3 ACTIVE INGREDIENTS:Iodosulfuron-methyl-sodium 50 g/kg plus a crop safener (mefenpyr-diethyl 150 g/kg) as a water dispersible granule
4 CHEMICAL GROUP: B.
Sulfonylurea
5 RELATED HERBICIDES:
Chlorsulfuron, Logran, Londax, Metsulfuron, Oust
6 GENERAL DESCRIPTION:
Iodosulfuron is used mainly as a post emergence herbicide for control of a range of grass and broad leaf weeds in wheat.
It is a selective and translocated herbicide that is absorbed through the leaves and roots. It is of low toxicity to mammals, birds and fish. Iodosulfuron acts on the AHAS (acetohydroxyacid synthase) 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 iodosulfuron have developed and are expected after repeated use.
7 APPLICATION METHODS AND TIPS:
Add a non ionic wetting agent or spraying oil such as Hasten®. Some spraying oils increase weed control but may cause crop damage.
Iodosulfuron is usually mixed with 30-100 l water per hectare and broadcast through hydraulic nozzles. It can be applied in ultra low volumes of carrier.
Acidifiers may increase iodosulfuron absorption, especially on waxy plants.
Weeds are most sensitive and crops most tolerant of iodosulfuron when they are young and actively growing. Under cold, wet or stressful conditions the weeds become more tolerant and the crop less tolerant of the herbicide.
For each 10 degree drop in temperature the crops ability to break down iodosulfuron drops by a factor of 2 to 5, thus under cold conditions crop damage is more likely.
Rain within 8 hours of application may reduce the effectiveness of post-emergence applications. Most of the herbicide is washed off leaves by the first 4 mm of rain.
Temperature and relative humidity have little effect on the effectiveness of iodosulfuron apart from their indirect effect on plant growth rates.
Crops physically damaged by wind, sandblasting, hail or insect attack may be damaged by the application of iodosulfuron.
Some crop yellowing and growth retardation may occur within a month of spraying especially if the crop is stressed.
Applications on dry sandy soils followed by leaching rains may result in crop damage.
Crop damage may occur on highly alkaline soils with a pH>8.5.
10 WATER QUALITY:
Hard or salty water may reduce its effectiveness.
Up to ox% of the iodosulfuron activity could be lost each day it is kept in the spray tank during warm weather if the water is acidic or acidifiers have been added.
Soil colloids have little effect.
11 COMPATIBILITY:
Non ionic surfactants and spraying oils increase the absorption.
Iodosulfuron is antagonistic with diclofop and other grass herbicides.
Iodosulfuron may be synergistic with hormone herbicides and metsulfuron.
Iodosulfuron forms stable metal and ammonium salts so it is incompatible with most trace elements including zinc and ammonium sulphate.
14 HERBICIDE RESISTANCE:
Plant populations tolerant to iodosulfuron are expected to occur naturally after repeated use. Plants that are resistant to group B (Sulfonylurea) herbicides will normally be resistant to iodosulfuron.
Tolerant crops can be developed.
Herbicide resistance is due to plants with a less sensitive enzyme or with an increased ability to break the herbicide down.
Black Nightshade are tolerant.
15 REPLANTING INTERVALS:
Some crops should not be planted for many months after iodosulfuron application. This is because they are sensitive to extremely low levels of iodosulfuron and not because of high levels of persistence of the herbicide in the soil.
Crop
Time
Barley
1 day
Beans
21 months
Bluegrass
9 months?
Canola
9 months
Cereal Rye
1 day?
Corn
9 months?
Cotton
9 months?
Flax
9 months?
Guar
9 months?
Lentils
21 months
Lucerne
9 months?
Lupins
9 months
Medic
21 months
Millet; Pearl
9 months?
Millet; Setaria
9 months?
Mung Beans
9 months?
Mustard
9 months?
Oats
9 months?
Onions
21 months?
Peas
21 months
Potatoes
9 months?
Ryegrass
9 months?
Safflower
9 months?
Sorghum
9 months?
Soybeans
9 months?
Sugar Beet
21 months?
Sunflowers
9 months?
Triticale
1 day?
Wheat
1 day
16 WITHHOLDING PERIODS:
Crop
Type
Time
All
Harvest
All
Grazing
17 RE-ENTRY PERIOD:
None required.
18 PROTECTIVE CLOTHING:
Overalls.
19 SOIL:
20 MODE OF ACTION:
Group B, sulfonylurea, ALS inhibitor.
Uptake and translocation:
Most of the iodosulfuron applied to leaves is absorbed on the day of application. Small amounts (5-10%) move out of the leaf to roots and shoot base with little moving upwards. Most is translocated in the phloem.
Broadleaf weeds have greater absorption and translocation than the grasses.
