Squash bug feeding behavior on watermelon and watermelon relatives

The squash bug, Anasa tristis, is a serious pest of watermelon in the United States and is a vector of cucurbit yellow vine disease (CYVD).  Previous feeding, survival and oviposition studies suggest that the squash bug prefers squash more than watermelon, but no work has been done with non cultivated watermelon relatives. Therefore, we tested yellow squash (cv. Lemon drop), watermelon (cv. Royal sweet) and four non cultivated watermelon relatives for squash bug feeding propensity measured as numbers of feeding tracks per bug. The leaves of the test plants exposed to squash bugs for 24 hours were stained with McBride’s stain and autoclaved to reveal the salivary sheaths.  The sheaths, or feeding tracks, were counted on the leaves of test plants. No choice tests (N=20) revealed that the squash bug left the most feeding tracks (mean) on squash (57.5) followed by Royal Sweet watermelon (7.9), Praecitrullus fistulosus PI 179660 (6.5), USVL 200 (5.8), Citrullus colocynthis PI 386015 (5.0) and C. colocynthis PI 525082 (4.5). This non-preference of the squash bug for the watermelon and its non cultivated relatives may be due to the sap content of the different hosts or to some physical structure of the host plants as these bugs were reared on the squash plants and fruits. The results of this study will be relevant to future screening of watermelon germplasm for resistance to squash bugs and to CYVD.