Abstract
ABSTRACT The effect of a crude extract of Annona crassiflora was evaluated on larvae of the soybean looper, Chrysodeixis includens (Lepidoptera: Noctuidae) in different stages of larval development. The extract was prepared with seeds of A. crassiflora fruits collected in the state of Mato Grosso, Brazil. The extract was diluted in water and solubilizer agent at the concentrations of 0.5, 1.0, 2.0, 4.0, and 8.0%; it was tested by ingestion of treated leaves and contact. The mortality rate of topically treated caterpillars of first, third, and fifth instars was significantly higher than that of the control group. For first instar caterpillars, mortality was observed within the first 24 h after application, while, for the remaining instars, it was significant after 72 h. For caterpillars fed treated leaves, no differences in mortality rates were observed within the first 120 h. These caterpillars were monitored until the end of the larval stage, during which mortality rates increased for first and third instar caterpillars. The mortality rate of fifth instar larvae was not significantly different between treatments. The treatment by ingestion was not efficient over a short period of time, but reduced the number of caterpillars that completed their development, decreasing the number of insects in the following generation. We concluded that the crude extract of A. crassiflora affected the development of C. includens and is a promising compound for the control of this pest.
Highlights
The soybean looper, Chrysodeixis (=Pseudoplusia) includens (Walker) (Lepidoptera: Noctuidae), has been reported infesting approximately 70 species of plants, among them soybean, cotton, beans, sunflower, tobacco, passionflower, tomato, and several vegetables (Moscardi et al 2012)
Pest control plans should use techniques and strategies based on the integrated pest management (IPM) that are less harmful to natural enemies and man
Given the few studies on A. crassiflora and its potential presented over other species of insects, this study evaluated the effects of the crude extract of A. crassiflora seeds on larvae of C. includens on 3 instars under laboratory conditions
Summary
The soybean looper, Chrysodeixis (=Pseudoplusia) includens (Walker) (Lepidoptera: Noctuidae), has been reported infesting approximately 70 species of plants, among them soybean, cotton, beans, sunflower, tobacco, passionflower, tomato, and several vegetables (Moscardi et al 2012). Since 2003, C. includens has become the main pest in several states (Bueno et al 2009; Moscardi et al 2012) This increase in the population levels of C. includens may have been caused by the increased use of fungicides required for the control of the Asian soybean rust. This decreased the populations of entomopathogenic fungi, which naturally controlled soybean looper, such as Nomuraea rileyi (Farlow), and resulted in an increase in populations of this pest in many soybean producing states (Sosa-Gómez et al 2003, Sosa-Gómez 2006). Pest control plans should use techniques and strategies based on the integrated pest management (IPM) that are less harmful to natural enemies and man
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