RESUMO Em experimento de campo quantificou-se a sobrevivência e a viabilidade de escleródios de Botrytis squamosa no solo. Cem escleródios multiplicados pela técnica de esfregaço de micélio em meio de cultura BDA foram colocados em saquinhos feito de tecido voal. Em armação de madeira contendo solo, colocaram-se 12 repetições respectivamente na superfície e enterrados a 10 centímetros. Mensalmente os saquinhos foram retirados de cada posição, lavados em água corrente e submetidos à compressão com dedo para constatar-se os mesmos mantinham-se intactos. Os escleródios intactos foram submetidos à assepsia com álcool 70% durante um minuto, hipoclorito de sódio 1,25% por três minutos e em água estéril para lavagem, em seguida depositado em placas contendo meio BDA e acondicionado em câmara de crescimento a 20ºC sem luz. Três dias após a incubação realizava-se a contagem dos escleródios germinados. Os escleródios coletados na superfície e enterrados perderam sua viabilidade após oito meses. Os escleródios de B. squamosa na superfície tendem a perderem sua viabilidade num período de tempo menor que os enterrados.
Weedy rice belongs to the same species as grown rice, and because it has similar morphophysiological characteristics, its control is difficult, bringing negative effects to the crop. Thus, the work aimed to evaluate the allelopathic potential of the main paddy rice cultivars sowing in Santa Catarina on weedy rice. In the laboratory, with treatments organized in a 4 x 5 factorial scheme, the aqueous extract of four paddy rice cultivars (SCSBRS Tio Taka, SCS 116 Satoru, SCS 121 CL and SCS 122 Miura) was evaluated in five concentrations (0, 25, 50, 75 and 100%). In a greenhouse, with treatments in a 4 x 2 factorial scheme, the straw allelopathy capacity of the same rice cultivars in two quantities (0.0 and 3.0 t ha-1) was evaluated to suppress germination and weedy rice initial growth. All experiments were carried out in a completely randomized design. In the first assay, the aqueous extract of the paddy rice cultivars used in the state of Santa Catarina did not have an allelopathic effect on weedy rice. In the second assay, it was found that the presence of rice straw reduced the density of weedy rice plants. However, the presence of straw on the soil favored the initial growth of the weed, significantly increasing the plant height, number of leaves per plant and shoot dry biomass.
Herbicide selectivity is the basis for chemical control of weeds; however, it depends on the interactions between herbicide, crop, and edaphoclimatic conditions. The objective of this work was to evaluate the selectivity of herbicides applied at the pre-emergence stage of soybean cultivars with different maturation times grown in different locations. The experiment was conducted under field conditions, in two crop seasons (2019/2020 and 2020/2021), in Lages and Curitibanos, state of Santa Catarina, Brazil. A randomized block experimental design was used, with treatments organized in 4×3 (2019/2020) and 4×4 (2020/2021) factorial arrangements, with four replications. The treatments consisted of interactions between four soybean cultivars: BMX Raio IPRO® (Raio), BMX Zeus IPRO® (Zeus), MONSOY 5947 IPRO® (Monsoy), and BMX Fibra IPRO® (Fibra) and three or four herbicide treatments: control with no herbicides, sulfentrazone + diuron, and diclosulam in 2019/2020; and control with no herbicide, sulfentrazone + diuron, diclosulam, and pyroxasulfone + flumioxazin in 2020/2021. The plots were evaluated for phytotoxicity of herbicides, canopy closure, plant height, stand of plants, number of pods per plant, one-thousand grain weight, and grain yield. The phytotoxicity of herbicides on the soybean plants was mild, under 11%, regardless of the cultivar and growth location. The soybean plants fully recovered from the injuries at 14 days after herbicide application. In Curitibanos, the cultivar Zeus presented higher grain yield in both crop seasons. The herbicide factor showed that sulfentrazone + diuron and diclosulam decreased the grain yield of the cultivars Raio and Zeus in 2019/2020. In the following crop season, only the cultivar Raio presented decreases in grain yield due to the application of diclosulam and pyroxasulfone + flumioxazin. In Lages, the soybean cultivar factor affected the grain yield; the cultivars Monsoy and Fibra were the most productive.
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