Increased probing activities of green peach aphid (GPA), Myzus persicae, on chitosan-treated caisim (Brassica juncea) monitored by electrical penetration graph (EPG)

Green peach aphid (GPA), Myzus persicae, is a major pest of most horticulture crops. Chitosan-based pest management emerges as an alternative to pesticides due to its biocompatibility and biodegradability properties. Population growth and electrical penetration graph (EPG)-based feeding behavior studies were conducted to assess the effect of chitosan application on caisim against GPA at three concentrations (0.1%, 0.5%, and 1%) including two controls of water and acetic acid. Evident GPA population growth reduction was observed in the chitosan-treated caisim. The effect of chitosan was further monitored by 10 h of EPG recording, which revealed a significant increase in probing activities due to frequent stylet withdrawal that generated high levels of short probing activities. Additionally, inter- and intracellular stylet punctures (waveform C and potential drop-Pd, respectively) displayed a significant increase. However, once the stylet reached the phloem tissue, GPA under chitosan treatment and water control can access the phloem tissue equally, either in terms of the number and duration. Therefore, we suggest that the reduced population growth due to chitosan treatment was related to extra energy consumption during frequent stylet withdrawal and intracellular puncture. This finding indicates the role of chitosan as a plant defense elicitor. However, further investigation regarding this topic is required.