Suitability of Brassica juncea (Brassicaceae) as a host plant for oviposition for Lygus lineolaris (Palisot de Beauvois) (Heteroptera: Miridae)

Abstract

Suitability of Brassica juncea (Brassicaceae) as a host plant for oviposition for Lygus lineolaris (Palisot de Beauvois) (Heteroptera: Miridae). Can. J. Plant Sci. 78: 139-143. The suitability of Brassica juncea (L.) Czern as a host plant for oviposition for Lygus lineolaris (Palisot de Beauvois) was measured by comparing egg laying on five experimental lines or cultivars of this species with that on B. napus L. (cv. AC Excel, a suitable host) in no-choice or choice tests during a 14-d period in the greenhouse and field. Egg laying was measured indirectly by counting newly hatched nymphs emerging from the plants. The numbers of nymphs emerging from B. juncea (cv. Cutlass) and four experimental lines of B. juncea were about two to ten times lower than from B. napus, indicating that L. lineolaris females lay fewer than half as many eggs on the former species than on the latter species and that B. juncea as a species is a poor host plant for oviposition. The inflorescence was the preferred region of the plant for oviposition on B. napus but not on B. juncea. The numbers of nymphs emerging from the inflorescence of B. juncea (cv. Cutlass) were 8.4 times lower than from the inflorescence of B. napus, indicating that the differences in oviposition on these species were due to the presence of an antixenosis-type of plant resistance factor(s) in the inflorescence of B. juncea. (Schwartz and Foottit 1992;Timlick et al. 1993;Gerber and Wise 1995;Turnock et al. 1995). Crop resistance, based on oviposition non-preferences (antixenosis) of Lygus bugs on species of Brassica and Sinapis, is of interest because this crop protection strategy might prove important in population suppression of these pest insects and in reduction of damaged seeds and yield loss. In preliminary tests evaluating oviposition preferences of L. lineolaris on six species of Brassica and Sinapis, Gerber (1997) found that among the Brassica, B. napus was the most preferred host plant for oviposition and B. juncea was the least preferred. About 4.1 times more eggs were laid on B. napus than on B. juncea. The objective of this research was to examine further the suitability of B. juncea as a host plant for oviposition for L. lineolaris. MATERIALS AND METHODS InsectsThe insects used in all greenhouse and field studies were adults of L. lineolaris. In the greenhouse studies, adults (usually < 1 wk old) were taken from a laboratory colony maintained at the Cereal Research Centre, Winnipeg, for several generations on fresh potato sprouts (Solanum tuberosum L.) and green beans (Phaseolus vulgaris L.) in environmental chambers at 22 ± 0.5°C, 70% RH, and a 16 L:8 D photoperiod. In the 1995 field studies, they were either overwintered adults collected on 1 June on stinkweed (Thlaspi arvense L.), or first-generation adults collected on 10 July on alfalfa (Medicago sativa L.) near Winnipeg. In the 1996 tests, they were either overwintered adults collect-