Which factor causes contact insecticides to lose effectiveness relatively quickly?

Which factor causes contact insecticides to lose effectiveness relatively quickly?

• A. Exposure to sunlight and washing
• B. Deep soil penetration
• C. High humidity alone
• D. Being applied to the soil

Answer: (A)

Contact insecticides work by killing pests on contact and usually don’t provide long-lasting residues. Their effectiveness drops quickly when the treated surfaces are exposed to sunlight because UV light degrades many active ingredients. They’re also easily washed off by rain, irrigation, or cleaning, which physically removes the product from the site where pests would contact it. In practice, this combination of sunlight exposure and washing is why these products lose effectiveness rapidly. Deep soil penetration would move the product away from where pests on foliage or turf blades are likely to touch it, so it doesn’t help with quick, surface-based contact kills. High humidity can influence some products, but it isn’t the primary reason contact insecticides fade as fast as sunlight and washing. Being applied to soil also reduces contact opportunities with target pests on above-ground surfaces.

Contact insecticides work by killing pests on contact and usually don’t provide long-lasting residues. Their effectiveness drops quickly when the treated surfaces are exposed to sunlight because UV light degrades many active ingredients. They’re also easily washed off by rain, irrigation, or cleaning, which physically removes the product from the site where pests would contact it. In practice, this combination of sunlight exposure and washing is why these products lose effectiveness rapidly.

Deep soil penetration would move the product away from where pests on foliage or turf blades are likely to touch it, so it doesn’t help with quick, surface-based contact kills. High humidity can influence some products, but it isn’t the primary reason contact insecticides fade as fast as sunlight and washing. Being applied to soil also reduces contact opportunities with target pests on above-ground surfaces.