Momentos para a primeira aplicação de fungicidas associados a multissítios na cultura da soja

Abstract

Soy is one of the most relevant crops in the world economy. In its cultivation, several diseases can lead to losses of productivity, with soybean rust being one of the main ones. Fungicides with site-specific commercial blends associated with multisite are still poorly used, despite the potential gains that this practice can provide. As a result, the objective of the present work was to evaluate different moments for the first application of fungicide in the soybean crop, associated to multisite products, the severity of Asian rust and yield variables. The experiment was conducted in a 3x3 factorial scheme, with four replications, from December 2017 to April 2018, and counted on three moments of entry of the first application of the fungicides and distributed in three programs: 1st program) fungicide specific site; 2nd program) fungicide specific site + multisite Mancozeb; 3 rd program) fungicide specific site + multisite Chlorothalonil. Weekly analyzes of rust severity were performed, used to calculate the area under the disease progress curve (AACPD), as well as yield variables such as height of insertion of the first pod, number of productive nodes, number of pods per plant, mass of one thousand seeds and productivity. Late applications of site-specific fungicides associated or not with different multisites resulted in greater severity of Asian soybean rust in both the lower and upper half of the plants, as well as significant productivity losses. Early applications and early symptoms with the fungicide association decrease this severity. Regarding the performance variables analyzed, no significant effects of the different moments were observed for the first fungicide application nor between the control programs tested.