Pest Control in a Tomato Crop with a Pollinator Nearby
A farmer grows tomatoes in a 0.5-hectare plot. Whiteflies have been found on 40% of plants, and the farmer wants to spray an insecticide. A beekeeper keeps two hives 200 metres from the plot, and the tomatoes are flowering. The farmer has three options: a broad-spectrum pyrethroid spray applied in the morning, a selective insecticide that targets whiteflies but is less harmful to bees, or yellow sticky traps plus releasing the parasitic wasp Encarsia formosa. The pyrethroid costs 20 dollars, the selective insecticide 35 dollars, and the traps plus wasps 50 dollars. The farmer's main priority is protecting the tomato harvest, but the beekeeper has asked for consideration.
1. Evaluate the three options against the farmer's priority and the beekeeper's request. Recommend one option and justify it.
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The broad-spectrum pyrethroid is cheapest at 20 dollars and will kill whiteflies quickly, but it is harmful to bees and other pollinators. Applied in the morning when flowers are open, it could kill foraging bees and reduce pollination, which may lower tomato yield and damage the relationship with the beekeeper. The selective insecticide at 35 dollars targets whiteflies and is less harmful to bees, so it offers a good balance between cost and safety if applied in the evening when bees are not foraging. The traps plus parasitic wasps at 50 dollars are the most bee-safe and sustainable, but they are slower to act and the highest cost. Given that the farmer's main priority is protecting the harvest and whiteflies are already on 40% of plants, the selective insecticide is the best recommendation. It controls the pest quickly while respecting the beekeeper's request, provided it is applied in the evening and label directions are followed.
2. Suppose the farmer chooses the pyrethroid. Describe two practices that would reduce harm to the bees and explain why each helps.
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Practice 1: Spray in the late evening or at night, after bees have stopped foraging. Bees are active during daylight, so evening application means the residue has time to dry or break down before the next foraging period, reducing direct contact. Practice 2: Avoid spraying open flowers and mow or remove flowering weeds around the plot before spraying. Bees are attracted to flowers, so reducing flowering material in and around the crop lowers the chance of bees contacting treated surfaces. A third practice is to notify the beekeeper at least 48 hours before spraying so hives can be covered or moved. These practices do not eliminate risk but reduce it substantially. The judgement is that timing and communication are as important as product choice when pollinators are nearby.