Fungus is the most common cause of disease on plants, according to the University of Missouri Extension. Among the many problems caused by fungus are fruit and root rots, conditions that affect a variety of plants and cause loss of yield, reduced vigor and, in severe cases, death of the plant. Discovering the exact organism causing these problems often requires testing by a plant pathology lab.
Numerous fungal pathogens cause similar symptoms in plants. Common root rot pathogens include Phytophthora, Pythium, Fusarium and Rhizoctonia. Phytophthora, Colletotrichum, Monilinia and Botrytis are common culprits of fruit rot diseases.
Root Rot Symptoms
The first above-ground symptoms of root rot include wilting, yellow foliage and general plant decline. If you dig below the soil surface and look at the plant's roots, you will find brown, slimy roots that lack the tiny feeder rootlets that healthy root systems possess. The brown material slides away, leaving the white core of the root exposed.
Fruit Rot Symptoms
Fruit rot is more obvious, with lesions occurring on the fruit. The disease begins when you observe soft, mushy, sunken spots on the fruit. Soon, spores cover the fruit with structures that look like warts or mold, and the fruit dries into a "mummy," as described by the Purdue University Extension.
Blossom-end rot is a common problem affecting tomatoes, peppers and eggplant. Although initial symptoms resemble the beginnings of fruit rot--sunken, leathery patches on the fruit--the condition is not caused by a fungus but by calcium deficiency, often brought on by dry conditions. In true fruit rots, you will eventually see evidence of the fungus.
Unfortunately, by the time you discover a root or fruit rot, it is often too late to treat the problem with fungicides. If you want to explore your options for saving the plant or crop, take a sample to your local extension office, since you'll need to identify the exact fungus causing the problem in order to treat it.
Because these problems are caused by fungi, however, you are able to take steps to prevent them. Prevent root rots by ensuring good drainage. Don't pile mulch too high, as it holds water around the roots and base of the plant. Plant fruit crops so that air flows easily between them.Remove any diseased fruit that you find and clean up dead plant material at the end of the season.