## 1 Introduction  
Rice is the main staple food for over 50% of the world's population and is mainly produced in Asia [1]. Much of that production occurs in intensified lowland agroecosystems [1; 2]. Pressures to increase rice production to feed Asia's growing population have led to further intensification through the expansion of rice production into previously natural areas, the adoption of high-yielding rice varieties, a high use of chemical fertilizers, and an increase in the frequency of pesticide applications [3]. However, high fertilizer inputs increase the susceptibility of rice to several insect herbivores, and particularly to phloem-feeding herbivores [4; 5; 6]. Furthermore, several studies have associated insecticides with increases in the frequency of planthopper and leafhopper outbreaks across Asia [7; 8; 9; 10; 11; 12], with insecticide-related mortality of natural enemies representing a major mechanism underlying these outbreaks [9; 13; 14; 15; 16]. Sustainable pest management strategies that maintain or enhance natural enemy abundance and activities, particularly under a high use of inorganic fertilizers, are therefore required for intensified rice production systems. Recent public research has focused on two main strategies for planthopper and leafhopper management. Firstly, research into the development of planthopper- and leafhopper-resistant rice varieties has begun to use novel molecular tools to search for and incorporate resistance genes from traditional varieties and wild rice species into modern, high-yielding rice varieties [17]. To date, over 60 genes for resistance to rice planthoppers and over 20 genes for resistance to leafhoppers have been identified. A large number of rice varieties with resistance have been tested, or released to farmers [18; 19]. Secondly, because insecticides were associated with a decline in regulation services provided by the natural enemies of rice herbivores, research into conservation biological control has gained traction in several Asian countries [20; 21; 22; 23; 24]. In particular, researchers have investigated possibilities to incorporate functional plants into rice ecosystems to augment natural enemy abundance and diversity and to improve natural enemy efficacy in regulating key rice herbivores. Research from China, Vietnam, Thailand, the Philippines, Bangladesh and Cambodia has indicated that, by planting flowering crops on rice levees (also known as bunds), the abundance and diversity of natural enemies can be increased [20; 21; 22; 23; 24; 25]. For example, nectar produced by bund flowers is thought to sustain the free-living stages of egg parasitoids [26]. Despite recognizing the importance of supplementary foods for natural enemies, little is known about the effects of honeydew on parasitism in rice ecosystems. Planthoppers and leafhoppers produce honeydew as a waste during feeding. Honeydew is excreted through the anus and often coats the host plant surface close to feeding locations (i.e., mainly around the stem base when rice is attacked by planthoppers) [27]. The composition of honeydew is strongly influenced by the rice variety on which planthoppers or leafhoppers feed, and particularly on whether the variety is resistant or susceptible to planthoppers [28; 29; 30]. For example, honeydew produced from planthoppers feeding on susceptible rice is mainly derived from phloem feeding, whereas planthoppers on resistant rice often produce honeydew that is predominantly derived from xylem feeding and is, therefore, likely to contain fewer nutrients [30]. Furthermore, honeydew composition is affected by crop fertilizer levels; for example, planthoppers feeding on rice grown in high-nutrient soils increase their phloem-based feeding (compared to xylem-based) and produce larger quantities of honeydew [31].