Management of Phoma spot in coffee plants

Phoma spot is an important disease in coffee plants, due to the significant damage it causes to production. Its severity is greater in high-altitude regions where low temperatures, cold winds and humidity in crops predominate. The susceptibility of our commercial cultivars, the exposure of the crop, the high capacity for multiplication of the fungus, its adaptation, resistance and/or survival are also factors linked to the severity of the disease (Krohling; Matiello 2011).

The fungus attacks coffee leaves, flowers, fruits and branches, producing very characteristic lesions. The damage caused by this disease is directly reflected in production, as flower buds and new shoots die, mummification of fruits and poor fruit granulation due to defoliation, compromising the development of production in the current harvest and the following year.

Phoma spot has been gaining notoriety among the technical and coffee producing community and its control has increasingly received notoriety through research results showing a reduction in very significant productivity losses.

The ideal condition for the development of the fungus lies in an average temperature below 20ºC and the presence of humidity (dew being sufficient as a humidity factor).

Chemical control of this disease is costly, as depending on the region it covers a very long period of protection. However, it is essential and should be recommended preventively for crops with good production prospects and especially in places where there is continuous humidity and low temperatures in the period from April to October (before harvesting until the coffee plant's seed stage).

When the disease is detected at the end of the rainy season (in April/May) attacking the new leaves and branches of the needle, one or two sprays should be carried out (at intervals of 30 days) with specific fungicides, with the aim of reducing the defoliation of the plant, the incidence of branch drought and the amount of residual inoculum that will favor the attack of the disease at the time of flowering and fruit formation (Matiello, 2010).

Knowing the times of highest incidence (which are related to favorable climatic conditions for the occurrence of the disease), the fungus' high capacity for multiplication, its adaptation, resistance and/or survival are fundamental factors for successfully controlling phoma.

Experiment

With the aim of better understanding the dynamics of the disease and its impact on coffee productivity, an experiment was developed in the municipality of Serra do Salitre, Minas Gerais, to evaluate coffee productivity according to different application strategies (times) (pre- harvest, post-harvest, pre-flowering and post-flowering) of the fungicide Boscalida at a dose of 180 grams per hectare (in each application), as well as defining the best model for the region of high pressure of the disease in question.

The work was carried out from April 2011 to June 2012, at Fazenda Engenho, located in the municipality of Serra do Salitre, in Minas Gerais. The variety used was Catuai Amarelo, planted in 1986 at a spacing of 4m x 1m, totaling 2,5 thousand plants/ha.

The region's climatic data during the experiment period were collected at the Cooxupé meteorological station, in Serra do Salitre, Minas Gerais (located in the same microclimate as the farm (same altitude and 7km from the farm), with collection being carried out daily as shown in Graphs 1 and 2.

 graphic 1

The average temperature in April was 19ºC and in May 17ºC.

graphic 2

To evaluate the experiment, four plants per plot were stripped and the sweeping coffee from the same plants was also collected.

The Boscalida fungicide application times were as follows: Treatment 1: Control (no application); Treatment 2: Pre-Harvest; Post-Harvest; Pre-Flowered; Post-Bloom; Treatment 3: Post-Harvest; Pre-Flowered; Post-Bloom; Treatment 4: Pre-Flowering; Post-Bloom; Treatment 5: Pre-Harvest; Pre-Flowered; Post-Bloom.

The pre-harvest took place in April, the post-harvest in August (soon after the end of the harvest), the pre-flowering in September (after the start of the rains in the swab phase) and the post-flowering in the month of October (after most flowers have fallen)

Other cultural treatments of the crop were carried out in accordance with technical guidance. It is also important to highlight that copper hydroxide was used at a dose of 2kg per hectare in the months of January 2011, August 2011 (along with post-harvest spraying) and January 2012 in all treatments.

The results obtained through the experiment are presented in Table 1.

Table 1 - Average coffee productivity (bags per hectare) depending on the times of application of the fungicide Boscalida. Engenho Farm, Serra do Salitre – MG, 2012

*Averages followed by the same letter do not differ from each other at 5% probability using the Tukey test.

CV% = 20

It is possible to observe that the highest yields were obtained in Treatment 2 (Pre-Harvest; Post-Harvest; Pre-Blooming; Post-Blooming) and Treatment 3 (Post-Harvest, Pre-Flowering and Post-Blooming), with Treatment 3 the most economically viable.

It is also important to highlight that the failure to control phoma, in Treatment 1 (Control), for a good set of blooms/bubbles, causes enormous losses to the producer with a 43% drop in production (loss of 18,5 bags per hectare) when compared as the most economically viable management (Treatment 3).

The control of phoma with the objective of good flowering must be preventive in the post-harvest, pre-flowering and post-flowering periods, as in years when climatic conditions are favorable to the development of the fungus it is impossible to carry out efficient control after the disease is already present in the crop during the coffee flowering phase, as this phase is short and the fungus develops very quickly. The protector cannot run the risk of waiting to see if this year there will be favorable weather conditions for the disease, and only then can he begin fungal treatment.

The coffee grower must have good knowledge of his operational capacity (machinery) and which plots have the greatest harvest projection in order to prioritize these areas in phoma control (especially during the pre-flowering spraying period, a phase that lasts a few days).

Therefore, it is extremely important to know the favorable environmental conditions for this disease and manage it correctly to reduce losses in productivity and profitability of coffee crops.

 

Click here to read the article in the online edition of Cultivar Grandes Culturas issue 185.