Parasitoid Complex of the Mealybug Oracella acuta (Lobdell) (Hemiptera: Pseudococcidae), in Georgia, USA

Abstract

The parasitoid complex of the mealybug Oracella acuta (Lobdell) was examined in two field populations in Georgia in 1995–96. Allotropa n. sp. and Zarhopalus debarri Sun were the primary endoparasitoids emerging from O. acuta. Adult abundance varied seasonally, with Allotropa n. sp. numbers peaking in June and Z. debarri in September. Parasitism rates of female O. acuta exceeded 60% at one site and ranged from 24 to 29% at the other site. The adult female was the preferred host stage for parasitism (76%), though Allotropa n. sp. and the endoparasitoid Acerophagus coccois E. Smith occasionally utilized second and third instar females as hosts. These two species exhibited gregarious parasitism, with up to 5 Allotropa n. sp. or 4 A. coccois emerging from a single host. Adult longevity of female and male Z. debarri averaged 6.4 and 5.3 days, respectively, and access to a food source usually increased adult lifespan. Female Z. debarri contained an average of 119 eggs, compared to 74 eggs per female for Allotropa n. sp.

Classical biological control program for the mealybug Oracella acuta in Guangdong Province, China

“…In addition, the seasonal population fluctuations may result in less overlap of mealybug generations throughout the year, which could leave emerging parasitoids without preferred life stages for parasitism. All three species prefer adult hosts, and Z. debarri utilizes adults almost exclusively (Sun et al ., 2004a). Although A. coccois and A. oracellae may parasitize second and third instars, the sex ratio of the emerging parasitoids may be skewed.…”

“…Populations in the US usually are kept at low levels by a suite of natural enemies, and noticeable populations only occur when this natural enemy complex is disrupted by insecticide applications or similar disturbances (Clarke et al ., 1990, 1992). Three species of parasitoids appear responsible for regulating populations of the mealybug in the US: the platygastrid Allotropa oracellae Masner, and the encyrtids Acerophagus coccois E. Smith and Zarhopalus debarri Sun (Clarke et al ., 1990; Sun et al ., 2004a). The latter is a solitary endoparasitoid, while the other two are gregarious endoparasitoids (Dorn et al ., 2001; Sun et al ., 2004b).…”

“…An unknown signiphorid species of Chartocerus , a probable hyperparasitoid, also was recovered. The parasitoids can quickly reduce population outbreaks, and in the absence of insecticide applications, parasitism rates can range from 50% to over 90% (Clarke et al ., 1990; Sun et al ., 2004a). Predators such as lacewing larvae and two species of cecidomyiid larvae feed on the mealybugs when population levels are high.…”