Aphid plant interactions: a review.

Aphids are economically important insect pests of agriculture and forest crops. They feed on phloem sap by extremely efficient mouthparts modified into long and flexible stylets. Adaptation to phytophagy is completed by an extremely ductile reproduction system that can alternate biparental and parthenogenetic generations. In order to reach plant phloem, aphids must overcome plant defences, either physically and/or chemically. However, plants respond to aphid attack by activating defence genes that lead to the production of physical barriers and/or chemical toxic compounds (direct resistance). In addition, attacked plants can attract the natural enemies of aphids by releasing specific volatile compounds (indirect resistance). We can take advantage of these different types of resistance in order to enhance the sustainable control of these phytophagous insects. In this review we summarize the main aspects of plant-aphid interactions, focusing on those issues that can have an economic application.