Biological method of insect control

• Eradication or Suppression of undesirable pest by encouragement, artificial introduction or increase 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 USA.
• It includes use of Predator, parasite and parasitoid.

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 preys
• Males, females, immature and adults may be predatory in nature.
• Free living, may be generalists-feeding on a wide variety of prey.
• Consume several to many preys during development.
• Insect Predators includes the following:

I. Lady Bird Beetle (Coccinellidae):

• The body of lady 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 lady bird beetle both predate on Aphids and Mealy bugs.

Common species of predatory lady bird beetles are:

• Two 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 preys.
• They feed on moths, crickets, and grasshopper.

iii. Tiger beetle (Cicinedellidae):

• It consists of six white spots on both of its elytra.
• Tiger beetle feed on rice ear head bug. 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 backwards to capture prey insects that wander over the ground.
• The fast-moving adults run down their prey.

iv. Green lacewing (Chrysopidae):

• Adult 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 preys like caterpillar and other many insects. The nymph and adults of Reduvid Bug suck the sap from the host body and kill host.
• The forelegs of Assassin bugs are strong, which facilitates to catch the prey. Predatory Reduviidae use the long rostrum to inject a 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 develop mandible.
• They are active in night. Adult are brown or metal color.
• They prey on soil dwelling insect 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 in ponds and streams.
• In other species, the larvae are insectivores and prey on aphids, thrips, and other plant-sucking insects. The body colors of hover flies are black or yellow.
• The adult Hover Flies are flower visitors and reported ass pollinators, where as their maggots predate on aphids, Scale insects and mealy bugs.
• The maggots are legless and mouth parts are pointed with projecting the head parts.

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

1. Dragonfly (Libellulidae) and Damselfly (Agriidae)

• Prey on mosquito adults, 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.

b. 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 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 host, adults are free-living, mobile and may be predaceous

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

Some Insect parasitoids

• Braconidae: Apanteles glomeratus– Larval parasite of Chilo Partellus.
• Trichogrammatidae: Trichogramma minutum-egg parasite of
• Ichneumonidae: Xanthopimpla predator-Pupal parasite of Chilo.
• Tachinidae: Tricholyga sorbillans and bomycis larval and pupa parasite of silkworms.
• Aphelinidae: Encarsia inaron

c. Bacteria:

• Bacillus thuringiensis attacks on the Lepidopteran larva.
• It enters through mouth and anus in insect and it produce endo-toxin and it breaks the intestinal lumen.
• It is used to control Gram pod borer, cabbage butterfly, cabbage moth, Indian meal moth, cabbage looper, confused floor beetle, Rhinoceros beetles.

d. Viruses

• More than 20 groups of viruses are known to be insect pathogens.
• They have been placed in 12 viral families, but many remain unclassified.
• Viruses specific for insects and related invertebrates are: Baculoviridae, Polyanaviridae and Ascoviridae.

e. Nematodes

• EPNs have been described as early as 1920s by the Swiss-born scientist, Gotthold Steiner.
• Belong to the families Steinernematidae and Heterorhabditidae.
• First field experiment with cultured nematodes against an insect pest was the Japanese beetle
• (Popillia japonica).
• Steinernema kraussei was the first reported species and Steiner could well be considered the “Father of Entomogenous Nematodes”.
• There are two families of nematodes used for control of insect. They are:

a. Stenernematidae (Stenernematids) (found less than 10 cm in soil surface)

b. Heterorhalotidae (Heterohalodits) (found more than 10 cm in soil surface)

• They have 3 different stage of life cycle i. e. egg, juvenile and adults. Thirds stage juvenile are more active and move for feeding.

f. Protozoa:

• Enters the insects by way of the mouth and digestive tract.
• Unlike other types of entomopathogens, usually produce chronic infections.
• The usual signs and symptoms are irregular growth, sluggishness, loss of appetite, malformed pupae or adults with reduced vigour, fecundity and longevity.
• Silk worm larvae: black pepper like spots on the integument, micro sporodian disease, known as Pebrine.
• Transparent cuticles: mosquito and other aquatic insects.
• Whitish masses of microsporidian spores may be visible scattered throughout the haemocoel.
• In most of the cases, dissect and examination is necessary to observe the reproductive form (cyst or spores) which is 2-20µm.
• Protozoa, the microsporidia are relatively host specific.
• They are obligate parasites and cannot be grown on artificial media.

g. Host plant resistance

• Host plant resistance is defined as the intentional use of resistant crop cultivars to reduce the negative impacts of pests or diseases on crop production systems (Stout, 2014).