Impact of Host Plant Connectivity, Crop Border and Patch Size on Adult Colorado Potato Beetle Retention

Abstract

Tagged Colorado potato beetles (CPB), Leptinotarsa decemlineata (Say), were released on potato plants, Solanum tuberosum L., and tracked using a portable harmonic radar system to determine the impact of host plant spatial distribution on the tendency of the pest to remain on the colonized host plant or patch. Results confirmed the long residency time on the host plant and showed that close connection of the plant to neighboring plants hastened dispersal between plants. Tracking walking CPB for over 6 h in small potato plots revealed that all types of mixed borders tested (potato/bare ground, potato/timothy and potato/woodland) acted as a strong barrier and retained beetles within the patch. In another experiment in potato patches surrounded by bare ground borders, tracked walking CPB displayed similar behaviour for up to four days. The distribution of turning angles in the CPB walking paths was not uniform and corresponded to beetles following the edge rows of potato patches in response to the crop border barrier or reversing their direction as they reached the end of a row and therefore a border. Patch size had no or little effect on beetle retention in the patch. The relative distribution of counts of tagged beetles detected among small (16 m2), medium (64 m2) and large size (256 m2) patches of potato four days after initial release remained similar to that of numbers released. Even though mixed crop borders were a strong barrier to walking CPB emigrating from potato patches, the departure rate of beetles over time was high. Results suggest that the effect of mixed borders is largely limited to dispersal by walking and does not apply to beetles leaving host patches by flight. The manipulation of crop borders and patch size seem to have limited potential for the management of CPB emigrating from potato fields.

Contribution of habitat type to residency and dispersal choices by overwintered and summer adult Colorado potato beetles

“…Significantly more CPB will fly off a host plant at bloom than from a vegetative potato plant (Mbungu & Boiteau, ). In a host crop, factors such as plant connectivity and mixed border barriers act together to reduce the level of emigration from the crop by walking beetle but have no limiting impact on dispersal by flight (Boiteau et al., ). On the host plant, the CPB is also confronted to a trade‐off between consuming large meals and capacity (wing loading) for flight (MacQuarrie et al., ).…”

“…Alternatively, dispersal level may be similar between host and non-host habitats but the number of CPB dispersing by flight over that by walking (dispersal mode) could differ. Emigration from potato by flight may have been underestimated because flight is difficult to monitor (MacQuarrie & Boiteau, 2003;Boiteau et al, 2014). Also, mixed vegetation crop borders act as temporary barriers to walking CPB but not to flight (Boiteau et al, 2014).…”

“…Emigration from potato by flight may have been underestimated because flight is difficult to monitor (MacQuarrie & Boiteau, 2003;Boiteau et al, 2014). Also, mixed vegetation crop borders act as temporary barriers to walking CPB but not to flight (Boiteau et al, 2014). The relative likelihood of CPB flying from crop, vegetation, or bare ground has not been established as such.…”