Abstract
ABSTRACT Weed control is essential to reduce or eliminate the interference of weeds on crops. Chemical control with the application of herbicides consists of the most used method, with this aim in grain producing areas. Information about the selectivity of herbicides to C. spectabilis (showy crotalaria) are scarce, which are critical for the management of this species as a crop. One field experiment was performed to evaluate the selectivity of herbicides applied in post-emergence of showy crotalaria. The herbicides bentazon (720 and 576 g ha-1), imazethapyr (106 and 79.5 g ha-1), pyrithiobac-sodium (84 g ha-1), flumiclorac (60 g ha-1), flumiclorac in sequential application (30 / 30 g ha-1), imazethapyr + bentazon (106 + 480 g ha-1), and clethodim + quizalofop (96 + 100 g ha-1) were applied in plants with four true leaves, also using a control without herbicide application. Pyrithiobac-sodium and flumiclorac isolated and the tankmix of imazethapyr + bentazon provided greater injuries to showy crotalaria, also affecting the final plant height. Pyrithiobac-sodium (84 g ha-1) was not selective to showy crotalaria. The herbicides imazethapyr (79.5 g ha-1), flumiclorac (sequential application), and bentazon (576 g ha-1), despite the association between clethodim + quizalofop, can be used for weed management in showy crotalaria crop.
Highlights
The change in cropping system of certain plant species, where the same shall be sown in large areas, makes it necessary to perform a greater number of cultural practices, as the increase in acreage provides changes in the interactions between fauna and flora, increasing pressure from pests and diseases due to the highest host offer
The plant protection management of a crop corresponds to care with three main biotic factors that affect plant development: disease-causing organisms, insects and invertebrate parasites, and weeds
At 7 DAA of the herbicides in the post-emergence of showy crotalaria, it was verified that the application of pyrithiobac-sodium caused higher levels of injuries, shown as intense yellowing, even in the young leaves emitted by the plants (Table 2)
Summary
The change in cropping system of certain plant species, where the same shall be sown in large areas, makes it necessary to perform a greater number of cultural practices, as the increase in acreage provides changes in the interactions between fauna and flora, increasing pressure from pests and diseases due to the highest host offer. The weeds have the potential to host pests and diseases, demonstrating that these have a wide relation with other biotic factors that compromise plant development (MOURELOS et al, 2014). Crotalaria spectabilis (showy crotalaria) showed an increase in cultivated area in the central region of Brazil, mainly by the control imposed on different nematodes species, beyond the availability of nitrogen in soil by biological fixation (ROSA et al, 2013). Despite this increase in cultivation, information about the tolerance of this species to the interference imposed by weeds remains scarce. In the literature, is has been reported that some crotalaria species showed great potential for weed suppression, with this effect being attributed mainly to soil shading and the biomass produced (TIMOSSI et al, 2011)
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