Spreader-stickers, or if you prefer, sticker-spreaders, are agents we can add to garden sprays to make them more effective. These additives are commonly used in commercial horticulture and in agriculture, but surprisingly most gardeners wouldn't know a spreader-sticker from a heptamerous flower.
Sticker-spreaders can be made of many different components, organic or inorganic. Often the actual ingredients in a particular brand of sticker-spreader will be kept secret, as a proprietary formulation known only within the company producing it.
Some brands use silicone-based surfactants, oils, emulsifiers and buffering agents, while others may use odd combinations of things like fish oil and fatty acid soaps. Several are made entirely from some sort of emulsified soybean oil. Actually, common dish soap will act as a sticker-spreader, it just won't be as effective as the commercial grade ones.
To be totally technically correct here, sticker-spreader is a combination of two adjuvants. Adjuvants are materials added to spray mixtures to increase the effectiveness of the main active ingredient.
If we want to be completely correct with our terminology, we probably ought to note too that spreaders are adjuvant surfactants. Surfactants are adjuvants that reduce surface tensions of solutions, helping them spread and cover leaves more effectively. Stickers are adjuvants that aid in the attachment to a surface.
The water-soluble wax product often used to spray Christmas trees to keep them turgid, Wiltpruff, is also sometimes used as a sticker-spreader.
I recently did some comparison spraying of roses in my own garden. I was spraying the roses with a homemade combination to keep the darn deer from eating them into the ground.
With both batches of spray I used (per gallon of water) two raw eggs, four cloves of garlic, and a cup of skim milk. I blended all the ingredients in a blender before putting them in the sprayer. I sprayed two different sections of roses. In the first section I used the above mix, with the addition of 6 tablespoons of dish soap. In the second section of roses I used the same mix but used two tablespoons of a commercial grade sticker-spreader.
What was the difference?
Both sprays did keep the deer from eating the roses, for awhile.
The spray with soap resulted in roses that were not eaten for six nights following the spraying.
Deer did not eat the roses sprayed with the sticker spreader mix for 15 nights. It seemed obvious to me that the sticker-spreader had indeed locked the smelly spray material onto the roses better than had the soap.
Sticker spreader is sometimes used to make leaves on foliage plants shinier, and this works pretty well, too. Or, for example, if you are spraying your roses with insecticidal soap (for aphids) and a little baking soda (for rust and mildew control) mixed with water and a bit of sticker-spreader, you'll immediately notice that the spray does cling to the leaves better and it also make them shine.
Spreader-stickers can also have somewhat of a synergistic affect when used with insecticides. It not only helps the insecticide adhere better to plant surfaces but it also helps the insecticide penetrate the bodies of insects it contacts. Perhaps most importantly, spreader-sticker also protects the insecticide or fungicide from washing off in the rain and from breakdown from sunlight.
Some of the insecticides I like most, organic botanical-based ones such as Neem are kind of pricey, and using sticker-spreader gets me more bang for my buck. I think I paid less than five dollars for a pint of spreader-sticker at a local nursery. A little bit goes a long way, so it seems inexpensive enough.
Oh yeah, almost forgot, a heptamerous flower… is one with seven parts in each whorl, right?