(a) Fig. 2.1 shows a locust swarm approaching farmland in an East African country. Fig. 2.1 (i) Describe two ways in which a locust swarm causes crop damage...

Labelled answer diagram:

(a)(i) Two ways in which a locust swarm causes crop damage:

1. Locusts consume large quantities of leaf tissue, stripping plants bare and preventing photosynthesis, which stops the plant from producing the carbohydrates it needs to grow and yield. [1]
2. They also feed on stems, flowers, and developing grain heads, directly destroying the harvestable part of the crop. [1]

(a)(ii) Locust outbreaks are difficult for individual farmers to control for three reasons:

1. Swarms are extremely large (sometimes covering hundreds of square kilometres) and affect areas far beyond the boundaries of a single farm, so one farmer's efforts cannot contain them. [1]
2. Swarms are highly mobile, travelling tens of kilometres per day on prevailing winds, making it impossible for an individual farmer to predict where they will land next or to mount a timely response. [1]
3. The quantity of pesticide required to treat a swarm is enormous and far beyond the financial resources of a single farmer. [1]

(b)(i) Two advantages of aerial spraying over ground-based spraying for locust control:

1. Aircraft can cover very large areas quickly, matching the scale and speed of the swarm. [1]
2. Spraying from the air can reach swarms in remote or inaccessible terrain (desert, rugged landscape) where ground vehicles cannot operate. [1]

(b)(ii) Two environmental concerns from large-scale aerial spraying:

1. Pesticide drift may contaminate rivers, lakes, and other water sources, harming aquatic organisms such as fish and amphibians. [1]
2. Non-target insects, including pollinators (bees) and natural enemies of other pests, may be killed by broad-spectrum pesticides, disrupting local ecosystems. [1]

(c) Early warning systems monitor weather patterns, soil moisture, and vegetation conditions in known locust breeding areas and can predict where swarms are likely to form. [1] This allows control teams to target young wingless hoppers in their breeding grounds before they develop into flying adults and form swarms, which is far more effective, cheaper, and less environmentally damaging than trying to control airborne adult swarms. [1]

(d) Two factors the farmer should consider when choosing a replacement crop (each explained for 2 marks):

1. Time remaining in the growing season: The replacement crop must have a short enough maturity period to be harvested before the rains end or before the next dry/cold season. Planting a long-season crop that cannot mature in time would result in a second total loss. [2]
2. Market value and demand: Since the farmer has already lost the millet crop and all the investment in it, the replacement should be a crop with strong local demand or a good market price to help recover the lost income as quickly as possible. [2]