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Innovative Management of Aphids and Viruses on Papaya Farms in Puerto Rico

Luis R. Pérez-Alegría, Ph. D., P. E
University of Puerto Rico
College of Agricultural Sciences
Agricultural and Biosystems Engineering Department
PO Box 9030
Mayagüez, P. R. 00681
787- 832-4040 ext. 3337
787-265-3853 (fax)
luperez@uprm.edu

Purpose Statement

This project will demonstrate innovative techniques to minimize damage to papaya crops using integrated pest management practices in Puerto Rico. The substitution of chemical pesticides will improve soil and water quality and reduced the human hazard posed by the handling and management of pesticides.

Project Duration: 2 years

Funding Request
Budget Category Funding Requested Matching Non-Federal Funds Matching
Federal Funds
First Year Funding
$27,827
$18,750
0
Second Year Funding
$17,696
$18,750
0
Total Funding
$45,523
$37,500
0

Executive Summary

This project will address soil and water quality concerns by incorporating IPM techniques into farmers’ daily agricultural practices. Field demonstration of IPM will show papaya farmers the availability of an alternative to control infestation of the cultivar with minimum use of chemical insecticides. Intercropping with plantain is an innovative, profitable and environmentally sound alternative of papaya production system that also eliminates the use of chemical insecticide. This technique will reduce insecticide applications by 70% per 1 ½ year per acre, and will save the farmers costs of up to 12 insecticide applications. Contamination hazards will be reduced by using more environmentally sound insecticides, such as botanical insecticide formulations, which are the least harmful insecticides registered for papaya.

This project is about a demonstration of IPM practices to reduce utilization of traditional chemical pesticides. In addition, an easy to read booklet will be developed to hand over during workshops and open field visits. Al activities and material developed in this project will be posted in the internet for a broader audience. We will conduct workshop presentations along with open field days demonstrations of IPM practices. As part of the program we will also make a presentation about Worker Protection Standard to make farmers aware of pesticide hazards and to reduce the risk of pesticide poisonings and injuries among agricultural workers and pesticide handlers by implementing safety and healthful practices in the work environment. Information available on booklets and Internet will provide easy to understand steps to evaluate viruses, aphids and other pests in papaya cultivars. This project will benefit participants and other audiences by transferring knowledge to farmers, agencies and general public about aphid control by using IPM practices to substitute pesticides in papaya fields.

Objectives

  1. Demonstrate innovative IPM practices to reduce insecticide use and control of aphid vectors and viruses transmitted by insects in papaya crops using the concept of on-site demonstrations in farms.
  2. Demonstrate appropriate (WPS) Worker Protection Standard techniques that are safe to the worker and the environment when chemical control is needed.
  3. Develop a booklet and database containing pest management methods presented in the field demonstrations.

Rationale

  1. It is essential to equip farmers with effective strategies to manage aphid and virus populations, and educate them to adopt environmental friendly and economic practices in their fields. Field demonstrations will show farmers feasible and effective techniques that can be readily put into practice to prevent high population levels of aphids and prevent viral diseases. Instruction of alternative methods to chemical control will lead farmers to make intelligent decisions focused on integrated pest management (IPM) techniques that are safe for the environment and economical. Methods, such as intercropping plantain into papaya fields will reduce aphid populations and minimize chemical insecticide use; therefore prevent soil and water pollution.
  2. The field demonstrations will encourage producers to apply WPS techniques when chemical pesticides are unavoidable and to develop new practices for pesticide handling and management. Implementation of WPS techniques will minimize human health risks and also prevent soil and water pollution. Farmers tend to learn by seeing and doing tasks that work. This objective will allow them to see and do WPS techniques.
  3. Producers will have an educative guide to consult when applying IPM practices and can also share it with other farmers. Non-chemical strategies carried out will reduce the use of insecticides. This information will also be available on a database located at the Internet page that resides in the College of Agricultural Sciences of the University of Puerto Rico at Mayagüez (UPRM).

Approach and Methods

Intercropping with plantain- Establishing plots of papaya with plantain as a crop border will prevent viral infection. The plantain plant is not a host for papaya viruses or any other disease affecting papaya and this characteristic makes it a suitable crop for this purpose. It is also a non-perennial crop like papaya. Non-persistent transmission viruses are characterized by presence of virus particles on the mouthparts and in the foregut of the aphid. Aphids rapidly lose their virus charge after brief feeding on healthy plants and must again feed on an infected plant to continue to transmit the virus to healthy plants. Aphids will feed first from plantain and will loose the virus, since aphids must sample ("taste") the epidermal tissue of a plant to determine its suitability as a host. Since, aphids are especially attracted to green-dark interfaces of field edges during their search for suitable host plant, aphids tend to land in greatest numbers in field edges.

