Metosulam is a foliar absorbed, selective and translocated herbicide for controlling broad leaf weeds in cereal and some grain legume crops.
It is of low toxicity to mammals, birds and fish. Metosulam acts on the ALS enzyme in plants which is not present in animals and this is the main reason for its low toxicity. It presents little hazard to the environment because it is used at low rates and degrades relatively quickly in most field situations. Plants resistant to metosulam are expected after repeated use.
7 APPLICATION METHODS AND TIPS:
Metosulam is usually mixed with 30-100 l water per hectare and broadcast through hydraulic nozzles.
Surfactants and spray oils usually increase weed control but may cause excessive crop damage in some crops and varieties or when mixed with other herbicides.
Young, actively growing weeds are most sensitive and crops most tolerant of metosulam. Under cold, wet or stressful conditions the weeds become more tolerant and the crop less tolerant of the herbicide.
Rain within a two hours of application may reduce the effectiveness. Most of the herbicide is washed off leaves by the first 4 mm of rain.
13 SPRAYER DECONTAMINATION:
Triple rinse with water. Quarter fill the tank with clean water and add a liquid alkali detergent (eg. Surf, Omo, Drive) at 500 mL per 100 L of water and circulate through the system for at least 15 minutes.
14 HERBICIDE RESISTANCE:
Broadleaf plant populations tolerant to metosulam are expected to occur after repeated use.
Although Metosulam is a sulfonylurea herbicide (Group B) it is not expected to cause increased herbicide tolerance in annual ryegrass. This is because it has little action on annual ryegrass and therefore does not cause selection for tolerant individuals.
15 REPLANTING INTERVALS:
16 WITHHOLDING PERIODS:
17 RE-ENTRY PERIOD:
18 PROTECTIVE CLOTHING:
20 MODE OF ACTION:
Uptake and translocation:
Most of the metosulam applied to leaves is absorbed.
Within the plant, metosulam stops cell division very quickly by its action on the ALS enzyme. Secondary effects on photosynthesis, respiration and ethylene production produce the symptoms of yellowing, reddening and leaf drop.
Residual Life and Breakdown:
Species tolerant to metosulam degrade it more quickly than do sensitive plants. Degradation products are non toxic and herbicidally inactive. Herbicide resistance appears to be due to plants with a less sensitive ALS enzyme.
It does not normally affect seed germination.
Wheat - Datatine and Cadoux appear sensitive.
Effect on Clover Species:
Effect on Medic Species:
Effect on Lucerne:
Effect on Native Plants:
22 DISEASE AND INSECT EFFECTS:
23 PLANT SYMPTOMS:
Growth stops soon after application. About a week later plants will start to yellow or redden. In broad-leaved weeds this may be an intervenal yellowing. Annual weeds are usually dead within 4 weeks of spraying. Under cold and wet conditions they may remain alive as severely stunted plants. Metsulfuron has little effect on germination and weeds may emerge and grow for a week or two before dying.
Metosulam does not affect the microbes associated with N fixation in legumes.
It is very toxic to blue green algae.
Mammalian toxicity - low.
Acute oral LD50 - 5000 mg/kg (rat and mouse) [For comparison table salt is 3000 mg/kg]
Acute dermal LD50 - > 2000 mg/kg (rabbit).
Skin - not irritating.
Eye - slightly irritating.
Vapour inhalation - LC50 - > 1.9 mg/L air (rat).
Chronic oral toxicity NOEL - <100 mg/kg/day for lifetime exposure. High dose levels causes kidney toxicity rats and dogs. An increase in kidney tumours has been noted in rats fed high levels at 100 mg/kg/day over extended periods.
Not mutagenic or teratogenic (i.e. does not cause cancer or reproductive problems).
Birds - low toxicity.
Fish - low toxicity LC50 > ppm.
Invertebrates - low toxicity.
Bees - low toxicity.
Earthworms - low toxicity.
Blue green algae - highly toxic.
25 TOXICITY SYMPTOMS:
Metosulam does not usually evoke any symptoms in animals under normal exposures.
The main enzyme (ALS) that is attacked in plants does not occur in animals.
27 ENVIRONMENTAL FATE:
Metosulam has a half life in soil of 6-47 days. It is degraded by microbial action. The half life is lowest when microbial activity is highest.
It does not accumulate in animal systems.
Little is naturally degraded due to exposure to sunlight and volatilisation.
It does not hydrolyse.
Metosulam may leach in very sandy soils. Residues are normally confined to the top 100 mm of soil.
Half life in water - It degrades slowly with an aerobic half life of 84 days and an anaerobic half life of 90 days.
Water solubility at 25 C. -
Octanol:Water ratio at 25 C. -
Vapour Pressure at 25 C. - Very low
Dissociation constant -
Melting point -
Molecular weight -
Field Crop Herbicide Information (A.J. Chambers):
2. Concentration of Active Constituent : 714g/kg
Trade Name : Eclipse DowElanco
3. Formulation : Water dispersible granule
4. Poison Schedule : 6
6. Product colour : Cream/brown granules
7. Product Flammability : Non flammable.
8. Dangerous Goods Class : Not relevant.
9. Shelf Life : Unlimited.
(When stored under ideal conditions- refer Page 4)
14. Effect of Soil Organic Matter on Herbicide : NA.
15. Mode of Action :
16. Application Timing : Early post-em.
17. Rate Variations : 5 - 10 g/ha.
18. Rates Selection : Where alternative rates are recommended for specific weeds, select the higher rate for situations with high weed pressure and/or environmental conditions not conducive to good weed control.
19. Weeds Controlled : ball mustard, capeweed, Indian hedge mustard, three cornered jack/Doublegee/spiny Emex, turnip weed, wild radish, wild turnip, yellow Burrweed/Amsinckia, subterranean clover, volunteer medics, volunteer peas, volunteer canola, Indian hedge mustard, Three horned Bedstraw.
20. Effect on Crop : Temporary yellowing and height reduction may occur.
21. Effect on Legume Species : Variable.
22. Soil Moisture at Application :
MOIST - Ideal.
WATERLOGGED - Poor control as plants under stress.
23. Frost Effects :
24. Frost Free Days Required After Application :
25. Effect of Application Water Quality on Herbicide :
29. Recommended Filter Size : Mesh size as suitable for nozzle being used.
30. Recommended Wetter : Various depending on situation - Uptake, D C Tron and BS 1000.
31. Other Additives : None recommended.
32. Rain Fastness : 2 hours.
33. Time Interval Before Effect is Noticed : 10 - 20 days, time taken is dependant on the environment. Under hot, warm, moist conditions the plants die faster. In cool, dry conditions weed kill will be slower.
34. Weed Symptoms : Typical symptoms of metosulam activity are yellowing or reddening of the weed leaves.
35. Effect of Herbicide/Disease Interaction on Crop : Brown leaf spot and insect damage may make lupins more susceptible to damage.
36. Withholding Period : 14-28 days.
37. Plant-Back Period :
38. Spray Tank Clean-Up : Triple rinse with water. Quarter fill the tank with clean water and add a liquid alkali detergent (eg. Surf, Omo, Drive) at 500 mL per 100 L of water and circulate through the system for at least 15 minutes.
39. Other comments : Poorer results noted when sprayed under overcast conditions and 40 points of rain on the following day compared to that sprayed 1 day before in fine sunny weather at Hyden 1995.
Numbered data based on Field Crop Herbicides by A.J. Chambers.
Collated by HerbiGuide. For more information see www.herbiguide.com.au or phone 08 98444064.