Egg Adhesion of the Codling Moth <i>Cydia pomonella</i> L. (Lepidoptera, Tortricidae) to Synthetic Substrates

ABSTRACT Previous studies on Cydia pomonella eggs have demonstrated reliable egg adhesion to the leaves and fruits of various apple cultivars. In contrast to biological substrates, this study is focused on standardised synthetic substrates to measure egg pull‐off forces and determine adhesive strength, allowing for an unbiased comparison with other, previously studied, organisms. Analyses using various microscopy techniques and white light interferometry at the interface between egg adhesive secretion and substrate helped to interpret the data. The results showed that codling moth eggs adhered more strongly to smooth, high‐surface‐energy substrates (such as hydrophilic glass) compared to low‐surface‐energy ones, achieving adhesive strengths of 138 kPa on hydrophilic surfaces and 22 kPa on hydrophobic ones. Correspondingly, the surface wetting by the adhesive egg secretion and egg contact area were both larger on hydrophilic than on hydrophobic glass, measuring 1.8 and 1.4 mm 2 , respectively. The adhesive layer was found to be remarkably thin, measuring only 10 nm on hydrophilic glass and 153 nm on hydrophobic glass. Egg adhesion to hydrophobic glass aligns with the conditions found on the waxy surfaces of apple host plants, although mechanical interlocking can be ignored on the smooth glass. The pull‐off forces required to detach eggs from substrates corresponded to 313,053 times the egg weight on hydrophobic glass and 2,442,220 times the egg weight on hydrophilic glass. We suggest that in an ecological context, the optimal egg adhesion, which can resist environmental impacts, is more crucial than the maximum bond strength. The consistency, surface wetting, speed of the hardening process, and adhesive potential of the egg secretion may inspire further developments in codling moth control and the synthesis of biomimetic adhesives.