Problems of Climate, Pests, Losses and Markets

1Key terms

• Climate variability: changes in rainfall and temperature from season to season and year to year, away from the usual pattern.
• Rain-fed farming: farming that depends only on rainfall, with no irrigation.
• Pest: an animal, usually an insect, that damages crops in the field or in store. A disease is harm caused by a fungus, bacterium or virus.
• Post-harvest loss: a fall in the quantity or quality of produce between harvest and the consumer.
• Credit: money borrowed now and repaid later, usually with interest. Collateral is property the borrower pledges, which the lender may take if the loan is not repaid.

2Problem 4: climate variability

Almost all Rwandan farming is rain-fed and follows two main seasons: Season A (roughly September to January) and Season B (roughly February to June). A late start, an early end or a long dry spell in the middle of a season can ruin the harvest.

The pattern is changing. The number of rainy days has fallen while torrential downpours have become more frequent, and the average temperature rose by roughly 0.7 to 0.9 °C over fifty years. Floods and droughts have both become more common over the last thirty years. The result is unstable harvests: national cereal yields swung between about 1.5 and 2.3 tonnes per hectare in the decade to the mid-2020s (AGRA-IFPRI, 2025).

3Problem 5: pests and diseases

Pests and diseases destroy crops in the field and in the store. Two recent arrivals show how serious they can be.

Fall armyworm (Spodoptera frugiperda)

• A moth native to the Americas. It was identified in Africa in 2016 and was first reported in Rwanda in 2017.
• Its caterpillars feed above all on maize, but they can attack more than 80 kinds of plant, including sorghum and rice.
• A female moth lays about 1,500 eggs, mostly on the undersides of leaves. In warm weather the whole life cycle takes only about 30 days, so numbers build up fast during a season.
• Young caterpillars eat very little, but the largest eat about 50 times as much, so the damage seems to appear overnight.
• Signs: ragged holes and papery "windows" in the leaves; wet, sawdust-like droppings in the funnel (whorl) of young maize; caterpillars boring into stalks and cobs. The caterpillar has a pale mark shaped like an upside-down Y on its head.

Cassava brown streak disease (CBSD)

• Caused by two related viruses. Whiteflies spread it from plant to plant as they feed on the leaves, and cuttings taken from infected plants carry it to new fields and districts.
• Signs: yellow blotches on the older, lower leaves; brown streaks on the green stems; and a dry, brown-black rot inside the roots that makes them unfit to eat.
• Yields can fall by as much as 70%, and roots with even moderate rot lose most of their market value.
• Because the rot is underground, many farmers only discover it at harvest, and some wrongly blame too much rain.

Other important problems include banana bacterial wilt, cassava mosaic disease and late blight of Irish potatoes in the field, and weevils, moulds and rats in stores.

4Problem 6: post-harvest losses

A good harvest can still be lost after it leaves the field:

• crops harvested late, or harvested and heaped while wet;
• maize, beans and groundnuts dried on bare ground, where they get dirty and mouldy. Some moulds produce aflatoxin, a poison that harms people and livestock;
• grain stored damp or in open sacks, where weevils, moulds and rats attack it;
• fruit and vegetables bruised in transport, or left to rot for lack of cool storage or nearby processing.

In 2020 about 16% of cereals and 18% of fruit produced in Rwanda were lost after harvest (AGRA-IFPRI, 2025).

5Problem 7: poor access to credit and markets

Credit. Seed, fertiliser, pesticides, a pump or airtight storage bags must be paid for before the harvest, but many farmers struggle to borrow:

• lenders see farming as risky, because one drought or pest outbreak can wipe out the harvest that should repay the loan;
• small, shared or unregistered plots make poor collateral;
• loans are small, so the lender's cost per franc lent is high, and interest rates can be high;
• many farmers live far from a bank or SACCO branch and keep no farm records.

Markets. Farmers also struggle to sell well:

• poor feeder roads, especially in the rainy season, and long distances raise transport costs. A 2025 IFPRI study found that farms further from markets use their inputs less efficiently;
• everyone harvests at the same time, so prices collapse at harvest;
• traders who buy at the farm gate may pay low prices to farmers who lack market information;
• world prices of export crops such as coffee and tea rise and fall;
• little produce is processed locally, so most is sold raw, at its lowest value.

Practice