Articles
ON THE BIOLOGICAL CONTROL OF BOTRYTIS CINEREA ON KIWIFRUIT CV “HAYWARD” DURING STORAGE
The recent tendency to reduce the use of chemicals in agricultural products make necessary the study of alternative control methods of this post-harvest disease.
A Botrytis cinerea Pers.: Fr. isolate from diseased kiwifruits kiwis, a Trichoderma koningii Oud. isolate of the laboratory collection and kiwifruits cv "Hayward" from commercial storage of Pieria storages were used throughout.
Essential oils from origanum (Origanum spp.), basil (Ocimum spp.) and thymus (Thymus spp.) were tested in these experiments.
PDA was used as a growth medium for both fungi and for tests in vitro work for the effectiveness of the oils.
From the three essential oils tested at the higher rate of 500 ppm only origanum oil showed positive results, killing the Botrytis. The same essential oil at the rate of 250 ppm proved to be only fungistatic, the fungus being active after transferring to the oil free PDA.
Kiwifruits were artificially inoculated with B. cinerea inoculum in two holes 5 mm deep made with a needle in the stem-end, and dipped in a 500 ppm water solution of Origanum oil.
The oil treatment had some effect on fungus growth in the fruit flesh, but at the same time reduced fruit quality making them completely unuseful.
Botrytis was killed by T. koningii in in vitro cultures but growth of the fungus into the fruit flesh was not reduced.
However, fruits inoculated with both fungi, as described previously, showed higher rotting caused by Botrytis. From uninjured kiwifruits dipped in a Trichoderma spores solution the fungus was isolated from the fruit flesh.
This ability of Trichoderma to penetrate into fruit flesh, possibly through natural openings or small lysis of periderm, resulted in severe adverse effects on fruit quality without any visual rot.