ABSTRACT
ABSTRACT Several studies have shown that the survival and reproduction of lacewings varies depending on the type of prey they consumed, especially during the first instar. In this study, we evaluated the effect of a diet consisting of Ephestia kuehniella (EK) and/or Planococcus-citri (PC) eggs offered to first instar Chrysoperla externa on subsequent development and survival. Larvae supplied only with P. citri (PC) nymphs had extended immature development, low survival, adults with lower weight and longevity, low fecundity and egg viability, and lower net reproduction rate (R0). Larvae submitted to the treatment EK+PC responded positively to the diet, showing results similar to those obtained in the control-EK treatment. Therefore, this mealybug supports suitable development and reproduction of C. externa when it is provided to second instar larvae after they fed on E. kuehniella eggs as first instars. As far as we know, this is the first report that demonstrates the effect of natural prey and alternatives on different larval stages of lacewings. This information is valuable in developing protocols for use of C. externaas a pest control agent.
ABSTRACT
ABSTRACT This study aimed to determine the consumption of Planococcus citri (Risso, 1813) (Hemiptera: Pseudococcidae) nymphs and the predator:prey ratio required for high predatory efficacy and survival of Chrysoperla externa (Hagen, 1861) (Neuroptera: Chrysopidae) larvae under different densities of prey, reared in rose bushes. Consumption by first-, second-, and third-instar larvae of C. externa was assessed. The predatory efficiency and survival of the predator were calculated for larvae in the second instar under densities of 20, 40, 80, 120, and 160 nymphs of P. citri and predator:prey ratios of 1:5, 1:10, and 1:20. The assessments were performed after 24 and 48 hours of exposure between species. There was increasing consumption throughout the larval development of C. externa. The predator:prey ratios 1:5 and 1:10 were the most efficient for P. citri population reduction, but the 1:5 ratio led to lower survival of larvae than the 1:10 and 1:20 ratios. There was a positive correlation between C. externa larval density and cannibalism (ρ = 0.45) and a negative correlation between predator density and P. citri population density (ρ = -0.81). Third-instar larvae consume more P. citri nymphs than second-instar larvae. Second-instar larvae of this lacewing released at a 1:20 ratio caused total mortality of mealybug nymphs within 48 hours, regardless the density of P. citri, with high larvae survival of C. externa.
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 predator:prey 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 predator:prey ratios of 1:5, 1:10, and 1:20. 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 predator:prey ratio and larval density, the higher the predatory efficiency and the lower the larval survival. The ratios 1:5 and 1:10 led to the elimination of younger and older aphid populations 72 hours into the interaction between species.