Fabian Cahenzli

Screening of 25 different natural crop protection products against Drosophila suzukii

Drosophila suzukii is a major pest of soft‐skinned fruits, and insecticides are often used to prevent fruit damage caused by oviposition. As D. suzukii produces many generations per year, repeated insecticide applications are required. Furthermore, D. suzukii attacks ripening and ripe fruits shortly before harvest. Therefore, the use of synthetic insecticides is limited by long pre‐harvest intervals and maximum residue limits. To be able to offer producers immediate and sustainable solutions, we tested 25 natural crop protection products with three different application methods in a laboratory screening. We show that application method is an important factor for the efficacy of the tested products. Of six natural insecticides, only Spinosad was toxic for D. suzukii and reduced the oviposition on treated blueberries. The tested oil products had no control effect and products based on different entomopathogenic fungi and Bacillus thuringiensis rather enhanced oviposition. Mineral products (Kaolin, CaCO3, Ca(OH)2 and clinoptilolith) applied as spray solutions were not toxic, but significantly reduced oviposition on blueberries. We provide the first study in which different application methods have been used to compare numerous, commercially available, natural crop protection products with different modes of action against adult D. suzukii. Our findings provide consultants and producers with important insights for the development of sustainable pest control strategies against D. suzukii.

The Distance Between Forests and Crops Affects the Abundance of Drosophila suzukii During Fruit Ripening, But Not During Harvest

Abstract Drosophila suzukii (Matsumura; Diptera: Drosophilidae) is an invasive pest with the ability to reproduce not only in various soft fruit crops, but also in numerous wild hosts. Forests and forest edges harbor many wild hosts, provide suitable microclimatic conditions and are therefore thought to enhance the abundance of D. suzukii. Although the comprehension of pest activity based on specific landscape elements is important to implement efficient management strategies, knowledge of how forests affect the abundance of D. suzukii in nearby crops is very limited. We conducted a monitoring study with liquid baited traps across different crops at different distance from the forests. During fruit ripening, more flies were captured in crops closer to forests (22.21 % decrease per 500 m distance), whereas there was no significant relationship during harvest. Since color can affect the efficiency of D. suzukii traps, we have used traps either with a red or black lid. Acquired data suggest that traps with black lids capture significantly more flies than traps with red lids. We provide a quantitative estimation of how and when distance from adjacent forests affects the abundance of D. suzukii in crop fields. Our results can help consultants and farmers to estimate the pest pressure of D. suzukii in crop fields near forested, noncrop areas and to implement appropriate control strategies when D. suzukii populations increase and fruit becomes susceptible to infestation.

Reduced crop damage by self-regulation of aphids in an ecologically enriched, insecticide-free apple orchard

Enhancing natural enemies for pest management in agriculture is an expanding approach offering new opportunities for pest control and the potential to reduce insecticide use. Numerous studies in a variety of cropping systems clearly have shown that adequate measures can benefit natural enemies. However, although carry-over effects from an increase in natural enemies and a subsequent decrease in pest populations leading to a reduction in crop damage are always assumed, they are rarely proven. We established an insecticide-free apple orchard optimized for the self-regulation of pests by supporting natural enemies with shelter, nectar, alternative prey/hosts, and pollen. For six growing seasons, we focused on the control of the major apple pest Dysaphis plantaginea. While fruit damage after the second fruit drop was not affected by aphidophagous insect guilds, it was negatively related to spider abundance in the previous autumn, when aphids immigrate back to the orchard to establish the next generation. In detail, we found that an increase in spider web area reduced the number of aphid fundatrices in spring and subsequently fruit damage. Our findings indicate the rarely proven carry-over effect of enhanced natural enemies on decreased crop damage and we show for the first time, how the rosy apple aphid can be managed without the use of insecticides.