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Store Your Herbicides And Adjuvants Properly
Some farmers are interested in purchasing bulk inventory of herbicides, other pesticides and/or adjuvants during the fall and winter months. Whether it makes economic sense or for other reasons, some want to start making pesticide purchases well before the growing season begins.
If that's your plan, Extension agronomist Dwight Lingenfelter recommends you begin now by working with your dealer to discuss these issues. The intent is not to stockpile products but to have a modest supply for use during the next growing season. Keep in mind that many herbicides (especially liquid products) typically don't have a long shelf life, so make sure to keep your inventory fresh and don't purchase more than what you can use within two to three years.
In general, dry products tend to last longer if properly stored, but their effectiveness still degrades over time.
Also, when placing herbicides on storage shelves, make sure to put the dry products on the upper shelves in case the liquid products leak so they won't contaminate the dry materials.
Aside from having a secure and dry storage facility, one of the biggest concerns when storing herbicides over the winter months is low temperatures in the storage room. In general, freezing temperatures can change and negatively affect the chemistry of some pesticides inside the container and can also damage the container itself. Premixed liquid products that contain multiple active ingredients seem to be affected more so by low temperatures than single active ingredient products. Some premixes tend to separate in the container and can be difficult to get back into a homogeneous liquid prior to use in the spring. Generally, pesticides are best stored at 40 to 90 degrees Fahrenheit. However, it seems that many herbicides, especially the newer formulation types, are not affected as much by low storage temperatures.
Many labels (e.G., atrazine, 2,4-D LV4, Acuron, Anthem Maxx, Corvus, metribuzin, Gramoxone 3.0, Sharpen, Enlist One, Valor, Osprey, Quelex, most dry herbicides, and many others) have no minimal temperature limit but simply state the product is to be stored in its original container and in a dry, secure location. Some stipulate that the product should not be in direct/extreme heat or sunlight. Others (such as Liberty, Prowl H2O/EC, Halex GT, Pursuit, Reflex, Crossbow, etc.) have specific minimum temperature limits that range between 40 degrees and minus 10 degrees depending on the product.
There are a few products, such as Prowl H2O, Engenia, Weedar 64 (2,4-D amine), and others, that can be frozen and used once thawed. But make sure to warm the product for several days and shake periodically slowly. However, if the contents do not redissolve into a consistent mixture, it probably should not be used.
During this process, check the container for cracks by slowly inverting or rolling it on the ground. To be sure, it is best to read the "Storage and Disposal" section of the product label, which provides specific details about that product. Keep in mind all these considerations are useful for adjuvant products as well.
Lastly, farm chemicals are expensive, so it's a good idea not to draw attention to your full storehouse; otherwise, you may find it not so full one morning. For more details and many useful links, please refer to the National Pesticide Information Center's webpage.
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Adjuvant Use With Herbicides: Factors To Consider
WS-7WS-7 (Reviewed 5/01)Purdue University Cooperative Extension ServiceWest Lafayette, Indiana
Thomas N. Jordan, Extension Weed Specialist-IPM
The terminology for herbicidal additives is confusing. It is often assumed that any material that lowers the surface tension of water in the spray mixture or increases the wetability of the spray solution on plant leaf surfaces is an adequate adjuvant. Since the exact role and function of agricultural adjuvants are not fully understood, the various terms that are used to describe spray adjuvants are often erroneously assumed to be synonymous.
The following discussion is intended to describe the different types of adjuvants that are used with herbicides and explain their role in increasing herbicide efficacy.
Adjuvants are used in herbicidal spray solutions as:
It is obvious that, with this array of uses and purposes, the term adjuvant encompasses a wider meaning than wetting agent or surfactant. While all surfactants or wetting agents are adjuvants, not all adjuvants are surfactants or wetting agents. There are many adjuvants that have little, if any, effect on herbicidal activity.
These types of adjuvants include:
Adjuvants are materials that facilitate the activity of herbicides or that facilitate or modify characteristics of herbicide formulations or spray solutions.
