Novel methodologies to asses feeding cessation of hemipteran vectors of plant diseases when exposed to insecticide treated plants

Some hemipteran species are extremely economically important pest in multiple crops around the world because of the direct damage they produce on plants and also because they vector plant diseases that can result in complete crop losses. Growers in many places rely on the use of insecticides to reduce populations of these insects. However, insecticides may take a few days to cause insect mortality and some do not reduce feeding. Reducing feeding of whiteflies, aphids and psyllids would decrease the physiological effects on plants as well as the sooty mold and potentially the transmission of viruses and bacteria. Measuring the reduction in feeding after the exposure of hemipteran vector species to an insecticide has proven difficult. A novel technique was developed to assess the effect of insecticides in the feeding of these hemipteran species. A series of laboratory experiments demonstrate the usefulness of fluorescence in determining Bemisia tabaci, Myzus persicae, Aphis gossypii, and Diaphorina citri feeding cessation. Fluorescein sodium salt is systemically absorbed by plants and also by the insects feeding on these plants. Insects start fluorescing shortly after the plant root system is submerged in the fluorescein sodium salt. The effect of several insecticides with different modes of action on the reduction in feeding of these hemipteran insects was evaluated and compared using this novel technique. It was determined that all these hemipteran insect vectors feeding on a plant treated with Cyazypyr™ presented a significant reduction of feeding when compared to insects feeding on plants treated with all other standard insecticides. The technique may prove useful to demonstrate the reduction of feeding of other insects such as several species of thrips.