Abstract
ABSTRACT: Macrodactylus pumilio Burm. (Coleoptera: Scarabeidae) and Naupactus cervinus (Boh.) (Coleoptera: Curculionidae) are considered primary pests in citrus crops in Brazil, causing damage to plants and decreasing productivity. However, few studies investigate the ecology of these insects. In this context, the use of stable isotopes analysis (SIA) emerges as an alternative technique to conventional studies of behavioral ecology because it is faster and may explain feeding behavior based on the food source for each species. Field sampling and laboratory experiments were carried out to examine the changes of carbon and nitrogen stable isotope ratios (δ13C and δ15N) among pests and host plants (C3 citrus and C4 grasses), providing means to examine trophic interactions. Beetles were collected at the municipality of Gaviao Peixoto, Sao Paulo State, identified and kept at 5 °C in saturated saline solution until the SIA. Two patterns for both species were found: δ13C value for N. cervinus was -23.6 ‰ and -13 ‰ for M. pumilio, indicating similarity between the results of δ13C of N. cervinus and citrus plants (-26 ‰) and dependence on grasses (-12 ‰) for M. pumilio individuals. The mean δ15N value was 4.3 and 5.8 ‰ for citrus plants and grass leaves, respectively, and the mean δ15N value was 4.4 ‰ for N. cervinus and 4.9 ‰ for M. pumilio. The results showed a higher affinity of N. cervinus for citrus roots since the larval stage compared with the alternative diet on M. pumilio.
Highlights
Brazilian citrus crop face several phytosanitary problems, despite being one of the most important agricultural activities in the country
The results showed a higher affinity of N. cervinus for citrus roots since the larval stage compared with the alternative diet on M. pumilio
Comparisons showed similarity between the results of δ13C of N. cervinus and citrus plants ( F 0.95 1,53 = 0.01158; p = 0.91471). Both were different of M. pumilio and grasses δ13C values, which were different from each other (Table 1)
Summary
Brazilian citrus crop face several phytosanitary problems, despite being one of the most important agricultural activities in the country. Some phytosanitary issues refer to the occurrence of Macrodactylus pumilio Burm., 1855 (Coleoptera: Scarabeidae) and Naupactus cervinus (Boh., 1840) (Coleoptera: Curculionidae), which are beetles considered primary pests in citrus orchards that cause direct and indirect damage to plants (Guedes and Parra, 2004; Guedes et al, 2005; Lanteri et al, 2002). The knowledge of the behavior and life cycles of these species are necessary for their rational and economic management. Both adult and larval stages of these species are polyphagous and have been recorded feeding on a wide variety of cultivated plants and weeds (Chadwick, 1965; Lanteri et al, 2002; Masaki and Kadoi, 1997). Brazilian entomologists have investigated the influence of such scenario on the feeding behavior of both species
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