Incorporating Beneficials in Your Greenhouse By Joe Lara

Mite. A four-letter dirty word among greenhouse growers. More specifically, the twospotted spider mite.

These common microscopic pests are one of the biggest nuisances professional greenhouse growers treat within their operations, as they can infest and completely wipe out a high-valued crop within a matter of days.

Twospotted spider mites are hard to control for a number of reasons. Due to their speedy and prolific reproduction rates, a mite population can quickly get out of control. A single adult female can produce hundreds of eggs in her short lifetime. And a mite's feeding behavior of sucking on the underside of a leaf makes it difficult to spot Ð that is until the damage starts to appear.

Once damage occurs, it is easily visible and can quickly render plants unsaleable. Growers will first see a stippled, silver pattern on leaves and flowers. Then as the mites continue to feed, leaves eventually drop from the plants and unsightly webbing occurs.

Twospotted spider mites feed on as many as 200 varieties of plants. They feed on almost any colored bedding plant, as well as roses, azaleas, and junipers, to name just a few.

While controlling mites can be a daunting task, especially when they are dispersed over a large area, is not impossible. Using sound cultural practices can help keep crops healthy and pests to a minimum.

The easiest way to avert mites is to prevent them from occurring in the first place. This can be accomplished by adhering to a few sound practices:

1. Follow proper sanitation. Establish proper sanitation practices within the operation, such as sterilizing benches with sanitizers and keeping dirty containers and tools separate. This helps create a clean and pest-free space.

2. Secure the greenhouse. Make sure ventilation systems have proper and secure ventilation systems to minimize unwanted pests from entering the space.

3. Stay clean. Keep crops weed free, as weeds can attract unwanted pests. Also, remove old or mature plants, as these often harbor mites.

4. Quarantine. Separate incoming plant material to prevent introducing pests to other parts of the facility. Check to ensure the supply is free of outside pests, which can quickly spread within the greenhouse.

5. Monitor. Keep a close eye on the crop, especially the underside of leaves. While twospotted spider mites thrive most in the summer during dry, hot temperatures, they can be found at any time of the year. If pests are found, understanding the source allows mitigation to start before populations begin to rise.

Using Beneficials

If mites are spotted on plants within the operation, don't panic.

An effective practice that greenhouse growers use for controlling mites is introducing beneficial insects into the crop. These "good" insects, sometimes referred to as predacious mites, are natural predators to the "bad" insects and can help rid the infestation without harming the plants.

While beneficials naturally occur in outdoor crops, they can be purchased from a supplier and introduced into greenhouse crops. It's important to consult with a supplier before starting a beneficials program to ensure they are used properly.

To integrate beneficials into a greenhouse, they must be introduced when the mite infestation is low, so monitoring and detecting prior to a severe infestation is essential.

Operations using beneficials to help control pest populations should train employees to understand the difference between mites that help protect plants and those that harm them. Differences can be subtle and difficult to see on such small arthropods, so accurate identification is critical.

Once beneficials are introduced, it's important to monitor their numbers and activity just as with other pests. Keep records of the predatory mites as well; since these records can be used to determine which beneficials provide the best control and at which population numbers.

When used appropriately, beneficials become a grower's partner, working 24 hours a day/seven days a week to help minimize a mite infestation. Since they not only attack unwanted mites, but continuously reproduce, the growing population of beneficials will continue to provide control for crops.

Supplementing a Biological Approach

Miticides are another targeted and reliable practice many growers rely on for controlling mite populations. Fortunately, there are many options available to growers wanting to use a chemical approach. Before choosing a miticide, it is helpful to understand how it works and what stages of the mites' life cycle it controls, as some only target certain stages.

Once it is decided that a chemical approach will be employed, always apply according to label. Restrictions may apply to the frequency and amount of product that can be used within a growing cycle. And many mites feed under the foliage and their eggs can be hidden in the leaf's folds or crevasses, so be sure to use a broad application.

Rotation — changing the different modes of action within the chemicals used on a crop — is a critical part of any chemical approach. Some mites, including the twospotted spider mite, have developed resistance to some chemistries; this makes it important to know what's been applied and when, and to use different modes of action to deter resistance.

If using beneficials on a crop, look for a miticide that eliminates the unwanted pests but is safe on beneficial insects and predatory mites, such as Sultan miticide. Its active ingredient, Cyflumetofen, is soft on beneficials, so growers are able to effectively sustain those programs without interruption. This new class of chemistry is ideal to introduce into an existing rotation program for mite control without running the risk of resistance.

No Silver Bullet for Mite Control

While there is no silver bullet for controlling mites, professional greenhouse growers do have options. Many growers believe that using beneficials help steward the chemical controls used within a greenhouse. If a grower introduces beneficials and they're working, they have the ability to use a conventional approach as well, either at the same time or in rotation.

While not all growers will implement beneficials for mite control, understanding the options, as well as how an integrated approach to managing pests works, is critical for any operation.

Using a comprehensive approach to pest control is critical for all successful growers. It's important to use a variety of management techniques to create a tailor-made program for each specific growing environment. With an integrated approach, growers can customize a successful solution for their exact problem and environment, and preserve crop quality and profits.

Incorporating Beneficials in Your Greenhouse

Joe Lara

Joe Lara is senior product manager for BASF Professional Turf & Ornamentals. He can be reached at

Latest Photos see all »

GPN recognizes 40 industry professionals under the age of 40 who are helping to determine the future of the horticulture industry. These individuals are today’s movers and shakers who are already setting the pace for tomorrow.