\m 19 6 91 2 1 'The Use and Purpose of Spray Adjuvants for Foliar Fungicides' \m 20 7 32 2 2 'Introduction' \m 36 14 33 2 2 'Terminology Associated with Spray Additives' \m 80 36 27 3 2 'All Adjuvants Are Not Alike' \m 98 44 118 3 2 'Adjuvants With Non-Systemic Fungicides' \m 122 56 35 3 2 'Adjuvants with Systemic Fungicides' \m 146 68 92 4 2 'Buffering Agents' \m 154 71 9 4 2 'Considerations for Adjuvant Use' \t'September 1983' 'VI D-' \a Dr. Tom Kucharek, Extension Plant Pathologist \a \a PLANT PROTECTION POINTER NO. 37 \a The Use and Purpose of Spray Adjuvants for Foliar Fungicides Dr. Tom Kucharek, Extension Plant Pathologist \h 1 'The Use and Purpose of Spray Adjuvants for Foliar Fungicides' \h 2 'Introduction' PLANT PROTECTION POINTER NO. 37 The Use and Purpose of Spray Adjuvants for Foliar Fungicides It is possible that chemicals added to a foliar fungicide spray (fungicide + water) could alter effects of the spray in relation to spray delivery efficiency, deposition on the target plant, and toxicity of the spray to the target pest(s) (fungus, bacterium, etc), target host, and other biologicals. Alterations may be beneficial or non-beneficial. Many alterations probably occur and are not recognized while other alterations are identifiable or purposeful. As the number of ingredients (fungicides, insecticides, nutrients, adjuvants, etc) increase within an agricultural spray (tank mixes), alterations in chemical make-up and effects of the final spray become less predictable without carefully conducted comparison tests. \h 2 'Terminology Associated with Spray Additives' Terminology Associated With Spray Additives: Certain agricultural chemicals are sold and used as spray additives with the primary purpose of improving some aspect of pesticide delivery or function. It is important to realize that fungicide formulations (that which you purchase) contain additives beside the active ingredient. Terminology associated with spray additives is confusing for farmers and everyone else. No single system of classification for additives is used colloquially or on a scientific basis. Some individuals use adjuvant and others use surfactant to represent chemicals added to the spray tank or incorporated within formulations that facilitate or modify the action of a pesticide (active ingredient). In practical terms, the words "facilitate" or "modify" should relate to enhanced control of pests or improved environmental safety. The future use of standard terminology is unlikely because adjuvants are considered by some to be non-pesticidal or even inert. In fact, and EPA registration is not necessary for adjuvants. The modes of action of formulated adjuvants are imperfectly understood rendering classification difficult. Finally, manufacturers commonly use or invent words to confer uniqueness to their product, thereby adding to existing confusion. This author uses the term "adjuvant" to encompass those chemical additives, not classed as pesticides, that are designed primarily to enhance pest control, spray operations or environmental safety. Adjuvants include surfactants, supplements, detergents, wetting agents, penetrants, oils, crop oils, vegetable oils, phytoblands, stickers, film foamers, extenders, spreaders, spreader- stickers, deposit builders, binders, thickening agents, film makers, foams, emulsifiers, dispersants, antiflocculants, stabilizing agents, synergists, sequesterents, safeners, coupling agents, co-solvents, compatibility agents, buffering agents, humectants, antifoam agents, modifiers, all purpose spray adjuvants, etc. Many of these terms are used interchangeably. For example, wetting agents and spreaders might be used interchangeably indicating that surface tension of the spray on the target surface is reduced. Stickers, binders, extenders, etc, are adjuvants that allow spray residue to resist washoff. \bSome individuals might classify some pesticides as adjuvants because some pesticides added to a fungicide spray modify the performance of the spray. For example, when maneb or mancozeb fungicides are added to copper fungicide sprays, bacterial spot control is enhanced on tomato and pepper. By definition, however, maneb or mancozeb are not adjuvants in the marketing sense because they are used primarily as pesticides. \h 2 'All Adjuvants Are Not Alike' All Adjuvants Are Not Alike: Growers often purchase adjuvants, not realizing that all adjuvants are not the same in function. If an adjuvant is available and the price is right, a purchase is often made with the idea that one adjuvant functions the same as another. If the grower knows what he wants an adjuvant to do, he should read the labels of the many available products to determine what claims, if any, are made and then determine which product is suitable. It is possible that the type of adjuvant that is needed may have to be ordered by your dealer. He may maintain an inventory of products that do not include what you need. For example, the dealer may stock Ortho X-77 which is a spreading agent but does not contain a sticking agent. He may stock Chevron Spray Sticker which is a sticker and not a spreader. Your dealer may stock Triton B-1956, a spreader- sticker, which is designed for high-volume sprays, not those volumes (3-10 gpa) used by aircraft applications. For aerial applications the spreader-sticker Triton CS-7 is