Mass rearing and release of Trichogramma for biological control of insect pests of corn in China

Corn (Zea mays L., Poaceae) is ranked first as food crop in planting area and in total yield production in China. Asian corn borer, Ostrinia furnacalis, is the most destructive pest of corn in China, causing 6–9 million tons of yield loss per year on average. Trichogramma has been released for control of Asian corn borer at large scale since the 1970’s, partly triggered by the fact that Trichogramma dendrolimi can be successfully mass reared on eggs of the Chinese oak silkworm, Antheraea pernyi. Eggs of different hosts, such as Eri-silkworm, Samia cynthia ricini, A. pernyi, the Rice moth, Corcyra cephalonica, the Angoumois grain moth, Sitotroga cerealella and also artificial host eggs were tested and successfully used to mass-rear various Trichogramma species in China since then. The mass production technology and release technique of Trichogramma have been greatly improved in recent years making Trichogramma production and field application more practical and cost efficient. Nowadays, nearly 4 million hectares of corn are treated with T. dendrolimi, Trichogramma chilonis and Trichogramma ostriniae annually, mainly in North-east China. Large ecological and economic benefits have been achieved in areas where Trichogramma have been released continuously for many years. This includes an increase of natural populations of Trichogramma and other natural enemies in cornfields, the avoidance of any insecticide treatments in corn, a reduction in mycotoxin contamination and overall higher yields. The release of Trichogramma for controlling Asian corn borer and other lepidopteran pests became one of the key measures in corn IPM in China. Trichogramma applications combined with other non-chemical control measures for corn insect pests IPM began a new era in China as the new concept of “Public Plant Protection, Green Plant Protection” was put forward in 2006 as the guideline for plant protection in China. The future prospects and challenges of Trichogramma application are also discussed in this review.