Crop borders planted with non-virus host plants, such as plantain, can provide a landing site where aphids can "clean" their mouthparts from non-persistent viruses prior to their immigration to papaya shrubs. Plantain borders will control activities of aphids by preventing viral transmission. Intercropping of plantain is a cultural practice that will benefit farmers in many ways. Farmers will also profit from plantain harvest, hence increasing total farm income. Another advantage of crop borders is that they act as windbreaks, which are necessary in areas where strong winds prevail.

An application of Trilogy will be scheduled every 2 months, if needed. Weeds will be controlled before establishing crop plots. This practice will significantly reduce the use of herbicide and weeding expenses. Some farmers have already started to experiment with plantain as a crop border under supervision of the AES specialist Mr. Zamora with great results on aphid and virus control.

Farm demonstrations- Field demonstrations will be coordinated with papaya growers. Three farms have been selected from the main producing region in the Island; some producers have already agreed to perform field demonstrations in their farms (see Appendix E). Producers and workers of participating farms will be trained in IPM field practices during the development of the crop by project PI’s. Demonstrations will be carried out almost entirely in the field. Producers and workers will have the opportunity to perform these techniques during the presentation. Mr. Zamora will show how to establish papaya plots with plantain as a crop border and will discuss the benefits of using this starchy crop. This AES specialist will also discuss its impact on aphid and virus management, papaya and plantain production, water and soil quality, and economic profits. Farmers will also receive training in the establishment and maintenance of the plantain crop.

Experimental demonstration field plots will be set up along traditional agricultural practices to compare IPM strategies that emphasize minimum insecticide use. Economic analysis and environmental gains will be highlighted in on-site demonstrations. Growers, scientists and educators will have the opportunity to actively participate on demonstrations and work together to solve management problems. The AES will assist farmers implement non-chemical management strategies learned on demonstrations.

Background Information

Vectors and Viruses- Papaya is a tropical fruit crop that is normally consumed fresh and is valued as a health food because it's elevated levels of vitamins C and A. However, papaya is severely damaged when infected by the papaya ringspot potyvirus (PRSV) and the Papaya Mosaic Virus (PMV). In fact, PRSV causes the most serious virus disease of papaya worldwide. It is not transmitted by seeds, but it is transmitted from infected plants to healthy ones by aphid insects such as Myzus persicae (Sulzer) [green peach aphid], Aphis gossypii, A. neeri, A. citricola and A. spiraecola Patch [green citrus aphid]. More than 60 species of aphids are considered to be able to transmit PRSV. The PRSV is transmitted in a non-persistent way; this virus does not need a period of incubation to be transmitted. Once it is caught by the insect, it can be inoculated immediately. This type of diseases can cause production losses between 5% even 100% depending on the age in which the plant is affected.

Overview of Puerto Rico (2002) - Papaya is a very important fruit crop in Puerto Rico (and overseas) with 99,817 fruits harvested in 642 acres of land with 641,501 young and mature trees. Insecticides registered in Puerto Rico for papaya include: Dimethyl phosphorodithioate of diethyl mercaptosuccinate, neem oil, azadirachtin and emulsion of pyrethrin and rotenone. Table 1 shows costs for each insecticide:

Table 1. Insecticides registered in PR for papaya (table available upon request)

Insecticide, Commercial brand, Price per unit*

Chemical control- The hazards of chemical pesticide use are now widely recognized, although statistics are hard to find. Malathion® is considerer by the Pesticide Action Network (PAN, see references) a potential water contaminant, carcinogenic, highly toxic for humans and with toxic effects, even mortality, on aquatic life and others. This is one of the most used insecticides by papaya growers and the least expensive. The safest for the environment are the botanical (neem oil) insecticides Azatin® and Trilogy®. Azatin® is classifies by the PAN as toxic to fish, amphibians and insects. Although this is a botanical insecticide and is not listed as toxic for humans, severe skin and gastrointestinal irritation and central nervous system stimulation have been observed. The formulated product Azatin-EC® which contains the active ingredient azadirachtin is considered a water pollutant.

