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
The biology of Orius insidiosus (Say) fed on thrips Caliothrips phaseoli (Hood) was studied in a climatic chamber at 25±1°C, 70±10 percent RH and 12h photophase. Nymphal developmental time (10.2 days) was the same for males and females. The durations of the nymphal instars were 1.9, 1.7, 1.4, 1.8 and 3.1 days for the 1st, 2nd, 3rd, 4th and 5th instars respectively. Nymphal survival was 69 percent, and the highest mortality occurred at the 2nd instar. O. insidiosus consumed 73.7 C. phaseoli throughout its nymphal stage. The amount of prey fed upon by O. insidiosus nymphs increased during the successive instars: 6.1, 9.0, 11.4, 16.7 and 29.3 thrips from the 1st to the 5th instar respectively. Females laid 77.8 eggs. Egg development in O. insidiosus took 5.3 days and only 71.6 percent of the eggs hatched. Female longevity was significantly higher (21 days) than that of males (12.4 days); consequently, females ate more thrips (159.1) than the males (60.7). The search time of O. insidiosus was the same for all instars. Thus, adults of C. phaseoli were proved suitable to the development and reproduction of the predator O. insidiosus.
A biologia do percevejo predador Orius insidiosus (Say), utilizando como alimento, adultos de Caliothrips phaseoli (Hood), foi estudada em câmara climática com temperatura de 25±1°C, 70±10 por cento de UR e 12h de fotofase. O período de desenvolvimento ninfal foi de 10,2 dias, não apresentando diferença significativa para machos e fêmeas. A duração do estágio ninfal foi 1,9, 1,7, 1,4, 1,8 e 3,1 dias para o 1°, 2°, 3°, 4° e 5° ínstares, respectivamente. A viabilidade ninfal foi de 69,0 por cento, sendo que a maior mortalidade ocorreu no 2° ínstar (16,0 por cento). O. insidiosus predou 73,7 tripes durante todo o estágio ninfal. O consumo de presas pelas ninfas de O. insidiosus aumentou com os sucessivos instares: 6,1, 9,0, 11,4, 16,7 e 29,3 tripes do 1° ao 5° ínstares, respectivamente. Não houve diferença no tempo de busca para os diferentes ínstares do predador, sendo que durou em média 52 min., a captura da presa foi dificultada pela intensa reação de defesa apresentada pela mesma, que consistiu na sua maioria, em saltos e pequenas corridas. As fêmeas ovipositaram 77,8 ovos com viabilidade de 71,6 por cento e com um período embrionário de 5,3 dias. A longevidade das fêmeas (21 dias) foi significativamente maior que a dos machos (12,4 dias). O consumo das fêmeas foi de 159,1 tripes e o dos machos de 60,7 tripes. Não foi observada diferença no tempo de busca para os diferentes instares de O. insidiosus. Os resultados indicam que adultos de C. phaseoli são presas adequadas ao desenvolvimento e reprodução do predador O. insidiosus.