Biodiversity - a form of natural pest control

Lukas Pfiffner

Sponsor(s)/Partners

Cantons of Bern and Fribourg; Fonds Landschaft Schweiz, a foundation for Swiss agriculture.

Purpose

To assess whether strips sown to wildflowers and herbs can improve natural pest control and whether sowing these strips can yield measurable results in terms of the efficacy of populations of beneficial organisms.

Methods

The parasitism rates of three pests, Mamestra brassicae, Pieris rapae and Plutella xylostella in unsprayed cabbage crops, cauliflower and red cabbage, were determined. Caterpillars and eggs of these pests (P. xylostella - larvae only) were counted and collected on 6 (cauliflower) or 9 (red cabbage) dates from each of three treatment areas: i) adjacent to a wildflower strip, ii) within 10-90 m of a wildflower strip; or iii) without a wildflower strip or semi-natural habitat nearby = control. The trials were conducted in the Grosses Moos (Bern-Fribourg) region in Switzerland.

Results

The results show the potential of wildflower strips to enhance natural pest control by increasing the diversity and number of predators. In this trial, caterpillars of M. brassicae and P. rapae were parasitized at the highest rates in fields near a wildflower strip whereas P. xylostella caterpillars were parasitized most in the control areas. Overall, parasitism of eggs was low, but more prevalent in the fields adjacent or near to wildflower strips.