Philipp Kirsch
IPM Technologies Inc., 4134 N. Vancouver Ave., Portland, Oregon 97217, USA
Key words - sex pheromone, mating disruption, integrated pest management, commercialization
Issues in the development framework for semiochemical products
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Conceptually, the commercialization of semiochemicals takes place within several spheres of influence, and it is important to manage product development to overcome the impact of expectations and barriers that these spheres present. In a diagram, these spheres of influence can be presented like concentric rings, with society being the outside sphere and the controlled release formulation the inner core.
Commercial pheromone-based products continue to offer considerable promise and solutions to modern issues in pest management strategies. Safety and specificity are the most obvious. Efficacy with very low rates of active ingredient is another. However, widespread implementation of insecticides has presented western society with worm-free apples for the past three decades, and it requires considerably more knowledge and careful management to attain toxicant based quality standards with a behaviour modifying chemical.
Semiochemicals are shadowed with the expectations asked of conventional pest control materials. These products need to compete with chemicals in registration requirements, efficacy standards, cost structure and ease of application.
Registration requirements. By definition, in most countries semiochemical products are classified as pesticides as soon as claims are made that they can mitigate a pest. Progress in implementation of North American pheromone products has resulted from the U.S. Environmental Protection Agency's (EPA) aggressive revision of semiochemical product registration data requirements, including the following: (1) Establishment of a toxicology based tier testing data requirement for biochemicals (longer term toxicology studies are only triggered by adverse results in acute testing); (2) establishment of a completely separate division, the Biopesticide and Pollution Prevention Division, to manage the registration of semiochemicals and other biologically based products; (3) exemption of arthropod pheromones as a class from the requirements of tolerance (companies are no longer required to obtain a food use clearance for each compound); (4) exemption of inert ingredients in removable formulations (i.e. hand applied, discrete point sources) from the requirements of tolerance (companies now have the flexibility to continuously improve and modify formulations without needing to seek new registrations for each modification; (5) exemption from the requirements of an Experimental Use Permit for arthropod pheromone testing on areas less than 250 acres (testing area has been increased from less than 10 acres, to less than 250 acres).
The biggest development in the recent time has been removal of the distinction between retrievable (i.e. mostly hand applied) and non-retrievable (i.e. mostly sprayable) formulations. EPA have accepted the argument and extended the exemptions to include all semiochemical formulations for the following reasons: there is no real difference in aerial exposure to pheromone concentrations from either retrievable or non-retrievable formulations, and likewise there is no difference in the crop residue (the inert ingredients were already exempted for food use when use in retrievables, so the exemption could be expanded to include all formulations).
Smashing the North American regulatory glass ceiling was only achieved through the concerted efforts of a partnership of pheromone scientists, crop protection entomologists, semiochemical companies and aggressive lobbying by farmers' organisations. It is now time to make a similar concerted effort seeking such regulatory relief on a global basis.
Efficacy standards and economics. Semiochemical products are often burdened with a premium price. It is difficult to get a commercially acceptable return on investment for products predisposed for low usage due to pest specificity and activity at molecular rates, while at the same time dependent on synthesis and production of exacting molecules. A product for codling moth will only be sold for apple and pear pest management. However, a premium price demands premium protection, especially when in competition with conventional chemicals, and this leaves little room for wormy apples or compromise in product efficacy.
If we charge high prices for mating disruption, the products have to work, and we better understand the conditions that preclude acceptable efficacy. Further progress in commercial implementation will require ongoing advancement in our basic and applied knowledge of the behavioural mechanisms of semiochemical control. I would suggest that the models of mating disruption will need to be configured for each pest, each semiochemical blend and each formulation. Smashing this glass ceiling requires a harmonious marriage of chemistry and entomology.
Ease of use. Widespread implementation of semiochemical products will only be possible if application is cheap and easy. The semiochemical industry has developed a wide palette of formulations that can be sprayed, twisted, clipped, pumped and puffed. Innovative application technique will facilitate rapid acceptance and implementation of commercial products. A good example is the transfer of the plastic bag closure from consumer products into codling moth and other tree fruit mating disruption applications. Orchards can be treated in 75% less time using the closure and a pole applicator, when compared to the prior technique of climbing a ladder and twisting each dispenser individually around the branch.
Ecology of the crop and environs
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Semiochemical product performance is considerably influenced by environmental factors. Behaviour of the molecules is influenced by interactions between the crop and the climate.
For example, elegant European research has carefully documented the differences in pheromone concentration and distribution in vineyards as canopies mature over the season. Similarly, Japanese colleagues were able to document different pheromone concentrations in tea canopies and relate this to differences in the levels of mating between field edges and the field center.
While it is difficult to change the environment, we can now select treatment sites that favor successful implementation of semiochemical products, and we can predict those locations where successful implementation will require the integration of other control strategies. An ideal orchard will have a uniform crop canopy, with no missing trees or rows, an even slope and trees of the same age and type. Missing trees, and even slope can modify the distribution of both pest and pheromone, and such orchards often require supplementary insecticide applications to field edges, or hot spots within the block.
