Cranberry Project > Integrated Pest Management:Overview

by Hilary A. Sandler

Excerpted from Executive Summary of SP-127: Cranberry Production-A guide to Massachusetts.
1998 UMass Extension Publication.

Introduction
Integrated Pest Management (IPM) is an ecological approach to pest control, based upon sound biological knowledge and principles (8). IPM has also been defined as the intelligent selection and use of pest control actions that will ensure favorable economic, ecological and sociological consequences (10). The philosophy of IPM is centered around the integration of biological, cultural, and chemical controls to manage pests. An integrated approach to pest management is based upon dynamic principles rather than a definitive set of rules for control of a particular pest situation.

IPM combines cultural, chemical, and biological strategies into a broad-based approach to control the most economically threatening pests. Cultural practices, such as late water floods and sanding, can greatly influence the severity of a pest problem. Pesticides are used in IPM programs, along with other control measures. Though a decrease in spray applications is common, participation in IPM does not always result in less pesticide use. Pesticide recommendations are based upon monitoring techniques that more accurately estimate current pest pressures, and in some cases, dictate an above average number of applications.

History
In the 1950’s, scientists began to realize the limitations associated with the reliance on pesticides for insect damage control including possible pesticide resistance of the target population, reduction or elimination of beneficial species, resurgence of the target population, outbreaks of secondary pests, and other undesirable non-target effects. The tremendous reliance on pesticide use underscored the need to implement an integrated approach to pest management.

Use of IPM infers that the grower has an understanding of pest management philosophy. Integrated control (1) was defined as the blending of biological control agents with chemical controls. Pest management (4) expanded the concept to include the consolidation and evaluation of all available techniques into a unified program to manage pest populations so that economic damage is avoided and adverse side effects on the environment are minimized (9).

Significant federal support for IPM extension, research and field programs began in 1972, with major contributions coming from the EPA, USDA, and the National Science Foundation (6). Since 1973, IPM administered through the Extension Service has focused on the implementation and development of programs among grower organizations, consultants, and private industry. The IPM program for the state was initiated in 1983 at the UMass Cranberry Experiment Station. Since then, the UMass IPM program has been looked upon as a leader in the development and dissemination of IPM information by the cranberry producing regions in North America and other countries worldwide.

The demand for high quality fruit compels the industry to strive in all efforts to maximize yield. In addition, cranberry growers must confront increasing public pressure to reduce pesticide use. Balancing environmental concerns and consumer demands against pest and market pressures is a delicate and potentially volatile enterprise. Cranberry growers continue to take the challenge of delivering a dependable commodity in the wake of rising environmental pressures. IPM offers growers a means to reach maximum productivity with minimal environmental distress.

Biological Principles
An IPM program consists of pest control strategies that attempt to capitalize on natural mortality factors, such as natural enemies, unfavorable soil conditions, weather, etc., and utilize control techniques that minimize the disruption of these factors. Pest management revolves around optimizing control, rather than maximizing it. Consequently, control tactics are aimed at the suppression of a pest rather than seeking its eradication.

Understanding fundamental biological concepts is paramount to appreciating the tenets by which a successful IPM program functions. Ecosystems are self-sufficient habitats where living organisms and the nonliving environment interact to exchange energy and matter in a continuous cycle, e.g., a pond or forest (9). Modern agriculture is intensive and creates a specialized complex of interacting biotic and abiotic factors, defined as agricultural ecosystems.

Agricultural ecosystems (agroecosystems) differ from typical ecosystems in several ways. They contain less plant diversity (most are primarily a monoculture), less insect diversity, and are intensively manipulated by humans via different agronomic practices, such as mowing, irrigation, and application of chemicals. The interplay between diversity and stability within an ecosystem is an important ecological precept. In brief, the more species diversity present within an ecosystem, the more stable the system.

Agroecosystems are more apt to be shifted out of equilibrium in response to the pressures of one species on another than other ecosystem. Without intervention, they are more likely to experience catastrophic events caused by pest pressures. The main emphasis of IPM is to restore and maintain insect and plant diversity within the primary agroecosystem. This, in turn, allows the ecosystem to be as stable as possible.

