MANAGEMENT STRATEGIES FOR HERBICIDE-RESISTANT WEEDS BY USING DIFFERENT HERBICIDES IN SEQUENTIAL APPLICATION FOR EFFECTIVE AND SAFE WEED CONTROL IN WHEAT.

Three field experiments were carried out during the successive winter seasons on 2017/2018 and 2018/2019 at Sids Agricultural Research Station farm, A.R.C., Bani Swif Governorate, Egypt, to management resistance development by using herbicides with different sites of action (SOA's) in the sequential application at reduced rates with adjuvants (mineral oil) on productivity, quality and associated weeds of wheat (Triticum aestivum L.). Experiment No.1 studied the efficacy of certain graminicide Topic 15% WP (clodinafop propargyl), Eferst 70% WG (flucarbazone sodium), both used at full rate, alone, and in sequence at reduced rate with mineral oil 1%, Experiment No.2 studied controlling broad leaved weeds herbicides Garenary 75% WG (tribenuron-methyl), Brominal 24 % EC (bromoxynil-octanoate), both used at full rate, alone, and in sequence at reduced rate with mineral oil 1% and Experiment 3: studied controlling grassy and broad-leaved weeds used herbicides Otheilo OD 5.25% OD (diflufenican 5%+ iodosulfuron methyl sodium 0.25+ Mesosulfuron methyl 0.75%) a ready formulated at full rate, alone, and the sequential application (Topic, Eferst, Garenary and Brominal) at reduced rates with mineral oil. All experiments included hand weeding at 20 and 40 days after sowing and weedy check. Each experiment was laid out in a Randomized Complete Blocks Design with four replicates. Results of Exp.No.1 indicated that the sequential application of herbicides at reduced rate Eferest (10 g/fed.) followed by Topik (70 g/fed.) both with mineral oil (1%), gave more efficiency weed control than that obtained by each alone, whereas, the fresh weight of grassy weeds were (23.3 and 33.5 g/m 2 ) and grain yield (22.88 and 23.70 ardab/fed.) in the 1 st and the 2 nd seasons, respectively. Exp.2: Results showed that the sequential application of Gerenary (4 g/fed.) followed by brominal (500 cm 3 /fed.), both at reduced rate plus mineral oil at 1%, better decreasing fresh weight of broadleaved weeds by (29.0 and 34.0 g/m 2 ) as compared to other treatments with while, increasing on wheat yield (23.45 and 24.12 ardab/fed.) in both seasons, respectively. Results of Exp.No.3: showed that the maximum weed control efficiency was achieved with sequential application of Gernary in combination with Topik both at reduced rates with mineral oils (1%), whereas, gave decreasing total weeds fresh weight by (55.75 and 48.0 g/m 2 ) compared to the other treatments, similar trend was observed in grain yield of wheat and its components. Therefore, it could be concluded from this study that, to avoid the appearance of the development herbicide-resistant weeds should be chosen various herbicides with different site of action in sequence application at reduced rates with adjuvants (mineral oil) to achieve efficiency of weed control without loosing in wheat yield and its components.