A vegetable grower finds caterpillars feeding on young kale plants. Rather than spraying every plant immediately, the grower is considering planting strips ...
Question 1 Report
A vegetable grower finds caterpillars feeding on young kale plants. Rather than spraying every plant immediately, the grower is considering planting strips of flowering plants around the crop. These flowers provide food for insects that prey on the caterpillars. The grower must balance crop production, pesticide costs and possible effects on other organisms in the field.
(a) Explain how planting flower strips could reduce damage to the kale crop. [3]
(b) Complete the food chain using the organisms in this situation.
kale plant → caterpillar → __________ [2]
(c) Describe two possible disadvantages of using a broad-spectrum pesticide on the field. [3]
(d) State one reason why a farmer might still use a pesticide when pest numbers are very high. [1]
(e) Suggest two measurements the grower could make to decide whether flower strips are effective. [2]
Answer Details
(a) Flower strips provide food or habitat for insects that prey on caterpillars. This increases the number of predators, so more caterpillars are eaten. Fewer caterpillars feed on kale leaves, reducing damage and potentially increasing yield. [3]
(b) The completed chain is kale plant → caterpillar → predator insect, such as a ladybird or parasitic wasp. The arrow represents transfer of biomass or energy from the caterpillar to the predator when it is eaten. [2]
(c) A broad-spectrum pesticide can kill non-pest organisms, including pollinators and natural predators of caterpillars. It may also enter water and harm aquatic organisms, and repeated use can select for pesticide-resistant pests. Any three valid disadvantages gain credit. [3]
(d) A pesticide may be used when pest numbers are very high to prevent a large loss of crop yield and protect food production. [1]
(e) Suitable measurements include counting caterpillars per plant, measuring leaf area damaged, counting predator insects, or comparing kale yield in plots with and without flower strips. Any two. The comparison should use the same method in both types of plot. [2]
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