A study was carried out at the Advanced Weed Science Research Nucleus , UNESP/Botucatu, to verify the effect of herbicides on different collected accesses of water hyacinth in hydroelectric reservoirs in São Paulo. The different genetic materials were chosen based on studies of genetic variability, using the RAPD technique. The herbicides and rates evaluated were imazapyr at 62.5 and 125.0g a.e. ha-1, glyphosate at 480 and 960 g a.e. ha-1, diquat at 1.680 and 3.360g a.i. ha + 5% V/V of Extravon and 2.4-D at 670 and 1.340g a.i. ha-1. Six chosen accesses were placed in a box of 28.0 x 14.0 x 12.0 cm containing 4 L water. Herbicide was applied by using a spray simulator pressurized with compressed air, with four ''Teejet'' 110.02 VS flat fan nozzles. The constant work pressure was 1.6 bars, and the solution volume, 193 L ha-1. Application speed was 3.69 km/h. During herbicide application, the air temperature was 25 ºC and the relative humidity, 73%. Visual control evaluations were carried out on the 3rd, 5th, 7th, 11th, 21th and 28th days after herbicide application. All the tested herbicides and rates provided an efficient control of water hyacinth plants, with the six accesses showing similar responses to the herbicide treatments.
2,4-D; glyphosate; imazapyr; diquat; Eichhornia crassipes
