Resistance mechanisms of sugarcane cultivars to spittlebug Mahanarva fimbriolata

Abstract

The spittlebug Mahanarva fimbriolata (Stål) (Hemiptera: Cercopidae) is one of the most important pests of sugarcane in Brazil. Measures for population control are currently restricted to the use of chemical insecticides and fungus Metarhizium anisopliae, in part because very little information exists regarding resistance of sugarcane cultivars. Therefore, the aim of this study was to evaluate resistance mechanisms of 12 different sugarcane cultivars to M. fimbriolata to provide information for growers for pest management. Isolated buds of each cultivar were planted in pots and kept in a greenhouse for approximately three months. The pots were then moved to climate test chambers (26 ± 1 ºC; 70 ± 10 % relative humidity; 12 h photoperiod) to carry out laboratory tests to evaluate adult feeding and female oviposition preferences (using both free-choice and no-choice tests) as well as the effects of cultivars on nymph development and cultivars tolerance to pest attack. The least attractive cultivars for adult feeding were

Resistance of sugarcane cultivars to Mahanarva fimbriolata

“…Conversely, RB855536 and RB92579 were among the most highly favored cultivars for both feeding and shelter, which was also true for oviposition. Similar results were obtained by Dinardo-Miranda et al (2016), who worked 2.8 ± 1.7 ab 2.3 ± 0.5 abcd 2.8 ± 0.9 abcd 2.3 ± 0.9 abc 2.6 ± 0.1 bcd RB966928 3.3 ± 1.3 ab 2.3 ± 0.6 abcd 3.3 ± 0.6 ab 1.8 ± 0.8 abc 2.7 ± 0.4 bcd SP81-3250 2.3 ± 0.6 ab 3.5 ± 0.9 ab 3.3 ± 0.6 abc 1.5 ± 1.0 abc 2.7 ± 0.5 bcd CTC 20 3.5 ± 1.3 a 2.8 ± 1.0 abc 3.3 ± 0.5 ab 3.3 ± 0.9 ab 3.2 ± 0.1 abc with 12 sugarcane cultivars and M. fimbriolata, and also observed that adult M. fimbriolata feed and shelter more frequently in the cultivars that they prefer for egg laying. A correlation between adult attractiveness and oviposition preference has also been observed in others insect species, such Bemisia tabaci (Genn.)…”

“…Similar results were reached by Garcia et al (2011), who reported a lack of significant differences in egg viability when M. fimbriolata nymphs and females were maintained on different sugarcane cultivars and by Dinardo-Miranda et al (2016), who kept adults to feed, shelter and lay eggs on 12 sugarcane cultivars. The mean viability varied from 65.5 (SP80-1842) to 78.2% (CTC4).…”

“…Cultivars SP80-1842 and SP81-3250, which were used as a standard for susceptibility, were less attractive to adults than RB855536, but they were some of the most attractive cultivars, differing from RB867515 and others cultivars (Table 1). Dinardo-Miranda et al (2016) have already reported differences among sugarcane cultivars in relation to the attractiveness to adult spittlebugs, in experiment carried out with 12 genotypes.…”

“…For the tolerance studies, 5-L pots were used. All pots were filled with a mixture of clay soil and agricultural substrate (1:1) and treated with a slow-release fertilizer (14-14-14, NPK; 200 g/25 kg soil + substrate), as described by Dinardo-Miranda et al (2016).…”

“…The equation MR = NC1/NC0 was used, where NC1 = the number of couples in generation 1; NC0 = the number of couples in the initial generation (5); and NC1 = NE (EV/100) (NS/100) 0.5 (Dinardo- Miranda et al 2016). Since the nymphal stage duration could be affected by the host cultivar, the standardized multiplication rate (MRst) was estimated, considering the nymphal stage duration on the considered cultivar (NSDc) and on the longest stage duration observed (NSDl), according the equation MRst = MR (NSDl)/NSDc.…”