Surfactants are materials that facilitate and accentuate the emulsifying, dispersing, spreading, wetting, or other surface modifying properties of liquids.
Wetting agents are compounds that, when added to a spray solution, cause it to cover plant surfaces more thoroughly.
Adjuvants are either included in herbicide formulations as part of the total product, or are sold as an additive to be mixed with herbicide products in a spray tank. Adjuvants can be classified according to their type of action, and the choice of an adjuvant should be based on the specific need to facilitate the herbicide being applied.
There are three basic types of adjuvants used with herbicides:
Activator adjuvants which include surfactants,wetting agents, penetrants, and oils.
Spray modifier agents which include stickers, film formers, spreaders, spreader-stickers, deposit builders, thickening agents, and foams.
Utility modifiers which include emulsifiens, dispersants, stabilizing agents, coupling agents, Co solvents, compatibility agents, buffering agents, and anti-foam agents.
Spray modifier agents and utility modifier adjuvants, are usually found as part of the herbicide formulation, and thus, are added to the herbicide product by the manufacturer. Activator agents are the best known class of adjuvants because they are normally purchased separately by the user and added to the herbicidal solution in the spray tank. However, there may be a need, at times, to add an adjuvant from any of the three classes to a spray solution to achieve a desired result.
Most of the commonly used postemergence herbicides will show increased activity when an activator agent is added to the spray mixture. The manufacturer of the herbicide will specify on the produce label the specific type of adjuvant to add, as well as the concentration at which the adjuvant should be added in order to maximize the efficacy of the herbicide.
When an adjuvant is required in a herbicidal spray mixture, keep in mind the purpose for adding the adjuvant, and use the type of adjuvant that meets the required need.
If spray drift onto sensitive areas is a problem, buy a product to help control drift, not one which increases penetration of the herbicide into the plant foliage. If foaming in the spray tank is a problem, a product which will lower foaming activity should be considered.
Other than adding an adjuvant to decrease spray drift risk or prevent excessive foaming of the spray solution, on-farm adjuvants should primarily be used in accordance with the product label instructions to increase wetting and penetration of foliar applied herbicides.
SurfactantsConfusion frequently occurs concerning the proper selection and use of surfactants with herbicides. It is wrong to assume that any product that lowers the surface tension of water or increases the wetability of a spray solution can be used as a surfactant.
For example, such products as household soaps and detergents can combine with hard water to form precipitant or scum that will interfere with the performance of spray equipment.
Also, most liquid detergents have a fairly low concentration of surfactants (10 to 20%) compared with a 50 to 90% concentration which is usually found in agricultural surfactants. Agricultural surfactants do not form precipitants, and tire equally effective in hard and soft water as well as cold or warm water.
There are four basic groups of agricultural surfactants:
Anionic and cationic surfactants form electrical charges in water (negative and positive, respectively). Nonionic surfactants, do not form an overall charge. While amphoteric surfactants may or may not form a charge depending on the acidity of the spray solution. Nonionic surfactants are the type usually sold for adding to herbicide spray solutions.
These surfactants are good dispersing agents, stable in cold water, and have low toxicity to both plants and animals. Cationic surfactants can be toxic to plants and are not generally used with herbicides. Anionic surfactants have good foaming abilities and are often blended with nonionics to provide the wetting and emulsifying properties of a herbicide formulation.
Crop OilsCrop oils and crop oil concentrates, like surfactants, improve coverage of plant surfaces. However, crop oils keep the leaf surface moist longer than water, allowing more time for the herbicide to penetrate, and thus, increasing the amount of herbicide that will enter the plant.
Before the early 1970's, crop oils contained only 1 to 2% surfactant and were used at rates of 1 to 3 gallons per acre with herbicide solutions. Today, crop oil concentrates contain (80 to 87% oil and 13 to 20% surfactants and are used at rates of about 1 to 2 quarts per acre.
