. "Appendix L: Witches' Broom Disease Outbreak in Brazil and Control Attempts: Success and Failure in Bahia, Brazil (1989–2009)." Strategic Planning for the Florida Citrus Industry: Addressing Citrus Greening. Washington, DC: The National Academies Press, 2010.
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Strategic Planning for the Florida Citrus Industry: Addressing Citrus Greening Disease
Strategies of Control
The first measure of control attempted was the eradication of the disease by eliminating and burning plants in the focus area (Pereira et al., 1996). However, while the first focus was being eradicated, another one was detected around 100 km apart from the first outbreak and so this measure was determined to be totally ineffective.
The second measure of control attempted was the use of fungicides and biological control agents. Both of them, despite the encouraging results in preliminary trials, did not result in an effective way of controlling the disease.
The third measure, which is most widely used in producer countries having the disease and attempted in Brazil, was the phytosanitary pruning. This is quite efficient when the outbreak of this fungal disease severity is low. However, in the first years of the disease in Bahia, the climate conditions to the disease development and the frequent flushing of the plant, resulted in high severity, many plants having hundreds of infected branches (brooms). Despite its efficiency, many farmers stopped doing it because of the high cost involved, aggravating the situation for neighboring farms that took total removal of brooms as their only hope to contain the disease. With the use of more resistant varieties of cacao (as cited below), the number of brooms per plant was reduced and the local epidemiological studies pointed to more regular periods of pruning. This measure of control became widely used in the region but has not proved sufficient to remove the massive disease pressure of the inoculums.
The fourth measure of control was the use of resistant germplasm; some of them were introduced or developed in the region a long time before the introduction of the disease in the region. However, these varieties despite resistance to witches’ broom, were either susceptible to other diseases introduced in the region after the witches’ broom (Ceratocystis wilt) or did not reach the levels of yield expected. Recently, new clones were developed and have been released to farmers, without those limitations. Today, around 150 thousand hectares of susceptible varieties were replaced by resistant ones. While this has shown some promise, over the last 20 years there has been little or no progress towards recovery in Bahia.
Lastly, with the overwhelming impact of the disease in Bahia, there is a very serious concern that witches’ broom potential to escape into areas where new planting of cacao has begun. The situation today is as dire as it was in 1989!