Fluctuation of Piezodorus guildinii (Westwood) (Hemiptera: Pentatomidae) populations in soybean and alfalfa in Paysandú, Uruguay

Abstract

Piezodorus guildinii (Westwood) is a key pest in agricultural-grazing production systems in Uruguay. The objective of this work was to determine the behavior of this species in soybean and alfalfa. Samplings were carried out weekly in the Experimental Station «Dr. Mario A. Cassinoni» (Paysandú) on soybeans (6ha) and alfalfa (5ha). Samples were taken on three border lines of soybean on five sites/line, each one with 2-3 plants, to determine the abundance of egg masses. Fluctuation of nymphs and adults was recorded weekly using a sweep net (100 strokes) in both crops. On soybean the vertical beat sheet was also used (5 times). Population of all developmental stages of P. guildinii peaked at R5-R6 soybean stages (pod-filing). On alfalfa the population of adults peaked at 1/25 (101 adults). P. guildinii adults dispersed from alfalfa to soybean fields when the soybean was in R4 stage. Initial infestations of adults and 1^st and 2^nd instars nymphs were detected earlier with vertical cloth than with sweep net, in soybeans.