Seletividade de herbicidas aplicados em pós-emergência na mandioca e feijão-caupi

Abstract

In family production systems it is common to deployment of multiple cropping systems. The consortium with cassava and cowpea, is quite usual mainly in the North and Northeast of Brazil, as they are importates cultures in these regions. Chemical weed control in consortium system is limited due to physiological differences and crop response to the application of herbicides. Given the need to implement effective methods of weed control that can be implemented in consortium systems cassava / cowpea, objective with this research was to evaluate the selectivity of different herbicides applied post-emergence in the early stage growth. There were two different experiments in order to evaluate the tolerance of cassava (cultivar Aciolina) and cowpea (cultivar BRS Aracê), application of herbicides in postemergence. The experiments were conducted in a greenhouse. They used eight commercial herbicides, based on their active ingredients, two mixtures of herbicides and the control treatment. The herbicides were applied in the initial phase in both cultures. We valued the effects of treatments in variable height and number of leaves each week until 21 days after herbicide application (DAAH). Visual notes assessments of toxicity of herbicides were used up to 21 DAAH, and was measured dry matter of shoot (leaf and stem) and root, total dry matter and leaf area in two cultures at 21 DAAH. The results indicate that treatments Haloxyfop and Quizalofop were selective in both cultures. The herbicides (Imazetapir and Clorimuron) showed different behavior between cultures, cowpea showed regular response to Imazethapyr, while cassava is its committed development, but the reverse was found with chlorimuron. The herbicides Lactofen, Fomesafen and Bentazon had high initial damage to both the cultures, but both showed signs of recovery, although the severe effects caused by Lactofen has undertaken the development of crops. The commercial herbicide formulated Bentazon + Imazamox, showed some selectivity to cowpea, but for cassava caused significant damage that appeared 14 DAAH, in the new leaves. In general the two mixtures of herbicides applied to crops of cowpea and cassava (Lactofen + Quizalofop and Fomezafen + Quizalofop) caused severe damage phytotoxicity, the highest damage was seen with the application of the mixture Lactofen + Quizalofop.