Pest behaviour and ecology
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In developing any pheromone product, it is critical to research and understand the behaviour and biology of the target insect as completely as possible. Important factors include the following: Time of day for mating; duration of female calling behaviour; quantity of female pheromone release rate; location of female calling within crop; male searching behaviour.
Table 1 Commercial application of semiochemicals by pest control sectors
| Sector | Monitoringa and detection | Mass trappinga | Anti-aggregation, repellents | Attract and kill | Mating disruption |
| Consumer | detection | stink bugs; wasps | mammalian repellents |
muscids; tephritids |
|
| Pest control operators |
detection | cockroach | |||
| Turf and ornamental, Landscape | detection | Japanese beetleb | mammalian repellents; bark beetles | ||
| Government detection and quarantine programs | detection; population delineation | management: tephritid fruit flies; eradication: boll weevil | tephritid fruit fly bait sprays | gypsy moth | |
| Agriculture | detection; population forecasting | tropical weevils; armyworms;c aphids; leafminers; stem borers | mammalian repellents; aphid alarm pheromones | tephritid fruit fly bait sprays; Diabrotica feeding stimulant bait; PBW;d CMe | cotton; fruit and nut pests; rice; sugar cane |
| Animal production | detection | muscids; tabanids | screwworm; tsetse fly | ||
| Forestry | detection; population forecasting | bark beetles | bark beetle anti-aggregation | bark beetle tree baits | defoliators; tip moths |
| Stored products | detection | Indian meal moth; flour beetles | Indian meal moth |
a Using pheromone traps, unless specified otherwise;b pheromone/kairomone traps;c Spodoptera spec.;d pink bollworm, Pectinophora gossypiella;e codling moth, Cydia pomonella
Wine - pheromone chemistry
Production of a pheromone product requires pairing chemical synthesis with controlled release development. Solutions need to be found in the following areas: Synthesis; stabilization and longevity (pheromone molecules are environmentally labile and need to be stabilized from photochemical, thermal, oxidative and hydrolytic degradation, and from isomerization and racemization); blend quality (purity; composition).
Skin - the controlled release substrate
The second component of pheromone product development is selection of a suitable substrate. It is important to consider the following in making this choice: Production issues (cost, manufacturing ease, consistency and reliability, quality control) and application issues (shape and flexibility in design).
Wine and skin - the pheromone product, a controlled release device
Pheromone products are developed through the integration of pheromone chemistry with selection of the correct polymers. Development needs to produce a device that performs according to the following biologically determined parameters: Quantity and quality of released compound(s); timing of release; location in field; temperature effect on release rate; effect of field ageing on release rate profile.
This means that the right amount of the right pheromone has to be released into the field at the right time and in the right place. Overall, it must be at the right price. In summary, semiochemical product performance is a dynamic between the choice of formulation, the age of the formulation, the rate of release and population pressure.
Semiochemical applications in all sectors of pest management
Products based on semiochemical active ingredients are now available in almost all sectors of pest management. Product applications can be summarized into use patterns, and categorized by industrial sector and mode of action (Table 1). In agriculture, pheromone based traps are standard population detection and monitoring tools. The most outstanding applications of pheromone trapping can be summarized as follows.
Largest pheromone trapping programs, 1996
The bollweevil eradication foundation in the southern United States used approximately 12.5 million bollweevil lures. The 1996 national gypsy moth monitoring program used over 300 000 lures. Pheromone traps and lures form the basis of pest management monitoring programs throughout California tree fruit, vine and nut production.
Commercial applications of mating disruption technology
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Mating disruption technology has also gained commercial acceptance against a wide range of pests in many different crops and regions. While the technology has inherent limitations, it is a very effective pest management tool when cautiously monitored and carefully supervised within an overall integrated pest management program. The most outstanding applications of mating disruption can be summarized as follows:
Largest single pheromone sale and largest agricultural program, 1996. Pheromone tender award for pink bollworm mating disruption in Egypt, for a total of $US 5.3 million and a total treated area in excess of 200 000 acres.
Major horticultural applications of mating disruption, 1996. Codling moth management on 10 000 ha in Western USA; grape pest management on 14 000 ha in Germany; codling moth area-wide management on 3 000 ha in Italy; and rice stem borer disruption-based management on 4 000 ha in Spain (pest management for an environmentally sensitive watershed).
Global implementation of mating disruption is summarised in Table 2. A quick review indicates that over 30 target species have been controlled successfully, over 50 different products have been developed commercially, 10 different companies are active in the field and research, development and commercial implementation is underway in all geographical regions. This indicates that mating disruption is alive and well in 1996.
