Using Amaranthus palmeri pollen to mark captured tarnished plant bugs

Abstract

Wild host plants play an important role for tarnished plant bug (TPB) Lygus lineolaris, populations when cultivated crops are not flowering. Determining dispersal into/out of cropping systems and native habitats is important for managing this insect pest. Mark and capture techniques, ‘novel proteins’ or dyes to determine insect dispersal are time consuming, costly and can cause problems to insects and people. Pollen analysis of insects is easy and marking them with pollen does not injure insects or people. Although pollen has been used to determine dispersal and food sources of many insects, it has not been used for TPB. As a preliminary study, we wanted to test if pollen could be used as a marker and to determine TPB dispersal and food. Adult TPB were allowed to feed on Amaranthus palmeri flowers for 72 hours, then sacrificed at 0, 1, 3, 6, 12, 24 and 96 hours. Rinsing the insects three times with 95% ethyl alcohol prior to acetolysis removed 99% of the external pollen. There was a significant reduction in the number of pollen grains found in acetolyzed adults from the 0 to 96 hour time interval. At 0, 1 and 3 hours, 100% of the TPB contained pollen and at 96 hours, 55% contained pollen. Overall, 89% of the TPB examined contained pollen. Insects examined at 0 hours contained the greatest number of pollen grains (757) and those at 96 hours contained the least (26). If a TPB contained more than 10 A. palmeri pollen grains, there is a high probability that this individual fed within 12 hours. Amaranthus palmeri pollen worked well as a natural marker. Determining the pollen retention of various wild hosts in the gut helps in the management of this insect pest because it gives entomologists a time frame and a way to ‘track’ these insect pests.