Vegetable oils mixed in small quantities with stored grain legumes are active against eggs and larvae and disable the female to oviposit. The pest in the context is:

Correct option is B

The pest referred to in this context is Callosobruchus spp. , commonly known as the pulse beetle or bruchid beetle. This insect is a major pest of stored legumes, especially pulses such as chickpeas, cowpeas, lentils, and mung beans.
�� Why Vegetable Oils Are Effective Against Callosobruchus:
· Vegetable oils (e.g., mustard, groundnut, neem, or sunflower oil) are used in small amounts (0.5–1.0% w/w) to coat stored legume seeds.
· These oils:
· Block egg-laying sites, preventing females from ovipositing.
· Smother eggs and larvae, interfering with respiration and hatching.
· Create a barrier film on the seed surface that is toxic or repellant to the beetles.
· It is a low-cost, eco-friendly method used especially by small-scale farmers for grain protection.
Explanation for Each Option
(a) Rhizopertha ❌
· Refers to Rhizopertha dominica, the lesser grain borer.
· A serious pest of cereal grains like wheat and rice, not legumes.
(b) Callosobruchus ✅
· Correct answer.
· This genus includes Callosobruchus chinensis and C. maculatus , notorious for infesting stored legumes.
· Target pest for vegetable oil treatments in pulse storage.
(c) Tribolium ❌
· Includes flour beetles like Tribolium castaneum, pests of flour and broken grains, not whole legumes.
(d) Oryzaephilus ❌
· Includes the saw-toothed grain beetle, a pest of processed and stored cereals, not a primary legume pest.