The experiments were conducted in semi-field and field environments and the findings open the possibility for a sustainable pest management strategy.
The scientists from Rothamsted, which were funded by DEFRA and strategic funding from BBSRC, systemically dyed the flowers of a white-petalled oilseed rape variety using food colouring solutions that were taken up by the roots of the plant. They assessed the attractiveness of the plants to the pollen beetles by measuring the number of beetles found on plants of the different colours - white (control), yellow, red and blue. Yellow and white were most attractive while red was least attractive. Doing further experiments the scientists also tested for the effect of odour and found there was no significant difference between the treatments, which confirmed that the beetle preferences were due to changes in petal colour.
Dr Sam Cook, a Rothamsted agroecologist and lead scientist of the study said: "This is an exciting and intriguing finding. Significantly more beetles were found in the white plants and plants dyed yellow than on the plants dyed blue or red. " She added "This was the case both in controlled environmental conditions and in experiments conducted in the field over two consecutive years."
Further insight was also shed into the mechanism that drives the observed behavioural response. The light wavelengths at which the beetles show more sensitivity were analysed and correlated with their attraction to the plants.
The results showed that pollen beetles are attracted to objects that show high reflectance of ultraviolet light (UV) such as the white and yellow colours tested in the study. Dr Cook said: "These findings are important as they can be used to help us develop highly attractive traps or less attractive crop varieties for improved pollen beetle control."
Professor John Pickett said: "It is essential that we look for sustainable pest control strategies to maximise crop yield". He emphasised that "understanding how pests use visual cues to identify and select hosts can provide us with more evidence-based sustainable pest management solutions for farmers."
Oilseed rape is currently the most important source of plant derived oil grown in Europe. The use of oilseed rape for biodiesel has increased dramatically and the demand for high yields increases continuously as the demand for biofuel increases. Given this importance of oilseed rape, it is imperative to identify novel management practices for pollen beetle. It is a major pest of the flowering stage of the plant and threatens the sustainability of the crop due to the spread of populations resistant to insecticides.