IPM is based upon the principles of applied ecology, which is applying biological knowledge and current technology to bring about the desired modification within an agroecosystem (8). The IPM practitioner or consultant must be able to synthesize the interactions of all the organisms involved, (pests and beneficials), as well as the impact of accepted agricultural practices on the environment as a whole.

Definitions
Economic concepts are an integral part of IPM. Examples of economic benefits would include increase berry quantity and quality, healthy and productive vines, and less money spent on pesticides. The concepts discussed below should be used to determine when a control measure is economically justified, balanced by consideration of the risks involved with those control measures.

A pest is an economic concept, and has no ecological validity. An insect, weed, or pathogen is defined as a pest because it is in direct competition with the productivity of human activities. An insect that is a pest in one system could very well be of no concern or beneficial in another agricultural system.

Quantitative terms are employed in IPM to assess economic pest damage. Economic injury level (EIL) has been defined as “the level at which damage can no longer be tolerated, and therefore the level at which it is desirable to initiate deliberate control activities (9).” It is an estimate of the pest density at which the cost of control measures equals the potential damage of the pest.

The economic threshold (ET) is a central concept in IPM philosophy (5). ET is defined as “the density at which control measures should be applied to prevent an increasing pest population from reaching the economic injury level (13).” The mere presence of a pest population does not always indicate an economically damaging situation where benefits will necessarily exceed the cost of control. The ET is always lower than the EIL.

The action threshold (AT) is a practical estimate of the economic threshold. ATs are typically based upon the average number of insects gathered at a particular sampling time. Examples of ATs currently established for insect pests in cranberry production include: 4.5 cutworms, 4.5 cranberry weevils, and 18 spanworms (all values per sweep set). ATs for other important pests, such as Sparganothis fruitworm, remain to be determined.

Since many pest control measures have social and environmental impacts in addition to economic ones, benefit/risk and benefit/cost ratios are considered to determine the value of a particular control measure. The benefit/cost ratio must indicate that the additional costs involved for pest management are less than or equal to the added benefits. Usually management costs (e.g., pesticide applications) are considered to be production costs, and benefits are increased yield (8). The benefit/risk ratio weighs the social economics of pest management. For example, growers weigh the risk of possible environmental hazards associated with using a particular pesticide (society level), and their own safety in applying the chemical (individual level) against the need to reduce the pest population that will produce benefits in the form of increased yield and profits.

Status of Cranberry IPM in Massachusetts
In 1983, 16 acres were scouted under the UMass IPM program. The number of acres covered by the program peaked in 1985 at just over 600, hovered around 400 acres through the 1989 season, and has since returned to the initial year’s acres. One goal of the University-based program is to encourage the adoption of IPM programs by the private sector. The total number of acres under private IPM programs and UMass combined has increased in the last 15 years from approximately 870 acres to almost 7,500 acres. In 1998, approximately 60% of all cranberry growers in Massachusetts were participating in a formal IPM program. Costs to participate fall within the range of $70-100 per acre.

A typical cranberry IPM program may consist of: sweep net sampling for 6-10 weeks; use of pheromone traps for Sparganothis fruitworm, cranberry girdler, and black-headed fireworm moths to aid in the timing of insecticide sprays; inspection of berries in July-August for cranberry fruitworm eggs; fertilizer recommendations based on soil and plant tissue analysis; determination of crop phenology (% out-of-bloom) for timing cranberry fruitworm sprays; yield estimates; and mapping of weeds. Consultants and growers usually converse weekly to discuss management strategies (7).

ALTERNATIVE PRACTICES
Biological Control Agents

B.t.-Based Products
Several products containing the bacterium, Bacillus thuringiensis, are available to control lepidopteran pests of cranberries. These products act as a stomach poison for the control of the caterpillar stage of blossomworm, false armyworm, spanworms, and gypsy moths. These products are very low in mammalian toxicity. B.t.-based products are specific to caterpillars and are not harmful to bees, wildlife, or beneficial insects. Growers can apply these products by air or through the irrigation system (chemigation).

