No abstract

Tribolium castaneum Herbst 1797 (Coleoptera: Tenebrionidae), an important pest of stored grains and byproducts, is naturally infected by Gregarina cuneata Stein 1848 (Apicomplexa: Gregarinidae). Changes in the life cycle of insects caused by the parasite development in the midgut were studied. Trophozoites, gamonts (solitary and associated), and gametocysts were present in the midgut of the insects. In young trophozoites, the apical region differentiated into an epimerite that firmly attached the parasite to the host epithelial cells. With maturation, trophozoites developed in gamonts that were associated with the initiation of sexual reproduction in the cell cycle, culminating in the formation of the spherical gametocyst. Morpho-functional analyses indicated that gregarines absorb nutrients from infected cells and can occlude the midgut as they develop. Consequently, nutritional depletion may interfere with the host's physiology, causing decreased growth, delayed development, and high mortality rates of the parasitized insects. These results suggest G. cuneata could be an important biological agent for controlling T. castaneum in integrated pest management programs.

Sitophilus zeamais Motschulsky, 1855 (Coleoptera: Curculionidae) is one of the most aggressive pests of stored grains, causing significant decrease in the nutritional quality of the grains and major losses in economic trade. The ability of this pest to damage grains and other products is directly related to the morphology of the alimentary canal. Considering the importance of the foregut in the digestion, this study aimed to describe the morphology of the crop and proventriculus in S. zeamais adults. The tissues were isolated, processed, and analyzed by using light microscopy, scanning electron microscopy, and transmission electron microscopy. The crop functioned as a storage organ, and its cells showed functional characteristics related to protein synthesis. High densities of prokaryotic microorganisms and spicules were found in the lumen. The proventriculus exhibited eight chitinous teeth, which were responsible for grinding and filtering food particles. This organ formed the stomodeal valve, which controlled the unidirectional flow of food through the alimentary canal. The alimentary canal is the primary surface of contact between the external environment and an insect's internal environment, and knowledge of its morphology is required to better understand the physiology of stored-grain insect pests.

No abstract

To evaluate the toxic effect of commercial formulations of neem oil, Azadirachta indica A. Juss, pre-pupae (PP), young pupae (YP) and old pupae (OP) of Diatraea saccharalis F. (Lepidoptera: Crambidae) were sprayed with the diluted extract in distilled water at concentrations of 0.0, 0.3, 0.5, 1.0 and 2.0%. The neem extract caused concentration-dependent effects on mortality of pupae, and the pupae that failed to emerge in adults had multiple abnormalities. The longevity of pupae that emerged in adults (YP and OP group) did not differ from the control group. The abnormalities found in adults were related to mortality in all treatments, except at the concentration of 1.0%. Fertility was assessed according to the oviposition of adult females from the YP group that showed no abnormalities, through the evaluation of the number of deposited eggs and the rate of undeveloped eggs. The results showed a reduction in the number of eggs laid and an increase in the percentage of undeveloped eggs. These results show that neem oil has a high potential to control the toughest stage of the sugarcane borer and also reduces the further development. Therefore, commercial formulations of neem oil have a toxic effect on pupae and adults of D. saccharalis.