Effect of Ear Wounding and Cultural Practices on Abundance of Carpophilus freemani (Coleoptera: Nitidulidae) and Other Microcoleopterans in Maize in Northeastern Mexico

Abstract

Field experiments were conducted from 1993to 1997in northern Tamaulipas, Mexico, to identify the sap beetles and other microcoleopterans attracted to maize ears, and to evaluate their abundance in relationship to growing season (spring or fall), ear wounding (caterpillars, birds, and artificial), crop phenology, cultivar, and aflatoxin contanlination. During the 5-yr study, 14 species of microcoleopterans in 7 families were identified. However, only 3 of these species comprised 97% of the total captures: Carpophilus freemani Dobson (Nitidulidae), Cathartus quadricollis (Guerin- Meneville) (Cucujidae), and Sitophilus zeamais Motschulsky (Curculionidae). G.freemani was by far the predominant species, comprising nearly 90% of all collections regardless of growing season, crop management, or type of ear damage. Sap beetles occurred commonly during both the spring and fall growing seasons. Compared with undamaged ears, microcoleopterans were 2- to 5-fold more abundant in caterpillar-damaged ears, and 5- to 28-fold more abundant in bird-damaged and artificially damaged ears. G.freemani seemed to respond more to ear wounding (5- to 10-fold) than C. quadricollis and S. zeamais (2- to 4-fold). A maximum average density of 57 sap beetles per ear was observed in artificially damaged ears during the spring of 1993. Maximum abundance of microcoleopterans occurred from dough-hard to 25% kernel moisture stages. C. freemani was abundant during all maize reproductive stages, whereas C. quadricolis and S. zeamais were common only when kernels were drying down (15-20% moisture). Number of sap beetles varied significantly among cutivars in both undamaged and damaged ears. Infection by Aspergillus flavus Link:Fr and aflatoxin contamination of maize were enhanced by ear wounding and incidence of sap beetles.