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Hot Water Treatment to Reduce Pesticide Usage

Project Coordinator

Arnold H. Hara
Dept. of Entomology, University of Hawaii, CTAHR
461 W Lanikaula St
Hilo, Hawaii 96720
808-935-2885
808-934-7520 (fax)
arnold@hawaii.edu

Abstract

Farmers in Hawaii use toxic pesticides in dip tanks to disinfest flowers, foliage and propagative materials of insects, mites and nematodes that are of quarantine significance. Apparently, toxic pesticide solutions are disposed weekly by applying the used solutions to “registered site”. Certain amount of pesticide solution will inadvertently reach “unregistered sites” contaminating ground water, streams and soil. In addition, potted plants infested with root mealybugs and nematodes are drenched with insecticides/nematicides which flow out of pot drains into the ground. Many of these modern pesticides are not highly residual and persistent in water or soil, but because of repeated weekly discharges, they do pose acute and chronic toxicity to humans, beneficial insects, fish, domestic animals and wildlife. The purpose of this project is to implement a hot water dip treatment at farms to replace toxic pesticide dips. The hot water treatment was designed and tested by University of Hawaii researchers. Results have demonstrated that the hot water treatment can be effectively used to disinfest flowers, foliage and propagative materials of insects, mites and nematodes without significant effects on plant quality. Interestingly, hot water treatment enhances propagative and vase life qualities of certain plants. Successful implementation of the hot water treatment by farmers will significantly reduce the use of toxic pesticides.

Objectives

  1. Demonstrate the effectiveness of the hot water disinfestation treatment to farmers.
  2. Implement the hot water dip system at farms for export flowers and foliage and for propagative materials.
  3. conduct educational outreach programs on the hot water treatment including field days, workshops, newsletters and informational packages.

Justification

A major bottleneck for shippers of plant exports is shipment rejections by other states (e.g. California) and foreign countries (e.g. Japan) because of live insect pests in shipments. Since 1988, over 6,000 plant shipments (flowers, foliage, herbs, vegetables, propagative materials) have been rejected by the State of California alone, because of contamination by live pests such as mealybugs, scales, ants, whiteflies on flowering ginger, birds of paradise, cut foliage and proteas. A conservative estimate of losses (value of sales, cost of fumigation at port of entry & damage to flowers by treatment) is over $3.0 million during 1990 to 1994. Shippers are avoiding markets in California and Japan because repeated quarantine rejections will result in revoking the shippers’ United States Department of Agriculture (USDA) Limited Permit Stamp. Most importantly, growers and shippers are using toxic pesticide dips prior to shipment.

Additionally, plant propagative materials infested with insects and mites have been-causes for quarantine shipment rejections, and for new pest species or chemically resistant strains to establish in a new locality. For example, propagative chrysanthemum cuttings have been implicated as a source of spread of the agromyzid leafminer, Liriomyza trifolii, originally a major pest of chrysanthemums in Florida. Subsequently L. trifolii was introduced into numerous nurseries in England, France, and Netherlands in 1977 from a propagating nursery in Kenya that was regularly supplied with infested plants from Florida (Spencer 1981). Furthermore, the original population in Florida had probably already developed resistance to commonly used insecticides (Nakahara, 1982) .

In many importing countries of chrysanthemums and gypsophila, the agromyzid leafminer is now a quarantine pest, and these countries ban the entry of infested flowers (Yathom et al., 1990). Toxic insecticidal dips and fumigants, including methyl bromide, have been used to disinfest cuttings, but environmental and human health risks from such dips and fumigants are well documented.

Presently, most of the 240 firms (Hawaii Dept. of Agriculture 1995) that export floral and nursery products are dipping their commodities in large capacity tanks (25 - 200 gallons) filled with toxic insecticidal dips (Malathion, Diazinon, Dursban, Mavrik) and apparently, the toxic pesticide solution is disposed weekly by applying the used solution to a “registered site”. In addition, potted plants (mainly palms) infested with root mealybugs and nematodes are drenched with insecticides/nematicides which flow out of pot drains, onto greenhouse benches and into the ground.

A conservative estimate of this potential and/or occurring nonpoint source pollution of pesticides to soil, groundwater, surface water, streams and coastal waters is a weekly disposable of (240 farms x 25 gallons) 6,000 gallons of used pesticide solution. Many of these modern pesticides are not highly residual and persistent in water or soil, but because of repeated weekly discharges, they do pose acute and chronic toxicity to humans, beneficial insects, fish, domestic animals and wildlife. The use of a hot water dip treatment by farmers will eliminate the need of approximately 6,000 gallons of toxic pesticide solution per week in Hawaii.

