Plant Pathology Guidelines for Master Gardeners
Contact: Dr. Richard Raid
Chemical Methods For Disease Control
As a last resort, judicious use of chemical applications may be used to mitigate plant disease losses. There are three major classes of chemical treatments:
- Soil Treatments
- Seed Treatments
- Foliar Sprays
Seed treatments consist of dusts or slurries applied to seed to protect primarily against damping-off caused by soil borne pathogenic in fungi.
In this picture the fungicide coating of the seed has been activated by the moisture in the soil and now forms a protective chemical barrier around the seed.
Use only the recommended fungicide (not what is on sale, is left over from last season, etc.).
Use only the recommended amount.
Time the spray effectively. This often means starting earlier in the season than one might initially expect.
Time to look more closely at those materials and approaches needed to help in your diagnostic effort and ways to seek assistance.
Try to gather as many "disease books" for reference as you can, especially those with color photographs.
Many county offices will have library or file copies of these valuable books and materials.
An extremely useful source of diagnostic information on specific plant diseases is the collection of fact sheets and plant protection pointers put out by the plant pathology departmental of the University of Florida. Unfortunately, many of the color fact sheets are out of print. Some of these fact sheets are now available on the University of Florida, IFAS, Dept. of Plant Pathology Web site. Just click on extension publications when you get to the departmental home page.
When a client comes in with (or even phones about) a plant health problem, it is important that you gather as much information as possible about the situation. This additional information can be critical in making the correct diagnosis. And remember to ask - clients very often will not think to offer such information unsolicited.
Things to ask include:
- Number of plants affected
- Pattern of development in the field or garden
- The relative severity of the problem
- Recent cultural practices (e.g., pesticide sprays) and localized weather conditions
There are times when you simply cannot figure out what the problem is. In consultation with the Master Gardener coordinator, you may decide to send a sample to one of the regional University of Florida plant disease clinics. When you do so, a form as shown will accompany the sample here:
Form to accompany sample sent to a plant disease clinic. It is important to the clinic personnel that you fill in as much information as possible. This will suggest avenues to pursue for the highest likelihood of success.
This picture illustrates the best way to submit plant samples.
Moisten the root ball (soil or soil mix around roots) and enclose only the root ball in a plastic bag that is secured with a rubber band or similar method. Do not enclose the foliage in the plastic bag, as it will rot by the time it gets to the clinic. Then the entire plant can be put in a paper bag.
Fruits can be wrapped in soft paper and place to in a cardboard box.
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