Management of pineapple rot in sugarcane

Brazil is the world's largest producer of sugar cane, with a cultivated area of ​​approximately 8,5 million hectares (2012/2013 harvest). It is estimated that for the 2013/2014 harvest, the increase will be 3,7% (approximately 8,8 million hectares). Around 90% of Brazilian production is concentrated in the Center-South region, with emphasis on the state of São Paulo, which was responsible for 56% of the total produced in the 2012/2013 harvest.

In the Center-South region of the country, most sugarcane planting is carried out from the second half of September, until April. During this period, temperature and humidity favor the development of the crop, resulting in rapid sprouting, growth and tillering of the crop. However, with the increase in cultivated areas, planting ends up extending to practically every month of the year.

Therefore, winter planting has also been consolidated, which covers the period from May to the first half of September. However, during this period of the year, the crop is exposed to low temperatures which, associated with short days and dry weather, cause delays in the sprouting of setts, favoring the incidence of pineapple rot, caused by the fungus Thielaviopsis paradoxa. Therefore, when there is a need to plant during periods favorable to the fungus, it becomes essential to use measures that contribute to increasing the speed of emergence, especially in areas with a history of the disease.

As sugarcane planting is carried out through vegetative propagation, the propagules themselves can be the “vehicle” for transporting fungus spores, contaminating new areas.

Pineapple rot

The disease is commonly called pineapple rot and is caused by the fungus Thielaviopsis paradoxa (Ceratocystis paradoxa). It is a polyphagous fungus and occurs in all regions where sugar cane is cultivated. The disease is influenced by soil conditions, temperature and humidity.

The fungus penetrates the plant through cuts and wounds, and does not penetrate the setts through natural openings. This factor is extremely important in the case of sugar cane, as at the time of planting, the stalks are sectioned, favoring the entry of the fungus.

Every year, large areas of sugarcane fields that do not germinate are lost due to fungus attack.. The manifestation of pineapple rot is essentially a reflection of the delay in sprouting that can occur as a result of low temperatures, the use of old buds when planting, seedlings placed in very deep furrows and/or planting in dry or waterlogged soils.

The disease seriously affects bud sprouting, bud development and vigor. Failures that occur due to damage caused by the disease can cover large areas, requiring replanting, which is a very expensive operation.

The spread of pineapple rot occurs mainly through spores present in the first 25cm of soil depth and, occasionally, through infected seedlings. In addition to being a polyphagous fungus (it has been reported on banana trees, coconut trees, palm trees, pineapple, among others), it can survive in the soil for periods longer than 15 months.

Symptoms

The initial symptoms are waterlogging at the ends of the setts, however, as the infection progresses, the color changes, evolving to gray, dark brown and finally black.

Infected setts do not germinate or germinate slowly, producing weaker plants, easily dominated by weeds or competition with neighboring tillers.

One of the typical symptoms of this disease consists of the fermentation of setts that begin to exude a characteristic odor, reminiscent of pineapple essence, which justifies the name given to the disease.

Control

Choosing the planting time is considered the simplest technique to minimize the occurrence of the fungus, however, minimizing the effects of the disease is achieved with measures that stimulate rapid sprouting of the setts or that protect the wounds through which the fungus penetrates. Therefore, measures such as the use of varieties with rapid sprouting, application of biostimulants that induce better sprouting and rooting and the use of fungicides that protect the wounds of the setts are essential for the successful establishment of the sugarcane field. Likewise, the use of biological control with other fungi with an antagonistic effect on the disease has shown promising results..

Higher planting densities also constitute a measure to reduce the impact of pineapple rot, as they use greater quantities of buds per meter of furrow, compensating for possible sprouting failures. However, this measure leads to higher costs and also a reduction in operational income.

Soil preparation and planting depth should also be considered as complementary measures. Soil preparation reduces compaction and eliminates clods, providing better conditions for bud sprouting. You should opt for shallower planting, not delaying the sprouting of the seedlings.

Field results

In field experiments carried out in 2013 in the interior of the state of São Paulo, during the months of May to September, an area with no history of the disease was compared with another inoculated with the fungus that causes pineapple rot and a third inoculated, however, treated with fungicide in the furrow.

The results showed that with an average disease severity of 35%, gains in tiller emergence range from 13% to 22% in the first 100 days after planting when the tillers are treated with fungicide in the planting furrow. This emergency gain is crucial for the establishment, maintenance and development of the sugarcane stand.

Evolution in tiller emergence in relation to the area free from the presence of the pathogen (considered as 100% for the situation).

Click here to read the article in issue 178 of Cultivar Grandes Culturas.