The oil component of crop oil concentrates can be derived from either petroleum oil or vegetable oil. One of the most important uses of crop oil concentrates is postemergence herbicides used in corn and soybeans.
Inorganic SaltsRecently there has been an interest in using inorganic salts as additives to herbicide solutions. While this practice is becoming increasingly popular, there is still relatively little known about the mechanism of action of inorganic salt additives in herbicide sprays. Several popularly used herbicides have included on their label the use of inorganic salts, alone or in combination with surfactants or crop oil concentrates.
Most research indicates that inorganic salts of the monovalent cations of ammonium ( NH4+), potassium ( K+) , or sodium (Na+) salts generally result in the greatest increase in phytotoxicity of water soluble herbicides, with ammonium sulfate being the most popular salt additive. Other salts of divalent and trivalent cations such as calcium (Ca++), zinc (Zn++), and iron (Fe++), for the most part, decrease the activity of commonly used translocated herbicides such as 2,4-D or glyphosate.
Caution should be taken to use the correct inorganic salt that is suggested on the herbicide label, add it to the spray solution at the recommended concentration, and with the suggested surfactant or crop oil that is listed on the herbicide product label.
When purchasing a suitable agricultural adjuvant for herbicide use consider the following suggestions:
Do not purchase products made for household use. Many of these detergents are more expensive and less active than agricultural adjuvants. They may be mixed or combined with products that interact with herbicides to reduce the level of weed control. These products can cause foaming or equipment malfunction.
Do not consider isopropyl (isopropanol ) and other alcohols or water as active ingredients. Some products list these solvents as part of the active ingredient or as functioning agents. Most spray adjuvants will clearly show on the label, active ingredients, inactive ingredients, and principal functioning agents as a percentage of the total.
There are no "miracle" adjuvants. Most adjuvants are good products and will increase the performance of foliar applied herbicides when used at the recommended rate suggested on the herbicide label. No adjuvant used in a herbicide spray solution can justify a greatly increased price per unit, and none is so effective that the use rates can be lowered below those recommended on the herbicide label.
Soil applied herbicides do not need additional adjuvants. Maximum weed control for soil applied herbicides can best be obtained by applying the proper use rate.
ReferencesREVISED 4/94
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New Adjuvants For Accelerated And Enhanced Antibody Response
Production of commercial neutralizing antibodies or specific antibodies for biological research relies heavily on adjuvants—compounds that may have different biological roles but all result in increase of either humoral or cytotoxic immune response. One should discriminate between local adjuvants and so-called central action adjuvants. Whereas the first group of compounds changes the properties of an antigen (creating a depot of antigen, improving antigen delivery to antigen-presenting cells or attracting effector cells to the site of injection), the second group affects the recipient of the antigen by increasing its immunocompetence, which can be defined as the ability to give strong immune response to presented antigen and is related to the number of and the state of activity of immune cells participating in the desired type of immune response.
Short peptides, which often originate from protein processing in tissue, may act as immunomodulators by changing the number and activity of immune cells and thus affect (activate or suppress) the ability of the antigen recipient to develop either humoral or cytotoxic immune response1. On the basis of short peptide activating motifs that have been discovered to affect the immune system2, we have developed a family of short synthetic peptides with immunomodulating properties. These artificial peptides, with a maximum size of eight amino acids, have demonstrated the properties of both local and central action adjuvants, thus affecting the general immunocompetence of the recipient as well as promoting immune response at the site of injection. One of them, named IMMACCEL-R™, showed advantageous properties and excellent performance in accelerating immune response.