available. \h 2 'Adjuvants With Non-Systemic Fungicides' Adjuvants With Non-Systemic Fungicides: Enhancement of non-systemic, foliar fungicide effects with adjuvants is attained primarily by utilizing those adjuvants that possess spreading (wetting) and sticking properties. That is, one is attempting to evenly cover as much of the leaf surface as possible with the spray, thus the need for a spreader, and further one is attempting to maintain the spray residue on the leaf surface for periods of time, thus, the need for a sticker. Protectant fungicides such as Bravo 500, Difolatan 4F, Du-ter, Manzate fungicides, Dithane fungicides, Manex, Botran, Dyrene and copper-containing fungicides function on the surface of the plant tissue. Extremely small amounts of these fungicides may enter within host tissue with or without spray adjuvants, but these fungicides function primarily as protectants on the plant surface against penetration by fungi and bacteria. Although certain spray adjuvants might facilitate some penetration of non- systemic fungicides into plant tissue, this effect is not necessary or even desirable for most available, non-systemic, foliar fungicides. For example, phytotoxicity may occur when adjuvants that increase solubility of fungicides or increase penetration of fungicide into the plant are used. If one were adding an adjuvant to some herbicide sprays, one would want some penetration enhancement. \h 2 'Adjuvants with Systemic Fungicides' Adjuvants With Systemic Fungicides: Some systemic fungicides such as Benlate, Bayleton, Baycor, Tilt, Mertect and Ridomil (Subdue) are protective and therapeutic. The use of adjuvants that spread the spray deposition on the plant surface or aid in retention of a systemic fungicide on the plant, until most of the chemical is absorbed into the plant, should be beneficial with systemic fungicides. However, using spreader-stickers with systemic fungicides for enhanced disease control does not result in consistent results. Where a synthetic oil is used in conjuction \bwith a fungicide like Benlate, increased control is apparantly due to the pesticidal nature of the oil, not to the enhancement of Benlate. Synthetic oils used as adjuvants have been known for some time to be mildly fungicidal or fungistatic to numerous fungi. Synthetic oils have been used by themselves for disease control. As logical as it might seem that increased penetration of plant tissue with systemic, chemotheraputant fungicides should result in better control of a disease, such is not always the case. With some systemic fungicides possessing therapeutic properties, numerous spray adjuvants have been shown to increase fungicide residues within the plant but the degree of control was not enhanced nor could spray intervals be increased. The use of adjuvants with systemic fungicides is recently attracting more research efforts because of the increased number of systemic fungicides and the uncertainties that exist on this subject. \h 2 'Buffering Agents' Buffering Agents: In some situations, buffering agents are needed to adjust pH of the final spray mix. For example, the effectiveness of Benlate is reduced if the water pH is too high. Absorbtion of Benlate into the plant is enhanced with lower pH values of water. \h 2 'Considerations for Adjuvant Use' Considerations for Adjuvant Use: BECAUSE OF THE MANY UNCERTAINTIES THAT EXIST WITH SPRAY ADJUVANTS AND THE MULTITUDE OF AVAILABLE ADJUVANTS IN THE MARKETPLACE, THE FOLLOWING CONSIDER- ATIONS FOR ADJUVANT USE WITH FUNGICIDES IN FLORIDA ARE PRESENTED. 1. Determine what type of adjuvant, if any is needed. 2. Read the labels of those fungicides you will use in the spray to determine what the fungicide manufacturers have to say about adjuvant usage with their products. If the manufacturer has collected a data base to substantiate the benefits or shortcomings of adjuvants with their product, the label should indicate such. Admittedly, ambivalent statements about use of an adjuvant with certain fungicides exist on certain labels. In such a situation, growers should conduct their own tests to determine the benefits or short- comings of adjuvant use. Because of the multitude of adjuvant products and their unknown direct or indirect effects, manufacturers are naturally reluctant to make definitive statements about such on labels. Generally, for wettable powder fungicide formulations, spray adjuvants possess- ing spreading AND sticking agents will enhance effectiveness to some degree when used at the prescribed rate. Spectacular enhancement in disease control should not be expected. Use of adjuvants with spreading or sticking agents in conjunction with flowable fungicide formulations does not appear to be as essential as with the wettable powder formulations. In fact, some flowable fungicide labels clearly discourage use of adjuvants with favorable fungicides (Difolatan 4F). The manufacturer of Bravo 500 states "do not combine Bravo 500 in the spray tank with...surfactants...unless your prior use has shown the combination physically compatible, effective and non-injurious under your conditions of use." (Obviously the responsibility is on you.) Some manufact- urers of flowable fungicides (Manzate Flowable, Manex, Dithane FZ) do not make any statement on the label regarding use of adjuvants with their product and verbally representatives