Root consumption and damage estimates caused by Phyllophaga capillata and Aegopsis bolboceridus (Coleoptera, Melolonthidae) larvae in soybean and maize in central Brazil

Abstract

Phyllophaga capillata (Blanchard) and Aegopsis bolboceridus (Thomson) (Coleoptera, Melolonthidae) are important soil pests in soybean and maize crops in central Brazil. The aim of this study was to evaluate the capacity of root consumption by larvae of P. capillata in soybean and A. bolboceridus in maize under controlled conditions and to estimate the damage caused by these species in the field. Root consumption was evaluated in a screened nursery (Brasília/DF, Brazil). Pots with soybean and maize plants were infested separately with different instars and larval densities (0, 1, 2, 4, 6, 8, and 10 larvae/plant) of P. capillata or A. bolboceridus. After 24 h, the weight, area, and length of the roots were evaluated. Damage estimates were calculated for soybean (Brasília/DF, Brazil) and maize (Cabeceiras/GO, Brazil) production in fields with and without severe white grub infestations. In the crop production stage of the experiment, we evaluated the number of plants per linear meter, weight of 1000 grains, productivity, number of pods per plant (soybean), and weight and length of ears (maize). For the two species of white grubs, root consumption was relatively low for first-instar larvae, high for second-instar larvae, and especially high for third-instar larvae. The third instars reduced the root system by approximately 25% in soybean and 64% in maize. We observed that P. capillata and A. bolboceridus damaged all evaluated variables, reducing overall soybean productivity by 58.62% and maize productivity by 59.76%. Our results suggest that it is necessary to monitor the presence of these species by sampling and include them in the integrated pest management programs of these crops in the regions where these species occur.