The fall armyworm, Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae), is a major pest of maize and frequently demands control measures. The timing of insecticide application is a key factor in determining its efficiency, so an experiment was designed to investigate this. Application of insecticide was based on three criteria: (i) the number of trap-caught moths in a Delta-type trap with a commercial sex pheromone lure placed in the center of the target area, soon after plant emergence; (ii) the percentage of plants exhibiting pinhole-type damage (10% or 20%), and (iii) the percentage of plants exhibiting shot hole-type damage (10% or 20%) compared to a check plot without any control measures. We found that the number of trap-caught moths was, compared to the other methods, the2 best means of deciding on insecticide application in maize to control the fall armyworm. Using pheromone traps, we obtained the best performance of the insecticide Spinosad, causing >90% larval mortality. Without insecticide application, maize yield reduction due to fall armyworm larva damage was 39%.
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Aphis gossypii Glover (Hemiptera: Aphididae) is a polyphagous species frequently associated with the presence of sooty mold and viruses lethal to plants. The purpose of this work was to characterize possible resistance categories of cotton genotypes against A. gossypii. Initially, a preliminary test was carried out with 78 genotypes, 15 of which were selected for infestation ability assays and the determination of the cumulative aphid-day rates. Posteriorly, these genotypes were also evaluated through antixenosis and antibiosis assays. The genotypes FM 910, FM 966 LL, Mocó, Gossypium hirsutum var. punctatum L. (Malvaceae), Variedade Reba = BTK-12, Deltapine, Hi-Bred, Acala 4–42, IAC PV010-1664, IAC 21, Reba B-50 PR and FMT 709 inhibited the aphid colonization. In the infestation ability assay, G. hirsutum punctatum, IAC PV010-1664 and Acala 4–42 were the least infested. In a multiple-choice assay, Deltapine Smooth Leaf and Variedade Reba = BTK-12 were significantly less infested, suggesting antixenosis. In the antibiosis assay, Gossypium arboreum L. (Malvaceae) 1 showed the lowest number of nymphs, number of nymphs per adult per day and, number of nymphs at 10 d after the birth of the first nymph in addition to reducing the reproductive period, nymphal survival, adult longevity and, developmental time. In the FM 910, the number of nymphs produced per day and, at 10 d after the birth of the first nymph decreased, which also indicated resistance. The results obtained here are unprecedented and can be explored in breeding programs to develop insect-resistant cotton cultivars.
Diabrotica speciosa is considered one of the most important agricultural pests in Latin America. Attacks various plant species including fructiferous, vegetable, cucurbit, dicotyledonous, and gramineous crops. The goal of this work was to evaluate the influence of different host plants, offered during the larval and adult stages of D. speciosa on their development, reproductive capacity, and foliar consumption. The insects were reared with corn in the larval stage and offered common bean, corn, soybean, forage turnip and wheat in the adult phase. In another essay, the larvae were reared with bean, soybean, forage turnip, corn, wheat, potato and adult stage offered only leaves of common beans to the insects. The insects reared with corn and fed on common bean leaves in the adult phase produced bigger numbers of eggs in contrast to the insects fed on other host plants. The longevity of adult specimens and the oviposition period were greater when adults of D. speciosa were fed on soybean, forage turnip, and common bean leaves, but these parameters were reduced in the insects fed on corn and wheat leaves. The viability of D. speciosa during the immature stage was greater when the larvae were fed with potato tubers or corn seedlings. However, the larvae reared on potato tubers exhibited a longer development period in contrast to larvae fed on other plants. In the foliar consumption tests, common bean leaves were preferred by adult of D. speciosa in contrast to other plants (soybean, corn and forage turnip) offered under free-choice conditions. On the other hand, in confinement conditions, common bean was preferred by insects when compared to turnip or corn leaves. The results showed that corn was the best food for the larval development of D. speciosa while common bean represented the most suitable host for the adults.
Temperature is one of the abiotic factors that strongly influences the biology and behavior of insects. In this study, we assessed the development of egg parasitoids Ooencyrtus submetallicus and Telenomus podisi parasitizing Euschistus heros eggs at different temperatures, and estimated the average number of generations for seven representative soybean-producing regions in Brazil. A comparative biology study was conducted, where the percentage of parasitism and emergence, life cycle duration (egg–adult), and longevity were found to be similar between O. submetallicus and T. podisi. The sex ratio and the number of individuals emerged from parasitized egg were higher in O. submetallicus in all regions. In the study of thermal requirements, temperatures of 16, 19, 22, 25, 28, 31, and 33 °C were tested. O. submetallicus and T. podisi developed at temperatures between 16 and 31 °C. The base temperature (Tb) for O. submetallicus and T. podisi was 9.3 and 6.7 °C, respectively; the thermal constant (K) was 336.9 and 272.7 degree-days, respectively. The estimated average number of annual generations of both parasitoids was higher than the host. O. submetallicus and T. podisi have the same ability to parasitize and develop in eggs of E. heros under the conditions studied. Both parasitoids exhibited satisfactory development and parasitism at temperatures between 19 and 31 °C. The development of both parasitoids was faster than their host, and the number of generations was higher for the seven studied localities.
Chrysodeixis includens is an important pest of soybean crop who has gained more visibility in the Brazilian Cerrado due to damage caused in this region. Foliar consumption, feeding period and mortality level of soybean loopers in laboratory, as well as their control in the field conditions, were evaluated after application of the ChinNPV virus in soybean plants. In the laboratory, were tested six concentrations of isolate Chin-IA (I-A) (1 × 1011, 2 × 1011, 4 × 1011, 6 × 1011, 8 × 1011 and 10 × 1011 PIB ha-1), one dose of methomyl chemical insecticide (172 g ai ha-1) and distilled water (control). The field experiment was carried out in the 2016/2017 season using the same cultivar and laboratory treatments, except for the lowest virus concentration. The population density of small and large larvae was evaluated before and at 5, 8 and 12 days after application (DAA) of the treatments in soybean plants. All concentrations of the isolate Chin-IA (I-A) have reduced the soybean loopers consumption and their feeding period, showing 100% of mortality after 3 – 4 days without differing from treatment with the chemical insecticide. After eight DAA of virus in the field, the population density of small and large larvae was reduced, providing satisfactory levels of control. These results showed the evident potential of ChinNPV in the reduction of defoliation power and maintenance the soybean loopers population under of control level, and thus may be used as complementary method in the integrated management of this pest in soybean crops.
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