Food consumption of Rhammatocerus schistocercoides Rehn (Orthoptera: Acrididae) infected by the fungus Metarhizium flavoviride Gams & Rozsypal

Abstract

Foliage consumption by nymphs and adults of the grasshopper Rhammatocerus schistocercoides Rehn infected with the fungus Metarhizium flavoviride Gams & Rozsypal was evaluated. Sixth and eighth instar nymphs and female adults consumed on average (±SEM) 6.9 ± 0.36 cm² (60.7 ± 2.92 mg of dry matter), 11.0 ± 1.35 cm² (74.9 ± 9.24 mg d.m.), and 16.0 ± 0.50 cm² (126.5 ± 6.35 mg d.m.) of sugarcane leaves per day, equivalent to 85.4, 35.9 and 41.9% of the insect body weights, respectively. Eighth instar nymphs and female adults inoculated with M. flavoviride (5,000 conidia / insect) ingested less food from day three onward and showed at day 10 an average consumption 74.5 and 45.6% lower than control insects, respectively. Adult females topically treated with a sub-lethal dosage (3 ml of a 8 ppm suspension / insect) of the chemical insecticide diflubenzuron showed consumption rates comparable to untreated insects (P=0.065). The combination fungus + chemical did not show results different from those obtained with the fungus alone (P=0.405). A strong correlation (r²=0.998) between production of fecal pellets by R. schistocercoides and food consumption was observed. These results confirmed the high voracity of R. schistocercoides and showed a remarkable adverse effect of the fungus on food intake by infected nymphs and adults.

Susceptibility of three orthopteran species to infection by Metarhizium acridum (Hypocreales: Clavicipitaceae)

“…Although our results confirmed the susceptibility of all three orthopteran species to M. acridum, differences on the susceptibility level among these species are difficult to determine, due to methodological variation. Despite the voracity of these species and the absence of the 'knock down' effect of the fungus, we observed that insects are affected by infection and their feeding and mobility behaviour differed from healthy insects, as also reported in previous studies (Faria et al, 1999;Magalhães et al, 2001). The consumption of plant leaves by the infected groups before death was less than observed in the control groups.…”

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

“…A strong correlation (r 2 = 0.998) between production of fecal pellets by R. schistocercoides and food consumption was observed. These results confirmed the high voracity of R. schistocercoides and then showed a remarkable adverse effect of the fungus on food intake by infected nymphs and adults (Faria et al 1999). Leaf consumption for S. robusta was highly affected by M. anisopliae var.…”

BIZARRE INTERACTIONS AND ENDGAMES: Entomopathogenic Fungi and Their Arthropod Hosts

“…These studies show that although insects killed by entomopathogenic fungi often take longer to die than if treated with chemical pesticides, damage to crops is decreased during the disease incubation period because infected insects eat less than healthy ones. Studies evaluating food consumption and infection have focused on phytophagous hosts, including lepidopteran larvae (33, 35, 37, 99), acridids (1, 15,101), and coleopterans (20,26). Most studies investigating insect species infected with the hypocrealean fungi, Metarhizium sp.…”