Black foot of the vine worries producers in Brazil

One of the main problems in the wine growing sector refers to diseases that can cause losses of up to 100%. In Brazil, anthracnose, mildew, powdery mildew and, more recently, rust are among those that require control, reaching 30% of the total cost of production. In recent years, the death of vines has also been observed, as well as symptoms of decline caused by the disease known as black foot of the vine and in other countries such as blackfoot, which has worried producers and technicians due to the lack of knowledge on this topic in Brazil and also the absence of prevention and control strategies.

Blackfoot disease of grapevines was first reported in France in 1961. From the 1990s onwards, it began to take on greater proportions in Europe, becoming one of the main problems for winegrowers. In Brazil, since 1999 the presence of plants with symptoms of the disease has been noted and, after studies, their presence was verified in vineyards in the Serra Gaúcha. In addition to having been reported in the Southern states, it has recently been observed in the Northeast.

The main causal agents of the disease are fungi of the genera Cylindrocarpon, Campylocarpon e Cylindrocladiella. Cylindrocarpon spp. They are soil inhabitants, where they survive for long periods of time as hibernating mycelium, in the form of chlamydospores, in plant debris and in attacked plant organs, having a wide range of hosts. They are highly adaptable and can be found in soils from tropical forests to arctic tundra.

Epidemiology

Vegetative propagation material, rootstocks and ready-made grafts, have been widely cited as an important vehicle for the dissemination of pathogens responsible for the decline of young vines, including blackfoot and Petri's disease, caused by another fungus. Phaeomoniella chlamydospora. The attack is basically on the rootstock, where the reproductive structures (conidia) are disseminated by rain splashes and soil particles. It is believed that the fungus penetrates the base of the plant or wounds on the roots resulting from transplantation and colonizes the host's tissues, causing necrosis. Infections are more severe when plants are in a situation of water, nutritional or soil compaction-related stress. Furthermore, the fungus produces resistance structures called chlamydospores, which ensure its presence in the soil for years.

Symptomatology

Currently, grapevine blackfoot is considered one of the main threats to cultivation and stable production in viticulture, mainly affecting young vines, two to eight years old, when the vines are at their peak of production, making their replacement necessary. in the vineyard. The disease can cause losses of more than 50%. Symptoms are distributed both in the aerial part and in the root system. The most common, caused by infections of Cylindrocarpon spp., are observed on the rootstock and include, in the vine wood tissues, the presence of blackened lesions in the form of striations. In the aerial part, there is a delay in phenological stages, reduced vigor, shorter internodes, fewer shoots and a chlorotic appearance, progressing to sudden wilting and, consequently, the death of the plant. In the roots, the symptoms are less evident. Initially, despite being healthy, they develop shallowly and parallel to the soil surface. Later they become necrotic and even rot, depending on the intensity of the pathogen attack.

Root necrosis caused by the pathogen

Sudden wilting of the aerial part

Absence of sprouting

Control

Both straight and grafted vines have been shown to be susceptible to the pathogen, which has made it difficult to direct research, since there is a lack of material with resistance. As it is a soil pathogen, chemical control is not very efficient, even with good results in experiments. vitro under laboratory conditions. In this complex environment, the product is subject to physical-chemical and biological interactions, which reduces its effect on the pathogen and also makes it difficult for it to reach the target organism. In Brazil, there is still no fungicide registered to control grapevine blackstem.

Winegrowers are currently using commercial products based on a beneficial fungus known as Trichoderma spp. which, in addition to acting on Cylindrocarpon spp., acts on other fungi that cause diseases in grapevines. In addition to being a biocontroller, Trichoderma spp. It is also a growth promoter, increasing root development. In addition to Trichoderma spp., studies indicate the mycorrhizal fungus Glomus intraradices as a pathogen control agent. Another form of control that has been studied is physical control using hot water at 50ºC to immerse cuttings for a period of 30 minutes, which has eliminated a large part of the inoculum.

Once present in the vineyard, this disease does not have an effective form of control. Therefore, management practices that suppress the effect of the disease must be adopted, such as using pathogen-free seedlings, avoiding areas with a history of the disease, poorly drained areas, compacted soils and maintaining good nutritional management, avoiding stress, which will confer greater resistance on the part of the plant.

Click here to read the article in Cultivar Vegetables and Fruits 82.