1a.Objectives (from AD-416):
Although aphid endosymbionts are known to confer resistance to attack by some parasitoid species, very little is known about the impacts such endosymbionts have on biological control of pest aphids. We will determine whether the aphid endosymbiont HAMITONELLA DEFENSA affects parasitism by APHELINUS species being considered for introduction against pest aphids.
1b.Approach (from AD-416):
We will test whether parasitism of APHIS CRACCIVORA by APHELINUS species that are candidates for introduction against soybean aphid is affected by the presences of HAMITONELLA DEFENSA.
In several experiments on the effect of HAMITONELLA DEFENSA, a bacterium living in aphids, on resistance of the cowpea aphid, APHIS CRACCIVORA, to parasitism by APHELINUS GLYCINIS, APHELINUS ATRIPLICIS and APHELINUS CERTUS, neither parasitism nor adult body size of progeny were affected by the presence of H. DEFENSA. Thus although H. DEFENSA has been shown to confer resistance to parasitism by braconid wasps that attack aphids, it does not confer resistance to aphelinid wasps that attack aphids. We found 11 strains of bacteria in 6 genera in 44 populations of the aphid cowpea aphid, APHIS CRACCIVORA. However, prevalences of bacteria were lower than in other well-studied aphids. ARSENOPHONUS was prevalent in cowpea aphid on locust but rare or absent on other plants; HAMILTONELLA was prevalent in cowpea aphid on alfalfa but rare or absent on other plants. HAMITONELLA provides protection against some parasitic wasps, but ARSENOPHONUS does not, so aphids on different host plants may have different levels of parasitism.