Powdery mildew is a fungal disease that can affect a wide range of plants (e.g. tomato, pumpkin, zucchini, lettuce and peas). Powdery mildew of tomato is caused by the fungus Oidium neolycopersicum. Symptoms include white powdery spots on the leaves and stems. As the disease progresses, the spots get larger and more dense. Powdery mildew grows well in environments warm and dry temperatures. Greenhouses provide an ideal environment for the spread of the disease.
This trial has been set up to evaluate the efficacy of particular biofungicides against powdery mildew (Oidium neolycopersici / OIDINL) in tomato (Lycopersicon esculentum / LYPES).
Untreated, Kumulus, Karma, Agricolle, AQ10, Fytosave, Limocide, PM17/006, PM14/008
In this trial we tested the efficacy of 8 biopesticides (either authorized products or products that are authorized in another crop or country) in comparison with an untreated control. As the germination of Oïdium lycopersicum-spores isn’t optimal in the presence of water and the treatment of water can inhibit the development of the mycelium, the untreated control was treated with water.
Sixteen plants per plot were planted the 25th of April, 2017. The variety Cappricia (Rijk Zwaan, sensitive for powdery mildew disease) was grafted on a Fortamino rootstock.
As biopesticides generally work only preventively, we started the first treatment one week after planting, before the first symptoms could appear. All products were applied in the same treatment frequency with an interval of one week. The number of treatments (15) exceeded the authorized treatment frequency. From the 31st of May onwards assessments were done weekly before each treatment. Despite of adapted climatic conditions in favour of a natural infection of powdery mildew, no symptoms could be detected Mid of July. Therefore, we decided to artificially inoculate the plants with infected leaf material of two growers on the 18th of July, 2017. The first symptoms appeared two weeks after the artificial inoculation, though only on a couple of plants in the greenhouse. From the 8th of August, clear symptoms could be observed across the entire greenhouse compartment.
As of the first assessment (8th of August, 2017) clear differences could be observed between the different objects. At that time, only a slight degree of infestation could be detected within the trial with a maximum of 2.9 %. At the end of the trial (5th of September, 2017) the disease was nicely developed; 43% of the leaf surface was affected in the untreated object, and approximately 60% in the trial products PM17/006 and PM14/008. Kumulus and Karma showed the best efficacy against powdery mildew in tomato, already from the first assessment (respectively 1.3 % and 1.0 % infested leaf). Limocide and Agricolle displayed a good efficacy in this trial (respectively 3.1 % and 4.0 % infested leaf surface). This trend could be observed until the end of the trial, with Limocide being nearly as effective as Kumulus in the final assessment. AQ10, Phytosave and the two test products didn’t perform better than the untreated control.
It is important to notice that Kumulus left a visible residue, both on the leaf and on the fruit. In the object treated with Karma, the most effective product in this trial, we could detect a slight greasiness of the fruit from the seventh treatment onward. The number of recognized applications is limited to six.
In this trial we tested the efficacy of eight biofungicides against powdery mildew disease in tomato. From this, we can conclude that from the start clear differences in efficacy between the treatments were apparent. Karma, Kumulus and Limocide showed the best results, with Karma the most effective. AQ10, Phytosave and the two test products didn’t perform better than the untreated control.
Report Efficacy of biofungicides against powdery mildew in tomato 2017
This trial was performed in the framework of the InterregV-project “BioProtect: 'Biological crop protection in practice: optimization of the efficacy of (new) biological crop protection products in the field”.
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