There have been several questions asked by farmers developing their fungicide spray programs for 2015. A repeated question has been: “Is it possible to mix two generic or single mode of action fungicides to create a product similar to the bottle mixed multi-mode of action products?”
The short answer: Yes, and often times it is cost-effective because one or both products may be generic. There are, however, more points to consider when determining which strategy is best for the farm operation.
Tank-mixing of single mode of action fungicides:
- The use of one or two generics in creating the tank mix may help reduce the cost of the overall fungicide application. This, of course, is dependent on the price of both fungicides and the pre-mixed fungicide.
- Tank-mixed fungicides are usually just as effective as pre-mixed fungicides. A study by Brent Holtz in San Joaquin County has shown that 20 fl oz of Fontelis (FRAC 7) mixed with either 8 fl. oz of propiconazole (FRAC 3) or tebuconazole (FRAC 3) was just as effective in controlling scab as 6.0 fl oz of Luna Experience (FRAC 3/7), 6.0 fl oz of Luna Sensation (FRAC 7/11), or 6.5 fl oz of Merivon (FRAC 7/11). Trials in Colusa County by Dr. Jim Adaskaveg, UC Riverside, showed similar results with 14 fl oz of Fontelis mixed with 8.0 oz of tebuconazole as with 6.0 fl oz of Luna Experience, 5.0 fl oz of Luna Sensation, or 6.5 fl oz of Merivon for controlling almond scab.
- Selecting multiple single mode of action fungicides provides the flexibility to choose chemistries that work for the disease complex present within the orchard. This may be of more importance in areas that have resistant populations of Scab or Alternaria leaf spot or when trying to manage other diseases that may not be affected by a fungicide (e.g. Jacket Rot and FRAC 3 -DMIs). Also, by having the choice to pick and choose fungicides, there is flexibility in developing fungicide rotation programs.
- Pre-mixed fungicides often have one chemistry with a reduced rate. Using the high rate of two separate fungicides may mean more active ingredient per acre which, in theory, would provide greater control. The rate of one fungicide may be reduced within label standards and which may reduce the cost.
- Mixing of generic formulations may lead to phytotoxicity or reduced efficacy. For example, propiconazole mixed with dodine would damage the tree, and mixing of two different trade names of the same FRAC group would lead to loss of efficacy;
- Low number of generics. A limited number of generics are available and many of these belong to FRAC 3. Over reliance on this chemistry will most likely lead to resistance;
- More time and thought required. Mixing of fungicides creates complications on the farm management side. These multi-product programs require more inventory, record keeping, and container disposal.
Pre-mixtures of multiple mode of action fungicides:
- The use of pre-mixed fungicides provides some level of convenience as only one fungicide container needs to be measured, poured, stored, and disposed. There is no need to determine rates of individual fungicides being applied. Label of the pre-mixture fungicide states the recommended rates to use for listed diseases. Record-keeping is simpler and pesticide inventory is reduced.
- Availability of different fungicide molecular chemistries. Some pre-mixed fungicides contain unique chemistries and formulations that may not be available in other products. This aids in increasing efficacy, managing resistant populations, or providing some other benefits for that product.
- Pre-mixed fungicides have been tested to determine the most effective rate for consistent disease control. Efficacy studies have shown that pre-mixed fungicides are more effective than single mode of action fungicides.
- Resistant management. These products create a less complicated spray program at the farm level which aids in chemistry rotation.
- These products are generally more expensive.
- Lack of flexibility. Some pre-mixtures do not match the disease spectrum of the orchard and the rates have been pre-determined.
For more information on fungicides, mode of actions, and efficacy, please see the 2013 Fungicide Efficacy Tables.