Bioclimatic effects on the production and storage of Aphelinus perpallidus (gahan) (Hymenoptera: Aphelinidae), a primary parasite of the blackmargined aphid of pecans, Monellia Caryella (fitch) (Homoptera: Aphididae)

Abstract

The feasibility of developing effective rearing and cold storage procedures for Aphelinus perpallidus (Gahan), a hymenopteran parasite of the blackmargined aphid of pecan, Monellia caryella (Fitch), was investigated. The optimum rearing temperatures for A. perpallidus were 240280C, with the females producing 1 1.1 and 12.7 mummies, respectively, during a 48 hr. period. At densities of 0.75-1.0 aphid/cm2, parasite fecundities were 9.8 and 8.6 mummies for 48 hr. The highest fecundity of unmated and mated females at 240 and 280C, respectively, was 14 mummies. Mated A. perpallidus females produced both male and female progeny while unmated females produced only male progeny. Maximum male emergence (55-64%) occurred at 200-280C and was significantly higher than maximum female emergence which occurred at 240 (21%) and 280C (29%). Male development time ranged from 13 days at 280C to 31 days at 160C while female development time ranged from 12 days at 280C to 28 days at 160C. Parasite emergence and development period was not affected aphid density. Cold storage studies revealed that emergence of A. perpallidus adults was significantly affected by acclimatization, mummy age, storage temperature, and storage period individually and interactively. The highest total emergence ranged between 61-72 % and occurred from thermal y acclimated older mummies exposed to 4.40, 7.20, and 1 OOC stored for 7 days and at 7.20C stored for 15 days. Female and male emergence under the same conditions ranged from 33-39% and 14-34%, respectively. Generally development time from younger mummies was longer when subjected to experimental conditions compared to their older counterparts. Storage conditions which yielded the highest emergence usually resulted in minimal retarded parasite development. Under optimum conditions for emergence, development time of A. perpallidus ranged from 18-22.5 days for females and males. The number of days required to emerge after removal from storage ranged from 3.5-11 days for females and males. This research enhances the possiblity for the augmentation of field parasite populations during peak M. caryella populations. The integration of this research with current aphid management practices could result in more effective control of M. caryella .