Abstract
Among pest insects that attack soybean crops, Chrysodeixis includens (Walker, 1858) (Lepidoptera: Noctuidae) looper caterpillar deserves attention due to its key pest status in soybean crops. The spatial distribution of C. includens eggs should be investigated in order to understand the behavior of this species in the area. The aim of this study was to investigate the spatial distribution of C. includens eggs in soybean crops. The experiment was conducted with SYN 9070 RR soybean variety in an experimental area of the Teaching, Research and Extension Farm (FEPE) of FCAV/ UNESP, Jaboticabal, SP, Brazil. The area of 0.6 ha was divided into 60 equidistant plots of 100 m² each. For the study of the spatial distribution of P. includens eggs in the area, the following dispersion indexes were used: variance / mean ratio (I), Morisita index (Id), Green coefficient (Cx), k exponent of the negative binomial distribution for each sampling. Regarding the probabilistic models that describe the spatial distribution of a given variable, the data adjustment to the Poisson and negative binomial distributions was tested. According to values obtained for dispersion indexes, egg distribution occurred in an aggregate way, and the negative binomial distribution was the most appropriate probabilistic model to represent the distribution of C. includens eggs in the study area.
Highlights
Among insect pests that attack soybean crop, looper caterpillar, Chrysodeixis includens (Walker, 1858) (Lepidoptera: Noctuidae) stands out, which consumes about 64 to 200 cm2 of the leaf area and causes high losses of the photosynthetic area (Bueno et al, 2011).The species has globular eggs with approximate diameter of 0.5 mm
The probabilistic model was obtained in each sampling, where adjustments to the Poisson and negative binomial distribution were tested, because variances were equal to or greater than the mean, respectively
According to the dispersion index results, the mean number of C. includens eggs found in soybean plants was 0.23 ± 0.07 in the first evaluation, increasing gradually until reaching a peak of 5.63 ± 0.46 at 72 days after emergence (DAE) (Table 1)
Summary
Among insect pests that attack soybean crop, looper caterpillar, Chrysodeixis includens (Walker, 1858) (Lepidoptera: Noctuidae) stands out, which consumes about 64 to 200 cm2 of the leaf area and causes high losses of the photosynthetic area (Bueno et al, 2011).The species has globular eggs with approximate diameter of 0.5 mm. The probabilistic model was obtained in each sampling, where adjustments to the Poisson and negative binomial distribution were tested, because variances were equal to or greater than the mean, respectively. Mis the sampling mean, k is the estimate of the negative binomial k exponent, P(x) is the probability of x individuals occurring in the sampling unit.
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