Studies related to the effect of insecticides on insect pests and nontarget organisms, such as natural enemies, are traditionally accessed by the estimative of lethal effects, through mortality data. Due to the limitations of the traditional methods, recent studies in the past three decades are assessing the sublethal effects of insecticides upon several important biological traits of insect pests and natural enemies. Besides mortality, the sublethal dose/concentrations of an insecticide can affect insect biology, physiology, behavior and demographic parameters. In this chapter, many sublethal effects of insecticides were addressed for several chemical groups, such as botanical insecticides, carbamate, diamide, insect growth regulators, neonicotinoid, organochlorides, organophosphates, pyrethroid and others. An accurate assessment of these effects is crucial to acquire knowledge on the overall insecticide efficacy in the management of pest insect populations, as well as on their selectivity toward nontarget organisms.

Spodoptera frugiperda is a major pest in several crops due to its polyphagous habit. Studies on the use of essential oils for pest control have been increasing over the years, presenting itself as a promising alternative with less environmental impact. Chemical profile evaluations of essential oils enable the knowledge and use of major compounds, providing a better understanding of their actions in the life history of insects. Thus, the study evaluated the effects of the major compounds limonene, trans-anethole and the combined effects upon nutrition, reproduction and testicular apoptosis in S. frugiperda. Larvae of third instar were submitted to the LD of the compounds by topical contact and 48 h later the amounts of lipids, proteins, total sugar and glycogen were evaluated. The testicular apoptosis was evaluated in the treated larvae after 48 h and the reproductive parameters were evaluated after adult emergence. All treatments reduced the amounts of lipid, protein, total sugar and glycogen when compared to control. The most significant results were obtained by the association of compounds. All treatments reduced the number of eggs, oviposition period and adult longevity when compared to control. There were no changes in the pre-oviposition and post-oviposition periods. Testicular apoptosis was observed in the limonene and in the combined treatments. It is concluded that limonene and trans-anethole, especially in association, cause adverse effects upon nutrition and reproduction in S. frugiperda, altering essential parameters for its survival and establishment on crops.

Spodoptera frugiperda (Smith 1797) (Lepidoptera: Noctuidae) is a major pest of maize, Zea mays L. Its control is often achieved through repeated applications per season of insecticides, which may lead to adverse effects on the ecosystem. Thus, the study of alternative methods with less environmental impact has expanded to include the use of essential oils. These oils are products of the secondary metabolism in plants, and their insecticidal activity has been widely demonstrated in populations of many pest insects. This study evaluated the insecticidal activities of essential oils from Eucalyptus staigeriana, Ocimum gratissimum, and Foeniculum vulgare on Spodoptera frugiperda. Gas chromatography–mass spectrometry profiles and contact toxicity of these oils as well as their sublethal effects on larvae and reproductive parameters in adults were evaluated. All three oils had sublethal effects on S. frugiperda; however, the oil of O. gratissimum showed the best results at all doses tested. These essential oils may have promise for control of S. frugiperda.

The predatory ladybird beetle Tenuisvalvae notata (Coleoptera: Coccinellidae) (Mulsant) is a polygamous species and its morphology, as well as the storage capacity of seminal fluid in the spermatheca, may affect its reproductive performance. Thus, the present study evaluates the spermatheca morphology of virgin and mated T. notata females using light and scanning microscopy. The results show that the spermatheca of T. notata is kidney shaped and consists only of the receptacle and spermathecal duct, being morphologically similar in virgin and mated females. There is no secretion in the spermathecae of virgin females and, in mated females, only once it was not possible to observe the presence of spermatozoa. By contrast, females mate multiple times it is possible to observe spermatozoa in the lumen of the spermatheca surrounding the secreted material. Polygamy in T. notata might be related to the maintenance of viable spermatozoa in the spermatheca, in which case the female would prefer to copulate more times during its adult life than to store spermatozoa for a longer period of time.

No abstract

Essential oils and their isolated constituents are constantly being studied for the control of insect pests. In this context, the present research reports the chemical composition of Piper marginatum (Jacq.) oil aiming to: 1) establish lethal concentrations LC30 and LC50 for this oil and the compound geraniol, 2) histologically examine the embryonic development of Spodoptera frugiperda (J.E. Smith) through light microscopy and scanning electron microscopy (SEM), as well as 3) compare the efficacy of the P. marginatum oil with that of the botanical insecticide azadirachtin, the synthetic insecticide deltamethrin, and acetone as a negative control. Semithin sections of S. frugiperda eggs revealed that the oil, geraniol, azadirachtin, and deltamethrin affected embryonic development at both concentrations. However, geraniol and the oil were more efficient because they caused more significant damage, even at lower concentrations. SEM revealed that all products altered the morphology of the eggs, modifying the structure of the chorion and making the eggs nonviable. Thus, this work demonstrates that P. marginatum oil is effective in the control of S. frugiperda because it results in embryonic damage even at the lowest concentrations.

No abstract

No abstract