An efficient method for mass rearing Dastarcus helophoroides (Coleoptera: Bothrideridae), an important natural enemy of longhorned beetles

Dastarcus helophoroides (Coleoptera: Bothrideridae) is an important biocontrol agent of wood-boring longhorned beetles, but artificial rearing of the parasitoid on the factitious host Zophobas morio (Coleoptera: Tenebrionidae) is laborious. High rearing costs are the greatest impediment to biocontrol applications of this parasitoid in China. In this study, a rearing tube was designed and natural infestation methods with (NwT) and without (NnT) tubes were developed to improve on the traditional artificial infestation method (AM) for mass rearing the parasitoid. Fitness parameters of the parasitoid were compared among these three methods, including parasitism rate, emergence rate, the total numbers of cocoons and emerging adults, total developmental time, and the labor required, using four different parasitoid-host ratios. The cost of producing 10,000 parasitoid adults with each method was then calculated. The results showed that the NwT method significantly increased numbers of cocoons and emerging adults per rearing box compared with either AM or NnT, and total developmental time was significantly shortened. Parasitism rate in the NwT treatment was significantly higher than that in the AM treatment. The labor required for the NwT and NnT treatments was significantly less than that for the AM treatment and the cost of producing 10,000 adults was reduced by 75-87% in NwT, whereas, it was reduced by 35-77% in NnT. The study showed that the NwT treatment enhanced the efficiency of mass-rearing D. helophoroides and reduced costs, and that the highest efficiency was achieved at a parasitoid-host ratio of 10:1.