Efeito do silício na resistência de plantas de milho a Rhopalosiphum maidis (Fitch.) (Hemiptera: Aphididae) e sua interação com inseticida no controle de Spodoptera frugiperda (J.E.Smith) (Lepidoptera: Noctuidae)

Abstract

The action of pest insects is one of the factors responsible for the low level of yield of the corn in Brazil, and in this context, the corn aphid and the fall armyworm are considered the main corn pests. The control, chiefly, of the fall armyworm is accomplished almost exclusively by insecticide applications, which can cause, inclusive, damages to the environment. Therefore, one must search control methods which aim to increase the degree of resistance of the plants to the attack by pest insects as the use of silicon. In this way, this research was intended to evaluate the effect of silicon in the induction of resistance of corn plants to the corn aphid as well as its interaction with insecticide lufenuron in the control of fall armyworm. So, both the biological development of the aphid and its feeding behavior were evaluated by utilizing the techniques of "Electrical Penetration Graphs" and of "Honeydew Clock". To evaluate the effects of silicon on the efficiency of the insecticide lufenuron in the control of fall armyworm and on the development of corn plants, laboratory and field experiments were performed, in which the mortality of larvae and their injuries as well as some agronomic characteristics of the plants. The results demonstrated that application of silicic acid did not affect the stylet penetration of the aphid. However, it provided increases in the times of release of the first drop of "honeydew" and of the interval between the drops. The biology of the corn aphid did not affected by silicon. In addition, the results demonstrated that silicon interacted positively with the insecticide lufenuron in the control of fall armyworm, making it possible a reduction in the dosage of the insecticide as well as it strengthened the structure of the corn plant for increasing the stem diameter. However, other trials, mainly in the field, should be performed aiming to evaluate dosages, application methods and operational costs of this alternative technique of pest insect management in corn culture.