Do I Apply Fungicide and Fertilizer Together?

General Fertilizing

• In general, fertilization is needed for plants or a lawn more regularly than fungicide. Fertilizers add nutrients to the soil that provide the plants with elements and minerals necessary to their healthy growth. If they are needed in your garden, you will generally add fertilizer once or twice a year. The most important addition of fertilizer is immediately before plants begin creating new growth, in late March or early April. A second fertilization may be a good idea just after plants go into dormancy in the early fall, if your lawn or plants had issues over the growing season.

Fungicide Timing

• Fungicide is not generally necessary for regular use. Brown spots in lawns can be caused by fungus, and copper fungus may affect citrus trees or other plants, but fungicides should be used with precaution as many fungi are actually beneficial to plant growth, and fungicides don't differentiate. It is best not to use fungicide as a preventive measure, but only to mitigate a problem that is already upon your garden. Fungicide is best applied in February, regardless of temperate zone or the plant in question.

Interrelated Timing

• If you are using fungicide as a preventive measure for a fungus problem that has not yet emerged, it is perfectly fine to use it simultaneously with a fertilizer. Again, the best time to use it is earlier in the season, but using fungicide with fertilizer won't hurt anything. If, on the other hand, you already have a fungus problem in your yard, it is best to apply fungicide at least a week before applying fertilizer. If fertilizer is added first, or in conjunction with fungicide, the fungus may be encouraged to grow faster than it is killed off.

Fungicidal Fertilizers

• In the event that you are using fungicide as a preventive measure, there are actually multiple products available that are combination fungicide and fertilizer, just as there are combination herbicide and fertilizers for grass growing. Again, these are perfectly fine to use for preventive applications, but using a fungicidal fertilizer on a lawn or garden that is already experiencing fungus problems will likely only exacerbate the fungus problem.