Entomopathogenic nematodes in the control of cassava root mealybug Dysmicoccus sp. (Hemiptera: Pseudococcidae)

Abstract

The objective of this work was to evaluate the efficiency of entomopathogenic nematodes in the control of cassava root mealybug Dysmicoccus sp. under laboratory and greenhouse conditions. Cochineals were reared in “Cabotiá” pumpkin in climatic chambers at 27 ± 1 °C, with relative humidity (RH) of 70 ± 10%, and without photoperiod. The selection test was carried out with 15 isolates, and the ones which caused the greater percentage of insect mortality were used in concentration tests (0, 5, 10, 20, 50 Infective Juveniles/cm²), in sand column displacement, in the in vivo production of Galleria mellonella larvae, and in pathogenicity tests in greenhouse. The isolates NEPET11 (Heterorhabditis sp.) and RSC05 (H. amazonensis) showed the greatest virulence to cochineals in the selection trial, with mortality percentages of 93% and 90%, respectively, and did not differ between each other. In the concentration test, the isolate NEPET11 showed the greatest insect mortality in lower concentrations. With regard to the displacement test, both isolates showed 100% insect mortality, with no significant difference. In the G. mellonella larval production trial of NEPET11 and RSC05 isolates, approximately 7.0 x 104 and 7.2 x 104 infective juveniles/g larvae were produced, respectively, with no significant difference between treatments. Tests in greenhouse pots did not produced significant results.

Performance of entomopathogenic nematodes on the mealybug, Dysmicoccus brevipes (Hemiptera: Pseudococcidae) and the compatibility of control agents with nematodes

“…Virulence variability for isolates from different species of nematodes on the same host was expected (Lewis et al, 2006), and has already been reported in the work of Ferreira et al (2015) for D. brevipes and other similar species of mealybugs Alves et al, 2009a;Andaló et al, 2004a;Guide et al, 2016). The factors that may contribute to the difference in interspecific virulence include morphological differences, behavioral habits (foraging strategy), co-evolution with the host insect, as well as the various factors that involve the symbiotic nematode-bacteria complex during the infection process (Alonso et al, 2018;Shapiro-Ilan et al, 2017;Simoes and Rosa, 1996).…”

“…Even in other cultures, the management of these insects is considered unsatisfactory, due to their underground their habits, which impedes control by most natural enemies and agricultural pesticides Heterorhabditis amazonensis and H. indica on D. brevipes: Zart et al (Alves and Moino, 2009;Guide et al, 2016;Souza and Ribeiro, 2003).…”

Pathogenicity and virulence of entomopathogenic nematodes against Dichelops melacanthus Dallas (Hemiptera: Pentatomidae)

“…Other studies, under laboratory and greenhouse conditions, demonstrated the virulence of isolates of genera Steinernema and Heterorhabditis in the coffee root mealybug Dysmicoccus spp. (Hemiptera: Pseudococcidae) (ANDALÓ et al, 2004;ALVES et al, 2009a;GUIDE et al, 2016). These differences can be explained by the specificity of different isolates for different hosts due to several factors, such as its efficiency reaching the host, penetrating and causing infection, and the ability to "trick" the insect's immune system (LEWIS et al, 2006).…”

“…The persistence of entomopathogens in the environment is an important characteristic of biological control programs, and some studies have proven the high persistence of several species of EPNs under field conditions (DEL VALLE et al, 2008;ALVES et al, 2009b;GUIDE et al, 2016).…”

Le manioc, entre culture alimentaire et filière agro-industrielle

“…La présence de poils (pubescence) sur la plante repoussant ou gênant les ravageurs lors de leurs déplacements ou pendant la ponte en est une illustration ; -chimique ou biologique (antibiose), la plante émet des substances chimiques qui repoussent ou intoxiquent le ravageur. (Guide et al, 2016).…”