question_answer 68)

  Write the modes by which insects affect the crop yield.

Answer:

  Some common insect pests of stored grain and their mode of infection are (i) Gram dhora or Pulse beetle (Callosobruchus maculatus) Its grubs, damage the stored gram (ii) Rice weevil (Sitophilus oryza) Both grub and beetle (adult) damage rice (iii) Khapra or Wheat weevil (Trogocterma granarium) Infests stored wheat (iv) Grain and flour moth (Sitotroga cerealella) Its caterpillars bore into grains of rice, wheat, barley, maize and jowa (v) Rust red flour beetle (Tribolium castaneum) Both larvae and adult damage flour and flour products (vi) Rice moth (Coccyra cephalonica) Larvae damage rice and maize (vii) Lesser grain borer (Rhizopertha dominica) Both grub and adult (beetle) damage the grains, reducing them to perforated shells