Absorption by roots from the soil solution is not as efficient.
Physiological effects:
Within the plant, iodosulfuron stops cell division very quickly by its action on the AAHAS enzyme. Secondary effects on photosynthesis, respiration and ethylene production produce the symptoms of yellowing and reddening of grasses and leaf drop in broad-leaved weeds.
The safener mefenpyr-diethyl acts by increasing the rate of breakdown of the product in crop plants.
The growth of seedlings may be stimulated at low dose rates.
It does not normally affect seed germination.
Residual Life and Breakdown:
21 SELECTIVITY:
Species tolerant to iodosulfuron such as the cereals degrade it more quickly than do sensitive plants. Differences in tolerance to post emergence applications to wheat varieties is due to differing rates of breakdown. Sensitive varieties produce less spikelets/ear. Degradation products are non toxic and herbicidally inactive.
Black Nightshade are tolerant.
Crop tolerance:
The tolerance of crops to iodosulfuron is reduced in soils with high pH, sandy soils, soils with marginal zinc, manganese or copper levels, if leaching rains occur soon after spraying or if crops are waterlogged before or after spraying.
On areas where iodosulfuron has induced trace element deficiencies the following may reduce losses;
1 kg zinc sulphate plus
1 kg copper sulphate (or 0.5 kg copper oxychloride) plus
4 kg manganese sulphate (or 6 L Mangasol) plus
250 mL wetting agent in 100 L/ha of water applied in the cool of the day or at night.
5-7 days later spray a mix of 30 kg Urea in 100 L/ha water in the cool of the day. Pre mix urea in water to prevent freezing in the spray tank.
Varietal sensitivities:
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 post emergence applications. About a week later plants will start to yellow or redden. In broad-leaved weeds there may be an inter venal yellowing. Annual weeds are usually dead or severely stunted within 4-6 weeks of spraying. Symptoms can be quite slow to develop and assessment of weed control should be at least 6-8 weeks after spraying. Under cold and wet conditions they may remain alive as severely stunted plants with few roots and die from water stress in spring. Iodosulfuron has little effect on germination and weeds may emerge and grow for a week or two before dying.
SECONDARY EFFECTS:
Iodosulfuron does not affect the microbes associated with N fixation in legumes.
Iodosulfuron and residues in the soil from previous applications may make the crop more susceptible to Take-All, CCN, Rhizoctonia and zinc, copper and manganese deficiency.
It has no impact on N or P nutrition of cereals.
24 TOXICITY:
Summary:
May damage eyes. Wear goggles or a face shield.
Oral Toxicity (ingestion by mouth) - Low.
Dermal Toxicity (absorption by skin) - Low.
Toxicity to Other Species - Low.
Details:
Poison Schedule - 5
Mammalian toxicity - low.
Acute oral LD50 - >5000 mg/kg (rat). [For comparison table salt is 3000 mg/kg]
Acute dermal LD50 - > 5000 mg/kg (rabbit).
Skin - Slightly irritating (rabbit). Non sensitising (Guinea pig).
Iodosulfuron does not usually evoke any symptoms in animals.
The main enzyme (AHAS) that is attacked in plants does not occur in animals.
26 FIRST AID:
Telephone 13 11 26.
If Swallowed - do not induce vomiting. Wash mouth out with water. Keep patient at rest. Seek medical advice.
If on Skin - Wash with soap and water.
If in Eyes - Wash out with water immediately and SEEK URGENT MEDICAL AID.
If inhaled - Remove patient to fresh air.
Advice to doctor - The product is a severe eye irritant and can cause irreversible damage to eyes. Consult an ophthalmologist. For other routes of exposure treat symptomatically. If large amounts have been swallowed, pump out stomach and administer charcoal and sodium sulphate. Monitor liver and red blood cell function. There have been no documented cases of poisoning up to 2001.
27 ENVIRONMENTAL FATE:
Broken down mainly by microbial activity.
Iodosulfuron has a half life in soil of about xxx. Its half life is much longer in soils with high pH (up to 9 months).
Little is naturally degraded due to exposure to sunlight and volatilisation. Iodosulfuron has an EPA classification for soil mobility that ranges from
It is not expected to cause ground water contamination problems due to its relatively rapid degradation in plants and soils, low use rates and low toxicity.
Bio Accumulation:
Iodosulfuron does not accumulate in the milk or tissues of animals. Most is excreted intact in the urine of mono gastric animals or as a conjugate in ruminants.
31 PROPERTIES:
Water solubility at 25 C. - Partially soluble, disperses.
Octanol:Water ratio at 25 C. - at pH 5; at pH 7
Vapour Pressure at 25 C. - Low. 6.7 x 10-9
Dissociation constant - pKa
Melting point - C.
