Unraveling the Complexity of Coffee Leaf Rust Behavior and Development in Different Coffea arabica Agroecosystems

Abstract

Crop health management systems can be designed according to practices that help to reduce crop losses by restricting pathogen development and promoting host plant growth. A good understanding of pathogen and host dynamics, which are interdependent, is therefore needed. In this article, we used a holistic approach to explain the behavior of coffee leaf rust (CLR), a major coffee disease. We monitored coffee plant and CLR dynamics simultaneously in plots under different disease management and agroforestry systems. Diseased leaves were also collected to characterize inoculum stock and rust life stages (latent rust area, area with uredospores, necrosis due to rust) through picture analysis. We used structural equation modeling to obtain an overview of CLR pathosystem functioning on a plant scale. This overview integrates processes such as disease dilution by host leaf renewal, direct and indirect effects of fruit load on CLR development, antagonistic effects of shading depending on rust life stages, the tonic effect of copper-based fungicides on leaf retention, and effects on rust life stages depending on fungicide types. From our results, we also deduced that the inoculum stock could be calculated in unsprayed plots from the rust area with uredospores, with uredospores at 58 × 103 cm−2, on average.

Interaction between Mycodiplosis and Hemileia vastatrix in three scenarios of coffee crop management (Coffea arabica)

“…No significant differences (p=0.2686) were found in the distribution of Mycodiplosis in the strata of the plant (Table 2). Merle et al (2019) found that, in the strata of coffee plants, the area with uredospores was similar under the shade or in areas exposed to the sun, which reinforces the results obtained in the present investigation, since larvae had the same food availability in the three strata, therefore its distribution was similar.…”

“…This is due to the applications of fungicides that helped reduce rust severity and, therefore, there was less food availability for larvae. Similar results were reported by Merle et al (2019), who showed that its natural enemy (Lecanicillium lecanii) was also more abundant in areas with more rust. We assume that in all areas, the population of the diptera helps reduce Hemileia vastatrix populations, since it feeds off the uredospores, which could delay the beginning of the infection or contribute to reducing initial infections (Nutman and Roberts, 1963).…”

“…The data show that the applications kept rust severity at lower levels than in places in which no chemical control was applied. Fungicides act directly on the intensity of sporulation and they limit the areas with uredospores (Merle et al, 2019). However, the fluctuation of the severity was greater in Santa Lucia and Cuetizapan, unlike in San Bernando, where it was stable (Figure 1).…”

“…Los datos demuestran que las aplicaciones mantuvieron la severidad de la roya en niveles más bajos que en donde no se realizó un control químico. Los fungicidas actúan directamente sobre la intensidad de esporulación y limitan las áreas con uredosporas (Merle et al, 2019). No obstante, la fluctuación de la severidad fue mayor en Santa Lucia y Cuetizapan a diferencia de San Bernando, en donde se mantuvo estable (Figura 1).…”

Discovering weather periods and crop properties favorable for coffee rust incidence from feature selection approaches

“…The main limitation of this measurement for CLRI monitoring is the possible error in the categorization of infected or healthy leaves. Also, the incidence is a descriptor of the dynamics of both CLR and coffee plant (Merle et al, 2019). Although the definition of incidence is uniformly accepted, there are many different ways of choosing the set of plants and leaves to be examined, and even of determining if a leaf is diseased or not.…”