Biological method of insect control

• Eradication or Suppression of undesirable pests by encouragement, artificial introduction, or increase of natural enemies such as predators, parasites, and disease-causing organisms is called biological control.
• The first insect scientifically employed for biological control program was the vedalian beetle (Rodolia cardinalis)in 1872 from Australia to the USA.
• It includes the use of Predators, parasites, and parasitoids.

a. Predator:

• Adults and immature are often generalists rather than specialists
• Their body develops a certain type of predatory arms.
• They are generally larger than their prey
• Males, females, immature, and adults may be predators.
• Free living, may be generalists-feeding on a wide variety of prey.
• Consume several too much prey during development.
• Insect Predators include the following:

I. Lady Bird Beetle (Coccinellidae):

• The body of the bird beetle is oval and has a domed shape.
• Lady beetle larvae are dark and alligator-like with three pairs of prominent legs, with 7-8 mm body length.
• The adults and larvae of the ladybird beetle both predate on Aphids and Mealy bugs.

Common species of predatory ladybird beetles are:

• TTwo-spotted lady beetle (Adalia bipunctata)
• Seven spotted lady beetle (Coccinella septempunctata)
• Nine spotted lady beetle (Coccinella novempuntata)
• Thirteen spotted lady beetle (Hippodamia tredicimpunctata)
• Vedalia beetle (Rodalia cardinalis)

ii. Preying Mantid (Mantidae):

• They have elongated thorax to create a distinctive ‘neck’.
• Front legs are modified as raptorial graspers with strong spikes for grabbing and holding prey.
• They feed on moths, crickets, and grasshoppers.

iii. Tiger beetle (Cicinedellidae):

• It consists of six white spots on both of its elytra.
• Tiger beetles feed on rice earhead bugs. Tiger beetles often have large bulging eyes, long, slender legs, and large curved mandibles.
• The larvae of tiger beetles live in cylindrical burrows as much as a meter deep.
• They are large-headed, hump-backed grubs that flip backward to capture prey insects that wander over the ground.
• The fast-moving adults run down their prey.

iv. Green lacewing (Chrysopidae):

• Adults of lacewing feed on nectar, pollen, and aphid honeydew, but their larvae are active predators.
• Adult Green lacewings are pale green with long antennae and bright, golden eyes. They prey on aphids, mites, whiteflies, moths, small caterpillars, etc.

v. Assassin Bugs (Reduviidae):

• They most commonly have an elongated head with a distinct narrowed neck, long legs, and a prominent, segmented tube for feeding.
• This kind of bug sucks the fluid from its prey like caterpillars and other many insects. The nymph and adults of Reduvid Bug suck the sap from the host body and kill the host.
• The forelegs of Assassin bugs are strong, which facilitates catching the prey. Predatory Reduviidae uses the long rostrum to inject lethal saliva that liquefies the insides of the prey, which are then sucked out.
• The saliva contains enzymes that predigest the tissues they swallow (Extra-oral digestion).
• The saliva is commonly effective at killing prey substantially larger than the bug itself.

vi. Ground Beetle (Carabidae):

• Larvae of ground beetle are long with well-developed mandibles.
• They are active at night. Adults are brown or metal color.
• They prey on soil-dwelling insects and snails.

vii. Hover Flies (Syrphidae):

• As their common name suggests, they are often seen hovering or nectaring at flowers; the adults of many species feed mainly on nectar and pollen, while the larvae (maggots) eat a wide range of foods.
• In some species, the larvae are saprotrophs, eating decaying plant and animal matter in the soil or ponds and streams.
• In other species, the larvae are insectivores and prey on aphids, thrips, and other plant-sucking insects. The body colors of hoverflies are black or yellow.
• The adult Hover Flies are flower visitors and reported as pollinators, whereas their maggots predate on aphids, Scale insects, and mealy bugs.
• The maggots are legless and the mouth parts are pointed with projecting the head parts.

viii. Fire Flies (Lampyridae): They prey on snails, slugs,s etc.

1. Dragonfly (Libellulidae) and Damselfly (Agriidae)

• Prey on mosquitoes adult maggots flies etc.
• Dragonflies are important predators that eat mosquitoes, and other small insects like flies, bees, ants, wasps, and very rarely butterflies.

1. Water Giant Bug (Belostomatidae): Mosquitoes and other pest insects in the water.
2. Water Scorpion (Nepidae): Mosquitoes and other pest insects in the water

xii. Robber Fly (Asillidae ): Predate on different Flies.

2. Parasite and parasitoids

• A parasite obtains its nourishment from a host organism without benefiting or killing the host, and does not prevent reproduction while parasitoids spend a part of their life obtaining nourishment from a host organism – however, unlike parasites; parasitoids ultimately kill their host and prevent reproduction.
• Major characteristics of insect parasitoids:

I. They are specialized in their choice of hosts.

ii. They are smaller than the hosts

iii. Only the female searches for hosts

iv. Different parasitoid species attack different life stages of the hosts

v. Eggs or larvae are usually laid in, on, or near the hosts.

vi. Immature remain on or in the host, adults are free-living, mobile, and may be predaceous

vii. Immature almost always kills the host, in which they remain feeding.