Research on the first B.t.-based product introduced to the cranberry market was initiated by scientists at Ocean Spray Cranberries, Inc. in 1986. The registration for DiPel ES on cranberries came in 1989. Since 1995, other B.t. products, such as MVP, Mattch, and Agree have become available for use in commercial cranberry production.

Effective applications of these products require the grower to apply the chemical under a strict set of conditions. Bog size, product choice and method of application may also affect efficacy (12). If a grower has to apply more than two sprays, the cost may exceed all other control options. Current research is focusing upon the development and testing of other strains and formulations of B.t. for control of caterpillar pests.

Nematodes
Biological control of black vine weevil, strawberry root weevil, and cranberry girdler is possible with use of beneficial nematodes. Nematodes are microscopic worms that parasitize and kill the immature stages of these cranberry pests. Beneficial nematodes are specific to soil-inhabiting insects and should not be confused with the plant parasitic nematodes that may infect other plants.

A biological insecticide formulated with the nematode, Steinernema carpocapsae, is a registered product for use in cranberry beds. This product is nontoxic to plants, animals, and beneficial insects and will not contaminate groundwater supplies.

Projects researching the efficacy of beneficial nematodes began in 1985. The cranberry industry was the first food crop in North America to employ beneficial nematodes as a biological control agent on a commercial basis. Growers have been using nematodes for black vine and strawberry root weevil control since 1988. Good control of these pests in Massachusetts cranberry beds has been observed. Excellent control has been observed with the use of nematodes for the control of cranberry girdler larvae. The cost of nematode applications can range from $125-250 per acre.

Current research is aimed at the development of different application techniques as well as looking at the efficacy of several other Steinernema spp. The efficiency of a nematode in finding its host is affected by temperature. Since nematodes are applied to vines during the spring or fall when the temperatures are cool, some strains of Steinernema are less efficient at controlling girdler larvae and immature stages of the weevils than other species that prefer the cool temperatures. Projects are currently underway investigating other cold-hardy Steinernema species.

Biological Control Projects in Progress.

Projects utilizing biological control agents include: two parasitoids against cranberry fruitworm, microbial pathogens against various insect pests, a fungal organism for control of false armyworm, blossomworm, brown spanworm and cranberry fruitworm, and applications of fungi (mycoherbicides) for control of dodder.

Nutrient Management
Best management practices for nutrient management recommend that growers use moderate application of nitrogen fertilizers (2). Using appropriate amounts of nitrogen limits overgrowth of vines that can encourage infection from fruit rot organisms. Also, lush vine growth can provide a suitable habitat for tipworm and flea beetle infestations. Growers can reduce these pest problems through judicious use of fertilizer.

Fish Fertilizer

Cranberry growers began to try fish hydrolysate, made using recycled products from the state’s fishing industry, as a nutrient source in 1989. Fish fertilizer is an efficient material; it remains in the root zone longer than inorganic soluble fertilizers. Use of this slow-release, organic material is particularly well-suited to those areas that have a high leaching potential, i.e., do not hold water very well. Sandy, upland bogs fall into this category.

Fish hydrolysate research, which began in 1987, indicated that it can be a suitable alternative to inorganic soluble fertilizers. Studies on the use of fish fertilizer included: the impact of fish fertilizer with routine cranberry practices; proper timing of fish on cranberry beds; and use of lower doses to capitalize on the efficiency of the fertilizer. Fish hydrolysate, made from low oil species of fish and generally stabilized with phosphoric acid, has been recommended in the CES Management Guide since 1990.

Chemical Control Options

Alternative chemical control practices recently introduced into cranberry management programs aim to maximize the efficacy of any applied chemical. These techniques have quickly become important components for many IPM programs. Typical practices include: timing pesticide applications to coincide with the pest and/or plant life cycle; use of reduced rates of pesticides alone, or in combination with biological control products; and spot treatment of affected areas on the beds.

Research efforts are currently investigating the use of synthetic and natural growth regulators for control of insect pests. Herbicides, such as Scythe, contain naturally occurring active ingredients (e.g. pelargonic acid) are being tested in the field and may be important for obtaining weed control in cranberry production.