Main properties of IMMACCEL-R
IMMACCEL-R, when injected into the recipient animal, stimulates induction of cytokine cascades that closely resemble those seen at the early stages of inflammatory response, thus making the animal more prone to give a strong immune response when injected with the antigen. Among the genes affected are those encoding main cytokines and their receptors, as well as several chemokines typical of the inflammatory response (Fig. 1). When mixed with antigen and delivered together at the site of injection (intradermal or subcutaneous), IMMACCEL-R further improves the immune response by enhancing presentation of processed antigen by dendritic cells (data not shown) and increasing the specific proliferation of T-helper or T-killer cells, depending on the antigen. Owing to IMMACCEL-R's effect on immune response, earlier and stronger antibody responses are observed, as well as earlier switch of specific antibody from immunoglobulin M (IgM) to IgG1 and IgG2 isotypes. By day 28, the titer of specific antibodies is already up to 30 times higher for IgGs of γ1 and γ2a isotypes, and 2–4 times lower for IgM (Fig. 2). The adjuvant works equally well for all mammalian species tested (mouse, rabbit, goat and swine). A slightly changed version of the molecule is also effective in birds (chicken). The adjuvant is nontoxic and works with all tested types of antigens: proteins, glycoproteins, peptides and haptens conjugated to a carrier.
Figure 1: mRNA expression for different cytokines, as detected by RT-PCR.Mice were injected with either antigen (KLH; blue) or IMMACCEL-R without any antigen (orange); 48 hours later the mRNA profiles for cytokines expressed in spleens were compared to a control untreated mouse of the same sex and age. Data presented as multiples of the respective mRNA levels relative to those in the control sample (spleen of unimmunized mouse). A strong similarity is observed between expression profiles for immunized and IMMACCEL-R–treated naive mouse.
Figure 2: Antibody production.(a) Sera from mice that had been injected once with DNP-KLH, with or without IMMACCEL-R, were collected at days 0, 7, 14 and 28 and analyzed for the presence of antigen-specific antibodies of a certain isotype. (b) The relative titer of specific antibodies was analyzed by ELISA for samples from day 28. Data are shown as mean + s.D.; three mice in every group.
Use for development of antibodies
Unique adjuvant properties of IMMACCEL-R allowed PickCell to develop an accelerated protocol for production of specific antisera in rabbits. Immunization with IMMACCEL-R achieves, within 28 days, specific-antibody IgG titers in rabbits similar to those obtained with a standard 80-day protocol. When prepared against strong peptide antigen, the affinity-purified antibodies can be used in many applications and do not differ in affinity or specificity from those obtained through a standard immunization scheme (Fig. 3). We also tested the adjuvant for immunizing mice for hybridoma development. Mice were injected with E7 recombinant protein of HPV16 or HPV18 in a mix with IMMACCEL-V, and their spleens were used for fusion on day 10 after booster immunization on day 7. About 20% of all isolated clones were positive for specific antibodies to the protein used for immunization, with over 90% of clones producing antibodies of the IgG isotype.
Figure 3: Quality of sera prepared using IMMACCEL-R in 28-day immunization scheme.(a,b) Immunohistochemistry analysis of formalin-fixed sections of mouse mammary gland using antibodies to whey acidic protein (a) and mouse cytokeratin-18 (b). (c,d) Immunoblotting analysis of mouse mammary tumor cells using antibodies to mouse cytokeratin-18 (c) and mouse cytokeratin-19 (d).
Further development
As effective humoral immune response requires the presence in antigen of active T-helper epitopes and effective delivery of antigen to dendritic cells, we produced a new carrier molecule with adjuvant properties that combines dendritic cell–targeting sequences with effective T-helper promiscuous epitopes and molecules increasing the antigen presentation by dendritic cells. This new adjuvant, called MAD™, is especially effective in inducing a strong immune response to weakly immunogenic recombinant proteins and works with both standard and accelerated protocols, always providing higher titers of specific antibody. Thus, for small fusion proteins (15–30 kDa), using MAD we obtain, on average, 4–20 times higher titer while using 4 times less antigen than in immunizations without MAD.
Conclusions
Using new adjuvants from PickCell strongly accelerates the response, increases the specific antibody titer and enhances immunogenicity of poor antigens, all while using substantially less protein. This technology, already tested and used in thousands of custom antibody projects performed by PickCell, may be highly useful to all groups producing antibodies or hybridomas. Additional product information is available at PickCell's website, http://www.Pickcell-labs.Com/.
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