Crops
Protection methods
If we want to effectively control attacks of Didymella bryoniae on cucurbits, it is essential to implement additional control methods either preventively or as soon as the very first symptoms appear. It is also advisable to be particularly vigilant for the cultures located in wet zones or under shelter. Note that cucurbits are rather predisposed to attacks from this parasitic fungus, this because of a rather dense foliage and the continual realization of injuries during pruning and picking. We should add that it is essential to properly control lesions on leaves and stems if we do not want to suffer severe attacks on fruits in the field, such as during storage and preservation.
- During cultivation
Under shelter, producers should be aware of the influence climate of the greenhouse on the development of the disease, and therefore of the importance of its management. By heating and ventilating them, the grower helps to reduce relative humidity and, very often, prevents the presence of free water on the plants and the phenomenon of guttation. For example, in crops nearing harvest, where "high" temperatures are maintained overnight, the disease develops much less. This measure will often seem costly to them. It is up to them to decide to what extent it is applicable depending on the current economic conditions. Of course, sprinkler irrigation should be avoided.
In the open field, it is desirable to avoid water being present for too long on the plants or near them, for example on the ground. For this, it is advisable to water more often, adding less water at the same time. The irrigations sprinkler will be carried out in the morning or during the day, but never in the evening, so that the plants breathe quickly.
Spoiled fruit, leaf stripping and disbudding debris will be quickly removed from greenhouses and fields, destroyed or composted.
The chemical control to be effective, must be relatively intensive, especially indoors. It is necessary to carry out sprays every week ** ( e-phy ). Azoxystrobin should be used sparingly as resistant strains have been reported fairly soon after its use in the United States. It should be remembered that chemical control is sometimes unsatisfactory on Cucurbits, because the plants grow very quickly and the parts of recently formed plants are not always well protected. To be effective, treatments must be repeated frequently, often every 7 days. Let us add that the ammonium bicarbonate associated or not with a mineral oil would have conferred a certain protection on plants confronted with this fungus.
Lesions beginning on stems can be brushed with a thick fungicidal mixture, made up of a combination of several active ingredients.
At harvest, the fruits should be handled with care to avoid injuries, and they should be healed. They will then be stored at low temperatures (at 12 ° C for cucumber), in order to reduce the development of black rot without affecting their shelf life. Special attention should be paid to winter squash and pumpkins in order to avoid them as much as possible. They will be dried in good conditions to promote hardening of their skin and healing. Under proper drying conditions, injured areas heal and form corky tissue. Drying at 20-25 ° C or more, and for 1 to 2 weeks, hardens the skin. Their storage can take place at temperatures between 11-16 ° C (the optimum is at 13 ° C), with a relative humidity of around 60%).
At the end of cultivation, plant debris will be removed from shelters and fields, transported far from the plots and destroyed. In the open field, they can also be buried deep in the ground.
In the open field, it is desirable to avoid water being present for too long on the plants or near them, for example on the ground. For this, it is advisable to water more often, adding less water at the same time. The irrigations sprinkler will be carried out in the morning or during the day, but never in the evening, so that the plants breathe quickly.
Spoiled fruit, leaf stripping and disbudding debris will be quickly removed from greenhouses and fields, destroyed or composted.
The chemical control to be effective, must be relatively intensive, especially indoors. It is necessary to carry out sprays every week ** ( e-phy ). Azoxystrobin should be used sparingly as resistant strains have been reported fairly soon after its use in the United States. It should be remembered that chemical control is sometimes unsatisfactory on Cucurbits, because the plants grow very quickly and the parts of recently formed plants are not always well protected. To be effective, treatments must be repeated frequently, often every 7 days. Let us add that the ammonium bicarbonate associated or not with a mineral oil would have conferred a certain protection on plants confronted with this fungus.
Lesions beginning on stems can be brushed with a thick fungicidal mixture, made up of a combination of several active ingredients.
At harvest, the fruits should be handled with care to avoid injuries, and they should be healed. They will then be stored at low temperatures (at 12 ° C for cucumber), in order to reduce the development of black rot without affecting their shelf life. Special attention should be paid to winter squash and pumpkins in order to avoid them as much as possible. They will be dried in good conditions to promote hardening of their skin and healing. Under proper drying conditions, injured areas heal and form corky tissue. Drying at 20-25 ° C or more, and for 1 to 2 weeks, hardens the skin. Their storage can take place at temperatures between 11-16 ° C (the optimum is at 13 ° C), with a relative humidity of around 60%).
