Marcos Rafael Gusmão

Economic injury level and sequential sampling plan for Bemisia tabaci in outdoor tomato

Abstract:  This work aimed to determine the economic injury levels and to establish sequential sampling plans for nymphs and adults of the whitefly Bemisia tabaci Genn. (Sternorrhyncha: Aleyrodidae) in tomato fields. Densities of nymphs and adults, as well as crop yield were evaluated in 13 commercial tomato fields to determine the economic injury levels. The whitefly nymphs were sampled by direct counting in a leaf from the lower part of the canopy and the adults were sampled by beating an apical leaf against a white plastic tray. The sequential sampling plan was based on data collected in eight commercial tomato fields. The validation of the sequential sampling plan was carried out based on the curves of operational characteristics and average sample numbers. The decisions reached with the conventional and the sequential sampling plans in 21 commercial fields were compared for the intended validation of the sequential plan. The economic injury levels were four nymphs per leaf and one adult per tray. The decisions taken based on the sequential sampling plan were similar to those obtained through the conventional sampling plan. Most of the decisions taken with the sequential sampling plan were obtained through the minimum number of seven samples per field for nymphs and 11 samples per field for adults, with reductions of 84.44% and 54.17% in the number of samples required to reach a decision with the sequential sampling plan compared with the conventional sampling plan.

Seletividade fisiológica de inseticidas a vespidae predadores do bicho-mineiro-do-cafeeiro

The selectivity of the insecticides chlorpyrifos, deltamethrin, dimethoate, ethion, monocrothophos and permethrin to the predatory wasps Apoica pallens Fab., Brachygastra lecheguana Latreille and Polistes versicolor versicolor Olivier (Hymenoptera: Vespidae) was studied, in laboratory, using 50% and 100% of the dosages used for controlling the coffee leafminer, Perileucoptera coffeella Guerin-Meneville (Lepidoptera: Lyonetiidae). Deltamethrin was selective in favour of P. versicolor versicolor and A. pallens. Ethion showed median selectivity in favour of P. versicolor versicolor and A. pallens and good selectivity to B. lecheguana. The other insecticides were not selective in favour of the predatory wasps. The order of tolerance to deltamethrin was: P. versicolor versicolor > A. pallens > B. lecheguana. To ethion, the order was: B. lecheguana > P. versicolor versicolor > A. pallens. Chlorpyrifos, deltamethrin, dimethoate, monocrothophos and permethrin presented similar toxicity to the wasps in both dosages used. On the other hand ethion reduced its impact on A. pallens and P. versicolor versicolor when applied in subdosages.

Seletividade de inseticidas a Polybia ignobilis (Haliday) (Hymenoptera: Vespidae) predador de Ascia monuste orseis (Godart) (Lepidoptera: Pieridae)

The selectivity of carbaryl, deltamethrin, methyl parathion, permethrin and thrichlorfon to the predator Polybia ignobilis (Haliday) was evaluated in dosages which killed 90% of 4th and 5th instars of Ascia monuste orseis (Godart). Methyl parathion (86% average mortality) and carbaryl (62%) were not selective to P. ignobilis; thrichlorfon and permethrin (4%) were more selective while deltamethrin showed intermediate selectivity (26% average mortality). Adults of P. ignobilis with yellow strips (38%) were more tolerant to carbaryl than those without this characteristic (86% average mortality).

Factors affecting colonization and abundance of Aphis gossypii glover (hemiptera: aphididae) on okra plantations

O controle de Aphis gossypii Glover (Hemiptera: Aphididae) em quiabeiro Abelmoschus esculentus (L.) (Malvaceae) consiste principalmente no uso de inseticidas, em virtude da falta de informacao sobre outros fatores de mortalidade. Objetivou-se com este estudo determinar os efeitos de predadores e parasitoides, altura de dossel, idade da planta, area foliar, compostos orgânicos foliares, niveis de nitrogenio e potassio, densidade de tricomas, pluviosidade e temperatura na intensidade de ataque de A. gossypii em dois cultivos sucessivos de Abelmoschus esculentus var. Santa Cruz. Estimou-se, mensalmente, o numero de A. gossypii e de inimigos naturais (inspecao visual) ocorridos nas folhas (uma folha/planta) localizadas nas partes basal, mediana e apical de 30 plantas/plantacao. Os fatores que mais contribuiram com a reducao da populacao de pulgoes foram a senescencia de plantas, area foliar e inimigos naturais, principalmente Adialytus spp., aranhas e Coccinellidae. Maior numero de pulgoes foi observado na parte basal que na mediana e apical de plantas de quiabeiro. A pluviosidade total pode reduzir a populacao de pulgoes. Tricomas tectores (nao-glandulares) ou baixa densidade destes, compostos orgânicos foliares e niveis de N e de K nao foram importantes para a reducao da populacao de pulgoes.

