Effect of bioinsecticides on the grey maize weevil Tanymecus dilaticollis

Abstract

Tanymecus dilaticollis is an important pest of maize and sunflowers in eastern Europe. In the present study, we examined the effectiveness of two commercially available bioinsecticides against T. dilaticollis adults under laboratory conditions: Naturalis<sup>®</sup> based on the Beauveria bassiana fungus and an azadirachtin-based botanical product NeemAzal T/S<sup>®</sup>. Our results suggested that adults of the pests are more susceptible to B. bassiana than to azadirachtin. Naturalis<sup>®</sup>, tested at six concentrations (2.3 × 10<sup>2 </sup>– 2.3 × 10<sup>7</sup> conidia/mL), showed a high lethal effect to T. dilaticollis adults, and 100% corrected mortality was observed in the treatments over 2.3 × 10<sup>5</sup> conidia/mL and 2.3 × 10<sup>6</sup> conidia/mL for females and males, respectively. NeemAzal T/S<sup>®</sup>, tested at four concentrations (0.5, 1, 2 and 4%) with two treatments, caused generally low to moderate mortality – 6–44% within 16 days. A field experiment consisted of two sprayings of maize experimental plots with Naturalis<sup>®</sup> at a rate of 200 mL/0.1 ha and then the recording the number of dead adults of T. dilaticollis in the treated and control plots was conducted in north-western Bulgaria. Twenty days after treatment, a significantly higher mean mortality of the pest caused by the mycoinsecticide than in the control variants was registered.

Effect of Beauveria bassiana (strain ATCC 74040) on two leaf beetle pests of maize under laboratory conditions

“…Recently, crataegi Germar 1824, but it was significantly higher than the mortality in the control variant (sterile water) after 28 days post treatment (Hirsch and Reineke, 2014). Toshova et al (2021) reported high (˃ 86%) lethal effect of Naturalis® at concentrations above 2.3 × 10 4 conidia/ ml on T. dilaticollis adults under laboratory conditions. Naturalis® have been showed to be effective in field/ semifiled conditions against several coleopteran pests (Paparatti and Speranza, 2005;Ladurner et al, 2009;Hirsch and Reineke, 2014;Sufyan et al, 2017;Toshova et al, 2021).…”

“…Laboratory assessment of entomopathogenic fungi is an important step in determining pathogenic strain prior to use in the field for insect pest control. The insecticide activity of B. bassiana strain ATCC 74040 on other important pest of maize in Eastern Europe, the grey maize weevil, Tanymecus dilaticollis Gyllenhal, 1834 (Curculionidae), have been demonstrated under laboratory and field conditions (Toshova et al, 2021). The present study aimed to investigate the effectiveness of Naturalis® against WCR adults and larvae and adults of CLB under laboratory conditions.…”