Efeito de bioinseticidas comerciais utilizados na cultura da cana-de-açúcar sobre o parasitoide Cotesia flavipes (Cameron, 1891) (Hymenoptera: braconidae)

Abstract

Among the pests that can cause injuries to sugar cane, we highlight the most important Diatraea saccharalis (Fabricius, 1794) (Lepidoptera: Crambidae) and Mahanarva fimbriolata (Stål, 1854) (Hemiptera: Cercopidae). Cotesia flavipes (Cameron, 1891) (Hymenoptera: Braconidae) is produced on a commercial scale in laboratories in Brazil and released in plantations of sugar cane showing to be efficient in regulating populations of D. saccharalis. Mahanarva fimbriolata currently can be controlled using the entomopathogenic fungus Metarhizium anisopliae (Metchnikoff, 1879) Sorokin, 1883 (Hypocreales: Clavicipitaceae). So the goal of this research was to evaluate the effect of commercial formulations based on Beauveria bassiana (Balsamo) Vuillemin, 1912 (Hypocreales: Clavicipitaceae) and M. anisopliae on the biological characteristics of the parasitoid C. flavipes. For the development of the first experiment ten females of the parasitoid were exposed in disposable cups with lids, a contact surface of 9 cm2 treated with 1 ml of the suspensions of commercial bioinsecticides Biometha WP Plus®, Biovéria G®, Metarril WP ®, Boverril WP ® e Metiê WP ® in three concentrations 1×109con.mL-1, 5×109con.mL -1 and 10×109con.mL-1. Were used separately two contact surfaces, which are leaves of sugar cane, disinfected with hypochlorite solution (0.02%) and paper filter. The experimental design was randomized comprising, each test consisted of 16 treatments with 5 replications with 10 parasitoid females, totaling 50 females per treatment and mortality was assessed daily after 24, 48, 72, 96 and 120 hours. In general, on the surface of the sheet of sugar cane all the bioinsecticides base M. anisopliae and B. bassiana caused low mortality to adults of C. flavipes after 24 hours application. Only Biometha WP Plus® (M. anisopliae) on the contact surface of filter paper caused higher cumulative mortality than the control in all concentrations tested and Metiê WP® (M. anisopliae) at a concentration of 1×109 con.mL-1 in the evaluation 48 hours after application. For the bioinsecticides based on the fungus B. bassiana at all concentrations were the most effective and did not cause mortality 24 hours after application. Analyzing the treatments that caused low mortalities through a linear regression was observed in both treatments until 72 hours after application occurred mortalities below 30% in adult of C. flavipes, allowing the adult parasitoid survive long enough to perform the parasitism of D. saccharalis, can then be performed releases of this natural enemy in the same area where applications of these biopesticides was used without being reduced efficiency in controlling D. saccharalis. The second xii experiment with the pupae of C. flavipes was composed of the same bioinsecticides in the same concentrations and the control without application of entomopathogens, totaling 16 treatments in a completely randomized design. In the first part of this experiment each treatment was represented by 10 mass of pupae C. flavipes and each repetition with a mass of pupae with potential emergence of 50 adults parasitoid. The biological characteristics evaluated: emergency, progeny, number of males and females, male and female longevity and parasitism. In a second part of this experiment was evaluated adult emergence of C. flavipes from the previously parasitized caterpillars and longevity of males and females (F1 generation). Commercial products Biometha WP Plus® (M. anisopliae) and Boverril WP® (B. bassiana) in the three concentrations had accumulated the highest mortality in the evaluations of 48 and 72 hours after application for both the contact surfaces. There were reductions in longevity of females in treatment Metarril WP® 10×109con mL-1 and longevity of males in treatments Metiê WP® 1×109con.mL-1, Biometha WP Plus® 5×109con.mL-1, Metarril WP®10×109con.mL-1, Biometha WP Plus® 1×109con.mL-1, Metarril WP® 1×109con.mL-1, Metiê WP® 10×109con.mL-1 and Metarril WP® 5×109con.mL-1 for products based on M. anisopliae. In the treatments with products based on B. bassiana the longevity of females and males was lower for Boverril WP® 1×109con. mL-1 and 10×109con.mL-1, but the reduction did not affect the parasitism of females of C. flavipes. Parasitism is the primary relationship between the host and parasitoid. Reporting that entomopathogenic fungi on contact with the pupae of C. flavipes this fact will not influence the control of D. saccharalis may then be feasible using interrelationship of these two forms of biological control in the culture of sugar cane.