Insect Pests of Fruit, Plantation, Medicinal & Aromatic Crops (2+1)

Insect predators

• A predator is a free living organism throughout its life, it kills the prey, usually larger than the prey and requires more than one prey to complete its development.
Differences between Predators and Parasitoids

	Predator	Parasitoid
1.	Very active	Sluggish
2.	Stronger and larger	Smaller and not stronger
3.	More intelligent than prey	Not more markedly more intelligent than the host.
4.	Habitat is independent of the host	Habitat is made and determined during their developmental period by that of host
5.	Life cycle is longer	Life cycle is short
6.	Seized prey is killed and eaten immediately	Takes a longer time to kill the host
7.	Several insects are attacked in a short period	Require only one host
8.	Attack on prey is meant for obtaining food for the attacking predator	It is for providing food for the off spring
9.	Organs of locomotion and mouth parts are well developed	Not so well developed
10.	Ovipositor not well developed	Ovipositor well developed
11.	Not specialized in food habits	Exhibit food specialization


Adaptations in insect predators
1. Vision

• i) Compound eyes are large. (eg) Dragonfly – the compound eyes are holoptic each eye with 20,000 immatidia. The entire head is covered by the compound eyes. Even slight movement can be perceived in the field of vision.
• ii) Mobility of head enhances the vision (eg) preying mantis.
• iii) Protruberant compound eyes (eg) Robberfly
2. Special organs

• i)Mask: Labium is modified as prehensile organ in naiads of dragon fly. It is an elongated joined structure bearing hooks at the apex. When it is not in use, it is folded kept over the face and forms mask.
• ii)Raptorial leg or grasping leg. The femur and tibia are toothed, spines and the prey is caught between femur and tibia. (eg) Preying mantis, water scorpion.
• iii) Basket like leg arrangement found in Dragonflies to capture the prey while at flight.
• iv). Mandibulosucktorial mouth parts for piercing and sucking body fluid, (eg) Dragonfly adult.
3. Fast flying capacity is found in most of the flying predators for chasing and capturing the prey.
4. Rapid pounce upon the prey while at flight (eg) Robberfly adult.
5. Trapping

• Ant lion grubs and ground beetle grubs construct conical and vertical pits, respectively for trapping the prey.
6. Stinging predators

• Few wasps sting and paralyse the victims and store them as food for the young ones. They keep a caterpillar per nest and lay an egg in each nest. The nest is then closed by the wasp.
I. Insect predators of agricultural importance

Insects Order and Family	Name	Prey insect
1.Coleoptera
i)Coccinellidae- (Lady bird beetle)	Coccinelia septumpunctata C.rependa Scymnus coccivora Menochilus sexmaculata Rodolia cardinalis Chilocorus nigritus Cryptolaemus montrouzieri	-Aphids -Aphids -Grape vine mealy bug -Mealy bugs and scales -Cottony cushion scale -Tapioca scales -Grape vine mealy bug
ii)Carabidae (ground beetle)	Parena lacticincta Ophionea sp. Paederus fuscipes	-Coconut black headed caterpillar -Rice BPH -Rice leaf folder
iii)Cicindellidae (Tiger beetle)
2.Hemiptera
i.Reduviidae (Reduviid bug)	Rhinocoris fuscipes Platymeris laevicollis	-H.armigera -Coconut rhinoceros beetle
i.Miridae (Mirid bug)	Cyrtohimus lividipennis	-Rice hoppers
ii.Velidae (Riffle bug)	Microvelia atrolineata	-Rice leaf and plant hoppers
3. Neuroptera
i.Chrysopidae (Lace wing fly)	Chrysoperla carnea	-Aphids, scales bollworms mealy bug
i.Chrysopidae (Lace wing fly)	Chrysoperla carnea	-Aphids scales bollworms mealy bug
ii.Myrmeliontidae (Antlion)
4.General predators
i.Dragon flies	Naiads and adults	On small insect, butterflies
ii. Damsel flies	Naiads and adults	On small insects, caterpillars
iii. Preying mantids	Naidas and adults	Grasshoppers, caterpillars, butterflies
iv. Giant water bug	Adults	Small aquatic insects
v.Robber flies	Adult	Small insects
vi.Hover flies (Syrphids)	Larva	Aphids
vii.Wasps	Adult	Caterpillars
Other
i.Arachmids	Spiders scorpions and mites	On insects and mites
ii.Fishes	Gambusia offinis, Fundulus	On mosquito larvae
iii.Amphibians	Frogs and toads	On small insects
iv.Birds	Ducks, Owls King crow, Mynah, Wood pecker	Rice BPH On rats Caterpillar
v.Reptiles	Lizards,Snakes	Small insects, Rats

