000			04424nam a22001697a 4500
999			_c157910 _d157910
082			_a630 _bAPA/DI
100			_aAparna K K
245			_aDiversity of echinochloa spp. and their response to select herbicides
260			_aVellanikkara _bDepartment of Agronomy, College of Horticulture _c2017
300			_a76p.
502			_aMSc
520	3		_aThe most important biological constraint to rice production is weed infestation. Echinochloa spp. are the most devastating and serious graminaceous weeds associated with rice. Herbicides which selectively kill Echinochloa are commonly used by rice farmers, as hand weeding is often ineffective due to its close morphological similarity to rice. Of late, some new types of Echinochloa are seen in the major rice tracts of Kerala, and farmers report that these new types are tolerant to most herbicides used by them. The present study was conducted to study the diversity of Echinochloa spp. in the rice tracts of Palakkad and to test the efficacy of select herbicides against them. The efficacy of herbicides was evaluated for the major Echinochloa species collected from Kuttanad and Kole lands too. Surveys were conducted twice in the major rice tracts of Palakkad, once during January-February, and the other during August-September in 2016. Three major Echinochloa types were identified infesting rice fields, leading to severe crop competition. The three types were E. colona, with awnless spikelets and two types of E. crus-galli viz., E. crus-galli (type A) having short awns and E. crus-galli (type B) having long awns. Other than the length and arrangement of awns, there were no other significant differences in the morphological characters of the latter two types. There was no specific association between the Echinochloa types and soil nutrient parameters, probably as there were no drastic differences in the chemical properties among the different locations. Saturated soil moisture regime was observed in all the rice fields of surveyed areas. The major species in Kuttanadu and Kole area was E. stagnina, which was found only in flooded soils. This species differed morphologically from the other three types collected from Palakkad rice tracts. All the types, except Echinochloa crus-galli (type B) exhibited seed dormancy. Pre-treatment with ethanol (1M) for three days under darkness was most effective for promoting germination of Echinochloa. The efficacy of pre and post emergence herbicides on various species of Echinochloa was evaluated as pot culture study. The pre emergence herbicide treatments included pretilachlor, oxyfluorfen, pyrazosulfuron ethyl, pendimethalin, pretilachlor + bensulfuron methyl and oxadiargyl, and all were applied to both puddle sown and dry sown condition. All the herbicides except pyrazosulfuron ethyl were completely effective against all the four types of Echinochloa. Post emergence treatments were applied at the four leaf and eight leaf stages of Echinochloa spp. and the treatments included cyhalofop butyl, bispyribac sodium, penoxsulam, fenoxaprop-p-ethyl, ethoxy sulfuron and metamifop. Bispyribac sodium and metamifop were effective against E. colona at both four leaf and eight leaf stages, whereas penoxsulam was effective only at the four leaf stage. Bispyribac sodium at the eight leaf stage was highly effective against E. crus-galli (type A). Echinochloa crus-galli (type B) was effectively controlled by metamifop when sprayed at the four leaf and eight leaf stages, fenoxaprop-p-ethyl at the four leaf stage and penoxsulam at the eight leaf stage. This indicated that though the two types of E. crus-galli were morphologically similar except in awn characters, they had varying response to herbicides. E. stagnina was tolerant to all the herbicides tried. However, cyhalofop butyl and fenoxaprop-p-ethyl although effective at the four leaf stage in reducing the survival percentage, resulted in highly persistent survivors. The study showed the importance of optimal use of the correct herbicide against each species of Echinochloa at the most susceptible stage of the weed. Constant monitoring of the Echinochloa population in the field is important so that appropriate control strategy can be adopted.
650			_aAgronomy
700			_aMeera V Menon (Guide)
856			_uhttp://krishikosh.egranth.ac.in/handle/1/5810140552
942			_2ddc _cTH