Crop protection

The business unit Greenhouse Horticulture develops strategies and techniques for sustainable crop protection. Biological pest control; conscientious application of agents with the appropriate technique; and the utilisation of soil and crop resistance, the climate, and the environment are all examined individually and as a total system and then optimised.

Our experts in the fields of plant pathology, entomology, cultivation, climate, and technology work together with entrepreneurs and scientists from a range of fields. This collaborative approach combines innovations with the latest scientific knowledge and important and relevant questions from the professional field.

Application techniques and crop protection agents

Crop protection agents are applied using treatment techniques attuned to the crop and the space: spray boom, spray mast, spray rod, LVM, fog equipment, etc. It is essential that the agents are only applied at the location of the disease or pest to be combated.

Many diseases and pests are found in specific locations such as the underside of the leaves and/or deep within the plant. Limiting the number of agents used means that these agents will need to be used more often, giving the disease or pest a greater chance of developing resistance to these agents. Optimisation of various compressed-air application techniques has resulted in greater concentrations of agents deposited on the underside of leaves. Employing 'upside-down spraying' also results in clear improvements to the concentration of deposits.

This results in improved effectiveness and reduced frequency of spraying. Consequently, there is less chance that the disease or pest will develop resistance to the agent. Reducing the frequency of applications of agents also reduces emissions.

The research involves collaboration with the business community.

Contactpersoon: Marieke van der Staaij

Healthy substrate and soil

A healthy substrate and healthy soil is an important foundation for cultivating healthy horticultural crops. Sustainable application methods and cultivation measures are important for guaranteeing crop resistance.

This helps prevent loss caused by disease and pests. Examples of this include plant strengtheners, soil strengtheners, biostimulators, biofertlisers, crop protection agents, and natural enemies of diseases and pests such as nematodes, bacteria (excessive root growth), and fungi (Fusarium, Verticillium, Rhizoctonia). The emphasis is on sustainability and in particular on achieving zero emissions and zero residue formation on the product and on successfully combating pathogens.

To combat diseases like Phytophthora, Pythium, and downy mildew, plants are given added resistance during propagation stages so that they are adapted to stressful growing conditions such as the planting-out and flowering stages. It is also possible to introduce adaptations to the substrates and soils themselves, such as increased stability, better drainage, and support for beneficial fungi and bacteria which increase growth and resistance. Applications range from soil adaptations, propagation materials, potting mixtures, growing substrates (stone wool, coconut, perlite), and organic substrates to new soilless culture techniques like the Teelt de Grond Uit ('Growing crops without soil') programme for bulbs, field vegetables, and ornamental cultivation.

Measures are developed as part of a systematic approach which focuses on the effects of climate and the effects on above-ground and underground diseases and pests, as well as on corporate social responsibility and human capital.

Contactpersoon: André van der Wurff

Viruses and viroids

Viral diseases have an important influence on the cultivation of various greenhouse crops. In both vegetable and ornamental cultivation, viruses can result in loss of yields, even if no symptoms have been detected.

A mechanically transmittable virus can be introduced via infected plant material and seeds. The virus can spread rapidly through mechanical transmission, contact, and crop handling. An example of a mechanically transmissible virus is cucumber green mottle mosaic virus in cucumbers. As well as through mechanical transmission, plant viruses can also be spread by vectors (insects, fungi, nematodes).

Like viruses, viroids can cause symptoms such as malformation, reduced growth, and deviations in colour in their host plants, and the transmission methods are also similar. Many viroids can be transmitted through contact such as crop handling. The business unit Greenhouse Horticulture is carrying out research with the aim of making it possible to take adequate prevention measures at a sufficiently early stage. This research is designed to increase knowledge regarding the behaviour of viruses and viroids and the interaction between the virus, the plant, the plant's environment, the host plant, and the vectors. The research is being carried out for and in collaboration with the professional field.

Contactpersoon: Caroline van der Salm

Business hygiene and disinfection

It is not possible to directly combat viruses, viroids, and bacteria in a plant. Therefore it is necessary to prevent infection from arising in a crop in the first place. It is important to use clean propagation material and to take the appropriate hygiene measures. A hygiene protocol can offer excellent assistance in this regard. The business unit Greenhouse Horticulture has written hygiene protocols for preventing various diseases.

It is recommended that thorough cleaning and disinfection be carried out when crops are rotated. Knowledge about the pathogens present in the crop is essential to ensure the use of the appropriate measures and disinfectants. The business unit Greenhouse Horticulture regularly carries out research into the effectiveness of various disinfectants.

A number of plant pathogens are transmitted via water. It is therefore important that nutrient solution be disinfected before reuse. The business unit Greenhouse Horticulture is working on new disinfectant equipment and methods. Research is being carried out to determine whether the equipment is effective against various pathogens, and in particular which dose is most effective.

Contactpersoon: Ineke Stijger

Insects and mites

Nearly all greenhouse crops are subject to damaging pests. These may be insects such as aphids, mealy bugs, whitefly, or thrips; or mites such as spider mites, thread-footed mites, and russet mites.

Research focuses on new natural enemies, methods to support natural enemies, interactions between natural enemies, biological and chemical agents, side effects of agents on natural enemies, odours for pests and natural enemies, and the development of total concepts for integrated crop protection.

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Contactpersoon: Gerben Messelink

Fungi and bacterial diseases

Most diseases affecting greenhouse-cultivated crops in the Netherlands are caused by one or more fungal or bacterial infestations. Some fungi and bacteria primarily damage the root system (such as the fungi Fusarium, Pythium, and Phytophthora and the bacterium Agrobacterium rhizogenes), while others primarily manifest above ground (like the fungus Phytophthora infestans or bacteria like Clavibacter michiganensis subsp. michiganensis).

Bacteria cannot be combated using crop protection agents, so solutions have to be found in prevention and in competition with other bacteria. Unlike bacteria, fungi can be treated using crop protection agents. However, public opinion and the market are increasingly insisting on a residue-free product, making the use of crop protection agents against fungi more problematic.

As a result, it is necessary to find new methods of crop protection and disease combating which take the condition of the plant into account. The business unit Greenhouse Horticulture researchers are working on alternative methods and applications based on prevention (business hygiene), antagonism and competition (other bacteria or fungi), climate control (ventilation), or physical solutions (light).

Contactpersoon: André van der Wurff

Soil disinfection

The necessity of soil disinfection is clear: monocultures and very intensive cultivation systems allow diseases like Verticillium and pests like root-knot nematodes and Meloidogyne to easily and rapidly reproduce in a plot. Soil disinfection is the only solution. Chemical soil disinfection is prohibited in greenhouse crops, while steaming is currently the most widely-used form of greenhouse soil disinfection in the Netherlands.

But steaming is merely a short-term solution. Results from the professional field show that steaming loses effectiveness each year it is used. Diseases and pests recover more quickly each time. In some cases, the disease can be so stubborn that steaming does not provide sufficient results or the greenhouse must be steamed so often that cultivation is impossible. Mediocre steaming results, exhaustion, the increasing costs of fossil fuel, and the effects on the environment make it necessary to find a different approach.

Wageningen UR Greenhouse Horticulture is working on alternative methods and influencing soil resistance. The research utilises natural agents and ecological principles which influence and prevent the development of diseases and pests. An example of this is biological soil disinfection, a natural process which suppresses Verticillium and nematodes while simultaneously increasing soil resistance.

Resilient crops and healthy environment

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