Response of Pinus halepensis Mill. y Pinus pinaster Ait. to herbicides in nursery

Abstract

The use of herbicides in croplands forestation is needed in order to control weed competition for water, light and nutrients with tree seedlings. As selectivity of our forest species to herbicides and mode of aplication are scarcely known, we have studied the effect of three herbicides, hexazinone, pendimethalin and simazine on emergency and growth of Pinus halepensis and P. pinaster sowed in Forest-Pot during November and February inside a non-climatized greenhouse. Treatments were made in pine preemergency, one week after each sowing. Mean time emergency of two species of pine was minor in February than November sowing, however, thermic integrals (sumatory of temperatures > 5 °C since sowing time until mean time emergency) are not differents. Herbicide treatments did not influence emergency of pines, but later some of then caused mortality in seedlings. Hexazinone at doses of 1.5 kg a.i./ha caused mortalities of 84 % and 71 % in P. halepensis seedlings belonging to November and February sowings, respectively, and in P. pinaster, 93 % in seedlings of both sowings. Hexazinone at doses of 0.75 kg a.i/ha caused mortalities of 31 % and 18 % in P. halepensis seedlings belonging to November and February sowings, respectively, and 49 % and 61 %, in P. pinaster, respectively. Pendimethalin at 2 kg m.a./ha did not cause mortality in pine seedlings and simazine at 3 kg m.a./ha was tolerated for two pine species in February sowings, but in November sowings caused mortalities of 29 % in P. halepensis and 32 % in P. pinaster.