A General Classification of Available Small Seeded Legumes as Hosts for Three Aphids of the “Yellow Clover Aphid Complex”12

Abstract

The inter-relationships of over 70 small seeded legumes with the spotted alfalfa aphid (currently known as Therioaphis maculata (Buckton) or Ptero-callidum sp.), yellow clover aphid (Pterocallidum trifolii (Monell), and the sweetclover aphid (Myzocallidium riehmi (Borner) have been studied largely in the greenhouse in cooperation with the Agricultural Research Service U.S.D.A. The sweetclover aphid finds its hosts in the 2 genera, Melilotus and Trigonella; the other 2 species have differing host relationships through-out Medicago, Melilotus, Trifolium, and Trigonella. Species (12) in these genera were immune to resistant to all 3 aphids. Plants of other genera are generally immune to all 3 aphid species. Of the plant species studied about 15 were susceptible to the sweetclover aphid while twice this number were susceptible to each of the other 2 aphids. Alfalfa is not attacked by the yellow clover aphid or the sweetclover aphid; and most plants of sweetclover are not injured by the yellow clover or the spotted alfalfa aphid. Six plant species in Melilotus and Trigonella serve as hosts about equally well for all 3 aphid species. Within most of the plant species studied, individual plants differing in resistance or susceptibility to one or more of the aphid species were evident. At least two-thirds of the hosts of the spotted alfalfa aphid were variable in their aphid reactions. Numerous legume species are reported as hosts of these aphids for the 1st time. Detailed lists are given. The classification given is that of the most susceptible plant tested.