Literature Review

Efficacy of Hot Water against Pests

Most insects on or in flowers, foliage and roots, including ants, foliar and root aphids, armored scales, soft scales, foliar and root mealybugs and whiteflies are killed at 49 C (120° F) from 5 to 12 minutes (Table 1, Hara et al. 1993 1994, 1996). In addition, hot water treatment at 49° to 50° C for 10 mm. is highly effective against burrowing, citrus, lesion and root knot nematodes (Baines et al. 1949, Birchfield 1954, Lear & Lider 1959, Kaplan 1982). Hot water dip is more effective against many cryptic insect and mite pests because heat penetrates plant tissue while insecticidal dips are only contact in action.

Effects of Hot Water on Propagation and Vase Life

Hot water will increase, decrease or have no effect on the vase life of flowers and foliage (Table 2) . Hot water treatment has been observed to improve the postharvest quality of certain cut flowers and foliage (e.g., Heliconia spp., ti, Cordyline fructicosa) by protecting against physiological disorders, enhancing natural resistance to pathogen infection and/or reversibly inhibiting maturity (Klein & Lurie 1992).

Hot water treatment stimulates rooting and shooting of propagative materials including plumeria, anthurium, gardenia and Dracaena spp. When progagative cuttings are treated at 49 C for 10 mm. followed by a basal application of 0.8% IBA (indole-3-butyric acid) rooting and/or shooting of cuttings are significantly enhanced (Hata et al. 1994). Unrooted chrysanthemum cuttings survive 490 C for up to 6 mm., but root mass is lowered after a 1 to 2 mm. dip (Hara et al in press) Most foliar aphids, thrips, spider mites, and Liromyza leafniners (95-99%) infesting chrysanthemum cuttings should be killed after 2 mm in 49 C.
The taro root aphid is effectively killed at 490 C for 5 mm, and taro planting material can tolerate hot water at 490 C for 10 minutes without negative effects on growth; The root mealybug, Rhizoecus hibisci in potted Rhapis palms is eradicated when the internal ràot ball temperature reaches 460 C, with no significant phytotoxic injury to the potted Rhapis (Hara et al., unpublished data).

The limiting factor for disinfesting cut flowers and foliage with hot water is phytotoxicity to some plant species. Certain cut flowers are more susceptible to heat injury during the fall and winter seasons rather than the spring and summer seasons. Conditioning flowers in hot air at 39 to 40 C (102° F) for 2 h before hot water treatment eliminates seasonal phytotoxicity (Hara et al. 1996). Probably, heat shock proteins in flowers and foliage are produced by conditioning in hot air; these induce heat tolerance.

Cost/Benefit Analysis

Water is inherently more efficient than water- saturated air (vapor heat) as a heat transfer medium, and treatment systems based on hot water is less expensive than those based on vapor heat. A prototype commercial—size hot water dip system (300 gallons) was successfully designed and tested to meet the demands afford ability and practicality by University of Hawaii researchers (Fig. 1, Tsang et al. 1995). An investment of less than $6000 ($3500 for hot water unit, $2500 for hot air unit) by the farmer will result in an environmentally sound and cost effective alternative to methyl bromide fumigation. Presently, farmers in Hawaii spend approximately $0.20 per stem for scrubbing and chemical dipping, which will be eliminated by the hot water dip. Therefore, after treating only 200 dozens of red ginger per month for one year, the cost of the hot water dip unit will be recovered.

Regulatory Acceptance

Hot water efficacy data has been submitted to the USDA, Animal and Plant Health Inspection Service (APHIS) and is presently under review by USDA, Agricultural Research Service (ARS). The Japan Ministry of Agriculture, Fisheries and Forestry (MAFF) has stated that since Hawaiian flowers are not prohibited, MAFF is not in the position to accept or deny the hot water treatment. The key to his issue is that MAFF will inspect flowers on arrival and if there is no live insects, they will be released. Mr. Ralph Iwamoto, APHIS Attaché to Japan, stated, “I assume that the MAFF inspectors will quickly learn that the treated flowers will have a very low pest risk and the shipments will eventually be passed through.” (Memo, 10/16/95)

After dissecting hot water treated flowers and foliage infested with magnolia white scale, spiraling whitefly, mealybugs, aphids, earwig and ants, Dr. Ray Gill, CDFA entomologist in Sacramento, CA concluded “This hot water treatment of cut flowers and florals certainly appears to have merit in controlling an otherwise serious problem with those insect pests which could hitchhike on these plants.” (Memo, 05/17/95)

