Field Trial with the Entomopathogenic Fungus Metarhizium anisopliae var. acridum against Bands of the Grasshopper Rhammatocerus schistocercoides in Brazil

The efficacy of a mycoinsecticide formulated in vegetable oil was tested in Brazil against the grasshopper Rhammatocerus schistocercoides . A set of experiments was conducted in the Chapada dos Parecis region (Mato Grosso state), a permanent zone of outbreaks for this pest. Experiments were performed in zones of natural vegetation, against grasshopper bands in the third nymphal instar. Three nymphal bands were treated with a mycoinsecticide formulation based on conidia of the entomopathogenic fungus Metarhizium anisopliae var. acridum ( =M. flavoviride ), strain CG 423. Three non-treated bands were used as control. The application was made with the aid of a hand-held ULV sprayer adjusted to deliver 2 l of the formulation ha -1 , each containing 1 ×10 13 conidia. Treatments were limited to the surface of the grasshopper bands and their immediate borders (5-10 m). The efficacy of the mycoinsecticide was evaluated through band survival after treatment (grasshopper numbers, surface, density, behaviour and daily movement of the band), allowing the insects to move freely in their natural environment. Insects were regularly surveyed and maintained in the laboratory, allowing estimates of the infection rate. Field and laboratory studies showed a clear effect of the product 10 days after treatment. At 14 days post-spraying, mortality caused by the mycoinsecticide in the field was approximately 88%.     

Effects of a Mycoinsecticide on Feeding and Fecundity of the Brown Locust Locustana pardalina

The entomopathogenic fungus Metarhizium anisopliae var. acridum is being developed for use as a mycoinsecticide against locusts and grasshoppers in Africa. In addition to causing significant mortality, studies have shown the pathogen to cause reductions in feeding of a number of target species during the disease incubation period. The present study extends this work by demonstrating significant reductions in feeding following infection in another important pest species, the brown locust Locustana pardalina (Walker). Insects collected from the field following a spray application and subsequently maintained in a field laboratory showed a significant reduction in per capita feeding, as indicated by faecal production, as early as 2 days after treatment; this was before any pathogen-induced mortality. This per capita reduction in feeding by infected individuals contributed to a total reduction in feeding of 65% relative to controls. In addition to this laboratory based assessment, experiments were conducted to examine the effects of infection on mortality, feeding and fecundity in the field. Mortality rates of infected individuals in the field were significantly slower than those in the laboratory (average survival time of approximately 39 days compared with 6 days), although total mortality and percentage mycosis were equivalent. Treated individuals showed a significant reduction in body fat accumulation at sexual maturity compared with controls. This may reduce dispersal ability and total reproductive fitness. However, treated individuals exhibited a reduced pre-oviposition period resulting in them laying more eggs than untreated individuals within the first weeks following fledging. Thus, no significant reductions in fecundity were recorded by the end of the assessment period when mortality of treated individuals exceeded 90%. Given that many untreated locusts were still alive and had the potential to continue oviposition for several more weeks, however, it is likely that differences in fecundity would have become apparent if the assessment had continued. These results provide important insights for evaluating overall impacts of spray applications of the mycoinsecticide.     

Infection of the Coffee Berry Borer Hypothenemus hampei (Coleoptera: Scolytidae) by Brazilian Isolates of the Entomopathogenic Fungi Beauveria bassiana and Metarhizium anisopliae (Deuteromycotina: Hyphomycetes)

The virulence of four fungal isolates (three Beauveria bassiana and one Metarhizium anisopliae ) against adult female coffee berry borers (CBB) was investigated. The most virulent isolate from initial bioassays, B. bassiana LPP1, with a LT 50 of 3.4 days, was further investigated by application to berries prior to infestation and to berries already infested with CBB. At the highest concentration applied to berries (1 ×10 7 conidia mL -1 ), CBB mortality was 83% (berries inoculated prior to infestation) and 62% (berries inoculated after infestation).