Is the common sowthistle (Sonchus oleraceus) a primary host plant of the cotton bollworm, Helicoverpa armigera (Lep., Noctuidae)? Oviposition and larval performance

Abstract

Helicoverpa armigera (Hübner) is a polyphagous pest that has a relatively strong affinity in the field for the European weed Sonchus oleraceus L. in parts of Australia. The oviposition preference of H. armigera was examined in relation to sowthistle and some crop hosts on which it is a pest. In a group test with simultaneous exposure of moths to common sowthistle, maize, sorghum and two cotton cultivars, H. armigera females consistently showed strongest affinities for common sowthistle, irrespective of moth age or the original host of the test insects in the field. Females (n = 20) exposed individually to a choice between common sothistle and cotton, varied substantially in preference. Among the females tested, 67% showed a stronger affinity for common sowthistle, about 5% preferred cotton and 28% did not discriminate. Common sowthistle was also the most preferred by newly hatched larvae among the five host plant types presented in a multiple choice test. Larvae fed on common sowthistle flowers had a higher survival rate and body weight than those fed on cotton flowers. These results and previous field observations suggest that S. oleraceus may be a primary host plant (or one of the primary host species) to which H. armigera became adapted at the time of speciation.