INFLUENCE OF COLD STORAGE ON THE VIABILITY OF VEDALIA BEETLE, Rodolia cardinalis (MULSANT) (COLEOPTERA: COCCINELLIDAE)

Abstract

The vedalia predator Rodolia cardinalis considered as a main natural enemy for the biological control of mealy bugs, Icerya purchasi, I. aegyptiaca and I. seychellarum. Laboratory studies were conducted to determine the effect of cold storage on the developmental stages of R. cardinalis. Eggs of the predator were stored for 5, 10, 15 and 20 days at 6, 10 and 14 °C, , larval instars were stored for 5, 10, 20 and 30 days at 10 and 14 °C. R. cardinalis pupae were stored 5, 10, 20, 30 and 40 days at 6, 10 and 14 °C, while adults were stored for 5, 10, 20 and 30 days at 6 and 10 °C. Hatchability percentage of eggs decrease with the increase of storage period at 6°C, it averaged 84 ±10.2 (eggs one day old) and 78 ± 11.6 (eggs two days old) after 5 day of storage at 6°C, however at 6°C and 10°C eggs one and two days old, no egg hatching was observed after 25 days of storage. All eggs held for 25 days at 6°C and 10°C failed to hatch. The survival of third and fourth instar larvae stored at 6°C and 10°C was higher than the first and second instar. The fourth instar larvae of R. cardinalis were the most tolerable for cold storage. These results also provide novel findings that the fourth larval instar and eggs of R. cardinalis can be stored for twenty days at 10 °C, adult and pupae stored at 6 °C for twenty days with no reduction in viability for each stage. The results indicate that a cold storage of R. cardinalis could be used for maintaining and accumulating these predators during mass propagation for release in a biological control program and increasing the shelf-life of predators in clean agriculture.