Ministry of Agriculture & Lands
Tree Fruit Leader, Vol. 3(2) July 1994
How Environmentally Friendly are Your Pest Management Practices?
by Hugh G. Philip, P.Ag., Extension Entomologist BCMAFF, Kelowna
In 1992, scientists at Cornell University in New York published a paper in which they described a method for measuring the environmental impact of pesticide active ingredients used in vegetable and fruit production (Kovach et al, 1992). The authors collected toxicological and environmental impact data on the active ingredients and organized the information so that an Environmental Impact Quotient (EIQ) could be calculated for each active ingredient based on a model. The model consisted of three principal components: farm worker, consumer, and ecological.
The farm worker component included data on factors that affect applicators and pickers such as acute dermal (not oral) and chronic toxicity, and half-life of the active ingredient on plant surfaces. The consumer component consisted of factors such as mode of action of the active ingredient and environmental fate. Aquatic and terrestrial factors were included in the ecological component-environmental fate, toxicity to fish, birds, bees and other beneficials. From this model, an equation was developed to calculate an EIQ for each active ingredient using a rating system based on how toxic or harmful each factor was.
Once the EIQ for individual active ingredients was determined, an EIQ Field Use Rating could be calculated to better compare the environmental impact of pesticide products and pest management strategies. To compare the environmental impact between pesticide products, an EIQ Field Use Rating is calculated for each product using the formula
EIQ Field Use Rating = EIQ x % Active ingredient (AI) x Rate
For example, to determine which product, Diazinon 50 WP or Guthion 50 WP, is more environmentally harmful when applied for leafroller control at pink, the following calculations are made:
EIQ Diazinon 50 WP= 34.2 (EIQ) X 0.5 (% AI) X 4.5 (kg/ha) = 77
EIQ Guthion 50 WP = 43.1 (EIQ) X 0.5 (% AI) X 2.75 (kg/ha) = 59
The field use EIQ of Guthion is less than that of Diazinon and hence has less impact on the environment.
To calculate the EIQ for a particular pest management strategy, the EIQ Field Use Rating for each pesticide used is multiplied by the number of applications over the season, and the total of these values is the EIQ for that strategy. With this calculation, the EIQ's of various strategies can compared in order to select the least toxic strategy. However, the decision on which pest management strategy to select cannot realistically be made strictly on the EIQ. In today's competitive global marketplace, B.C. fruit growers must be aware of all factors that affect their cost of production such as crop protection products.
Table 1, below, lists various products used in tree fruit production, the target pests, the cost of product per hectare (based on 1994 prices and recommended rates), and the EIQ per application. Using this table, the EIQ of various products or pest management strategies and their product costs can be compared.
Table 1. The Environmental Impact Quotient (EIQ) and Product Cost per Application of Selected Tree Fruit Pesticides.
| Product | Target Pest | Product Cost ($/hectare) | EIQ |
|---|---|---|---|
| APM 50 WP | leafrollers fruitworms bud moth |
74.22 | 59 |
| APM 50 WP | codling moth | 37.79 | 30 |
| Belmark 30 EC* | pear psylla | 28.00 | 3 |
| Diazinon 50 WP | leafrollers fruitworms bud moth |
64.13 | 77 |
| Diazinon 50 WP | campylomma | 32.06 | 38 |
| Dipel WP | leafrollers fruitworms bud moth |
70.09 | 1 |
| Dormant oil (tank mixed) |
various pests | 44.21 (45 L/ha) |
1213 |
| Endosulfan 50 WP | fruitworms | 63.78 | 69 |
| Endosulfan 50 WP | aphids | 61.00 | 66 |
| Imidan 50 WP | codling moth | 55.22 | 39 |
| Insecticidal soap* | pear psylla | 141.25 | 244 |
| Supracide 24 EC | leafrollers | 91.35 | 96 |
| Dithane 75 DG | apple scab | 54.45 | 280 |
| Benlate 50 WP | powdery mildew | 57.20 (1.1 kg/ha) |
38 |
| Kumulus 80 SP | powdery mildew apple scab |
18.27 | 255 |
| Maestro 75 DF | apple scab | 50.47 | 86 |
| Morestan 25 WP | pear psylla pear rust mite powdery mildew | 200.25 | 50 |
| Nova 40 WP | apple scab powdery mildew | 77.70 | 6 |
| Polyram 80 DF | apple scab | 53.85 | 268 |
*1993 product price
Using the above table, let us compare the EIQ and product costs between two pest management programs to control resistant fruittree leafroller. If oil plus Supracide is used in delayed dormant, followed by a Dipel WP application at petal fall, the total EIQ is 1310 (96 + 1213 + 1) and the total product cost is $205.65 ($91.35 + $44.21 + $70.09). Alternatively, if two applications of Dipel are made (pink and late bloom), the total EIQ is reduced significantly to 2 (1 + 1) and total cost of product is reduced by $65.47/ha to $140.18/ha (2 X $70.09). You can use Table 1 to compare the environmental impact between products in order to select the least harmful control strategy. Remember, the cost and EIQ for each product is based on a per application basis. In some cases the least harmful strategy may be the most expensive so you may have to adjust the strategy to fall in line with costs you can accept.
