Effect of two dosages of Metarhizium anisopliae var. acridum against Rhammatocerus schistocercoides Rehn

Abstract

-The fungus Metarhizium anisopliae var. acridum, strain CG 423, was tested under field conditions against the gregarious grasshopper Rhammatocerus schistocercoides (Rehn) (Orthoptera: Acrididae). Conidia formulated in a racemic mixture of soybean oil and kerosene were sprayed under field conditions using an ultralow-volume hand-held atomizer Ulva Plus adjusted to deliver 2.9 L/ha. Bands composed of 2 nd instar nymphs were treated with either 5.0x10 12 or 1.0x10 13 viable conidia/ha. The number of insects in each band was estimated at day one following spraying and by the end of the field trial (15 to 16 days posttreatment). Reductions in population size reached, in average, 65.8% and 80.4% for bands treated with the higher and lower dosage, respectively. For both dosages, total mortality rates of insects collected at two days post-application, and kept in cages for 14 days under lab conditions, showed no significant differences as compared to that obtained with insects collected immediately after spraying. Healthy insects were fed to native grasses sprayed on the field with 1.0x10 13 viable conidia/ha. Mortality levels of the nymphs fed on grasses collected two and four days post-application were not affected when compared to nymphs fed on grasses collected immediately following application.Index terms: biological control, microbial pesticide, entomogenous fungus, grasshopper, oil formulation. Efeito de duas dosagens de Metarhizium anisopliae var. acridum contra Rhammatocerus schistocercoides RehnResumo -O fungo Metarhizium anisopliae var. acridum, isolado CG 423, foi avaliado em condições de campo como agente de controle biológico do gafanhoto gregário Rhammatocerus schistocercoides (Rehn) (Orthoptera: Acrididae). Conídios formulados em uma mistura racêmica de óleo de soja e querosene foram pulverizados no campo com a utilização de um atomizador rotativo manual Ulva Plus, calibrado para aplicação de 2,9 L/ha. Bandos com ninfas de 2 o estádio foram tratados com o equivalente a 5,0x10 12 ou 1,0x10 13 conídios viáveis/ha. O número de insetos em cada bando foi estimado no 1 o dia após a aplicação e ao final do experimento (15 a 16 dias após tratamento). Reduções populacionais médias de 65,8% e 80,4% foram observadas nos bandos tratados com a maior e menor dosagem, respectivamente. Para as dosagens avaliadas, a mortalidade total de insetos coletados aos dois dias após a aplicação e mantidos em gaiolas durante 14 dias, no laboratório, não apresentou diferença significativa daquela obtida para insetos coletados imediatamente após a pulverização. Insetos sadios foram alimentados com gramíneas nativas pulverizadas no campo com 1,0x10 13 conídios viáveis/ha. As taxas de mortalidade observadas nas ninfas alimentadas com capim coletado aos dois e quatro dias após a pulverização não foram afetadas quando comparadas com ninfas alimentadas com capim coletado imediatamente após a pulverização.Termos para indexação: controle biológico, pesticida microbiano, fungo entomopatogênico, gafanhoto, formulação oleosa.

Biological control of insects in Brazil and China: history, current programs and reasons for their successes using entomopathogenic fungi

“…Field trials with M. acridum for control of the grasshopper Rhammatocerus schistocercoides were carried out in Mato Grosso state with an oil-miscible flowable concentrate (conidia in soy oil diluted in kerosene oil before use, sprayed with ULV equipment). Control levels of nymphs were in the range of 65Á88% with doses equivalent to 0.5 (1)10 13 conidia ha (1 (Magalhães, Lecoq, Faria, Schmidt, and Guerra 2000;Faria et al 2002). Presently, due to extension of soybean and cotton monocultures in Mato Grosso, populations of this grass-feeding species have been at extremely low levels and control measures are not needed.…”

The use of Metarhizium anisopliae var. cridum against the grasshopper Rhammatocerus schistocercoides in Brazil

“…For both dosages, total mortality rates of insects collected at 2 d postapplication, and kept in cages for 14 d under lab conditions, showed no significant differences as compared to that obtained with insects collected immediately after spraying (p ≥ 0.282). When healthy insects were fed native grasses sprayed at the field with 1.0 X 10 13 con./ha, mortality levels observed at 2 and 4 d postapplication were not affected when compared to day zero (p ≥ 0.050) (Faria et al 2001).…”

Laboratory Trials of Metarhizium anisopliae var. acridum (Green Muscle®) Against the Saxaul Locust, Dericorys albidula Serville (Orthoptera: Dericorythidae)

“…Using petroleum products had been tested previously. de Faria et al (2002) showed that conidia of M. anisopliae var. acridum in a mixture of soybean oil and kerosene had a good effect on the locust, Rhammatocerus schistocercoides Rehn.…”