Population Dynamics of <i>Galerucella birmanica</i> and Its Aggregation Behavior in <i>Brasenia schreberi</i> Aquaculture System

The aquatic macrophyte Brasenia schreberi J. F. Gmel., widely cultivated in China, faces challenges including damage from pests such as Galerucella birmanica Jacoby. This study investigated the population dynamics and spatial distribution of G. birmanica in a B. schreberi aquaculture system from May to November. G. birmanica occurred for several generations, the first population peaked in July, with abundant eggs, larvae, pupae and adults all being recorded. The beetles were nearly absent during the peak summer heat in August, but the population rebounded extraordinary in September, with eggs accounting for 85.4% of the whole population. The distribution of G. birmanica exhibited a conspicuous aggregation phenomenon, with severely chewed area having an average G. birmanica abundance 21.6 times higher than that of the non or lightly chewed area. Further study revealed that there are four special volatile compounds with discrepancy in amount released from intact and damaged leaves, cis-3-hexenyl acetate, 2-phenylethyl isothiocyanate, undecane and methyl salicylate, among these, 2-phenylethyl isothiocyanate was more abundant in damaged leaves and significantly attracted G. birmanica adults, indicating that the damaged B. schreberi leaves may sacrifice themselves by attracting G. birmanica to small regions, thus protect the whole plant population from pest disturbance.