Control of Leaf Spot Diseases on Ecotypes of Faba Bean (<i>Vicia faba</i> L.) Produced in the Andean Region of Bolivia

Abstract

The basin of Lake Titicaca is a faba bean-producing microregion of Bolivia where the crop is destined for export. The most commonly cultivated ecotypes "Gigante de Copacabana" and "Usnayo" are affected by diseases that can cause production losses. The aims of the present work were to identify the causal agents of leaf spot affecting these ecotypes, to record disease intensity levels, and to estimate their effect on production. In 2004 and 2005, leaflet, stem and pod samples were taken from faba bean plants with leaf spot growing in the Lake Titicaca area, and from plants in an experimental plot established to determine the effect of five different treatments on production and disease intensity: T 1 = Control; T 2 = seed treatment with Trichoderma sp. + alternate foliar spraying with benomyl and mancozeb; T 3 = seed treatment with fludioxanil/metalaxyl M + alternate foliar spraying with benomyl and mancozeb; T 4 = foliar spraying with Trichoderma sp.; T 5 = alternate foliar spraying with cymoxanyl and mancozeb-chlorothalonil. Microscopic analysis of the samples revealed the presence of new fungal pathogens for faba beans in Bolivia (Cladosporium sp., and Lepthosphaerulina sp.) as well as emerging fungal pathogens (Botrytis cinerea, B. fabae, Ascochyta fabae, Alternaria sp. and Cercospora sp.). None of the treatments affected the disease progression curve (DPC) for incidence, although effects were seen with respect to disease severity. The seed + foliar treatments (T 2 and T 3 ) were more effective at controlling disease than leaf treatments on their own (T 4 and T 5 ). Modelling analysis showed faba bean leaf spot disease to be moderately destructive. Compared to chemical treatments, biocontrol with Trichoderma spp. preliminary was found to provide good control of the disease. Losses due to leaf spot disease of 36% were recorded, and a strong correlation detected between yield and disease severity.

Botrytis four species are associated with chocolate spot disease of faba bean in Latvia

“…B. fabae is viewed as the primary causal agent of chocolate spot disease. Several reports (Harrison, 1988;Coca-Morante, Mamani-Álvarez, 2012;Bilkiss et al, 2019) have mentioned B. cinerea as a pathogen of faba bean either separately or within a complex with B. fabae. Zhang et al (2010) identified and described the third species of Botrytis from faba bean in China -B. fabiopsis.…”

Field Performance of Trichoderma harzianum AAUT14 and Bacillus subtilis AAUB95 on Faba Bean (Vicia faba L.) Growth Promotion and Management of Chocolate Spot (Botrytis fabae Sard.)

“…Similarly, the application of different T. harzianum strains under field conditions resulted an increase of yield from 8-30% beside acting as the biocontrol agents of chocolate spot [10]. Seed treatment of bio-agents combined with foliar treatments were more effective for controlling leaf spot of faba bean than foliar spray only [11]. Moreover, a mixture of Rhizobium leguminosarum and T. viride tag4 as seed treatment and foliar spray increased the yield by 23% compared to the uninoculated control plants beside controlling chocolate spot [3].…”