Fruits
Senior 2 · Agriculture
Fruits
Lesson 4 of 5
24 min
Let's begin
A fruit tree planted badly stays a problem for twenty years. An avocado planted in a waterlogged valley bottom will die of root rot; one planted too close to its neighbours will shade them and become impossible to harvest. Because orchards are long-term investments, the decisions made before the first hole is dug matter most.
Spacing depends on the final size of the tree. Typical examples: avocado 7 m × 7 m to 8 m × 8 m; mango about 10 m × 10 m; citrus about 6 m × 6 m; passion fruit on a trellis with rows about 3 m apart and plants about 2–3 m apart in the row.
Plant population = area ÷ (row spacing × plant spacing), with the area in square metres (1 ha = 10,000 m²).
Worked example
(a) How many avocado trees fit on 1 ha at 7 m × 7 m? (b) How many passion fruit plants on 1 ha at 3 m × 2 m? (c) Mutesi has 0.25 ha. How many avocado trees can she plant at 8 m × 8 m?
(a) Each tree occupies 7 × 7 = 49 m². 10,000 ÷ 49 = 204.08, so 204 trees (round down: you cannot plant part of a tree).
(b) 10,000 ÷ (3 × 2) = 10,000 ÷ 6 = 1,666.7, so 1,666 plants.
(c) Area = 0.25 × 10,000 = 2,500 m². Each tree needs 8 × 8 = 64 m². 2,500 ÷ 64 = 39.06, so 39 trees.
| Problem | Crop | Signs | Control |
|---|---|---|---|
| Fruit flies | Mango, citrus, avocado and others | Maggots inside fruit; fruit rots and drops | Collect and bury fallen fruit; bait traps; harvest on time |
| Aphids | Passion fruit, citrus | Small sap-sucking insects on young shoots; they spread viruses | Natural enemies; remove weeds that host them; approved sprays if severe |
| Woodiness virus | Passion fruit | Distorted, mottled leaves; small, hard, woody fruits | No cure: plant clean seedlings, uproot infected plants, control aphids, disinfect tools |
| Root rot (Phytophthora) | Avocado | Small pale leaves, dieback, dying tree; dead feeder roots | Well-drained sites; avoid waterlogging; tolerant rootstocks |
| Anthracnose | Avocado, mango | Dark, sunken spots on fruit that spread as it ripens | Prune for air flow; remove infected fruit; avoid bruising; approved fungicides |
| Citrus greening | Citrus | Blotchy yellow leaves; small, lopsided, bitter fruit | Certified disease-free seedlings; control the insects that spread it; remove infected trees |
Combining these methods (clean planting material, hygiene, resistant varieties, natural enemies, and chemicals only when needed) is called integrated pest management.
Tip
Memory hook: population = "ten thousand over row times plant" for one hectare. Always round down.
Exam technique: in site-selection questions, give the factor and the reason: "well-drained soil, because avocado roots rot in waterlogged soil".
Give four factors to consider when selecting a site for an avocado orchard.
Solution: Any four: suitable climate for avocado; deep, well-drained fertile soil; gentle slope or terraced land; water supply; access to roads and market; shelter from wind; security; no old diseased roots.
How many citrus trees can be planted on 0.5 ha at 5 m × 5 m?
Solution: 0.5 × 10,000 = 5,000 m². 5,000 ÷ (5 × 5) = 5,000 ÷ 25 = 200 trees.
Why should the topsoil and subsoil be kept apart when digging planting holes?
Solution: Topsoil is richer in organic matter, nutrients and soil organisms. It is mixed with manure and placed at the bottom, where the young roots grow first.
State two reasons for pruning fruit trees.
Solution: Any two: to shape a strong framework; to remove dead, diseased or crossing branches; to let light and air into the canopy, reducing disease; to keep trees low enough to harvest; to renew fruiting wood.
A passion fruit plant has mottled, distorted leaves and small, hard fruits. Name the likely disease and two control measures.
Solution: Passion fruit woodiness virus. Uproot and destroy infected plants; replant with clean seedlings; control aphids; disinfect pruning tools.
Summary
Sources and credits
This lesson adapts CC BY-SA material and is shared under CC BY-SA 4.0.
