Evaluation of grasses for resistance to spittlebugs

Abstract

The grasses that had consistently fewer spittlebug nymphs in field plots over a three-year period were Andropogon gayanus Kunth cv. Planaltina, Brachiaria brizantha (Hochst. ex A. Rich.) Stapf cv. Marandu, Panicum maximum Jacq. cv. Colonião and Coloninho, Paspalum guenoarum Archevaleta and Paspalum plicatulum Michx. When given a choice, the spittlebug nymphs preferred plants of Brachiaria sp. over those of A. gayanus cv. Planaltina and P. plicatulum. Studies conducted in a screenhouse showed that grasses with high levels of antibiosis were B. brizentha cv. Marandu, P. maximum cv. Colonião, P. guenoarum and P. plicatulum; the grass A. gayanus cv. Planaltina was intermediate in this respect. Grasses A. gayanus cv. Planaltina, B. brizantha cv. Marandu, Brachiaria humidicola (Rendle) Schweickt cv. IRI 409, P. guenoarum and P. plicatulum showed good levels of tolerance. Grasses were evaluated for the feeding and ovipositional preference also. Three grasses, namely, Brachiaria decumbens Staf cv. Basilisk, Bachiaria ruziziensis Germain & Evrard, and Cenchrus ciliaris L. did not show any mechanisms of resistance. These three grasses and B. humidicola cv. IRI 409 favored spittlebug multiplication. Generally, the degree of resistance of a given grass species was the same for different spittlebug species.