Molecular weight -
Bulk density - approximately 0.7g/mL
Half life in water - days at pH5 and 35 C. days at pH8 and 35 C.
pH - 8.9 at 1% solution in water.
It has a leaching index of . (for comparison, trifluralin is 0-1 and chlorsulfuron is 25-30).
It has a half life days at 20 degrees and 50% WHC.
Auto ignition temperature - 378 degrees C
Corrosiveness - Non corrosive.
Field Crop Herbicide Information:
IODOSULFURON
2. Concentration of Active Constituent : 50g/kg
Trade Name : Hussar - Aventis
3. Formulation : Water dispersible granule.
4. Poison Schedule : 5
6. Product colour : Brown granules
Odour: aromatic.
7. Product Flammability : Non flammable. Avoid build up of dust as a dust/air mixture can be explosive.
8. Dangerous Goods Class : Not classified as a dangerous good for transport by road or rail.
9. Shelf Life : Unlimited. Do not store for prolonged periods in direct sunlight.
(When stored under ideal conditions)
10. Mixtures Compatibility :See label.
11. Registered Crop(s) : Early post emergence on Wheat.
12. Effect of Soil Texture on Herbicide : Crop damage may occur on light sandy soils when leaching rainfall follows application.
13. Effect of Soil pH on Herbicide : Don't use on highly alkaline soil with pH>8.5.
14. Effect of Soil Organic Matter on Herbicide : Do not apply to soils very low in organic matter as crop injury may occur.
15. Mode of Action : Selectivity due to detoxification in resistant species; action is by inhibition of cell division in the growing tips of roots and shoots in susceptible species. Both tolerant and susceptible species absorb iodosulfuron. Post-emergent:-foliar translocated.
16. Application Timing : Early post emergence on wheat.
17. Rate Variations : 150-200 g/ha.
18. Rates Selection :
19. Weeds Controlled : See label.
20. Effect on Crop : Temporary yellowing and stunting may occur.
21. Effect on Legume Species : Knockdown and residual control of clovers will be seen. DO NOT use in crops undersown with legume pasture species, eg medics, clovers.
22. Soil Moisture at Application :
DRY - Root uptake reduced thus efficacy reduced.
MOIST - Ideal.
WATERLOGGED - Poor control as plants under stress. May damage crop.
23. Frost Effects : Immediately prior to, during and after application possible decrease in efficacy as weeds are stressed. Immediately prior to and during application risk of temporary herbicide damage to crop. After application the greater the number of consecutive days of frost the greater the risk.
24. Frost Free Days Required After Application : Not just a function of frost - will depend on daily temperatures which will influence the rate of growth.
25. Effect of Application Water Quality on Herbicide :
Saline Water - Little effect.
Soil Colloids - Little effect.
26. Recommended Water Volume : 50-100 L/ha boom recommended by Aventis. Rates down to 20 L/ha are used by farmers.
27. Nozzle Type : Flat fan. Droplet size 200-300 micron.
29. Recommended Filter Size : Mesh size as suitable for nozzle being used.
30. Recommended Wetter : Non ionic wetting agent or Hasten Spray oil.
31. Other Additives : None recommended.
32. Rain Fastness : 8 hours.
33. Time Interval Before Effect is Noticed : 10 - 30 days, time taken is environmentally dependant. Under hot, warm, moist conditions the plants die faster. In cool, dry conditions weed kill will be slower.
34. Weed Symptoms : Typical symptoms of iodosulfuron activity are yellowing or reddening of the weed leaves.
35. Effect of Herbicide/Disease Interaction on Crop : CCN and Rhizoctonia: crop damage may occur. Generally the disease puts the crop under stress and therefore may cause crop injury. The effects of CCN and Rhizoctonia can be accentuated after application.
36. Withholding Period : 0 days for harvesting. 28 days for grazing.
37. Plant-Back Period : See above.
38. Spray Tank Clean-Up : Drain tank and flush with clean water for a minimum of 10 minutes. Fill the tank with clean water and add 300 mL household chlorine bleach (containing 4% chlorine)/100 L water, flush hoses and stand 15 minutes with agitation engaged, repeat. Rinse the tank thoroughly with clean water to remove traces of bleach. Remove the nozzles and screens and clean separately.
39. Other Comments :
In soils where there are marginal levels of zinc and copper, the use of iodosulfuron on wheat may induce a deficiency in these trace elements causing a subsequent yield loss. Do NOT empty tank washings near trees.
Dry conditions will favour high carry-over of iodosulfuron to the following year and residual damage may occur to susceptible crops.
Continuous agitation is required to maintain a suspension.
Numbered data based on Field Crop Herbicides by A.J. Chambers.
33 REFERENCES:
Acknowledgments:
Collated by HerbiGuide. For more information see www.herbiguide.com.au or phone 08 98444064.