Selectivity of insecticides to predators of aphids

Estudou-se a seletividade dos inseticidas cipermetrina, diclorvos, diazinon, etion, fenitrotion, malation, metamidofos, paration metilico, permetrina, pirimicarbe e vamidation para adultos dos predadores Cycloneda sanguinea (L.) e Eriopis connexa (Germ.)(Coleoptera: Coccinellidae). Folhas de tomateiro foram imersas em caldas inseticidas nas doses utilizadas para o controle dos pulgoes Myzus persicae (Sulzer) e Macrosiphum euphorbiae (Thomas) em tomateiro e tambem na metade das doses recomendadas. Os fatores em estudo foram os inseticidas, as doses, as especies de predadores e o sexo para C. sanguinea. Vamidation e o pirimicarbe foram os inseticidas mais seletivos a C. sanguinea seguidos do etion e diclorvos (3,2; 6,7; 49,7 e 52,5% de mortalidade, respectivamente). Para E. connexa o pirimicarbe foi o mais seletivo seguido pelo etion e cipermetrina (1,96; 71,28 e 81,92% de mortalidade, respectivamente). Os machos de C. sanguinea foram mais tolerantes que as femeas ao etion (33 e 66,5% de mortalidade) e permetrina (61 e 100% de mortalidade, respectivamente). A toxicidade da permetrina a E. connexa e do etion as femeas de C. sanguinea foi menor quando estes inseticidas foram aplicados em subdose (74,4 e 25% de mortalidade, respectivamente) do que quando estes foram aplicados na dose recomendada (100 e 66,5% de mortalidade, respectivamente) para o controle de pulgoes no tomateiro.

Seletividade de Inseticidas a Brevicoryne brassicae (L.) (Hemiptera: Aphididae) e ao Predador Doru luteipes (Scudder) (Dermaptera: Forficulidae)

The objective of this work was to study the selectivity of the insecticides acephate, deltamethrin, dimethoate, methamidophos, methyl parathion, and pirimicarb to first, second, and third instar nymphs and adults of the predator Doru luteipes (Scudder) (Dermaptera: Forficulidae) in comparison with last instar nymphs of the prey Brevicoryne brassicae (L.) (Hemiptera: Aphididae). Pirimicarb and deltamethrin were highly selective to all developmental stages of D. luteipes; the same was observed with acephate except for first instar nymphs to whom it showed median selectivity. Dimethoate showed median selectivity, but methamidophos and methyl parathion were low selective to the predator. Second and third instar nymphs and adults of D. luteipes were more tolerant to acephate, methyl parathion and pirimicarb than first instar nymphs. First and second instar nymphs showed similar tolerance to deltamethrin, dimethoate and methamidophos. Concentration-response curves for dimethoate (to adults and first and second instar nymphs) and methamidophos (to third instar nymphs) showed steeper slopes indicating an homogeneous response of these developmental stages to these insecticides.

Inseticidas seletivos à tesourinha Doru luteipes (Scudder) utilizados no controle do pulgão verde em brássicas

The selectivity of the insecticides acephate, deltamethrin, dimethoate, methamidophos, methyl parathion, and pirimicarb were studied on the last nymphal phase of the green peach aphid Myzus persicae (Sulzer) (Homoptera: Aphididae) and on first, second, and third instar nymphs and adults of the Doru luteipes (Scudder) (Dermaptera: Forficulidae). Pirimicarb was highly selective in favor of all developmental stages of D. luteipes. Deltamethrin, methyl parathion and dimethoate were of median selectivity in favor of third instar nymphs of D. luteipes, as was also observed for the first two of these insecticides regarding to nymphs of first and second instars, respectively. Acephate was little selective in favor of second and third instars nymphs, and the same was observed for methyl parathion, deltamethrin and methamidophos to first, second and third instar nymphs, respectively. Dimethoate and methamidophos were more toxic to nymphs of first and second instars of the predator than to the last instar nymphs of the green peach aphid. D. luteipes adults and second and third instar nymphs were more tolerant to acephate, methyl parathion, and pirimicarb than first instar nymphs. D. luteipes first and second instar nymphs showed similar tolerance to deltamethrin, dimethoate, and methamidophos. Concentration-response curves for deltamethrin, methamidophos, and pirimicarb (to all development stages of D. luteipes), for dimethoate (to adults and first and second instar nymphs of the predator), for methyl parathion (to first and third instar nymphs of the predator), and for acephate (to adults of the predator) showed steeper slopes than the concentration-response curves of these insecticides established to M. persicae.