Papaya farmers in Puerto Rico use insecticides as their main control strategy regardless of aphid populations. The number of insecticides registered for papaya are decreasing and pests develop resistance against chemicals due to indiscriminate use. Therefore producers are forced to search for new alternatives to manage pests. Health risks are increased due to improper management of insecticides. Most common violations to the WPS regulation are lack of record of applications, workers handling insecticides without protective equipment, and poor decontaminating areas. Also consumers are exposed to pesticide residues when eating papaya, since some insecticides are within the fruit, and cannot be washed off.

Traditional approach - Some management practices have been recommended for many years, but farmers do not practice them on a regular basis. Such techniques must be emphasized and taught in a non-conventional manner like field demonstrations at the farm level. Some of these recommended practices are as simple as starting plants from seed, propagating cuttings from healthy plants, inactivating the virus by disinfecting tools and pots and soaking them in freshly prepared 10% (1 part + 9 parts water) household bleach solution, and spacing plantings.

Previous Funding

Agency: University of Puerto Rico
Organization: Agricultural and Biosysems Engineering Department
Projects: X982441-01-0 and X8982441-01-0

Resources

Table 2. Personnel for farm demonstrations (table available upon request)

Dr. Pérez (PI) will be in charge of the field days and will coordinate all the activities with the participating farmers. Mrs. Bracero will be in charge of day-to-day activities of the project including continuous monitoring (aphid sampling, viral symptoms, number of leaves, plant height, fruit weight) of demonstration and control plots with the support of participating farmers. An AES agricultural agent will present sanitary practices such as selecting seeds for new plots, as starting plants from seed, transplanting, fertilization, disinfecting tools, spacing plantings and scouting.

Participants will evaluate the demonstrations by completing an evaluation instrument with questions related to insecticide applications, viral symptoms, fulfillment of WPS, production yields and others. This data will be analyzed with a statistics program. We will also access information from the Department of Agriculture and the PR Planning Board and compare the amount of insecticides imported and used by farmers in PR.

Measures and Outcomes

Papaya producers apply insecticides 9-18 times in 18 months. Intercropping with plantain is a profitable and environmentally sound alternative of papaya production system that also eliminates the use of chemical insecticide. This technique will save farmers costs comprising up to 12 insecticide applications, reducing insecticide applications by 70% per 1 ½ year per acre, plus labor costs for insecticide application. Not only insecticide applications will be reduced, but also contamination hazards will decrease by using more environmentally sound insecticides, like formulations of neem oil which are the least harmful insecticides registered for papaya. The best approach will be achieved when combining both strategies: plantain intercrop and fewer applications of botanical insecticide. Scouting and insect damage identification will avoid unnecessary insecticide applications and will reduce water and soil pollution. Presentation by the PRAL will make farmers aware of pesticide hazards, will reduce the risk of pesticide poisonings and injuries among agricultural workers and pesticide handlers and will ensure safety and healthful work environment. The farmer-scientist interaction will enable growers to apply low-risk integrated pest management tools and will decrease reliance on insecticides.

Outreach

The IPM literature presented in the demonstrations will be printed and made available on booklets to farmers. This field-pocket reference will have lots of color illustrations and techniques presented in field demonstrations. The Internet database will promote use of reduced risk pest control methods and will transfer knowledge to other farmers, agencies and general public and could be accessed all year round. Information available on booklets and Internet will provide easy to understand steps to evaluate viruses, aphids and other pests in papaya cultivars. Farmers will have tools for decision-making on insect and virus control and up to date information regarding IPM that will reduce the amount of insecticide applications.

Sustainability

Sustainability of all recommended activities proposed in this project will be easy because project participants work for the UPR- Agricultural Extension Service and the message is rapidly transmitted to a broader audience in Puerto Rico and elsewhere by publications generated as part of the project. In addition, all activities of the project will be documented in a booklet and posted in the www. The AES will support and recommend practices that are technically sound and economically viable for farmers and the environment.

Literature Cited

Timetable

Time (months) Activity
1 - 3

Literature review for booklet
Set up experimental field and control plots at participating farms
3 - 5 Edit text for booklets
5 - 18 Starts monitoring of field plots Coordinate demonstrations with the AES
17 - 20 Website construction
Translate booklets into English
20 - 22 Deliver field demonstrations in participating farms (three open field visits will be schedule in the three farms)
22 - 24 Analyze evaluations

Major Participants

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