(a) Outline the life cycle of the bean beetle [6 marks] (b)(i) Describe briefly four damages done by cotton stainer to cotton plants on the field. [6 marks]...
Question 1 Report
(a) Outline the life cycle of the bean beetle [6 marks] (b)(i) Describe briefly four damages done by cotton stainer to cotton plants on the field. [6 marks] (ii) Name four alternate hosts of cotton stainer [4 marks]
Answer Details
(a) Life cycle of the bean beetle (bean weevil, Callosobruchus maculatus)
- The adult female lays her eggs on the surface of the bean seeds, either on the field or in store.
- Each egg hatches into a larva (grub).
- The larva bores into the bean seed and feeds on the cotyledons inside.
- Within the seed the larva grows and then changes into a pupa.
- The pupa develops into an adult beetle.
- The adult bores its way out of the seed, mates and the female lays eggs again, so the cycle repeats. (Egg to adult in about three to four weeks.)
(b)(i) Four damages done by cotton stainer to cotton plants on the field
- It pierces and sucks sap from the bolls, buds and young shoots, weakening the plant.
- It stains the cotton lint yellow or brown, lowering its quality and market value.
- It introduces fungi and bacteria into the bolls, causing internal boll rot.
- It causes premature dropping of buds and immature bolls, reducing yield.
(b)(ii) Four alternate hosts of cotton stainer
- Okra
- Hibiscus (roselle/soborodo)
- Baobab
- Kola (and other Malvaceae plants)
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