New directions and future prospects
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Ongoing efforts to expand the implementation and acceptance of semiochemicals are now starting to look at research and development of new wines and new skins. Some of these programs include:
Attract and kill. A new Ciba-Geigy technology has demonstrated considerable promise in the formulation of pheromones together with insecticides in the same droplet. Excellent control has been achieved against codling moth in apples, and pink bollworm in cotton (Hofer & Brassel 1992; Charmillot & Hofer 1997).
Other blends. Several researchers have shown that mating disruption can be enhanced through the combination of pheromones and antagonists in the same treatment (c.f. Bengtsson et al. 1994). Further work should be undertaken in the evaluation of such novel blends.
New formulations. To facilitate mechanical application, several companies are developing better sprayable formulations (see also Rice et al. 1997). Further research is evaluating the application of very widely spaced, high-dosage dispensing devices to mist pheromone throughout the orchard (Mafra-Neto & Baker 1996; Shorey et al. 1996; Baker et al. 1997).
Conclusion
At present, the semiochemical industry worldwide has sales income that is probably larger than US$30 million. The industry continues to grow, with more product registrations and increasing adoption of already registered products. Ongoing growth will require continued multidisciplinary attention to the behaviour of pests and molecules and a comprehensive understanding of formulation performance. Pheromone companies, and semiochemical researchers should look at all combinations of wine and skins, and rewards and breakthroughs will be found with the infusion of new ideas.
Table 2 Mating disruption - types of formulation by region and company
| Hand-applied formulations | Sprayable formulations | |
| Australia and New Zealand | OFM,a CMb, LBAM,c leafrollers, currant borerd (Shin-Etsu) | |
| Chile and Argentina | CM,b OFMa (Shin-Etsu, Hercon
pine shoot mothe (Consep, Biosys, 3M) | |
| Egypt | PBWf (Biosys, Shin-Etsu, Troy Bioscience, Consep, Ciba-Geigy) | |
| Japan | tea tortrixg (Shin-Etsu, Nitto Denko) cherry tree borer,h diamondback moth,i beet armywormk (Shin-Etsu) | |
| South Africa | OFM,a CMb (Shin-Etsu, Consep, Hercon, Ecogen) | |
| USA | OFM,a CMb (Shin-Etsu, Consep, Hercon)
peach twig borerl (Consep, Hercon) tufted apple budmoth,m omnivorous leafrollern (Ecogen) grape berry moth,o peach tree borer,p diamondback mothi (Shin-Etsu) artichoke plume moth q (Ecogen) | PBWf (Ecogen, Consep, Biosys)
tomato pinwormr (Ecogen, Consep) gypsy moths (Hercon, Biosys) forest defoliators (three species) (Hercon) Mexican rice stem borert (Hercon) |
| Western Europe | OFMa (Shin-Etsu, BASF, Consep) CMb (Shin-Etsu, BASF, Isagro) peach twig borerl (BASF, Consep) summerfruit tortrixu (BASF, Isagro) apple clearwing,v European grape berry mothsw (BASF) rice stem borerx (Biosys) |
aOriental fruit moth, Grapholita molesta;bcodling moth, Cydia pomonella;c light brown apple moth, Epiphyas postvittana; dSynanthedon tipuliformis; e Eucosma sonomana; fpink bollworm, Pectinophora gossypiella; gAdoxophyes spec.; h Synanthedon hector; iPlutella xylostella; kSpodoptera exigua; l Anarsia lineatella; mPlatynota idaeusalis; nP. stultana; o Endopiza viteana; pSynanthedon exitiosa; qPlatyptilia carduidactyla; r Keiferia lycopersicella; sLymantria dispar; tEoreuma loftini; u Adoxophyes orana; vSynanthedon myopaeformis; wEupoecilia ambiguella, Lobesia botrana; xChilo suppressalis
Baker TC, Mafra-Neto A, Dittl T, Rice ME (1997) A novel controlled-release device for disrupting sex pheromone communication in moths (This volume)
Bengtsson M, Karg G, Kirsch PA, Löfqvist J, Sauer A, Witzgall P (1994) Mating disruption of pea moth Cydia nigricana F. (Lepidoptera: Tortricidae) by a repellent blend of sex pheromone and attraction inhibitors. J chem Ecol 20, 871-887
Charmillot P-J, Hofer D (1997) Control of codling moth, Cydia pomonella L., by an attract and kill formulation (This volume)
Hofer D, Brassel J (1992) "Attract and kill" to control Cydia pomonella and Pectinophora gossypiella. Bulletin IOBC wprs 15(5), 36-39
Mafra-Neto A, Baker TC (1996) Timed, metered sprays of pheromone disrupt mating of Cadra cautella (Lepidoptera: Pyralidae). J agr Entomol 13, 149-168
Rice RE, Atterholt CA, Delwiche MJ, Jones RA (1997) Efficacy of mating disruption pheromones in paraffin emulsion dispensers (This volume)
Shorey HH, Sisk CB, Gerber RG (1996) Widely separated pheromone release sites for disruption of sex pheromone communication in two species of Lepidoptera. Environ Entomol 25, 446-451