Crop Pests and Their Classification

Study Notes

Insect: Invertebrate animals with six legs, three body parts, and usually two pairs of wings. Insects are the largest group of pests.
Rodent: Small mammals with sharp teeth (e.g., squirrels, rats, mice, moles).
Bird: Warm-blooded egg-laying vertebrates with feathers (e.g., quelea, sparrows, crows, warthogs, baboons, monkeys).
Pathogen: Organisms that cause diseases (e.g., bacteria, fungi, viruses).
Mammal: Vertebrate animals that give birth to live young and nourish them with milk (e.g., warthogs, baboons, monkeys).
Weed: Plants that grow where they are unwanted, interfering with crop growth (e.g., blackjack, Mexican poppy, thorn apple).

Biting and Chewing: Mouthparts adapted to bite and chew plant tissue (e.g., grasshoppers, locusts, termites, beetles, armyworm, leaf miners).
Piercing and Sucking: Mouthparts adapted to pierce plant tissue and suck sap (e.g., aphids, bagrada bugs, mealybugs, scale insects).
Boring: Mouthparts adapted to tunnel into plant tissue (e.g., weevils, stalk borer, American bollworm).

Metamorphosis: Physical changes insects undergo.
- Complete metamorphosis: Four stages (egg, larva, pupa, adult).
- Incomplete metamorphosis: Three stages (egg, nymph, adult).
Aphid life cycle:
- Asexual: Reproduction mainly occurs during the summer/humid/rainy season (egg → nymph—multiple development—adult). Aphids produce many eggs without fertilization and reproduce parthenogenically.
- Sexual: Reproduction occurs during the winter/dry season (under unfavorable conditions).

Life cycle:
- Adult females lay eggs in protective pods underground.
- Eggs hatch into nymphs after nearly 30 days.
- Nymphs feed and grow into adults after 4 to 5 moults (lasts 40 days).
- Adult feeds and reaches sexual maturity after 45 days.
- Then, mating occurs, and females start laying eggs, thus initiating the next cycle

Life Cycle:
- Adult female and male moths mate.
- Females lay eggs in columns on a leaf or under plant sheaths.
- Eggs hatch into larva (caterpillar) after 10 days.
- Caterpillar bores into the stalk center, feeding on stem tissue.
- Mature caterpillar bores a hole, where it pupates.
- Larva period lasts for about 35 days.
- Pupa stage lasts for about 10 days.
- Moths emerge.
- Then mating and laying eggs thus completing a new cycle.

Plant disease: Abnormal plant condition due to internal disorders (nutrition, stress) or infections (pathogens).
Effects on crops:
- Reduced yields.
- Crop losses.
  - Stunted growth.
  - Discoloration (yellowing).

Climatic Requirements: Hot sunny climate with evenly distributed rainfall (around 450mm) and average temperatures of 24 °C.
Soil Type: Well-drained soils, from sandy to clay, rich in organic matter (pH range of 5.5 to 7.0).
Seedbed Preparation: Ploughing (25-30cm deep), breaking clods, leveling, and harrowing.
Planting Time: October to March in Botswana.
Planting of Maize: Applying seeds directly (22 kg/ha, spacing 90cm between rows, 30cm within a row), around 5-8cm deep.
Application of Manures: Basal dressing (2:3:2 +1% Zn at 1000kg/ha), kraal manure (broadcast and dug in. 5 weeks before planting at 30000 kg/ ha).
Top Dressing: Applying LAN (28%) 100 kg/ha 4 weeks after planting.

Mechanical: Physical methods (digging, cultivation, hoeing, slashing, hand-pulling).
Cultural: Good crop husbandry practices (mulching, crop rotation, early planting, clean seeds).
Chemical: Pesticides- Selective herbicides (kill specific weeds), Non-selective herbicides (kill any plant).

Harvesting, stocking, transportation, temporary storage, drying, husking, shelling, winnowing, weighing and pricing. Selling fresh/dried maize to individuals, traders, co-ops, and BAMB.