Education For Environmental Responsibility

The Search for OP Alternatives

This article appeared in California magazine in April, 2000

By Parry Klassen

Frank Zalom doesn’t need a crystal ball to predict there’s rough times ahead for organophosphate (OP) insecticides used in dormant orchard sprays.

"Look at what’s happening with the Food Quality Protection Act," says Zalom, entomologist and Statewide IPM Project Director for the University of California. "OP products are already losing uses. Now the Clean Water Act process is targeting runoff from OP dormant sprays into rivers."

Few would argue that OPs are under pressure. While this class of crop protection chemistry has been the backbone of fruit and nut pest control programs for decades, regulatory scrutiny at the state and federal levels doesn’t show signs of letting up. EPA made its first FQPA decisions last summer, eliminating or restricting uses of two important OPs, azinphos methyl (Guthion) and methyl parathion (Pencapp M). A more immediate concern is toxic levels of OPs being washed into Northern California Rivers after dormant season applications to orchards.

Zalom points out that OPs can be used effectively on orchard sites that don’t have a high potential for runoff or drift into waterways. But he has a pragmatic view of the long term future for OP insecticides. "I think we want to be ready in case we lose some uses."

That opinion is shared by the Almond Board of California and other grower groups that are promoting a recently released report on alternative dormant pest control practices authored by Zalom and UC Cooperative Extension Researcher Associate Mike Oliver. The report "Alternatives To Chlorpyrifos and Diazinon Dormant Sprays," examines more than 60 recent studies on fruit and nut pest control practices to find answers to the first questions on every grower’s mind: do they work and how much do they cost?

Not long after Zalom and Oliver began the study, it was apparent that answering those two questions was anything but simple. Even though similar pests plagued their target crops – almonds, cherries, peaches and prunes – orchards in different regions of the state have dozens of factors influencing pest control practices.

That’s when the researchers began mulling over the idea of creating a pest control "calculator." The tool would be accessible on the internet and allow growers to plug in their own pest control costs and compare them to alternative practices.

After six months of combined efforts by Zalom, Oliver, UC-IPM project staff and Cooperative Extension Advisors and Specialists, the calculator idea went on-line at the University of California IPM webpage.

"The ‘Dormant Spray Alternatives Calculator’ for almonds and other tree crops gives growers and crop advisors a quick, accurate tool to predict pest control costs," explains Oliver. "On the site, growers or crop advisors can key-in cost data from their own farming operations. The calculator then compares that information to alternative spray programs."

Above all, the calculator puts a grower or advisor closer to answering the question: what does the alternative practice cost? In the report, researchers compared the cost of conventional organophosphate dormant treatments in almonds, peaches, cherries and prunes to six different alternatives and their associated costs.

"The site lets growers and consultants make quick comparisons," says Oliver. "If they’re considering a change to an alternative practice, this lays out the parameters and should help them make a more informed decision."

The study did confirm one fact about alternative practices: they tend to be more expensive and complex to use than conventional OP dormant sprays. However, further analysis showed the higher costs increase only slightly the annual cost of producing a crop.

"The alternative practices we examined rely on much more field scouting throughout the growing season," says Oliver. "That is a cost that must be factored in."

In the study, the alternative practices are divided into six options, which are compared to a conventional dormant OP and oil spray targeted at Peach Twig Borer (PTB), San Jose scale, and aphid.

• No dormant OP treatment and in-season sprays as needed.
• Alternate year dormant sprays.
• Dormant oil only along with bloomtime Bt sprays.
• Spinosid and oil as a dormant spray.
• Non-OPs as dormant sprays.
• Dormant oil with pheromone disruption.

In the options where dormant OPs are eliminated, follow-up in-season sprays are typically not needed, especially in almonds and prunes, says Zalom. However, should field scouting indicate pest outbreaks, follow-up sprays during the growing season could be needed. While that strategy has shown to work in commercial field situations, its success is based on severity of pest populations and the material used during the season. Costs can also increase when secondary pests appear. "Depending on the in-season product used, there can be disruption of natural enemies," says Oliver. "As a result, secondary outbreaks of spider mites and other pests could require additional treatments."

The transition to alternative practices may in fact already be occurring. Recent studies of OPs usage in almond dormant sprays shows a 50% to 65% reduction from 1992 to 1997. Zalom and Oliver are hopeful their report and the online calculator will prompt more growers to look closely at the alternative practices, especially on orchard sites with runoff potential.

"The calculator helps give growers a broader perspective of their costs," says Oliver. "It allows review of all the input, material and labor costs associated with pest control." Growers can select their own preferences for product type or application rates or they can use default assumptions calculated from state averages.

"It serves as a reminder of the numerous components in a pest control program," Oliver explains. "Our goal is to allow growers to better understand the economics and perhaps justify selecting some of the alternatives to a conventional dormant OP program."