Desenvolvimento e reprodução do predador Brontocoris tabidus (Heteroptera: Pentatomidae) no campo após exposição à deltametrina / Development and reproduction of the predator Brontocoris tabidus (Heteroptera: Pentatomidae) in field conditions after exposition to deltamethrin

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

Insecticide usage can have a detrimental impact on the development and reproduction of natural enemys populations. Pyrethroids such as deltamethrin is widely used in agroecossystems and forest plantations where has shown selectivity to beneficial insects such as predatory bugs. The soldier bug Brontocoris tabidus (Signoret, 1852) (Heteroptera: Pentatomidae) is an important predator of caterpillars in Eucalyptus plantations. This study measured the effect of three 25 EC deltamethrin formulations (200, 400 e 800 ml/ha) and distilled water as the control, on nymphal survival, developmental time, adult weight and sexual ratio, and fertility and life expectancy table parameters for the predatory bug B. tabidus. Climatic conditions had mean values of 25,80 0,19 C to 15,41 0,18 C temperature, 83,4 1,7% RH, 2,9 1,1 mm of pluviosity and 11,90 0,05 h of photofase. Egg batches were in laboratory at 25 0,5 C, 70 10% RH and 12 h of photofase. Third-instar nymphs were exposed to eucalipt leaves impregnated with deltamethrin solutions or control according to treatmens. Nymphs that survived were transfered into cloth bags to field conditions, in plants of Eucalylptus urophylla, fed with Tenebrio molitor L. (Coleoptera: Tenebrionidae) pupae. Adults were weighted and 20 couples per treatment were set in cloth bags tied to eucalypt leaves. The deltamethrin doses showed effect on survival and duration of the third-instar nymphs given the fact that such instar was exposed to the pyrethroid. Survival of third-instar nymphs was reduced as the doses increased. Despite the high mortality caused by the overdose the survival immatures reached adult stage. Third instar duration of B. tabidus was increased by the effect of the doses however the total duration of the nymphal development and the adult weight and sext ratio were similar in all treatments. Female fecundity expressed by the pre-oviposition, oviposion and post-oviposition periods was similar in all treatments, and the mean egg and nymph numbers ranged from 508,8 76,4 eggs/female (control) to 567,9 98,3 eggs/female (800 ml/ha); and 358,6 59,0 nymphs/female (control) to 385,3 53,7 nymphs/female (400 ml/ha). Life table parameters of population growth of this predator showed a reproductive rate of 125.7 females/female, intrinsic rate of increase of 0.059 and a generation time of 11.6 days when exposed to the commercial dose of 400 ml/ha of deltamethrin. The commercial dose also showed the highest life expectancy and fertility point values of all treatments. The overdose showed high specific fertility but low survival rate. The deltamethrin low-dose and overdose showed similar life table values which demonstrates that growth and life expectancy of the predator were not harmed by the insecticide. Deltamethrin doses can be considered selective to B. tabidus and can be used with this predatory bug in the Integrated Pest Management programs.

ASSUNTO(S)

brontocoris tabidus brontocoris tabidus controle biológico deltametrina entomologia agricola biological control deltamethrin

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