Study highlights strategies for managing powdery mildew in cashew cultivation

Maintaining plant health is one of the first steps towards producing quality fruits. With this in mind, Embrapa Agroindústria Tropical launched the study “Chemical management of powdery mildew in different dwarf cashew clones”, addressing strategies for managing powdery mildew, a disease caused by the fungus Erysiphe quercicola and which causes damage to the production of nuts and peduncles. 

Powdery mildew is considered the main disease of Brazilian cashew farming. Therefore, chemical control is the immediate strategy to be implemented in the production system. The identification of dwarf cashew clones with greater tolerance to the disease means that epidemics do not result in serious consequences for cashew farming, such as a decrease in quality (changes in color, roughness and roughness) and quantity (decrease in the mass of nuts, almonds and peduncles). 

Powdery mildew epidemics can behave differently when certain dwarf cashew clones and fungicides with different characteristics are used, whether used alone or in combination. Therefore, the experiment carried out at the Pacajus Experimental Field (CE) presented the use of two types of fungicides as a management strategy: sulfur and trifloxystrobin + tebuconazole. In total, the effects of each substance and the behavior of clones CCP 76, BRS 189, BRS 226 and BRS 265 were verified alone or in combination during the treatment of the disease.

Disease variables were evaluated, such as incidence in nuts, final severity in panicles (flower branching), severity in maturis (area under the powdery mildew progress curve (AACPOID) and the incidence of cracked cashews.

The study also highlights that the chemical management of powdery mildew may require the use of different modes of action and mobility, depending on the environment (climate/region) and the clone cultivated by the producer. Thus, monitoring the disease contributes to choosing a fungicide with better efficacy, in order to maintain low levels of disease severity. For a susceptible clone, for example, the use of systemic fungicides with contact, curative and eradicating effects may be more efficient than those with only contact effects, such as sulfur.

Through the study, the researchers concluded that the use of resistant dwarf cashew clones becomes a potential strategy to be incorporated into the production system in the face of the presence of powdery mildew. The BRS 226 clone obtained, in the experiment, the lowest final disease and lowest AACPOID. On the other hand, BRS 189 showed the highest disease values. As for the fungicides applied, trifloxystrobin + tebuconazole showed greater efficiency against the cashew powdery mildew epidemic. Sulfur, in turn, demonstrated limited efficiency in an environment highly affected by the disease. With the substance, only more resistant clones managed to keep the disease at low levels.