At the end of cultivation, plant debris will be removed from shelters and fields, transported far from the plots and destroyed. In the open field, they can also be buried deep in the ground.
- Next crop
In the case of "traditional" field crops, healthy seeds should be used. These should only be recovered from healthy fruits, or exceptionally very partially rotten, otherwise they will be contaminated and very early attacks will be feared. The seeds can be disinfected. Peroxyacetic acid, followed by drying in an oven, would show some efficacy.
Of crop rotations of at least two to three years with non-host crops will be implemented. Note that a study conducted in Maryland showed that pumpkins ( Cucurbita pepo unworked ) grown on soil covered with Hairy vetch ( Vicia villosa ) significantly reduced the incidence of black rot on fruits, compared to crops on bare soil. The soil will be well drained and the planting density can be reduced in order to obtain a more aerated plant cover. For the same reason, the plots will be oriented in the direction of the prevailing wind.
It will be essential to use quality seeds and to monitor the health status of the plants.
Under cover, if monocultures of cucumbers are made in the ground, disinfection of the soil with steam or with a fumigant will be carried out. Solarization seems to be used as well.
The quality of the plastic film of the shelters would influence epidemics of gummy canker, especially on watermelon. Thus, UV absorbing films would greatly limit the damage of D. bryoniae , compared to ordinary transparent films.
The walls of the greenhouses will also be disinfected with a product authorized for this type of use ( e-phy ).
Controlling the climate of the shelter (which will not encourage the formation of water films on the plants) and controlling fertilization seem essential foundations for effective preventive protection.
We will also avoid any stress to the plants.
Preventive applications fungicide will be carried out with the active ingredients mentioned above ( e-phy ). The other pests of cucurbits must be perfectly controlled because the development of some (in particular powdery mildew for which a resistant variety can be used) would sensitize plants to D. bryoniae .
The vegetation debris accidentally present or kept nearby greenhouses are also the source of contamination, especially through ascospores that form on these, as soon as weather conditions permit. It is advisable to be as vigilant for the close surroundings as for the shelters.
Although varietal resistance has been demonstrated or sometimes used, no cultivar of cucurbits currently marketed in France is resistant to this fungus.
By way of example, let us quote some genotypes reported as more or less resistant * in cucurbits:
- watermelon: PI 164248, Pi 189225, PI 244019, PI 254744, PI 271771, PI 279461, PI 296332, PI 379243, PI 482276, PI 482284, PI 482322, PI 482379, PI 490383 and PI 526233;
- melon: PI 266934, PI 266935, PI 157082 and PI 511890, PI 266934, several species of Cucumis ( C. ficifolius , C. anguria - West Indian cucumber, C. figarei , C metuliferus metuliferous - cucumber, C. zeyheri , C . myriocarpus );
- pumpkin: cultivars 'Kirameki', 'Shelper', 'Ikky' and 'Agroceres', as well as 'Gherkin';
- cucumber: PI 200815, PI 390243, LJ 90430, PI 279469 and PI 432855, PI 299568 ( Cucumis myriocarpus ), PI 282450 ( C. zeyheri ), PI 299572 ( C. myriocarpus ) and PI 233646 ( C. anguria ), and the cultivars little john, transamerica and poinsett 76, marketer ...
- squash: resistance was observed in Cucurbita martineziik , C. moschata (201474 and 438579) and C. pepo (10107, 358969 and 442312);
- wax squash ( Benincasa hispida ).
It should be noted that grafting on rootstocks resistant to D. bryoniae would limit the damage of this fungus, in particular by preventing attacks on the neck and on the lower part of the stem. It will be necessary to be wary all the same during the realization of the transplants, because the wounds carried out can constitute entry doors for this fungus if it is present in the environment of the grafting site.
Some bio-pesticides have been tested on D. bryoniae in vitro and in the field in several countries around the world, with varying degrees of success: Trichoderma spp., Streptomyces spp ....
