Pros and cons of granular combination products
Performing two tasks with one effort saves time and money. This is the idea behind formulations that combine fertilizers and pesticides into one product. The benefits show up in time efficiency as well as reduced wear and tear on equipment, ideally without sacrificing effectiveness.
Combination products consist of fertilizers combined with other products, such as insecticides, fungicides, herbicides, soil penetrants, biotic elements or other products formulated as granules. Though a wide variety of such products are available, the ideal combination for a given situation may not exist. For instance, the fertilizer component might not be the right balance of nutrients, or the timing of the application might not be appropriate for both the fertilizer and the active ingredient. These are factors that you must consider before deciding whether to use a combination product.
Liquid formulations offer greater versatility for combining products. Tank mixing allows you to combine several materials, including chemicals that may not be available in granular form. You are not limited to what a manufacturer prepackages, and you can try any combination you like, provided you don't encounter incompatibilities or violate label instructions.
One of the most obvious advantages of using combination products is that you apply them with a spreader, which makes handling the material relatively simple and easy. Many applicators specialize in granular applications specifically because it is a "no fuss" method of application.
In addition, a homeowner who sees spray applied to a yard (even if it is just a foliar fertilizer) may think "toxic pesticide." When a homeowner sees a fertilizer spreader, on the other hand, the common perception is "fertilizer." These perceptions may not be accurate, but it never hurts to ease the fears of your customers or the public.
The quality of the fertilizer in combination products is important. Particles of different density and size will throw different distances from the spreader, resulting in uneven application and, often, a striped appearance in turf. The same problem with combination products can cause poor weed, disease or insect control in addition to striping. Thus, it's important that products are homogenized-that is, each granule has the same composition-or a quality blend, so that they spread uniformly.
The following discussion deals with specific types of pesticides. For a detailed listing of available combination products, see the Chemical Update on combination products (page 33).
Insecticides Insecticides are frequently used in combination with fertilizers. Although products such as deltamethrin (Deltagard) and chlorpyrifos (Dursban) are available for controlling surface pests, grub controls are perhaps the more significant type of combination insecticidal product.
Bendiocarb (Turcam), imidacloprid (Merit), halofenozide (Mach 2) and isofenphos (Oftanol) all are available in combination with fertilizer. These products are frequently applied in granular form anyway, so combining them with fertilizer is a straightforward way to save time without sacrificing efficacy.
Fungicides Nearly all fungicides developed before 1970 are contact products, which are not absorbed through the plant tissue. Because new foliage is unprotected by these materials, they require frequent applications. Such frequent treatments are not consistent with most fertilization strategies, so contact fungicides are more typically applied without fertilizers. However, at least one contact fungicide-PCNB-is available in combination with fertilizer.
Systemic fungicides are absorbed into the plant and provide both preventative and curative action. Locally systemic fungicides move only a short distance within the plant from the point of absorption. Uniform and thorough coverage of the foliage is important for good control. Therefore, these materials are better applied as a spray than as a granular application.
True systemic fungicides are absorbed by the plant material and move throughout most or all of the plant parts. Most systemics move from the root system or other point of absorption toward the leaf tips and tend to provide more extended protection. This makes them somewhat more suitable for fertilizer combinations because complete coverage is not so critical. Myclobutanil (Eagle), triadimefon (Bayleton), iprodione (26019) and thiophanate-methyl (3336) all are available in combination with fertilizers.
Herbicides The most commonly used combination products are fertilizer/herbicide combinations. Weed control starts with a vigorous, dense turf sward that competes well with weeds for light, moisture and nutrients. A well-managed turf avoids many weed problems.
* Pre-emergents. Some weeds will, of course, still manage to germinate no matter how dense your turf. This is where pre-emergents come in. Preventing weeds from becoming established not only makes turf look better, it reduces the costly task of subsequently removing difficult weed species from the turf.
A pre-emergence herbicide in combination with fertilizer is the most popular type of combination product. Most major pre-emergents are available in combination with fertilizers, giving you a wide choice of products.
Particle size can affect pre-emergent combination-product performance. Smaller particles improve application coverage and uniformity. In fact, this is true of most granular products.
* Post-emergents. As every turf manager knows, some weeds germinate despite your best efforts. At this point, post-emergent products become necessary.
Post-emergents are applied, as the name suggests, to weeds already growing. Most post-emergent combination products contain selective, systemic herbicides along with fertilizer. These are usually phenoxy-type herbicides that kill broadleaf weeds without harming turfgrasses.
Spraying liquid broadleaf herbicides maximizes coverage and generally provides better efficacy than granules. Thus, liquid applications are most common with commercial applicators and situations where maximum effectiveness is required.
However, granular fertilizer/phenoxy combinations can work surprisingly well. Plus, the use of a large-scale spreader allows you to treat large areas with great time efficiency.
To achieve consistently good results with broadleaf combination products, follow directions precisely. The turf must be wet so that the granules stick to the leaves of the broadleaf weeds. Thus, if the grass is not wet from rain or dew, irrigation prior to application will be necessary. Failures with granular broadleaf herbicides often can be traced back to inadequate moisture on leaf surfaces.
Next, it is essential to avoid any moisture from irrigation or rainfall for at least 24 hours (no different from liquid applications). This ensures that the granules will stay in contact with the leaves long enough for the herbicide to be absorbed by the plant. In addition, you must not mow the turf for at least 7 days to allow the material to translocate to the root system for complete control (again, similar to liquid applications).
The key to success with combination products lies in reading the instructions thoroughly and following the application rates and techniques precisely. Regular spreader calibration is important, as is matching the "pounds on the ground" with the size of the area treated.
Combination products aren't for every situation. But when the active ingredients, timing and rates fit your needs, as they frequently do, the efficiency of two applications in one is hard to beat.