2. Mass production of Cryptolaemus montrouzieri




Field release

• For citrus mealy bug and grape vine mealy bug, release 10 beetles/tree (or) vine. Before releasing the predators, the ant movement should be arrested.
Biological control – microbials

• Microorganisms which cause diseases in host insects are known as insect pathogens. Utilisation of insect pathogen and their products in the suppression of insect pests is known as microbial control (eg) virus, bacteria, fungi, protozoa, rickettsiae and nematodes.
• Desirable attributes of an insect pathogen: Highly virulent, Cost effectiveness, Harmless to other forms of life, Rapid prevention of pest feeding.
a. Insect viruses

• Insect viruses are often occluded in protein crystals called inclusion bodies.
  
• There are 3 types of inclusion viruses.
1. Nuclear polyhedrosis virus (NPV):Occluded singly or in groups in polyhedral inclusion bodies. Site of multiplication is in cell nucleus of epidermis, fat body, blood cells and trachea. Symtom is Wipfelkrankheit or top disease (eg) NPV of Spodoptera and NPV of Helicoverpa armigera.
2. Cytoplasmic polyhedrosis virus (CPV): Spherical virions are occluded singly in polyhedral inclusion bodies. Site of multiplication is cytoplasm of midgut epithelium (eg) CPV of cabbage looper Trichoplusia ni.
3. Granulosis virus (GV): Virions are occulded singly in small inclusion bodies called capsules. Site of multiplication is either cytoplasm or nucleus of epidermis, trachea and fat body (e.g) GV of Early shoot borer sugarcane. The important family among the viruses is Baculoviridae, which include nuclear polyheadrosis viruses (NPV) and granulosis viruses (GV). They are obligate pathogens requiring the living host insects for development and multiplication. Disease caused by the virus is called as virosis. They are highly specific and do not attack benficial insects besides safe to other animals including man.
a. Nuclear polyhedrosis virus (NPV)

• The virus consist of proteinaceous polyhedral occlusion bodies inside which the virions or virus rods are embedded.
Mode of entry

• The virus should be ingested to produce the disease (Per as). Due to alkaline gut juice, the virions are liberated from the polyhedral coat, which attack nuclei of cells of tissues viz., fat body tracheal matrix, haemocytes, sarcolemma of muscles, neurilemma and nerve cells of ganglion and brain.
Symptoms

• Insects become dull in colour, feeding rate is reduced and larvae become pinkish white especially in the ventral side due to accumulation of polyhedral. In advanced stage larvae become flaccid, the skin becomes very fragile and eventually rupture, Diseased larvae hand upside down from the plants. This is called tree top disease (or) Wipfelkrankeit
Incubation period

• 4-6 days depending upon the stage of the infection, weather conditions and dose of virus. Early instars are most susceptible to the virus.
1. Mass culturing of NPV of Spodoptera litura

• S.Litura can be mass cultivated using the natural food – castor leaves in plastic container under laboratory conditions. The steps involved in the production of S.litura


Dose

• The dose of S.litura virus is 250 larval equivalent (LE)/ha. The dose is expressed as LE and one LE is 6x109 POBs. One LE can be obtained from three fully grown up and virus infected or diseased larvae.
2. Mass culturing of NPV of Helicoverpa armigera





3. Mass production of NPV of Amsacta albistriga

• The A.albistriga larvae cane be collected form the groundnut fields from endemic areas, and reared in the laboratory using Calotropis leaves after removing the wax layer with the help of muslin cloth. The NPV treated Calotropis leaves are given to the preistarved larvae and the procedure for NPV production is similar as that of S.litura NPV.