Activity of plant and mineral oils in the control of Puccinia pelargonii-zonalis.

Effectiveness of plant oils from corn, olive, rape, soya and sunflower, oils recommended for plant protection (Dedal 90 EC, Olejan 80 EC) and mineral oils (Atpolan 80 EC, Ikar 95 EC, Olemix 84 EC and Promanal 60 EC) in the control of pelargonium rust (Puccinia pelargonii-zonalis) was studied. Oils were applied curatively as a plant spray at concentration 1%, 4 times at 7-day-intervals. After 4-week experiment more than 11 uredia per leaf were noted on control plants. At the same time, on plants protected with oils from olive or soya, Ikar 95 EC or Olemix 84 EC uredia number decreased at least 50%. The other oils were not effective in a suppression of uredia formation. On control plants no uredia were destroyed as compared to 11 to 71% destruction on plants protected with the tested oils. Oils from olive, soya and also Atpolan 80 EC, Ikar 95 EC, Olemix 84 EC caused drying off more than 50% uredia. Furthermore, some oils inhibited germination of urediospores on PDA medium (potato dextrose agar). Fourteen days after the last spraying more than 83% of germinating urediospores were found on control leaves. At the same time spores collected from protected plants germinated in 17 to 70%. Among tested products oils from rape, corn, sunflower and Dedal 90 EC, Ikar 95 EC, Olemix 84 EC were the most effective. In the next part of experiment, plants with visible sporulation of P. pelargonii-zonalis were sprayed with 1% oils. After 1 and 7 days of incubation, total number of spores and number of germinating spores were counted. One day after treatment, urediospores collected from leaf blades protected with oils germinated in 20 - 60%. Oils from olive, corn, Atpolan 80 EC and Ikar 95 EC caused inhibition of spore germination at least in 40%. Whereas urediospores from nontreated plants germinated in 86%. After 7 days, urediospores collected from untreated plants germinated in 65% whereas from plants sprayed with tested oils in 23 - 68%. Oils from olive, sunflower and Dedal 90 EC, Atpolan 80 EC were the most effective in suppressing urediospores germination.