Improvement of synthetic diet for the aphid Myzus persicae using plant juices, nucleic acids, or trace metals

Abstract

Growth on synthetic diet was markedly, though very variably, improved by the incorporation of various boiled and filtered juices pressed from mustard or lettuce. Optimal effects were obtained when mustard and lettuce juices constituted 2 and 10 per cent, respectively, of the complete diet. At higher concentrations growth was adversely affected, and radish juice at 5 per cent of the diet completely inhibited growth and caused high mortality. Greater and more consistent enhancement of growth was brought about by incorporating crude yeast or sperm nucleic acids at optimal levels of 400 to 600 mg per 100 ml of diet. Since a mixture of nucleotides (adenylic, guanylic, uridylic, and cytidylic acids) failed to substitute for crude nucleic acids, whereas a mixture of iron, zinc, manganese, and copper sequestrenes was a completely adequate replacement, it was concluded that the improvements in growth brought about by both plant juices and nucleic acids resulted from the presence in them of traces of these metals. Requirements for iron, zinc, and manganese were demonstrated individually. Deficiencies of iron or zinc become apparent in the first generation of larval growth, and of manganese, in the second generation. An apparent requirement for copper was demonstrated in one experiment carried through three generations. With the addition of these four metals, synthetic diet is apparently able to support Myzus persicae indefinitely. A culture is now, after 10 months, in its twentieth successive generation, with a stable generation period of about 2 weeks and with adults averaging about 350 μg in weight for the second and subsequent generations.