Post-emergence activity

The newest class of pyridine herbicides with pre- and post-emergent activity, the pyridinesulfoneamides, is typified by A7-(2-chloro-3-pyridme-sulloiiyl)-A7 -[2-(4-di loro-5,6-dimcthylpyrimidyl] urea. 

Such screening of synthetic compounds typically Involves greenhouse testing of up to a dozen or so Important crop and weed species for both pre-emergence and post-emergence activity. 

The example compounds had more post emergence activity than pre emergence and were more active on dicot than on monocot weeds. 

Oxyacetamides and tetrazolinones are new classes of herbicides characterized by excellent efficacy against many major annual grass weeds and certain dicotyledonous weeds, with pre- and post-emergent activity and long lasting weed control. 

Post-emergent herbicidal activity No post-emergent activity... 

Test results (2 weeks after treatment) showed that 1-2 and 2 had a significant better post-emergence activity then 1-1, 1-3, and 1-4 while 1-5 and 1-6 showed no activity at aU. Sodium l,l-dimethoxyethyl(methyl)phosphinate 2 was the most effective compound with 80-100 % control against tested weeds. It was speculated that 2 would hydrolyze to 1-2 in vivo (Scheme 1.16). 

These results indicated that phenoxyacetoxy moiety and proper substitution at phenoxyacetoxy moiety were very important for post-emergence activity. Acceptable post-emergence herbicidal activity of alkylphosphonates lo should have a reasonable combination of both phosphonate structural unit and proper substituted phenoxyacetate moieties. Detail study on alkylphosphonates lA-IK can be found in Chap. 2. 

All tested IIB in Table 3.12, showed higher post-emergence activity against dicotyledons than monocotyledons. 

Among the tested IIU, IIU-4 seemed to have better pre- and post-emergence activity than other compounds at 2.25 kg ai/ha. 

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