Cultural Control Options

Even though cultural practices have been utilized in cranberry production for many decades, incorporation of any appropriate cultural practices is an essential component to a modern management program. Examples include:

Manipulation of water resources within the bog system has been a traditional method of pest control. Holding late water (i.e., reflooding the bog from mid- April to mid-May) can decrease the inoculum potential of the fruit rot fungi, cause a general reduction of annual weeds, suppress the spread of Rubus spp. as well as suppress populations of certain insects and mites (3). Uniform application of sand on a regular interval may reduce infestations of cranberry girdler and green spanworm. Uniform sand applications can inhibit emergence of dodder seedlings (11). Sanding also encourages vine growth by improving aeration and water penetration in the upper layers of the soil.

Proper maintenance and calibration of the sprinkler system and other equipment is an important procedure that is practiced by growers involved in cranberry culture. Adequate pressure and clean nozzles are critical to ensure that proper amounts of chemicals are delivered to the vines. Periodic pruning of vines improves aeration in the vine canopy and makes the environment unfavorable for fruit rot infection. Removal of leaf trash from the bog area and improving drainage can also help mitigate pest pressures.

CONCLUSIONS
Pest management implies more than the application of chemicals at the appropriate time. Knowledge of the pest's life cycle, symptoms, as well as the conditions that predispose the plant to infection or infestation contribute to effective management of cranberry pest problems. Implementing cultural practices, such as trash removal, sanding, or improving bed drainage, offer the opportunity to broaden the baseline defense against crop loss due to pest pressures. As environmental concerns continue to limit the availability and application of registered pesticides, the importance of developing and integrating non-chemical control measures will become even more crucial.

REFERENCES

1. Bartlett, B.R. 1956. Natural predators. Can selective insecticides help to preserve biotic control? Agr. Chem. 11: 42-44, 107.
2. Best Management Practices Guide for Massachusetts Cranberry Production. 1996. C.J. DeMoranville, H.A. Sandler, and T. Bicki, eds. Univ. of Mass. Ext. Publ.
3. Cranberry Chart Book- Management Guide for Massachusetts. 1997. M.M. Sylvia, ed. Univ. of Mass. Ext. Publ., 40 pp.
4. Grier, P.W. and L.R. Clark, 1961. An ecological approach to pest control. In: Proc. Tech. Meeting Inter. Union Conserv. Nature Nat. Res. 8th, 1960, Warsaw, pp. 10-18.
5. Farrimond, D. 1997. 1996 Crop statistics. Cranberries 61(2): 21.
6. IPM Development. 1989. In: Alternative Agriculture, National Research Council, National Academy Press, Washington, D.C., pp. 176-189.
7. Lasota, J.A. 1990. IPM in Cranberries. In: Monitoring and Integrated Management of Arthropod Pests of Small Fruit Crops, N.J. Bostanian, L.T. Wilson, and T.J. Dennehy, eds. Intercept, LTD., Andover, Hampshire, pp. 283-292.
8. Metcalf, R.L., and W.H. Luckman, eds. 1975. Introduction to Insect Pest Management, John Wiley and Sons, Inc., New York, NY. 587 pp.
9. National Academy of Sciences. 1969. Insect pest management and control. Publ. 1695. Washington, D.C.
10. Rabb, R.L. 1972. Principles and concepts of pest management. In: Implementing Practical Pest Management Strategies. Proceeding of a National Pest Management Workshop. Purdue University, Lafayette, IN, pp. 6-29.
11. Sandler, H.A., M.J. Else, and M. Sutherland, 1997. Application of sand for inhibition of dodder (Cuscuta gronovii) seedling emergence and survival on cranberry Vaccinium macrocarpon) bogs. Weed Tech. 11:218-223.
12. Sandler, H.A. 1996. Field tests of B.t. products for control of cutworms, gypsy moths, and spanworms. Cranberries 60(1): 12-16,24.
13. Stern, V.M., R.F. Smith, R. van den Bosch, and K.S. Hagen. 1959. The integrated control concept. Hilgardia 29(2): 81

Selected IPM Articles:
2001 Annual Report
2002 Proposal
Integrated Pest Management: Overview
IPM Guidelines: Cranberry