## 1 Introduction
Honeydew represents a significant nutrient source for the parasitoids of phloem-feeding herbivores, such as aphids, in other cereal systems [32; 33; 34; 35]; however, to our knowledge, the role of honeydew as a food for the parasitoids of rice planthoppers or leafhoppers has not yet been studied. A small number of studies have quantified planthopper egg mortality due to parasitoids in fields with different rice varieties or fertilizer rates [5; 22; 36; 37; 38]. These different field experiments have produced inconsistent results [22; 37; 38] that, to some extent, may be due to the many varieties used in the studies. In particular, the semiochemicals derived from different varieties of rice during herbivore attacks likely vary in their effectiveness as synomones that 'call in' defending parasitoids [37]. However, semiochemical profiles might also change in response to resource availability (i.e., nitrogen, light, and water), often with plants increasing their defenses where conditions are most favorable for growth (i.e., Optimal Defense Hypothesis [39]). These ideas suggests that semiochemicals could be optimally matched with biocontrol agents through plant breeding or nutrient management to increase parasitoid-mediated mortality of insect pests in intensified field crops [40; 41; 42; 43]. Where parasitoids also gain a sugar source by feeding on honeydew, the correct blend of semiochemicals may interact with honeydew quality (i.e., available nutrients, consistency, or related kaironones) to further increase parasitism rates. In the present study, we examine interactions between rice resistance to planthoppers (_Nilaparata lugens_ ([PERSON]) (BPH) and _Sogatella furcifera_ ([PERSON]) (WBPH)) and a leafhopper (_Nephotettix virescens_ Distant (GLH)) and mortality due to egg parasitoids under varying soil nitrogen regimes. We examined whether parasitism of planthopper eggs was greater in fields with high-nitrogen applications as predicted by the Optimal Defense Hypothesis and suggested by evidence of semiochemical lures for egg parasitoids. We also hypothesized that parasitoids would respond to differences in the composition of planthopper honeydew by parasitizing a greater number of eggs in fields of susceptible rice and under higher levels of soil nitrogen (i.e., where honeydew has a higher nutrient content and is less water). Previous studies have indicated that egg parasitoids have increased fitness (e.g., female longevity [26]) after feeding on high-nutrient solutions, such as nectar and honeydew (compared to water), ultimately increasing parasitoid effectiveness as biological control agents [44; 45; 46]. We therefore predicted that higher proportions of planthopper eggs would be parasitized in fields of susceptible rice and under relatively high-nitrogen fertilizer inputs, at least partially in response to honeydew on the plant surface. We tested these predictions by exposing sentinel plants (susceptible and resistant to planthoppers) with planthopper eggs in replicated field plots planted with a highly resistant (IR62) and a susceptible (IR64) rice variety under two levels of nitrogenous fertilizer. We also manipulated honeybee coatings on sentinel plants by adding or removing honeydew, or by transferring honeydew between resistant and susceptible plants. We discuss our results in terms of better integrating host plant resistance into conservation biological control for rice planthoppers in tropical Asia.