Beneficial insects contribute to agriculture by controlling plant pests and pollination. Beneficial insects can be divided into two groups: predators and parasitoids. Predators consume more than one prey and are usually larger than their prey. Furthermore, predators are generalists and may be omnivorous. On the contrary, parasitoids are smaller than hosts and are highly specialized.
Commonly observed predators in Bhutan
- Lady beetles : are oval shaped and most are orange or reddish with black markings , the spot pattern is usually 1-4-2, on the orange or red forewings. Both adult and the larvae predate upon aphids in different crops , immature scale insect, mealy bugs, mites and other soft-bodied insect pests as well as insect egg. Check this link on common lady beetles in Bhutan: https://www.researchgate.net/publication/338422236_A_Field_Guide_to_the_Common_Lady_Beetles_of_Bhutan
- Green lacewings : are green with net- veined wings with gold- colored eyes. Larvae have long, piercing mandibles and prey on soft bodied insects.
3. Syrphid flies : Adult syrphid flies are commonly found on flowers and are also known as flower flies or hover flies. The flies vary greatly in color and size, but most are yellow with brown or black bands on the abdomen. Many resemble wasps, others closely resemble bees, but none sting. The larva have no legs or visible head and are a greenish, or light translucent color and prey on on aphids, scale insects and thrips.
4. Praying mantis : Praying mantids are usually large insects. The front legs are covered with spines and modified for grasping and holding their prey. Mantids are the only insects that have a freely moveable head, and it has a characteristic triangular shape. Mantids are generalist predators and wait for their prey with the front legs in an upraised position. Thus the name praying mantids.
5. Red tree ant : The red ant, Oecophylla smaragdina ( Fabricius) was used by the Chinese in citrus growers to control various foliage feeding pests. In Bhutan, these ants are commonly observed in citrus orchards predating on the citrus shield bug.
6. Assassin bug : Assassin bugs are generally black or brown, but many are brightly colored. The head is elongate with a short, curved beak. All species are predaceous and attack a wide variety of insects. Adult bugs pierce and suck the body fluids.
Parasitoids: The study on parasitoids of insect pests is limited in Bhutan. Hence, parasitoids species present and their efficacy against insect pests is unknown for now. To kickstart, the Entomology program will collect and identify parasitoids of cabbage white butterfly and diamondback moth ( main pests of Cole crops in Bhutan) in the coming season.
Pieris rapae caterpillar parasitized by Cotesia rubecula (Observed in Yusipang, Thimphu)
