3 ACTIVE INGREDIENTS: Glyphosate-trimesium 600 g/L as a water soluble liquid. 413 g/L glyphosate acid.
4 CHEMICAL GROUP: M.
Glycine
5 RELATED HERBICIDES:
None.
6 GENERAL DESCRIPTION:
A non selective, translocated, leaf absorbed, non residual herbicide used extensively before planting crops.
7 APPLICATION METHODS AND TIPS:
Glyphosate is applied by hydraulic nozzles or CDA (Controlled Droplet Application) equipment mounted on air craft or ground vehicles for broadcast application. It is usually mixed with water. Its low toxicity (to the operator) makes it ideal for directed application using hand held equipment.
Various wick type applicators have been developed for applying concentrated glyphosate solutions.
Glyphosate is most effective when applied on warm, sunny days when the plants are growing vigorously.
Drought or nitrogen stressed plants are difficult to kill with glyphosate.
If plants have been heavily grazed or defoliated they should be allowed to regrow until the root:shoot ratio is around 1 before application of herbicide or the rate of herbicide may need to be increased to achieve effective control.
Whilst glyphosate is not regarded as a soil residual herbicide, it appears to reduce germination of grasses for a few days after spraying. This may be due to direct contact of the herbicide on surface seeds.
Glyphosate reacts with calcium and other di and tri valent ions in water. 50 ppm calcium will reduce activity (Shea and Tupy, 1984). The ions form a complex chelate type structure with glyphosate which reduces absorption (Thelen et al, 1995). This antagonism may be reduced by adding crystalline sulphate of ammonia at a rate of 1 kg per 100 L of water.
10 WATER QUALITY:
Hard water - 50 ppm of calcium may reduce the absorption of glyphosate. The addition of 2 kg of crystalline sulphate of ammonia reduces this antagonism.
Colloids - Cloudy water containing clay reduces the activity of glyphosate. However, clearing agents usually leaves surplus ions in the water which also reduce the activity of glyphosate. Clearing water by chemical methods is generally not recommended.
pH
Selectivity:
Non selective.
11 COMPATIBILITY:
Glyphosate combines (chelates) with di and trivalent ions. Copper, zinc, manganese, calcium and magnesium seriously reduce the effectiveness of glyphosate. This chelation is related to pH and acidifiers can be used to reduce problems with hard water. Slightly salty water and phosphates have little effect on glyphosate activity.
Plant hormonal herbicides, like 2,4-D, generally reduce the absorption and translocation of glyphosate.
Spraying oils, non-ionic wetting agents, ammonium sulphate and ammonium nitrate are usually compatible with glyphosate. On some perennial plants, these adjuvants may increase the efficacy of glyphosate considerably. On annual plants it is usually more cost effective to use extra glyphosate rather than adjuvants.
14 HERBICIDE RESISTANCE:
In 1996, annual ryegrass populations tolerant to glyphosate were discovered in Australia. Practices to reduce the development of herbicide resistance should be integrated into systems reliant on glyphosate.
Crops tolerant to glyphosate can be produced by genetic engineering.
18 PROTECTIVE CLOTHING:
20 MODE OF ACTION:
Glyphosate is slowly absorbed through the foliage and translocated to growing parts of the plants. It inhibits an enzyme in the shikimic acid pathway which reduces the supply of aromatic amino acids (phenylalanine, tryptophan and tyrosine) and consequently stops protein synthesis. It also affect potassium metabolism. Affected plants turn yellow because no new green chlorophyll is produced. Absorption of glyphosate is reduced in plants with waxy, thick or dehydrated cuticles. Thus, water stressed plants absorb less glyphosate. Surfactants, oils, ammonium, sodium or potassium ions increase absorption but have a variable effect on phytotoxicity because of their variable effects on translocation.
Glyphosate absorption is increased at high relative humidity and at high spray concentrations (low water volumes). Under low relative humidity conditions, at the time of application, additional surfactant often improves efficacy. Rain within 6 hours of application will wash glyphosate off the foliage. Most of the herbicide is washed off by the first 4 mm of rain. Translocation in the plant parallels the movement of assimilates. Good growing conditions result in good absorption, translocation and phytotoxicity. Temperature has little effect apart from its indirect effect on growth.
23 PLANT SYMPTOMS:
Typically, young growth becomes yellow 7 to 14 days after application followed by older growth and then death of the plants. On broadleaved perennials there is often inter venal yellowing, sprouting of secondary buds and compact new growth that looks like 'witches brooms'. These grow for a period then yellow and die as glyphosate is translocated from within the plant to these new sites of growth. This may occur many months after treatment.
SECONDARY EFFECTS:
Glyphosate affects the growth regulating hormone (IAA) in plants. This stimulates the growth of secondary buds and causes abnormal growth.
Perennial broad leaved plants often produce growth that looks like a 'witches broom'. It has been reported to affect Rhizobium symbiosis with legumes. Field trials in Australia indicate that this is not likely to cause problems with normal application rates and use patterns.
24 TOXICITY:
Poison schedule - 5.
Mammalian toxicity - low.
Acute oral LD50 - 5000 mg/kg
Acute dermal LD50 - > 5000 mg/kg
Skin - moderately irritating (formulated product)
Eye - moderately irritating (formulated product)
Vapour inhalation - N.E.L. 12.2 mg/L air
Chronic oral toxicity - > 2000 ppm over 90 days
300 ppm over 2 years.
Birds - almost non toxic.
Fish - almost non toxic to slightly toxic.
Invertebrates (eg. Marron) - low.
Bees - low toxicity.
25 TOXICITY SYMPTOMS:
Glyphosate does not usually cause any symptoms because of its low toxicity. Some of the formulating agents may irritate eyes and skin causing a rash if the product is misused.
26 FIRST AID:
27 ENVIRONMENTAL FATE:
Glyphosate is inactivated on contact with clay particles. This bonding is so strong that glyphosate appears to be non residual and does not move through the soil. Microflora degrade glyphosate under both aerobic and anaerobic conditions at variable rates. This results in a half life ranging from a few days to over a year. Chemical and photolytic degradation are usually negligible though some photolytic degradation has been reported in water.
There is little risk of Glyphosate contaminating water unless it has been applied directly to streams or washed off foliage hanging over streams.
In flowing irrigation channels, up to 50% of the glyphosate applied directly to the water has moved 2 to 10 Km downstream.
Glyphosate is not degraded by the higher plants or animals. It is not accumulated in the tissues of land or aquatic animals. It is accumulated in plant tissues and especially in the storage organs such as tubers, bulbs, rootstocks and rhizomes.
Glyphosate is expected to have little or no lasting effect on ecosystems because of its strong binding to clay, low mobility, low volatility, rapid degradation by common micro organisms and low toxicity to animal systems.
27 ENVIRONMENTAL FATE:
It has a half life in soil of hours.
It has an EPA classification for soil mobility that ranges from
Ground water contamination
Replanting intervals - hours to weeks.
Accumulation in milk and tissues.
31 PROPERTIES:
Water solubility at 25 C. - ppm at pH ;
Oil solubility -
Octanol:Water ratio at 25 C. - at pH 5;
Vapour Pressure at 25 C. -
Dissociation constant - pKa
Melting point - C.
Molecular weight -
Half life in water - days at pH5 and 35 C.
33 REFERENCES:
Acknowledgments:
Collated by HerbiGuide. For more information see www.herbiguide.com.au or phone 08 98444064.