How has impact on the environment been affected by the loss of postbloom sprays and replacement by an integrated pest management strategy for pear psylla control? The EIQ's and costs of products used in the "Old" and "IPM" programs are presented in Table 2.
Table 2. EIQ and Product Cost per Hectare for the Old and IPM Pear Psylla Control programs.
| Psylla | Other Pests | Total | ||||
| EIQ | Cost | EIQ | Cost | EIQ | Cost | |
| Old program | 3839 | 1055.86 | 143 | 203.49 | 3982 | 1259.35 |
| IPM program | 2246 | 474.05 | 126 | 367.44 | 2372 | 841.49 |
The total EIQ has been reduced by 40% and the per hectare product costs reduced by 33% by adopting the IPM strategy. Therefore, adoption of IPM has lessened the impact of pear psylla control significantly and at a savings in cost of production. An additional reduction in EIQ can be made by using mating disruption for codling moth, however the control cost per hectare will rise by almost $80.
Let's compare the EIQ and costs between examples of a protectant and a protectant/eradicant program for control of apple scab. The protectant program consists of Polyram 80 DF (prepink), Dithane 75 DG (petal fall and summer), plus two Maestro (captan) 75 DF summer applications. The protectant/eradicant program consists of Polyram (prepink), Nova plus Maestro (petal fall), and summer applications of Nova plus Dithane and Maestro alone. The total EIQ and costs for the protectant program are 1000 and $263.69, respectively. For the eradicant/protectant program, the EIQ and product costs are 549 and $312.18. This comparison indicates combined eradicant/protectant control program is less harmful to the environment but would cost a little more under the same disease pressure. If sulphur was used solely as the defense against scab infection, about six applications would be required to replace the above treatments resulting in an EIQ of 1529, but at a product cost of only $109.62/ha for the season.
The EIQ model does not consider some important factors that can influence the impact of pesticides. For example, the model and field use rating formula do not consider the susceptibility of local natural enemies of pests. Thus a product may be less harmful in one region than another because important predators are tolerant to the rate applied. Timing of application can also affect the impact a product has on natural enemies. Petroleum oils and insecticides applied during dormant and delayed dormant will have much less impact than if applied later because most natural enemies are not yet active. Prebloom applications will also greatly reduce worker and fruit exposure.
This model is not perfect but it is the best attempt in my opinion to quantify the potential environmental impact of pesticides used in tree fruit and vegetable production. Comparisons can be made between control products and strategies to select the least harmful alternative. In terms of reducing the impact of pesticides on the environment, the application of this model makes more sense than simply deciding an arbitrary figure by which pesticide use will be reduced. Reducing pesticide use by 50% does not necessarily translate into a 50% reduction in impact on the environment.
As demonstrated in the insect and disease control examples above, such a reduction in environmental impact can be achieved through appropriate selection of control products or management strategies. New products such as insect growth regulators, improved formulations of Bacillus thuringiensis, sterol-inhibiting fungicides, and insect mating disruption offer future opportunities to minimize the environmental impact of pest and disease management programs. Unfortunately, many of these new products may not be registered in Canada and if they are, current trends indicate they may be priced beyond what producers can afford under current economic conditions. The development and implementation of alternative cultural and biological control methods to replace some of the traditional pesticides may free up resources to make the new products affordable.
Reference: Kovach, J., C. Petzoldt, J. Degni, & J. Tette. 1992. A Method to Measure the Environmental Impact of Pesticides. New York's Food and Life Sciences Bulletin No. 139, New York State Agricultural Experiment Station, Geneva, NY 14456.
