Energy Drain by Three Pecan Aphid Species (Homoptera: Aphididae) and Their Influence on In-shell Pecan Production

Abstract

An estimate of the energy requirements of the three species of aphids, Monellia caryella (Fitch), Monelliopsis pecanis Bissell, and Melanocallis caryaefoliae (Davis), that feed on pecan, Carya illinoensis (Wangenh.) K. Koch, indicated that during a lifetime, an individual of M. caryella consumes 8.4-fold more energy (301 J) than that of M. pecanis (36.1 J) and ca. 7-fold that of M. caryaefoliae (44.8 J). When expressed as an average-age individual typical of a season-long field population, M. caryella extracts ca. 8-fold more energy than M. pecanis or M. caryaefoliae . Most energy consumed by all three species was excreted as honeydew. Growth efficiency was low for all three species, but was highest for M. caryaefoliae (25%), followed by M. pecanis (19%) and M. caryella (5%). Regression models were derived to estimate the cumulative level of energy consumed by aphids of various ages for growth, respiration, excretion, and total energy removal. Determination of the season-long standing-aphid population (and aphid-days) in two different aphid management programs within a 70-yr-old ‘Stuart’ pecan orchard and influence of these populations on nut yield indicated that all three species are highly detrimental to nut production; extraction of 1 × 106 J, via feeding by M. pecanis or M. caryella , reduced in-shell nut production by 58.7 g per 70-yr-old ‘Stuart’ tree. A season-long standing population of one individual of M. pecanis per leaf of such trees reduced in-shell nut yield by 2.41 kg; 18.13 kg was lost because of the same level of M. caryella .