Even with very different sensitivities between cultivars, Pear Brown Spot has been a fearsome fungal disease for Italian pear tree growers since the 70s of the last century. Despite the chemical struggle that has allowed the damage caused by this disease to be kept within economically acceptable limits, in recent years the cultivation of pear trees, especially in the North East of Italy and in particular where the Abate Fétel variety is grown (Emilia Romagna, Veneto), has suffered very significant losses caused by these brown spots, due to the reduced availability of authorized active substances in plant protection treatments against this pathogen.
What are the brown spots in pears?
Stemphylium vesicarium, a pathogen of the brown spotting seen in pears is a fungi that overwinters on leaves and fruits that have fallen to the ground and then resumes its activity in all the green parts of the plant in the spring, promoted by high ambient humidity and temperatures between 22 and 26°C.
From this moment on, the fungus produces host-specific toxins that start with the appearance of spotting and subsequently turn into larger necrotic areas affecting plant tissues of sensitive cultivars. These same necrotic areas, which appear as dark-brown notches with a reddish border, later develop rotting caused by the same S. vesicarium but also by other opportunistic fungi.
S. vesicarium damage and varietal sensitivity
The necrotic areas characterized by the attack of the fungus and the subsequent release of toxins appear on leaves, herbaceous petioles and twigs with consequent impairment of photosynthetic activity and, in the most severe cases, partial or complete defoliation.
On the fruits, necrosis occurs above all in the area of the calyx and more in the fruits positioned in the outermost part of the crown, first affecting the epidermis but then extending to the pulp, which undergoes rotting, rendering the product unmarketable.
Not all pear varieties are equally susceptible to the pathogen: Abate Fétel and Conference are those most at risk, while General Leclerc and Kaiser are among the most tolerant.
Pear Brown Spot: Prevention and Defense
The withdrawal of active substances such as Thiram, Ziram, Mancozeb and Procymidone, previously used for the control of various phytopathogenic fungi including S. vesicarium , in fact, has greatly reduced the range of products applicable pear trees for the fight against Pear Brown Spot disease, contributing to the enormous damage reported by pear tree growers in Northern Italy in the 2020 and 2021 seasons. Another contributor was the lack of acceptance, by the competent bodies, of the request made by the Producer Associations and by Phytosanitary consortia, which have repeatedly invoked temporary authorizations for withdrawn active substances, pending the identification of valid alternative plant solutions. Therefore, currently, implementing agronomic factors such as irrigation and land management to prevent the spread of S. vesicarium is fundamentally important***m
Factors predisposing to the spread of brown spots
The occurrence of certain soil and climatic conditions, together with the adoption of certain cultivation techniques, are the basis for the increased predisposition of pear trees to suffer damage by brown spots. Persistent leaf wetting must be avoided, which is why we do not recommend overhead irrigation. Even soil management must be at the center of preventive techniques, given the fact that soil inoculation winters, and must take into account both the possible sterilizing of the sward (if any), and post-harvest fall fertilization with products capable of providing not only organic matter and nutrients, but also useful microorganisms, capable of positively influencing the soil surface microbiome.
With two products from the Terrapiù line, Agribios meets the needs for the efficient management of post-harvest fertilization of orchards, capable of returning to the soil the contents removed at the end of the season, to positively influence the nutritional status of plants as well as the phytosanitary status, with particular reference to the containment of S. vesicarium inoculum sources present in the sward and in leaves and fruits fallen to the ground, which represent the wintering forms of the fungus.
AGRI BIO AKTIV is a soil regenerator that, in addition to providing organic matter and nutrients, promotes and directs the proliferation in the soil of microorganisms useful for the development of plants. Its particular microbial composition, rich in Trichoderma, acts on the soil and the roots, limiting, via antagonism, the development of pathogens responsible for certain diseases affecting the root system or pathogens that overwinter on the ground.
TRICOD R contains Trichoderma, plant components and organic carbon. The high concentration of Trichoderma (1×10 9 u.f.c./g) exerts an antagonistic action against pathogens, such as Fusarium, Pythium, Armillaria, Sclerotinia, Phytophtora, Stemphylum and Rhizoctonia present in the soil. In its liquid and organic form, it does not require advance preparations with added supplements.