Population Dynamics of Two Species of Greenidea (Hemiptera: Aphididae) and Their Natural Enemies on Psidium guajava (Myrtaceae) and Ficus benjamina (Moraceae) in Central Mexico

Greenidea psiidi van der Goot and Greenidea ficicola Takahashi (Hemiptera: Aphididae), are Asiatic species that feed on guava, Psidium guajava and Ficus spp.; both of these aphids were reported as exotic pests in Florida in 2002 and in Mexico in 2003. The present study characterized the population dynamics of both aphid species and their natural enemies on guava and ornamental figs in the Bajio region of Central Mexico. This report represents the first record of G. psiidi on Ficus sp. in Mexico and the first report of the presence of both species in the state of Guanajuato. Greenidea psiidi and G. ficicola were detected on guava in Mar 2007 and on fig trees during the same year in Apr near Irapauto, Guanajuato. Populations of both alate and apterous forms of G. psiidi in Apr were greater on guava than on fig trees (W = 119.0; P = 0.0122), which coincided with new vegetative growth after leaf loss in winter on guava. In Apr populations of apterous forms of both species were significantly greater than winged forms on both guava and figs. No correlation was found between temperature changes and population densities of aphids. The indigenous predators, Chrysoperla comanche Banks, Chrysoperla exotera (Navás) and Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae), fed readily on the aphids and were found on both guava and fig trees, although densities of all 3 species were in greater numbers on Ficus. The combined population densities of the 3 predators had a positive correlation with that of G. ficicola (r = 0.74), with a best fit found with a quadratic model of simple regression: y (densities of Chrysoperla spp.) = 1.2479x2 4.3073x + 9.6493, and R2= 0.703. Nine species of coccinelid beetles (Coleoptera: Coccinellidae) were identified, the most common being of the genus Scymnus. Results suggest that non-deciduous ornamental fig trees may serve as reservoirs of beneficial insects for deciduous guava trees. Results from the present study provide basic biological data to aid in management of these 2 exotic species of Greenidea on guava in central Mexico.