Attracting Beneficial Insects
Increasing the availability of flowers is often the single most important strategy for increasing the abundance and diversity of beneficial insects. Like pollinators, such as bees, many insect predators and parasitoids feed on flower nectar or pollen during one or more of their life stages. Some predatory insects also feed on pollen as a supplemental source of protein—often when prey insects are in short supply or to increase the number of eggs they can lay. By increasing the availability of flowers, the numbers, longevity, and reproductive potential of beneficial insects is increased.
A succession of blooming flowers on the farm throughout the growing season provides a stable source of food that beneficial insects need in order to thrive as their prey populations rise and fall with time. Many predators and parasitoids will leave a farm if flower availability is low. Habitat with a diversity of flowers can also provide beneficial insects with alternative prey, allowing them to survive when crop pest populations are low. To attract beneficials to your garden or farm:
Use a wide variety of attractive plants. Plants that flower at different times of the year can provide beneficials with nectar and pollen when they need it.
Plantings that are at least 4′ by 4′ (1.2m x 1.2m) of each variety work best at attracting beneficials.
A bird bath or backyard water feature not only attracts birds (another predator of insects), but also attracts beneficials.
Tolerate minor pest infestations. The beneficial insects will get the memo before you do. This will provide another food source for the beneficials and help keep them in your yard.
More information about beneficial predatory insects: "The Natural Enemies Handbook", from the University of California Division of Agriculture and Natural Resources.
Below is a list of plants that attract beneficial arthopods.
Plants that attract lady beetles (aka ladybugs)
This is a partial list of flowering plants that are known to attract lady beetles.
Plants that attract minute pirate bugs
This is a partial list of flowering plants that are known to attract minute pirate bugs.
Plants that attract Green Lacewings
This is a partial list of flowering plants that are known to attract green lacewings.
Plants that attract parasitoid wasps
This is a partial list of flowering plants that are known to attract parasitoid wasps.
Plants that attract hover flies
This is a partial list of flowering plants that are known to attract hover flies.
Plants that attract predator mites
It has not been well documented which plants attract these beneficial predator mites, otherwise called phytoseiid mites. While it is true that phytoseiid mites are mostly known as predators of mites and soft-bodied insects, numerous species use pollen as a food source and develop on pollen diets with the highest reproductive potential. Considering the fact that important food elements such as proteins, free amino acids, carbohydrates, lipids, vitamins, flavonoids, and minerals are common in pollen grains, the advantages of ability of exploiting pollen as alternative food source for phytoseiid mites can be summarized as follow:
In the presence of pollen they can preserve their population at relatively high densities under conditions of their original prey scarcity or absence.
Pollen can be used in order to improve or facilitate experimental and commercial mass rearing of phytoseiids.
Pollen can be offered as supplementary or alternative food in commercial greenhouses and fields or as banker plants in greenhouses to improve the efficacy of predators.
Amblyseius swirskii, Amblyseius andersoni, Neoseiulus fallacis, Neoseiulus californicus, Galendromus occidentalis been documented to feed on pollen of flowering plants. Predatory mites belong to four categories – Type I, Type II, Type III, and Type IV. Traditional agricultural operations have typically used the purple flash peppers due to their long flowering period. However, other flowering plants like other agricultural peppers (bell, anaheim, poblano, etc) can also be used in farms. In fact many different species of pollen have been used in studies to rear predator insects. Everything from peach pollen to bee pollen has been used. Having a wide array of flowering plants proximal to the cannabis gardens would provide the most diverse environment for the predators to have a secondary food source in times of low pest pressure.
Studies have confirmed that mites also follow plant induced volatile chemicals. Several authors in science journals have reported on the olfactory responses of P. persimilis to individual spider mite-induced plant volatiles. Responses elicited by linalool, methyl salicylate, and β-ocimene have been documented. Linalool is found in high concentrations in lavender and basil, β-ocimene is found in basil. So running trials with companion planting with basil would be advised. Methyl salicylate is also produced by many species of plants, particularly wintergreens. It can also be produced by the plant when they're attacked. It has been suggested that soaking cotton balls in wintergreen (inside a perfortated plastic container) can be placed on the plants to attract beneficial predators.