insects can be stored, growers should consult their supplier on a few things. “I think the key points are what species, what life stage and what kind of packaging [they have],” Wainwright-Evans says.

Certain insects will survive if stored in a bottle for 48 hours after leaving the insectary, she says. However, if growers must wait much longer with the same insects, there could be an issue. These are reasons why she advises growers to contact their supplier about how long the insects have been in transport.

If growers store certain beneficial insects in refrigerators, they should place them in their own refrigerator that isn’t subject to people constantly opening it and altering the environment, Wainwright-Evans says.

“ You have to be careful in the fridge because you'll have warmer spots and cooler spots.”

“You have to be careful in the fridge because you'll have warmer spots and cooler spots,” she says. “We've done testing where we've put thermometers in there and data loggers, basically, and monitored the temperatures. My biggest pet peeve is I see a lot of people storing their beneficials in their breakroom refrigerators.”

Cucumeris and swirski mites, and Aphidius and Encarcia parasitic wasps, are some of the main beneficial insects used in produce greenhouses, Wainwright-Evans says.

Suppliers often package predatory mites in rounded containers, tubes, bottles and bulk bags, she says, advising that growers place these containers on their side. She notes that one company recently put their label on the side of their containers for this reason.

According to Wainwright-Evans, if predatory cucumeris mites are unable to be released in the greenhouse right away, growers can store them in the refrigerator around 50° F.

Aphidius wasps are sold as mummies, Wainwright-Evans says. If purchased from Europe, these can often make multiple stops in shipment and can be close to emerging by the time they arrive at a U.S. greenhouse. “But sometimes, because there is U.S. production, if they harvest them on a Monday, you get them on a Tuesday, it’s going to take a while for them to come out,” she says.

If products need to be stored in a refrigerator, growers should have a refrigerator specifically for beneficial insects.
Photo courtesy of Suzanne Wainwright-Evans

Aphidius can come in multiple types of packaging, such as carriers or blister packs. Suppliers can provide information about these packaging types.

Wainwright-Evans provides an example of why packaging matters: She says she recently visited a grower that stored sachets in the refrigerator.

“They put them in the refrigerator, and they actually were in there for like three or four days,” she says. “What happens is they dry up, and you can't have your sachets dry. You're better [off] putting them in a more humid environment.”

With other packaging types, growers should consider condensation, Wainwright-Evans says. If they are ordering from a supplier for the first time, they should ask about the packaging. Swirski mites, for instance, will remain healthy above 60° F, while below 60° F is better for cucumeris mites.

Wainwright-Evans advises growers to be prepared before beneficial insects arrive. “You should always know when your beneficials are coming in, how to release them — this is a discussion you should have with your supplier before the bugs even get there,” she says. “If it's a sachet, how do you put it out? If I'm getting mummies in a bottle, how do I put them out? You don't want to be surprised. Back in the ’90s when I actually sold biocontrol agents, any time I had a new customer, I would always be there for the first release to go over everything with them.”