Approach and Methods of Action

Demonstration

Commercial quality flowers and foliage will be supplied by major shippers on the Island of Hawaii. Flowers will be treated using the prototype hot water dip equipment at University of Hawaii, Waiakea Experiment Station in Hilo, Hawaii, at 49° C (1200 F) for 10 to 12 mm. to cause 99 to 100% insect mortality. Immediately following treatment, flowers will be cooled in a tank at ambient temperature (approximately 24°C) for a time equal to half the hot-water treatment. Hot water treated flowers will undergo simulated shipping conditions for 2 to 3 d or be actually shipped to other islands (Kauai, Oahu, Maui), the continental U.S. (California) and Japan for evaluation by commercial growers, shippers, wholesalers and florists. Specific instructions will be given for vase life and quality evaluation. Special permits will be obtained from USDA, Animal & Plant Health Inspection Service (APHIS) Japan Ministry of Agriculture, Fisheries and Forestry (MAFF) and California Dept. of Food & Agriculture (CDFA) to allow test shipments. Reports from clients will be collected to evaluate the replacement of insecticidal dip with hot water dip.

Hot water treatment demonstrations will be conducted at the Waiakea Experiment Station in Hilo, Hawaii and other agricultural producing localities throughout the State of Hawaii (Kauai, Maui, Oahu). Prototype hot water equipment designed and built by the University of Hawaii is portable and transportable to various locations among the islands.

Implementation

Once farmers and shippers are convinced of the tremendous benefit and profit of implementing the hot water dip, we will assist the shipper in installing a hot-water dip system to meet the demands of commercialization. The main components of the hot— water immersion unit will be obtained or constructed including: a 300 gallons or greater capacity insulated treatment tank, pump and water circulation system, instant gas water heater; temperature control and monitoring device; holding basket for plant materials; and cooling tank.

In cooperation with USDA, APHIS, California Dept. of Food & Agriculture and Hawaii Dept. of Agriculture, hot water treated commodities will be inspected and released for commercial shipments to California under a special Origin Inspection Program. The effectiveness of the hot water treatment at individual shipping firms will be evaluated by quarantine inspectors and entomologists and become a certified/recognized postharvest disinfestation treatment.

Educational Outreach
  1. The Hawaii Florist and Shippers Association and Hawaii Farm Bureau have agreed to support, sponsor and disseminate information via their newsletters, meetings and conferences regarding the commercialization of the hot water dip.
  2. Workshops and field days will be conducted at Waiakea Experiment Station and at shippers’ facilities who are foremost in implementing the hot water dip system.
  3. Informational packages will be developed for implementing the hot water dip treatment. One-to-one advice and assistance will be given to farmers interested in implementing the hot water dipping system by the project coordinator and the education specialist.
  4. Informational packages will be provided to extension agents to disseminate to clients. The project coordinator and educational specialist will train extension agents on the hot water dip treatment.
Impact Assessment

Number of shippers converting from insecticidal dip to hot water dip will be monitored and summarized at intervals before, during and after the project period. Data on reduction in pesticide purchase and use will be obtained from commercial farms and chemical suppliers Quarantine rejections or interceptions of treated plant materials will be compared between commodities that are pesticide dipped and hot water dipped. Reports will be gathered from buyers and end users of aesthetic quality and vase life of hot water versus pesticide treated commodities. Finally, approval and certification by quarantine agencies of hot water dip as an effective nonchemical treatment will eliminate the use of 6,000 gallons of pesticide solution per week, which contaminates Hawaii’s pristine ecoystem and cause human health problems and concerns.

Table 1. Hot-water efficacy tests (490 C) against pests of Hawaiian flowers and foliage.
Table 2. Effects of hot water (49°C, 10-12 minutes) on vase life and quality of cut flowers and foliage*. Commodities with increase and 110 effect on vase life could be commercially treated without conditioning. Commodities with mixed effects could be conditioned in hot air at 39 C for 2 hours to tolerate hot water (A. Hara et al., unpubl. data).
(Tables available upon request)

Appendix A - Literature Cited

Appendix B - Timetable

Timetable for project during 1996-97.

Appendix C - Major Participants

Farmers

Provide products for evaluation and these farmers are very interested in implementing the
hot water treatment.

Organizations
Project Coordinator

Arnold H. Tiara - Manage all aspects of the project for successful implementation
of the hot water treatment.

Project Budget

Project Period: October 1, 1996 - September 30, 1997

Funding Request
Funding Requested In-Kind Funding* Total Funding
$40,000
$3,000
$43,000

*In-kind funding provided by the County of Hawaii, Dept. of Research and Development.

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