Balancing Bees and Pest Management: Projected Costs of Proposed Bee-Protective Neonicotinoid Regulation in California.

Neonicotinoid insecticides are widely used in agriculture, including in many California specialty crops. With mounting evidence that these insecticides are harmful to bees, state and national governments have increasingly regulated their use. The European Union, Canada, and United States have imposed use restrictions on several neonicotinoids, such as on the timing of applications. In 2020, California proposed a draft regulation to mitigate harm to managed pollinators from four nitroguanidine-substituted neonicotinoids (NGNs): clothianidin, dinotefuran, imidacloprid, and thiamethoxam. We use data on California pesticide use from 2015 to 2017 to analyze the economic and pest management implications of the 2020 draft proposed regulation for seven crops: almond, cherry, citrus, cotton, grape, strawberry, and tomato. From 2015 to 2017, these crops accounted for approximately 85% of total hectares treated with NGNs and 87% of NGN use by kilograms of active ingredient applied in treatments that would have been affected by the proposed regulation. These insecticides often primarily target Hemipteran insect pests. In most cases there are alternatives; however, these are often more expensive per hectare and do not have the same residual effectiveness as the NGNs, which are systemic insecticides. Overall, we estimate that pest management costs for these crops would have increased an estimated $13.6 million in 2015, $12.8 million in 2016, and $11.1 million in 2017 if the 2020 draft proposed regulation had been in effect, representing a 61% to 72% increase in the cost of managing the target pests.

Increasing crop diversity mitigates weather variations and improves yield stability.

Cropping sequence diversification provides a systems approach to reduce yield variations and improve resilience to multiple environmental stresses. Yield advantages of more diverse crop rotations and their synergistic effects with reduced tillage are well documented, but few studies have quantified the impact of these management practices on yields and their stability when soil moisture is limiting or in excess. Using yield and weather data obtained from a 31-year long term rotation and tillage trial in Ontario, we tested whether crop rotation diversity is associated with greater yield stability when abnormal weather conditions occur. We used parametric and non-parametric approaches to quantify the impact of rotation diversity (monocrop, 2-crops, 3-crops without or with one or two legume cover crops) and tillage (conventional or reduced tillage) on yield probabilities and the benefits of crop diversity under different soil moisture and temperature scenarios. Although the magnitude of rotation benefits varied with crops, weather patterns and tillage, yield stability significantly increased when corn and soybean were integrated into more diverse rotations. Introducing small grains into short corn-soybean rotation was enough to provide substantial benefits on long-term soybean yields and their stability while the effects on corn were mostly associated with the temporal niche provided by small grains for underseeded red clover or alfalfa. Crop diversification strategies increased the probability of harnessing favorable growing conditions while decreasing the risk of crop failure. In hot and dry years, diversification of corn-soybean rotations and reduced tillage increased yield by 7% and 22% for corn and soybean respectively. Given the additional advantages associated with cropping system diversification, such a strategy provides a more comprehensive approach to lowering yield variability and improving the resilience of cropping systems to multiple environmental stresses. This could help to sustain future yield levels in challenging production environments.