* Mistrust, contradictory behavior towards D. bryoniae could be observed for the same plant material by different experimenters
** Chemical control : As the number of pesticides available for a given use is constantly changing, we advise you to always confirm your choice by consulting the e-phy site of the Ministry of Agriculture and Fisheries which is an online catalog plant protection products and their uses, fertilizers and growing media approved in France. This also applies to all biological products based on microorganisms or natural substances.
Of crop rotations of at least two to three years with non-host crops will be implemented. Note that a study conducted in Maryland showed that pumpkins ( Cucurbita pepo unworked ) grown on soil covered with Hairy vetch ( Vicia villosa ) significantly reduced the incidence of black rot on fruits, compared to crops on bare soil. The soil will be well drained and the planting density can be reduced in order to obtain a more aerated plant cover. For the same reason, the plots will be oriented in the direction of the prevailing wind.
It will be essential to use quality seeds and to monitor the health status of the plants.
Under cover, if monocultures of cucumbers are made in the ground, disinfection of the soil with steam or with a fumigant will be carried out. Solarization seems to be used as well.
The quality of the plastic film of the shelters would influence epidemics of gummy canker, especially on watermelon. Thus, UV absorbing films would greatly limit the damage of D. bryoniae , compared to ordinary transparent films.
The walls of the greenhouses will also be disinfected with a product authorized for this type of use ( e-phy ).
Controlling the climate of the shelter (which will not encourage the formation of water films on the plants) and controlling fertilization seem essential foundations for effective preventive protection.
We will also avoid any stress to the plants.
Preventive applications fungicide will be carried out with the active ingredients mentioned above ( e-phy ). The other pests of cucurbits must be perfectly controlled because the development of some (in particular powdery mildew for which a resistant variety can be used) would sensitize plants to D. bryoniae .
The vegetation debris accidentally present or kept nearby greenhouses are also the source of contamination, especially through ascospores that form on these, as soon as weather conditions permit. It is advisable to be as vigilant for the close surroundings as for the shelters.
Although varietal resistance has been demonstrated or sometimes used, no cultivar of cucurbits currently marketed in France is resistant to this fungus.
By way of example, let us quote some genotypes reported as more or less resistant * in cucurbits:
- watermelon: PI 164248, Pi 189225, PI 244019, PI 254744, PI 271771, PI 279461, PI 296332, PI 379243, PI 482276, PI 482284, PI 482322, PI 482379, PI 490383 and PI 526233;
- melon: PI 266934, PI 266935, PI 157082 and PI 511890, PI 266934, several species of Cucumis ( C. ficifolius , C. anguria - West Indian cucumber, C. figarei , C metuliferus metuliferous - cucumber, C. zeyheri , C . myriocarpus );
- pumpkin: cultivars 'Kirameki', 'Shelper', 'Ikky' and 'Agroceres', as well as 'Gherkin';
- cucumber: PI 200815, PI 390243, LJ 90430, PI 279469 and PI 432855, PI 299568 ( Cucumis myriocarpus ), PI 282450 ( C. zeyheri ), PI 299572 ( C. myriocarpus ) and PI 233646 ( C. anguria ), and the cultivars little john, transamerica and poinsett 76, marketer ...
- squash: resistance was observed in Cucurbita martineziik , C. moschata (201474 and 438579) and C. pepo (10107, 358969 and 442312);
- wax squash ( Benincasa hispida ).
It should be noted that grafting on rootstocks resistant to D. bryoniae would limit the damage of this fungus, in particular by preventing attacks on the neck and on the lower part of the stem. It will be necessary to be wary all the same during the realization of the transplants, because the wounds carried out can constitute entry doors for this fungus if it is present in the environment of the grafting site.
Some bio-pesticides have been tested on D. bryoniae in vitro and in the field in several countries around the world, with varying degrees of success: Trichoderma spp., Streptomyces spp ....
* Mistrust, contradictory behavior towards D. bryoniae could be observed for the same plant material by different experimenters
** Chemical control : As the number of pesticides available for a given use is constantly changing, we advise you to always confirm your choice by consulting the e-phy site of the Ministry of Agriculture and Fisheries which is an online catalog plant protection products and their uses, fertilizers and growing media approved in France. This also applies to all biological products based on microorganisms or natural substances.