The effectiveness of the decision support system in integrated management of onion downy mildew in Latvia
2012
Lepse, L. | Bankina, B. | Bimsteine, G.
Onion downy mildew, caused by Peronospora destructor, is one of the most important onion diseases that under field conditions of Latvia require several fungicide applications. The aim of the research was to find the most effective methods of integrated control of downy mildew in onion. Three plant protection schemes were applied: 1) control (without fungicides); 2) fungicide application according to the Dacom Plant Plus decision support system; 3) fungicide application according to a spraying scheme (traditional) based on the experience of the growers. Fungicides with active ingredients metalaxyl and mankoceb were used in the trials. Three onion hybrids were used: ‘Safrane’, ‘Hypark’, and ‘Alonso’. Disease severity was evaluated using a 0-5 index scale. Development of the disease was described by AUDPC (area under diseases progress curve). Downy mildew development differed depending on the hybrid and the year. Severity of the disease was higher in 2008, but the period of the disease progression was longer in 2009. The onion hybrid ‘Alonso’ exhibited the best resistance against P. destructor. Technical effectiveness of fungicide application fluctuated (6-91%) depending on the hybrid, the spraying variant, and the year of investigation. No significant differences were observed between the three plant protec¬tion schemes. However, Dacom recommendations had tendency for better control of the disease in the year 2008. Moreover, in 2009 this system recommendation demon¬strated considerably better results for all onion hybrids. The first time of fungicide spraying as recommended by Dacom was one week earlier in 2008, and two weeks later in 2009, than that advised by the standard schemes. The obtained data are disputable and more investigations are necessary.
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