Actividad biológica de aceites vegetales sobre estadios larvales de Spodoptera frugiperda en condiciones de laboratorio y casa de vegetación en el cultivo de maíz

Abstract

Maize is one of the main cereals grown in all regions of Ecuador as part of the food sovereignty and security of the people. In the Ecuadorian coastal region, where corn is produced on large extensions, one of the main problems is the attack of the fall armyworm (Spodoptera frugiperda), which causes damage to the plant from its early days of development. Consequently, applications of chemical insecticides are a frequent activity. The biological activity of vegetable oils was determined in larvae of S. frugiperda under laboratory and greenhouse conditions in corn cultivation, aiming to achieve highly sustainable and profitable agriculture. The research was conducted at the National Department of Plant Protection (DNPV), Portoviejo Experimental Station of the National Institute of Agricultural Research (INIAP). Four concentrations (2.0%, 3.0%, 4.0%, and 5.0%) were studied using two types of vegetable oils (castor [Ricinus communis L., Euphorbiaceae] and physic nut [Jatropha curcas L., Euphorbiaceae]), with a control (water) and a test oil (NEEM-X® - neem 2%), under laboratory and greenhouse conditions. The trials with physic nut and castor oils in the laboratory were conducted separately, using a DCA with six biological replicates and the non-parametric Kruskal-Wallis test (P<0.05). In the laboratory trials, the variables evaluated were leaf consumption, number of live and dead larvae. In the greenhouse trial, visual damage, weight (g), and height (cm) of the plant were evaluated. In the control, greater leaf consumption and higher percentages of S. frugiperda pupae and adults were observed. With the 4% castor treatment, S. frugiperda larvae showed the lowest leaf consumption at 0.6%. Higher larval mortalities were observed with different doses of castor and physic nut extracts. In the survival percentage of pupae and adults, lower values were observed with higuerilla, neem, and physic nut oil treatments at 4% and 5%. It is noteworthy that the treatment with 4% castor extract resulted in the longest larval-adult stage period. In the greenhouse experiment, plants treated with 2% castor oil showed the greatest height (13.6 cm), while control plants (12 cm) and those treated with 3% physic nut (9.6 cm) registered the lowest values. Physic nut and castor extracts showed effectiveness at the different doses used for the control of S. frugiperda larvae.