Researches regarding the measures applied for reducing the weeds infestation at seed hemp crops under the condition of Central of Moldova

Abstract

The hemp is one of the crops susceptible at weed infestation, weed appearance in the first vegetations phenophases lead at compromising the crop. Chemical intervention through herbicide application represents one method to control the weed appearance and spreading over the seed hemp crop. In this moment for seed hemp crop there is a limited range of approved herbicides. At A.R.D.S. Secuieni Neamț, for controling the weeds from seed hemp crop were experimentated a series of herbicides with different active substance to assess the product selectivity for the crop plant and efficacy under the climatic conditions of the years 2018 - 2019. During two years, the weeds identified from hemp crop was composed from 13 species, 11 from Dicotyledonate class and two from Monocotyledonate class. From Dicotyledonate class, the weed species which recorded the highest average density were Atriplex patula with 21.50 specimens /sqm and Polygonum persicaria with 15.05 specimens/sqm. Setaria glauca, the most representative species from Monocotyledons class recorded an average density of 5.88 specimens/sqm. By the weeds number/sqm, the species from Dicotyledonate class register a 89.20% share meaning a average density of 53.59 specimens/sqm and from the Monocotyledons class belong 6.49 specimens/sqm representing a share of 10.80% from the all the specimens identified. From all the 12 herbicides experimentated, two were applyed in preemergence and the rest of herbicides were applied to control the weeds after plant emergence. Regarding the hemp plant selectivity, the commercial products Lentagran 45 WP, Galera Super and Challenge 600 provoked different symptoms of phytotoxicity, but the hemp recovered after 30 days from applying the herbicides. The weeds control highest efficacy was obtained at the variant treated with Challenge 600 and it was 72%. For the herbicides Stratos Ultra, Fusilade Forte, Frontier Forte, Lontrel 300, Leopard Super și Select Super the efficacy had values between 62 and 67%.