Inter - and intraspecific relationships between Macrosiphum rosae (Hemiptera: Aphididae) and Chrysoperla externa (Neuroptera: Chrysopidae)

ABSTRACT

ABSTRACT The predator Chrysoperla externa (Hagen, 1861) (Neuroptera Chrysopidae) is a polyphagous species that has, among its wide range of acceptable prey, the aphid Macrosiphum rosae (Linnaeus, 1758) (Hemiptera Aphididae), an important pest of rose plants. We assessed the consumption of nymphs and adults of M. rosae by C. externa larvae, the predatory efficiency, and larval survival under different predatorprey ratios, densities of aphids, and ages of aphids. The bioassays were performed at 25 ± 1°C and 70 ± 10% RH under a 12-hour photoperiod, with aphids taken from roses of the cultivar Avalanche. Consumption was assessed by making young aphids (2nd and 3rd instars) and more developed aphids (4th instar and adult) available throughout the larval stage of the predator. The predatory efficiency and survival were studied for second-instar larvae offered M. rosae nymphs at densities of 20, 40, 80, 120, and 160 using predatorprey ratios of 15, 110, and 120. The assessments were performed 24, 48, and 72 hours after putting the species together. All of the C. externa instars consumed younger than older aphids. Larvae in the third instar consumed 80% of the young aphids and 77% of the older aphids. The higher the predatorprey ratio and larval density, the higher the predatory efficiency and the lower the larval survival. The ratios 15 and 110 led to the elimination of younger and older aphid populations 72 hours into the interaction between species.