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Fig Sclerotium Blight Info: Treating A Fig With Southern Blight

Fig Sclerotium Blight Info: Treating A Fig With Southern Blight


By: Bonnie L. Grant, Certified Urban Agriculturist

Fungal diseases are probably the most common issues in many types of plants, both indoors and outdoors. Figs with southern blight have the fungus Sclerotium rolfsii. It stems from unsanitary conditions around the root base of the tree. Southern blight on fig trees produces fungal bodies primarily around the trunk. According to fig sclerotium blight info, there is no cure for the disease, but you can prevent it fairly easily.

What is Sclerotium Blight?

Fig trees are grown for their attractive, glossy foliage and their delicious, sugary fruits. These gnarled trees are quite adaptable but may be prey to certain pests and disease. One of these, southern blight on fig trees, is so serious it will ultimately lead to the demise of the plant. The fungus is present in soil and can infect the roots and trunk of the fig tree.

There are more than 500 host plants of Sclerotium rolfsii. The disease is most prevalent in warm regions but can show up worldwide. Sclerotium fig symptoms show up first as cottony, white growth around the base of the trunk. Tiny, hard, yellowish-brown fruiting bodies can be seen. These are called sclerotia and start out white, darkening over time.

The leaves will also wilt and may exhibit signs of the fungus. The fungus will get into the xylem and phloem and essentially girdle the tree, stopping the flow of nutrients and water. According to fig sclerotium blight info, the plant will slowly starve to death.

Treating Southern Blight on Fig Trees

Sclerotium rolfsii is found in field and orchard crops, ornamental plants, and even turf. It is primarily a disease of herbaceous plants but, occasionally, as in the case of Ficus, can infect woody stemmed plants. The fungus lives in soil and overwinters in dropped plant debris, such as fallen leaves.

The sclerotia can move from plant to plant by wind, splashing or mechanical means. During late spring, the sclerotia produce hyphae, which penetrate the fig plant tissue. The mycelial mat (white, cottony growth) forms in and around the plant and slowly kills it. Temperatures must be warm and conditions moist or humid to infect figs with southern blight.

Once sclerotium fig symptoms are apparent, there is nothing you can do and it is recommended the tree be removed and destroyed. This may seem drastic, but the tree will die anyway and the presence of the fungus means it can continue to produce sclerotia that will infect other plants nearby.

The sclerotia can survive in soil for 3 to 4 years, which means it is unwise to plant any susceptible plants in the site for quite some time. Soil fumigants and solarization may have some effect on killing the fungus. Deep plowing, lime treatment and the removal of old plant material are also effective ways to combat the fungus.

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Background

Southern blight, caused by the soil-borne fungus Sclerotium rolfsii Sacc. (Atheliaceae: Athelia rolfsii (Cruzi) Tu and Kimbrough), is a serious disease for a wide range of plants, including vegetables, fruits, ornamental plants, and field crops (Mullen 2001). The fungus, also, attacks primarily bentgrass, bluegrass, fescues, and ryegrass (Smiley 1992).

The first symptoms of outstanding in turfgrass areas are round crescent-shaped yellow areas about 20 cm in diameter. Grasses grow yellowish over time and become sparse. As long as the disease continues to progress, diseased areas in the form of rings or patches die. But the grass in the center remains green. The color of the dead areas turns reddish brown over time. These rings, formed in dead turfgrass in summer and humid weather, expand quickly (about 20 cm per week). Sometimes, symptoms observed in these areas similar to the “frog eye.” In Agrostis and Poa species, the diseased areas caused by this disease are usually seen in the autumn. Under moist conditions, white mycelial growth which develops on the dead grass and later on sclerotia ranging from white or light to dark brown on the mycelium are observed (Smiley 1992).

S. rolfsii isolates can be diverged into different mycelial compatibility groups (MCGs) based on mycelial interactions among isolates. The role of MCGs is important in defining field populations of fungi and facilitating genetic variation in fungal species, where the sexual reproductive stage (teleomorph stage) of the life cycle has a minimal impact on the disease cycle (Kohn et al. 1991).

Nowadays, the plantation and conservation of turfgrass areas has become a huge industrial sector in the world. Cultural practices are not efficient for controlling the disease, that is why fungicide usage is very common and widely used in turfgrass areas all around the world. Chemical fungicides are extensively used in turfgrass areas in Turkey, and excessive use of chemical fungicides has led to deteriorating human health, environmental pollution, and development of pathogen resistance to fungicides (Balcı and Gedikli, 2012). Due to the harmful effects in controlling fungal diseases, new studies are needed to use alternative methods for plant protection, which are less dependent on chemicals and are more environmentally friendly. In this regard, biological control can be an alternative or supplement to current management practices for S. rolfsii (Sai et al. 2010).

The most commonly beneficial microorganisms used in the control of plant pathogens are the following bacterial strains: Bacillus, Pseudomonas, and Trichoderma spp. (Raaijmakers et al. 2010). For the biocontrol of S. rolfsii, some bacterial genera have been tested for their ability to control. Pseudomonas spp. and Bacillus spp. have been commonly studied to control S. rolfsii on various plants. It was detected that Pseudomonas and Bacillus strains restricted in vitro hyphal growth or reduced germination of sclerotia of S. rolfsii (Rakh et al. 2011 and Tonelli et al. 2011). Several commercial preparations, containing these bacterial and fungal agents, are also recommended on turfgrass diseases in the world. Bio-Trek 22G (Trichoderma harzianum ) is the first registered biopesticide for dollar spot, brown patch, and Pythium root rot on turfgrass (Harman and Lo 1996). Eco Guard TM (Bacillus licheniformis), Rhapsody (B. subtilis), Actinovate SP (Streptomyces lydicus WYEC 108), and Botrycid (Pseudomonas aureofaciens) are the other microbial biocides used against turfgrass diseases (Corwin et al. 2007). Among these, only Rapsody is recommended against the southern blight disease caused by S. rolfsii in turfgrass areas. But there is no registered microbial biocide against turfgrass diseases in Turkey so far.

The objective of this study was to molecularly identify S. rolfsii isolates in Turkey, and to detect their virulence and mycelial compatibility groups, using some domestic bacterial and fungal isolates under greenhouse conditions.


Bacterial Diseases

Bacterial diseases are generally fatal to ficus trees. Crown galls on ficus trees are caused by Agrobacterium tumefaciens. Slightly swollen areas on infected leaf veins, stems or roots, grow and become corky. No chemical preventative or control is effective. Affected plants should be destroyed to prevent the spread of infection. Xanthomonas leaf spot begins as tiny water soaked spots on the foliage. The spots enlarge rapidly and may develop bright yellow margins. Bactericides used according to the manufacturer’s directions may prevent Xanthomonas leaf spots. Infected plants should be destroyed.


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