Evaluación de Formulaciones en Aceites de Beauveria bassiana¹y Metarhizium anisopliae²Contra Chloridea virescens F.³

The objective of this work was to evaluate oil formulations of Beauveria bassiana and Metarhizium anisopliae against larvae of Chloridea virescens, the tobacco budworm that causes significant economic losses to tomato crops in Sinaloa. Each fungal formulation was done at a concentration of 1 × 108 conidia/ml, mixing mineral oil, corn oil, and soybean oil, adding an algal extract and an ultraviolet lightprotective dye as adjuvants. In the laboratory the two fungi formulations in mineral oil HF2-Ma and HF1-Bb killed 93.3 and 96.6% of third-instar larvae with a mean lethal time (LT₅₀) of 3 days, whereas those with corn oil (HF4-Ma y HF3-Bb), and soybean oil (HF6-Ma and HF5-Bb) had mortality of 63.3, 63.3, 50.0, and 53.3% with a LT₅₀of 3.5 days. The formulation with only mineral oil killed 36.6% with LT50 of 4 days, while the check with water had no mortality. This indicated that all formulations had biological activity to kill tobacco budworm larvae, killing most with conidia in mineral oil. The lethal time was shorter with the fungi in mineral oil than in vegetable oil and longer with only mineral oil. The HF2-Ma and HF1-Bb formulations were tested in a greenhouse sprayed at 3.0 × 10⁸conidia/ml over 'Saladette' variety of tomato plants artificially infested with second and third instar larvae, killing 64.5% (HF2-Ma) and 50.5% (HF1-Bb), with LT50 of 4 and 4.5 days. Larvae avoided direct contact with the formulations by moving away from the treated surface. However, 64.5 and 50.5% were killed, which were high compared with only 3.5% in the check. The persistence of conidia on the leaves was 14 days, showing the effectiveness of the formulations to kill larvae in 4 and 4.5 days. These results are considered promising to control C. virescens with the mixture of these fungi in mineral oil and evaluating mortality of younger larvae on tomatoes in the greenhouse.