A thrips pest pressure model for greenhouse climate control

The interaction between climate regimes and pest-pressure in dynamic greenhouse climate regimes has not yet been quantified and implemented in simulation models for climate control purposes. We examined the influence of dynamic climate regimes on thrips pest-pressure in greenhouses. Experiments showed that dynamic climate regimes significantly decrease thrips by a reduced influx from outdoor to the indoor environment. This was due to a strong reduction in vent opening from 33.4% in a regular climate regime to 6.9% in a dynamic climate controlled greenhouse. To quantify thrips pest pressure in different greenhouse climate regimes we designed a three componential simulation model. The model first determines the thrips population density outside the greenhouse. In the second step thrips influx and outflux to and from the greenhouse is simulated from greenhouse ventilation rate, which is calculated from wind speed and vent opening. The inner greenhouse thrips density is simulated in the third module that is separated in three zones: plant level (i.e. pest pressure on the plants), above plant level (thrips above the crop that horizontally move in the greenhouse) and greenhouse ventilation zone. A simple model that uses developmental time, mortality rate and the life cycle as functions of temperature as major components was created to simulate the population dynamics at crop level. Simulations support the findings that dynamic climate regimes can reduce the thrips pressure drastically. The model succeeded in calculating influx of thrips to the greenhouse and a difference between regular and dynamic climate regime was distinct. Compared to the regular regime about 5 times less thrips migrated into the greenhouse with the dynamic regime. When more measured data will be available, the model will be further validated in another paper and later used for climate control purposes.