To know whether crop protection in greenhouses is under control, growers must not only consider harmful but also beneficial insects. Rob Moerkens from Belgian Research Centre Hoogstraten spoke about this at the Tomato Conference last month.
Its provisional name is PeMaTo, an abbreviation for Pest Management Tool for Tomato Crops. It is the project name under which a decision model for biological control is being developed in Belgium. Rob Moerkens of Research Centre Hoogstraten elaborated on this at the Tomato Conference last week.
To make the right decisions with regard to crop protection it is necessary to know what is happening in the greenhouse. It's important to know not only how many harmful, but also how many beneficial insects are present in the greenhouse, and also how these populations evolve. With biological crop protection it’s not only about the moment but also about the developments and balance in the greenhouse.
Complex populations
Moerkens explained the complexity of ecosystems in the greenhouse on the basis of several models. Looking at two populations, developments can still be perfectly illustrated and simulated: if the population of harmful insects grows, the number of beneficial insects should also be increased because there is more food available. Then the point comes at which the population of beneficial insects gets the upper hand and the harmful insect population decreases. The beneficial insect population will then also decline because there is less food. Moerkens: "Ultimately we are working towards an equilibrium, a balance. This must be reached before there is damage to the crop. So it’s important to know in which section of the graph you are and whether you have to intervene chemically or not." But additional complicating factors - other populations that affect any of the populations, cannibalism, external actions - are not included in the model yet.
Models and tools
The project has already developed a model that measures the populations of harmful and beneficial insects by using sticky traps. This results in a heat map of the greenhouse that clearly shows the development of the populations. With this model Belgian tomato growers are currently already monitoring more than 60 hectares of greenhouses. Some growers choose to only monitor harmful insects, others also monitor the beneficial ones.
To move to a model that can make decisions, both harmful and beneficial insects must be monitored. "The whitefly is under control after 11 weeks, probably thanks to the predatory bugs. But if only the number of whiteflies were looked at the situation would seem very serious." Other factors that could have an impact on crop protection must also be taken into account. They should also be incorporated in such a model. Further research is being done in this regard.