A guide to the use of the exuding-stylet technique in phloem physiology

The use of exuding stylets holds considerable promise for the investigation of sieve-tube physiology. However, largely because of difficulties in cutting insect stylets, the technique has been applied to only a few plant species. Based on our experience, a comparison is made of the available means of obtaining sieve-tube exudate from the exuding stylets of phloem-feeding insects, including aphids, scale and mealybugs. Forty-one plant species and approx. 35 insect species were tested for their ability to provide stylet exudate. Stylets on all but a few of the plant species tested yielded at least some exudate, but the success rate and duration of exudation on many species were unsatisfactory for detailed investigations of phloem transport. Plant species appears to be the most important factor for obtaining reliably exuding stylets, although the size of the insect species used and the physiological condition of the plant are also important variables. Armored scale provide a simple and reliable source of exuding stylets, but are impractical for most experimental purposes. Radio-frequency microcautery of aphid stylets was substantially the most effective means of cutting stylets. Instructions are provided for constructing a microcautery unit at minimal expense, using a citizen's band radio as the radio-frequency source.