Honeydew as a newly described route of insecticide exposure to beneficial insects

A plethora of beneficial insects need carbohydrates to meet their requirements for daily physical activities and metabolic processes. In agricultural lands, beneficial insects find carbohydrates mainly in nectar and honeydew. Nectar is often scarce in most agroecosystems because it is limited to the brief flowering period of the crop (if present). This sugar can also be available in the spontaneously flowering plants that appear along crop borders, ditches and roadsides, but these plants are often removed to avoid competition with the crop. Instead, honeydew, the excretion product of many hemipteran insects such as aphids, whiteflies, coccids, mealybugs or psyllids, is highly abundant and accessible in agricultural lands throughout the year. For this reason, many beneficial insects rely on honeydew as a main carbohydrate source of their diet, especially when nectar is scarce.The use of systemic insecticides had been considered an excellent option for integrated pest management programs because once applied, they move systemically to all plant tissues, harming herbivores that feed on the plant. Yet, the fact that the insecticides move to all plant tissues, means that they also reach plant-derived food sources such as nectar or pollen. Many insects that feed on these food sources are therefore exposed to several systemic insecticides. The aim of this PhD thesis was to explore whether honeydew, like nectar, is a route of insecticide exposure for beneficial insects. This route of exposure could be more impactful than the route of nectar because honeydew is ubiquitous in agroecosystems.First, I present the newly described route of insecticide exposure to beneficial insects: honeydew excreted by hemipterans feeding on trees treated with some systemic insecticides contains insecticide residues that affect insects feeding on it. This route of exposure was demonstrated for: 1) two different crop species: citrus and soybean plants; 2) three hemipteran species: the citrus meal