Mechanism of Host plant resistance

1. Non-preference: Also called antixenosis ( identified by choice test)
2. Antibiosis: Insect try to feed but don’t develop properly due to lack of essential nutrients.
3. Tolerance

Note:

• Tolerance is identified by comparing the yield in tested and untested lant of same cultivars.
• Antibiosis is identified by study of chronic effects of allelochemicals on growth and development of insect larva, pupa and adult.
• X-ray photography determine effect of insect infestation on cotton seed quality.
• Phytophagous female insect consume more foliage than male.
• Rice seedling are more susceptible to brown plant hopper ( Plant hopper feed on xylem).
• DDT was discovered in 1939.
• BHC : 1941-42
• Era of 3^rd generation pesticides : Juvenile hormone ( 1967-75) ; Corpora alata
• Era of 4^th generation pesticide : Anti hormone ( 1976); Precacene
• Moulting hormone: Ecydison from prothoracic gland.

Hazard category and Acute oral LD₅₀ rate

Synthetic Organic insecticide

1. Chlorinated hydrocarbons: DDT, BHC, Chlordane, Aldrin, Eldrin, Endosulphan
2. Organophosphate compound (Contact): Parathion, Malathion, Dichlorovos.
3. Organophosphorous compound (Systematic): Dimethoate,Phorate, Monocrotophos.
4. Carbamate (Contact): Carbaryl, Nicotine
5. Plant origin insecticide: Pyrethrin
6. Fumigants: Aluminum phosphate