Neochetina Bruchi Research Articles

Life Cycle and Biology of Neochetina bruchi1, a Weevil Attacking Waterhyacinth in Argentina, with Notes on N. eichhorniae2, 3

Neochetina bruchi Hustache oviposited in the petioles of waterhyacinth, Eichhornia crassipes (Mart.) Solms, and the eggs hatched in 7.6 days. The larvae tunneled inside the petioles and crown of the plant, and completed their growth in ca. 32 days; they pupated underwater attached to a living root of the floating plant, from which they probably obtained oxygen. Prepuae required 7 days and pupae ca. 23 days for development. Female N. bruchi preferred the older bulbous leaves and N. eichhorniae Warner preferred the young central leaves for oviposition. Maximum feeding and oviposition of both species occurred at 30°C. Adult N. bruchi ate a maximum of 75 mm2 of waterhyacinth leaves/day, and N. eichhorniae ate 86 mm2/day; females ate 2.8 times as much as males. N. bruchi laid a maximum of 8.5 eggs/♀/day, and N. eichhorniae laid 7.3 eggs/♀/day. At cooler temperatures, N. bruchi fed and oviposited slightly more than N. eichhorniae . The intrinsic rate of increase of N. bruchi held at optimum laboratory conditions was calculated to be 0.05675, and generation time was 96 days; the population would double in 12.2 days. Because N. bruchi laid more eggs and its larvae developed faster, it killed waterhyacinth plants in the laboratory sooner than did N. eichorniae .