REDUCED NET PHOTOSYNTHESIS OF LEAVES FROM MATURE PECAN TREES BY THREE SPECIES OF PECAN APHID

Pecan, Carya illinoensis (Wang.) K. Koch, foliage from 60-year-old ‘Stuart’ trees infested by phloem feeding pecan aphids experienced a reduction in net photosynthesis (Pn) as the population density of Monellia caryella (Fitch), Monelliopsis pecanis Bissell, or Mellanocallis caryaefoliae (Davis) increased. The increase was curvilinear for M. caryella and M. pecanis, but linear for M. caryaefoliae.The degree of reduction by an individual aphid was similar for M. caryella and M. pecanis, but M. caryaefoliae was far more detrimental. When the densities of the three aphid species are within the currently recommended spray threshold levels, there is very little adverse influence on Pn.