Schorffungizide—Ihr Einfluss auf die Penetration von Kalziumchlorid in Äpfel

To examine the effect of fungicides against apple scab on the penetration of CaCl₂ in apples, experiments were conducted in a growth chamber using segments of Golden Delicious apples 89 days after full bloom in 2003. ⁴⁵CaCl₂ (5 g l^?1) and mixtures of the ⁴⁵CaCl₂ solution with the fungicides Baycor, Discus, Benomyl, Malvin, and Omnex at concentrations recommended for commercial practice were applied to the fruit segments. The penetration experiments were conducted with and without adding the alkylpolyglycoside Plantacare 1200 UP (0.2 g l^?1) as wetting agent in the ⁴⁵CaCl₂ solution and each mixture of fungicide + ⁴⁵CaCl₂ solution. The results show that a suitable wetting agent is necessary to obtain high rates of CaCl₂ penetration. While only 1.2% of the applied dose penetrated the fruit surface in the CaCl₂ control without the wetting agent, 17.9% penetration was found in fruit segments after 24-h incubation when the wetting agent was added. The mixtures of CaCl₂ solution with Baycor and Discus but without additional wetting agent resulted in penetration rates of 1.1% and 1.3% respectively of the applied dose within 24 h, and the mixtures with Malvin and Omnex resulted in 3.5% and 5.6% penetration within 24 h. Adding the wetting agent Plantacare 1200 UP to the CaCl₂-fungicide mixtures revealed penetration between 12.5% and 15.5% of the applied dose within 24 h. Thus, adding a wetting agent increased the CaCl₂ penetration by factors of 3 to 14. This promoting effect was not observed when it was added to the CaCl₂-Benomyl mixture. Adding the wetting agent to the applied CaCl₂ solution and the CaCl₂-fungicide mixtures lowered surface tension of all solutions below 30 mN m^?1. The importance of low surface tension is discussed with regard to calcium penetration via hydrophilic pores in the cuticle and to infiltration of lenticels by the fungicide-CaCl₂ solutions.