The socioeconomic benefits of biological control of western corn rootworm Diabrotica virgifera virgifera and wireworms Agriotes spp. in maize and potatoes for selected European countries

Abstract

Innovative biological pest control of the western corn rootworm (WCR) Diabrotica virgifera virgifera and wireworms Agriotes spp. in maize and potato cultivation in Europe is driven by (1) the economic damages caused and (2) the restrictions on chemical pesticides. We analyze the efficacy of biological control agents for WCR and wireworms based on European field trails. A partial equilibrium displacement model is used to estimate the changes in producer and consumer surplus for France, Italy, Spain, Germany, Austria and Romania given different adoption ceiling and adoption speed. Furthermore, the benefit of a potential reduction in pesticide use due to biological control application is evaluated. The results suggest a total annual welfare gain of ca. €190 million from biocontrol of WCR in maize production for the countries under consideration at an adoption ceiling and adoption speed of 30% and 2.41, respectively. In potato production, an annual welfare gain of over €2 million may be recorded in ecological and/or organic cultivation. Overall, the biological control methods provide an economical alternative in maize and can contribute to increase the competitiveness of European Union (EU) agriculture, while they look promising for certified organic potato production at the current level of control efficiency.

Appendix

The changes ($\Delta$) in the CS, PS, and total surplus (TS) in the linear partial equilibrium model above can be mathematically denoted (see, for example, Alston et al. 1995) as:

$$\Delta {\text{CS}} = P_{0} Q_{0} Z \left( {1 + 0.5Z} \right),$$

(3)

$$\Delta {\text{PS}} = P_{0} Q_{0} \left( {K - Z} \right) \left( {1 + 0.5Z} \right),$$

(4)

$$\Delta TS = P_{0} Q_{0} K\left( {1 + 0.5Z} \right),$$

(5)

where $Z = \frac{K\varepsilon }{\varepsilon + }$ and $K$ is the “proportional vertical shift in the supply curve” due to successful research resulting in cost reduction for adopters of the biocontrol technology. Following Alston et al. (1995), this K-shift due to research can be calculated as:

$$K = \left[ {\frac{E\left( Y \right)}{\varepsilon } - \frac{E\left( C \right)}{1 + E\left( Y \right)}} \right]$$

(6)

where E(Y) is the expected proportionate yield change per hectare given maximum adoption and E(C) is the proportionate change in variable input costs in order to achieve E(Y). The value of the $K$ shift for maize and potatoes at complete adoption, based on the field trials data collected in Austria and Switzerland, is as follows (please note that we used a supply elasticity, ε, of 0.7 for maize in the K-shift estimation in accordance with Banse et al. (2005):

For maize: $K = \left[ {\frac{0.26}{0.7} - \frac{0.31}{1 + 0.26}} \right] = 0.12$

For calculating the $K$ shift of potatoes, we use a supply elasticity, ε, of 1.5

For potatoes: $K = \left[ {\frac{0.5}{1.5} - \frac{0.07}{1 + 0.5}} \right] = 0.3$

The full K-shift is not immediate, but follows a logistic adoption function:

$$\theta (t) = \frac{{\theta_{\hbox{max} } }}{{\left( {1 + e^{ - (a + bt)} } \right)}},$$

(7)

where θ(t) is the adoption rate in year t, a the constant of integration, b the slope coefficient also known as the speed of adoption, and θ_max the long-run adoption ceiling.

The social incremental reversible benefits (SIRB) in present value are calculated by building the discounted sum of the annual total surplus using the discounting factor $\left( {1 + i} \right)^{t}$ over the time, where i is the interest rate and t is the time in years:

$${\text{SIRB}}_{\text{PV}} = \mathop \sum \limits_{t = 0}^{\infty } \left[ {{\text{TS}} \cdot \theta \left( t \right) \cdot \left( {1 + i} \right)^{ - t} } \right].$$

(8)

This can be converted to the average annual SIRB_a:

$${\text{SIRB}}_{\text{PV}} = {\text{SIRB}}_{\text{PV}} \cdot i.$$

(9)

Using the data from Table 9, we calibrated a as 1.08 and b as − 0.108. This resulted in the somewhat S-shaped adoption curve for biocontrol of wireworms in potato cultivation across Europe presented in Fig. 2.

Table 9 Expansion in organic cultivate fields in the EU-27 (2002–2011).