Brazil is the second largest producer of soybeans in the world, with the state of Mato Grosso having the highest production in the country. The soybean crop faces major phytosanitary difficulties throughout its cultivation, as is the case of pest incidence, especially the defoliating caterpillars that can cause intense defoliation of soybean and affect its productivity. Thus, the objective of this work was to evaluate the effect of different insecticides when applied in soybean seed treatment, on leaf consumption and survival of Anticarsia gemmatalis (Lepidoptera: Erebidae) and Chrysodeixis includens (Lepidoptera: Noctuidae) caterpillars. For this purpose, two trials were installed in the field, one in the Juscimeira Municipality/MT and the other in the Municipality of Itiquira/MT. The soybean seeds were treated with the insecticides (in g a.i./ha): chlorantraniliprole (62.5), imidacloprid + thiodicarb (75.0 + 25.0), fipronil (50.0), thiamethoxam (70.0) and cyantraniliprole + thiamethoxam (60.0 + 70.0) and a control treatment (without insecticide). Soybean leaflets were collected at different times after plant emergence and were offered to A. gemmatalis and C. includens caterpillars in the laboratory to evaluate leaf consumption and mortality. Cyantraniliprole + thiamethoxam (60.0 + 70.0) and chlorantraniliprole (62.5) treatments were found to reduce leaf consumption of A. gemmatalis and C. includens caterpillars. The highest mortality values of A. gemmatalis and C. includens were observed in the treatment cyantraniliprole + thiamethoxam (60.0 + 70.0), followed by chlorantraniliprole (62.5) when compared to the control treatment. The results showed that the treatment of soybean seeds with insecticides can protect the crop against defoliation and provide control of defoliating caterpillars, these effects being more pronounced in sandy soils than in clay soils.

Helicoverpa armigera (Hübner, 1805) (Lepidoptera: Noctuidae) is a cosmopolitan pest with wide geographical distribution in Brazil. This pest was officially registered in 2013 on cotton, soybean, corn, and some weeds, although this species may have been present in the country since 2008. The objective of this work was to evaluate the efficiency of eight insecticides (seven chemicals and a biological product) to control small and large H. armigera caterpillars. The experiment was conducted under laboratory conditions (T 22±1 °C; RH 70±10%; 12h photoperiod), with nine treatments (g a.i./ha dose): flubendiamide (72), chlorantraniliprole + lambda-cyhalothrin (30 + 15), chlorfenapyr (288), spinetoran (18), indoxacarb (120), emamectin benzoate (10), metomil (322.5), Bacillus thuringiensis (500), and control (water). A completely randomized design was used with four replications for each size of caterpillars (small and large), and each repetition (plot) consisted of five H. armigera caterpillars fed with bean leaves immersed in the different treatments evaluated. The larval mortality evaluations were performed at one, three, five, and seven days after contact with the treated bean leaves, determining the control efficiency (E%) through the formula of Abbott (1925). All chemical and biological treatments tested caused significant mortality of small and large H. armigera caterpillars, reaching a control percentage of 100% at seven days after treatment, demonstrating the possibility of using the insecticides tested to control this pest under field conditions.

The occurrence of phytophagous stink bugs in soybeans can result in production losses, if this pest is not properly controlled. Our objective was to study the vertical distribution (intra-plant) of nymphs and adults of Euschistus heros (Fabricius, 1798) (Hemiptera: Pentatomidae) in the leaf canopy of soybean plants, during the day. For this, fourteen soybean plants located in one meter of row were evaluated in the field, every three hours between 5 am and 8 pm. The sampled plants were divided into three strata (upper, middle, and lower), where nymphs and adults observed were counted in each stratum and sampling period. The treatments consisted of the three strata of the soybean plants and the different sampling points performed at each time of the day represented the repetitions. An irregular distribution of E. heros nymphs and adults was observed in the three studied strata of soybean plants, during the day. At 11 am and 2 pm, when the ambient temperature and solar radiation were highest, both the E. heros adults and the nymphs positioned preferentially on the upper stratum of the soybean plants and later migrated to the middle and lower strata when the temperature and solar radiation decreased. This information about the distribution pattern of E. heros in the soybean leaf canopy, during the day, provides knowledge for more effective monitoring and control of this pest in soybean crop.