Using guardian plants is a simple way to bolster your integrated pest management program. There are three different types of guardian plants that can be useful when growing cannabis.
An indicator plant is a plant species that is different from the main crop and that the concerning pest is decidedly attracted to. The indicator plant should be one that shows damage easily. An indicator plant will show damage warnings of all stages of the pest bug vs just adults. This is preferable to a yellow sticky trap that will only show flying stages of pests.
An example of an indicator plant for spider mites is a bush bean plant. Bush bean seeds are inexpensive and readily available at your local garden store. They are irresistible to spider mites and have large broad leaves that are sensitive to spider mite damage, making the first traces of the pests easy to observe. For example, it only takes three to four spider mites for the bean plant to start showing the characteristic stippling associated with the mite. By contrast, it could take double that amount to start showing damage on a cannabis leaf. For thrips, chrysanthemums work as an indicator plant, and for aphids, use nasturtiums.
Traps plants are along the same idea as indicator plants. They attract the unwanted pest, but in the instance of a trap plant it is one that the pest prefers over the value crop. Research has shown that when trap plants are placed amidst the favored greenery, they will actually ignore the main crop in favor of their preferred snack. The grower can simply monitor the trap plant and when it gets infected, remove and destroy it. Then use its former station as the introduction point for biologicals. It is really important to monitor the trap plant as the trap plant provides an ideal environment for the pests to multiply.
For spider mites the same bean plant that was used as an indicator plant can also be used as a trap plant. The same goes for thrips, the chrysanthemums that work as an indicator plant also work as a trap plant.
Banker plants are essentially the opposite of trap plants. Banker plants support predators by providing an additional food source, such as pollen for them to eat in times of pest scarcity. Additionally this method is especially helpful when using predators for the purpose of prevention. Banker plants can also support a host pest, that does not attack the primary crop grown. For example, Gerber daisies are a great banker plant for Orius Insidious because Insidious need the addition of pollen and nectar to their diet of thrips to really thrive. One of the most common banker plants is cereal plants for aphids and these can often be purchased at your local greenhouse store.