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Northern Territory weed management handbook



Northern Territory weed management handbook

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Weed management handbook


E-Publications; E-Books; PublicationNT




Made available via the Publications (Legal Deposit) Act 2004 (NT).; This manual has been developed to provide detailed information about weed control in the Northern Territory.


Date:2012; Includes: Weeds in the N.T. -- Legislative responsibilities -- Strategic & planned approaches to weed management -- Prevention -- Weed control methods -- Integrated weed control -- Using herbicides correctly -- Herbicide toxicity -- Modes of action -- Herbicide resistance -- Herbicide control techniques -- Using adjuvants, surfactants & oils with herbicides -- Factors affecting adjuvant use -- Records of use -- Disposal of excess chemicals & used chemical containers -- Chemical handling training -- Weed control option tables -- Publications -- Websites.




Weeds -- Control; Weeds -- Northern Territory -- Identification

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Northern Territory Government

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53 p., : ill. (chiefly col.) ; 30 cm.

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14 NORTHERN TERRITORY WEED MANAGEMENT HANDBOOK 2012 Using Adjuvants, Surfactants a nd Oils w ith Herbicides Some herbicides need assistance to spread across and penetrate the leaf surface of target weeds. An adjuvant is an additive to herbicide, intended to improve its effectiveness. Adjuvants c an be classifi ed as surfactants, crop oils, penetrants and acidifying buffering agents. Wetting Agents or Surfactants These are products that increase the spread of droplets, aiding the wetting of waxy or hairy leaf surfaces. The most commonly used surfactants are non-ionic, these remain on the leaf once dry and allow rewetting after rain, permitting additional herbicide uptake. Crop Oils M ost crop oils contain emulsifi ers which allow them to mix with water. Some contain various levels of surfactants. Some claims regarding oil adjuvants include reduced rain-fast periods, more uniform droplet size (drift reduction), less spray evaporation and better penetration of herbicide into waxy leaves. Mineral oils are usually a blend of mineral oil and non-ionic surfactant. Products such as Ad-Here have low levels of surfactant, whilst Uptake and Supercharge have higher levels. Vegetable oils contain a wide range of products. Products containing esterifi ed vegetable oil and surfactants are the most commonly used. They have claims for superior wax-modifying characteristics and penetrating ability. They should be used strictly according to the label with selective herbicides. Hasten is an example of this product type. Penetrants T hese are compounds that help dissolve waxy cuticles. Acidifying Buffering Agents T hese help lower the pH of the spray solution, making solutions more acidic. Most herbicides are most stable when the pH of the solution is between 6 and 7 (neutral or slightly acidic). Compatibility Agents C ompatibility agents are materials that reduce the likelihood of antagonism f rom other agents in the spray solution. The most commonly used compatibility agent is ammonium sulfate. It is also used to neutralise the effect of hard water on amine formulations such as glyphosate. An example of this product is Liquid Boost. Some products combine a number of the above roles, for instance Hot-up contains a surfactant, a compatibility agent and oil. There is also a range of other adjuvants t hat are added to herbicides during formulation to improve effi cacy, increase crop safety, or improve the ease of herbicide use. These include thickeners, spreaders, stickers, anti-foamers a nd safeners. Factors Affecting Adjuvant Use Adjuvants a re usually added to increase the effectiveness of herbicides. However, use of the wrong type or rate can reduce effectiveness. It should also be noted that the addition of an adjuvant can reduce herbicide selectivity. This is not an issue for fallow and pre-emergent herbicides. Hard water can lead to poor mixing of the chemical with water. This particularly occurs with emulsifi able concentrates. High levels of calcium and magnesium ions bind with amine formulations, causing them to be less soluble and therefore less effective.

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