3.Factors influencing population 2)Culture Prefer summer sowing to spring sowing; avoid mixture of both sowing seasons. 3)Natural enemy Over 70 predators and parasitoids found in China,such as pine caterpillar trichogrammatids,corn borer trichogrammatids and white muscardine fungi. 2) Culture Prefer summer sowing to spring sowing; avoid mixture of both sowing seasons. 3) Natural enemy Over 70 predators and parasitoids found in China, such as pine caterpillar trichogrammatids, corn borer trichogrammatids and white muscardine fungi. 3. Factors influencing population 3. Factors influencing population