Parasitism of Melanaphis sacchari (Hemiptera: Aphididae) by Lysiphlebus testaceipes (Hymenoptera: Braconidae) in the Greenhouse and Field

Abstract

The sugarcane aphid, Melanaphis sacchari (Zehntner), is an economically important invasive insect pest of sorghum, Sorghum bicolor (L.) Moench, production in the southern United States. Studies were conducted to: (1) assess the fecundity of Lysiphlebus testaceipes (Cresson) parasitizing M. sacchari in the greenhouse, and (2) examine the temporal synchrony between L. testaceipes and M. sacchari in the field during 2017 and 2018. Results indicate that after 96 h, the number of M. sacchari increased approximately 90-fold from a single adult in the greenhouse study. The percentage of mummification observed in the greenhouse study was 15.2 ± 3.3%. Of those mummies, L. testaceipes adults emerged from 88.7 ± 4.4%, with 38.6 ± 8.4% of those males. Field observations showed that L. testaceipes appeared in the sentinel fields in late July to August. The percentage of mummies observed in the June- and July-planted plots of 2017, and June-planted plots of 2018 were 4.5 × 10–4 ± 1.5 × 10–4%, 7.4 × 10–4 ± 4.4 × 10–4%, and 4.4 × 10–5 ± 1.7 × 10–5%, respectively. Even though parasitization of M. sacchari by L. testaceipes was observed in both field and greenhouse, the lack of wasps before late July and low rate of parasitization in the field suggest that this species is not well synchronized with M. sacchari populations. Additional natural enemies (e.g., other parasitoids, predators, and entomopathogens) or other adaptations will be necessary before this pest is managed using biological control in Georgia.