Herbicides synergism

Chelator matal chelated cone. (mM) Herbicide synergized System I . down... 

Lichtenstein EP, Liang TT, Anderegg BN. 1973. Synergism of insecticides by herbicides. Science 181 847-849. 

A computer survey of the patent literature made a year ago came up with 515 recent patents claiming herbicidal synergies. A perusal of the abstracts of 45 of them, chosen as a sample, showed that the patent community uses a broader definition of synergy than used here they believe that there is a synergism when two herbicides control more weed species than each separately. This would better be termed "complementarity. The overlap of control range allows a lowering of herbicidal rates, which may or may not be due to a metabolic... 

There is some evidence that a previously known synergy may be due to inhibiting an oxidase. Bromoxynil and ioxynil synergize amitrole it was later found that their degradation products (their respective acids) had the same effect (39). It was proposed that this effect was due to the release of oxydase inhibiting bromine and iodine from the herbicides (39). 

Synergism of active-oxygen generating herbicides by copper and zinc chelators... 

In considering whether MFO-catalyzed metabolism of herbicides is associated with cross-resistance in Lolium rigidum we have taken, initially, an indirect approach. Growth experiments with wheat showed that the MFO inhibitors aminobenzotriazole (ABT) and PBO synergized chlortoluron when the herbicide and inhibitors were added as a soil drench (34). This synergism was presumed to be due to the inhibition of MFO-catalysed metabolism of chlortoluron (27-29). Significantly, Kemp and Caseley (2) have shown that cross-resistant Alopecurus are relatively more susceptible to chlortoluron in the presence of ABT and other... 

The mixed-function oxidase inhibitors aminobenzotriazole and piperonyl butoxide can synergize herbicide activity in resistant Lolium growing in a hydroponic system. This indicates that at least one aspect of cross-resistance in Lolium rigidum may be related to enhanced metabolic activity of mixed-function oxidazes acting to detoxify herbicides. We are now concentrating on direct studies of herbicide metabolism in resistant biotypes. 

It was already recognised by the turn of the century that high doses of fertilisers, such as Chile salpetre (NaNOj), ammonium sulfate, calciiun cyanamide and kainite (KCl, MgSO SHjO) exhibit herbicidal action. Remy and Vasters (1914) were the first to observe the phenomenon of synergism in combined preparations. They established that 10% of kainite mixed with calcium cyanamide was more active than double doses of the single components used alone. A similar enhancement of action was observed by Bolley (1901) in the case of mixtures of copper sulfate and sodium arsenite. 

Pre-screen compounds for ability to elicit resistance to herbicides (protectants) or to synergize herbicide action. 

Synergic in vitro effects of some mixtures can be determined by Hill reaction inhibition. This method is useful only when the components have quite different herbicidal activities and one of them is not a Hill reaction inhibitor. With the help of paper chromatography, a 40% synergic effect of an atrazine-defenuron (3 2) mixture was detected (166). 

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