Abstract
ABSTRACT Callosobruchus maculatus, commonly known as cowpea weevil, is the main pest affecting stored cowpea Vigna unguiculata. The damage resulting from the penetration and feeding of cowpea weevil larvae within the grains or seeds of V. unguiculata leads to weight loss, reduction of germination power and nutritional value and commercial depreciation of this plant. The objective of this work was to evaluate the insecticidal activity and repellency of vegetable oils extracted from fennel, citronella, neem and 'moringa' against C. maculatus adults. To evaluate the insecticidal activity, we placed 20 adult insects in plastic containers lined with filter paper impregnated with different doses (0.0 x 106, 5.0 x 106, 1.0 x 105, 1.5 x 105, 2.0 x 105, 3.05, 4.0 x 105 and 5.0 x 105 L) of each vegetable oil. The number of insects was analyzed 24 hours later. To evaluate the repellency activity, we used an arena formed by five circular plastic containers with the central container interconnected symmetrically to the others by plastic tubes arranged diagonally. Samples of 30 g of cowpea were impregnated with different doses (5.0 x 106, 1.0 x 105, 1.5 x 105 and 2.0 x 105 L) of each vegetable oil. We released 50 adults of C. maculatus in the central container and counted the number of insects per container 24 hours later. Citronella and fennel oils at a dose of 3.0 x 105 L demonstrated a higher insecticidal effect on C. maculatus. However, citronella oil presented the best repellent action.
Highlights
Vigna unguiculata L. (Walp), commonly known as cowpea, is a leguminous plant of important nutritional value widely cultivated in the warmest regions of Africa, Asia and Americas (MOREIRAARAÚJO et al, 2018)
We aimed to evaluate the insecticidal activity and repellency of vegetable oils extracted from fennel, citronella, neem and ‘moringa’ against C. maculatus adults in cowpea beans
Specimens of C. maculatus submitted to 0.0 x 106 and 5.0 x 106 L doses of vegetable oils presented no significant differences in terms of survival (Table 2)
Summary
Vigna unguiculata L. (Walp), commonly known as cowpea, is a leguminous plant of important nutritional value widely cultivated in the warmest regions of Africa, Asia and Americas (MOREIRAARAÚJO et al, 2018). Pests such as Callosobruchus maculatus (Fabr.) (Coleoptera: Bruchidae), or cowpea weevil, can attack cowpea beans. This species stands out among the main pests to stored grain (MARSARO JÚNIOR et al, 2005). C. maculatus females deposit their eggs in the seed's coat and, after 3-5 days, the larvae migrate into the seed's cotyledons, where they complete their life cycle (ADENEKAN; OKPEZE; OGUNTADE, 2013). This causes great damage to grains and seeds of stored beans, compromising their quality and use for planting (BAVARESCO, 2007)
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