from different manufacturers are not uniform in their opinions concerning use of adjuvants with their respective flowables. Some have stated that spreader-sticker adjuvants might be needed with their flowable \bproducts on slick leaf crops like onions and crucifers. The available data on this subject is scanty and understandably manufacturers are reluctant to make definitive statements on their labels about this complex issue. The use of adjuvants with spreading agents in conjunction with flowable fungicides could conceivably encourage residue wash-off from rain because flowables generally contain some spreading agents within the formulation. Such could be said for wettable powder fungicides but field experience by numerous individuals indicates that inadequate spreading and sticking results when some wettable powders are used without such an adjuvant. 3. Read the label of various adjuvant products to determine if the adjuvant possesses spreading agents, sticking agents, spreading and sticking agents or other types of additives. 4. Consult with knowledgeable individuals about their experience with various products. 5. The use or non-use of spray adjuvants that enhance penetration of systemic fungicides into the plant should be decided after consulting with representa- tives of the fungicide manufacturer. 6. Considerations regarding leaf age in relation to need of adjuvant use must be made in relation to a specific crop at a particular growth stage. In fact, this consideration may be futile to reconcile or consider in practical terms. Extensive variation in wetting and absorbing characteristics exists in relation to leaf age as judged by numerous observations and investigations. It is generally agreed that waxes, cutins, pectins, and cellulose, that is those chemicals associated with the "skin" (cuticle and related structures) of leaf and stem tissue of plants, tend to decrease wettability, adsorbing and absorb- ing characteristics of plants. However, young leaves that contain less of these chemicals are considered by numerous individuals to be more difficult to wet. When one is discussing quantities of surface waxes in relation to leaf age, strong consideration must be given to whether old leaves refer to oldest leaves or those that have recently attained full size. New, fully expanded leaves can have more wax than oldest leaves. Waxes are reduced over time due to weathering and other factors. It has been experienced that greenhouse- grown plants of one species are more difficult to wet than those grown outdoors. 7. Hairy leaf crops or varieties are more apt to require the use of a spreading agent especially at lower spray volumes. Hairy leaf crops or varieties are less likely to lose spray deposits from water wash and therefore, the use of sticking agents on such plants become less influential if a spreader is used. 8. On crops or crop stages that are characterized primarily by vertically- oriented leaves, sprays with spreader-stickers should result in better initial spray coverage and spray retention. 9. The slicker (waxier) the leaf type at the time of spraying the more apt that a spreader-sticker will be beneficial. 10. The overall importance of spreader-sticker adjuvants becomes less critical when spray intervals are shortened, spray programs are started early in relation to disease severity and other disease control tactics are strictly adhered to. Keep in mind that most legal uses of fungicides are registered based on efficacy tests where adjuvants were not considered in testing and registering protocol. \v \b11. Avoid using detergents for spreading agents. Florida does not have soft water. Mineral content of water in Florida varies but all natural sources contain enough minerals to combine with ionic types of adjuvants, including detergents, resulting in scum and mineral deposits within spray equipment. Most commercially available adjuvants are non-ionic. Non-ionic adjuvants are less likely to combine with minerals in the water. 12. Generally, fewer problems result with non-ionic adjuvants (the most common type currently available). Non-ionic adjuvants are "less reactive" and are therefore less likely to produce undesirable effects in relation to the toxicity to the target pest(s), or target host(s). 13. Especially with non-systemic, wettable powder fungicides, the use of a spreader adjuvant should be accompanied by a sticker unless one desires easy spray residue loss (late season sprays on vegetables). Although spreaders enhance initial coverage of plant tissue they also facilitate easier wash off of the initial fungicide deposit, especially as spray volume is increased. With low volume sprays, spreaders can enhance initial spray coverage. Sticking agents can enhance redistribution of the fungicide on plant tissue. 14. In spray operations where small spray droplets are formed, as in high spray pressure situations, spreader adjuvants may reduce "bounce", thereby allowing a greater amount of the fungicide to remain on plant surface. 15. Producers of crops that sell their produce on the basis of cosmetic attraction (ornamentals, tobacco, numerous fruits and vegetables) should not use adjuvants in an extensive manner without first determining on a small scale if deleterious effects could result. 16. Growers should not expect adjuvants to perform miraculous functions.