Débora Mello da Silva

Do different casein concentrations increase the adverse effect of rutin on the biology of Anticarsia gemmatalis Hübner (Lepidoptera: Noctuidae)?

The flavonoid rutin is recognized as playing an important role in the protection of plants against lepidopterans. Bioassays with this compound are generally carried out using artificial diets. Proteins of high energy value, such as casein, are important ingredients of insect artificial diets as a source of essential amino acids. However, such proteins can generally increase the allelochemical activity. Our objective was to evaluate the effects of rutin on larvae of the velvetbean caterpillar Anticarsia gemmatalis Hübner by incorporating this allelochemical into diets with different concentrations of casein. Three casein concentrations (0, 7 g, or 14 g) combined with none, 0.65%, or 1.30% of rutin were added to the rearing diet and offered to the larvae from hatching to pupation. Rutin negatively affected larval development, the amount of food consumed, and pupal weight of A. gemmatalis. These negative effects were clearly seen in insects fed on diets with 7 g of casein to which any concentration of rutin was added. The effects of rutin when added to the diets without casein were stronger than in diets containing a suitable amount of casein (14 g). The greater negative effects of rutin in diets containing suboptimal concentrations of casein indicate that casein can increase the effects of rutin only when the diets are nutritionally unsuitable for insect development.

Biology of Spodoptera eridania and Spodoptera cosmioides (Lepidoptera: Noctuidae) on different host plants

Abstract The moths Spodoptera eridania (Stoll) and Spodoptera cosmioides (Walker) are pests of increasing importance in various grain production systems, causing defoliation and damage to reproductive structures of plants. This fact underscores the need for studies that analyze the nutrition and development of pests on different hosts. The objective of this study was to evaluate the development of S. eridania and S. cosmioides feeding on different host species. To this end, newly hatched larvae were separated individually into waxed cups and fed soybean, cotton, maize, wheat, oat leaves, or an artificial diet as control. The evaluated parameters were: duration of larval, pre-pupal, and pupal development (days), pupal weight (g), sex ratio (%), larvae-adult survival (%), oviposition preference, larval feeding performance, and weight gain on different hosts. Soybean and cotton were found to be more suitable hosts for development and oviposition of S. eridania and S. cosmioides than oat, wheat, and maize, all of which negatively affected larval development and survival. The maize cultivar ‘DKB 390’ did not allow for larvae to develop to adults and therefore proved to be inadequate for both studied Spodoptera species.

Bioecological characteristics of Chrysodeixis includens (Lepidoptera: Noctuidae) fed on different hosts

Chrysodeixis includens (Walker 1858), also known as soybean looper, is a polyphagous pest with increasing economic significance in various crops. The rate of infestation and its distribution can be influenced by feeding through direct and indirect effects on their life cycles. Thus, this study aimed to examine the biological characteristics, food preference and leaf consumption of C. includens on soybean (BRS 284), cotton (FMT 701), sunflower (BRS 323) and common morning glory leaves (Ipomoea sp.) as possible host plants. The experiments were conducted with specimens obtained from mass rearing in the laboratory. C. includens larval and larval‐adult stages were shorter in sunflower and longer in cotton. Also, larval preference was greater for sunflower and lower for cotton leaves. Soybean leaves were consumed the least in contrast to sunflower and common morning glory leaves, which were consumed the most. These results suggest that soybean, sunflower or common morning glory leaves were favourable hosts for C. includens development, whereas cotton leaves are less nutritionally adequate for insect development. In addition, sunflower leaves reduce C. includens development time and promotes a survival rate greater than 95%, and the leaves are more attractive to larvae when compared with the other tested hosts. This indicates sunflower is the most favourable host among the tested plants for C. includens.