Abstract
Insect pests are one of the factors that most impact plant yield. The magnitude of the losses and the spatiotemporal pest distribution in crops is a result of their interactions with the environment. Therefore, the understanding of the causes of production losses and the pest spatial patterns is important for the development of suitable sampling plans and pest management programs. Thus, this study aimed to quantify grain losses caused by insects and to determine the spatial distribution pattern of arthropod pest species in Bt and non-Bt corn. The prevailing insect pests in the corn ears were the earworm and fall armyworm caterpillars (Helicoverpa spp. and Spodoptera frugiperda), the cornsilk fly (Euxesta spp.), the maize weevil (Sitophilus zeamais), and the square-necked grain beetle (Cathartus quadricollis). The non-Bt corn was more attacked by the caterpillars and the weevil, while Bt corn was more affected by the cornsilk fly Euxesta spp. Spatial dependence was significant for the damage caused by the caterpillars, the grain beetle and the maize weevil in both the Bt and non-Bt corn genotypes. The range of the damage caused by the insects was between 9.0–9.7 m for the caterpillars, 6.9–12.20 m for the cornsilk fly, 10.7–80.4 m for the square-necked grain beetle, and 51.9–170.7 m for the maize weevil. The pattern of the spatial distribution of pest damage in both corn genotypes (i.e., Bt and non-Bt corn) was similar with a prevalence of moderate to strong spatial dependence and aggregate damage distribution. The plants near to the sampling points exhibited injury and infestation levels similar to those of the sampled plants.
Highlights
Insect pests can impact corn production by reducing the stand and plant production capacity, and corn quality by making corn ears unmarketable
High infestation levels of caterpillars, cornsilk flies, square-necked grain beetles, and maize weevils were observed on ears both in non-Bacillus thuringiensis (Bt) and Bt corn crops sampled in this study
Damage caused by these pests was more than 77%, 22%, 63%, and 10% of corn ears evaluated, respectively
Summary
Insect pests can impact corn production by reducing the stand and plant production capacity, and corn quality by making corn ears unmarketable. Damage to marketable structures directly affects crop yield [1,2,3], and ear losses are the most significant impact on total corn crop losses. These losses can be caused by insect pests, physiological plant disorders, fungi and rodents [2,4,5]. (Diptera: Otitidae) [6,7,8] These pest species directly compromise corn yield due to silk consumption (which causes the abortion of ovules) and the grain consumption as well, and can indirectly affect production while favoring fungal infestation and attacks by other insects on the damaged ears [9,10]
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