Resposta funcional e numérica de Scymnus (Pullus) argentinicus (Weise, 1906) (Coleoptera: Coccineilidae) a diferentes densidades do pulgão verde Schizaphis graminum (Rondani, 1852) (Homoptera: Aphididae)

Abstract

This research had as objective to study the functional and numerical responses of predator Scymnus (Pullus) argentinicus at different densities of greenbug Schizaphis graminum. To functional response were estimated also the search time and handling time by predator in factorial 3 x 5 in densities of10 25 e 35 nymphs of3— and 4- instars ofaphid and in lft, 2-, 3~ and 4a1 instars and adult predator in 10 repetitions. To numerical response were estimated the predation, fecundity (eggs number/ female/ day) embrionary period, eggs viabilityand biological cicle ofpredator in factorial 5 x 5 in 5 densities (10 20, 25,30 and 35 nymphs) of 3* and 4ainstars ofgreenbug and 5 predator females, in 5 repetitions. The tests were carried out in Insect Biology Laboratory ofthe Plant Protection Department at Federal University of Lavras. The tests material were kept in climatic camera with 25 ± Io C temperature 70 ± 10 % humitidy and 14 hours photophase. The tests showed influence of aphid densities in ali parameters studied. The functional response of larval and adult of Scymnus (Pullus) argentinicus showed that the amount predated nymphs increased with the increment ofaphid densities until reach a plateau (Functional Response Holling's type II, 1959). The time searchincreased gradually withthe age ofpredator while the handling time decrease withthe age. The ability ofsearchdecrease withthe increment ofthe densityofthe capture once that the possibilits of predator find the prey increase. In the numerical response, predation rate offemale influencied the eggs number (4.7; 4.4; 4.1; 5.7; 5.9) and the larvae number heacted (2.5; 2.6; 2.3; 3.2; 3.5). The pupal phase was that more influencied in redution ofdevelopment period. The egg embrionary period decreased with the increase ofthe preysto females ofS. (Pullus) argentinicus.