Developing sustainable pest management strategies against major pests of papaya in Hawaii

Developing sustainable pest management strategies against major pests of papaya in Hawaii

Summary

Hawaii is the biggest papaya producing state in the country, exporting most to the mainland U.S. continent. This project aims at developing sustainable pest management techniques against major papaya pests: white peach scale, thrips, mites, papaya mealybug and nematodes. Kaolin clay and horticultural oil are tested for insect and mite control, and sunnhemp is tested for nematode and thrips control. An economic analysis will provide insights in the viability of the proposed pest management practices. Results of the project will be disseminated to stakeholders and other interested parties throughout the duration of the project.

Objectives/Performance Targets

1. Examine the effectiveness of organic pesticides kaolin clay, petroleum oil and their combination against papaya insect pests.

2. Examine the benefits of sunn hemp living mulch as a trap crop for Thrips parvispinus.

3. Demonstrate the benefits of strip-till sunn hemp living mulch for nematode and soil health management in a papaya orchard;

4. Disseminate research findings to papaya growers and agricultural professionals;

5. Economic analysis of sustainable strategies for emerging pests of papaya in Hawaii.

Accomplishments/Milestones

During the first year of the project we worked with our four project cooperators testing the kaolin clay and horticultural oil, as well as farmer’s standard practice on Oahu and Hawaii Island. The horticultural oil was tested at 1% and the clay at 50 lb/50 gallons.
Pest density was assessed in new leaves (for mites and thrips), flowers (for mites and thrips), old leaves (for mites and mealybugs), and tree trunks for white peach scale. The pest monitoring was done at monthly intervals during the first seven months, and weekly intervals during the last two months (harvest period for the study). Yield data were collected once a week for a total of nine weeks. Results from from one of the field trials are summarized below:

1. The oil treatment significantly reduced the density of all pests evaluated in the study compared to the other treatments (Fig. 1, 2, 3 & 4).

2. The kaolin treatment had the highest density for all pests evaluated in this study (Fig. 1, 2, 3 & 4).

3. The oil treatment had the highest marketable yield and lowest unmarketable yield for large size fruit (Fig. 5).

4. The oil and standard treatments had similar total marketable yield and the oil treatment had the lowest total unmarketable yield (Fig. 6).

5. Results of an economic analysis showed that the oil treatment was the most cost-effective treatment tested in the study (Fig. 7).

We planted sunnhemp on Hawaii Island for nematode control, but the germination rate was very poor. We will repeat this again in November 2012.

During the second year of the study we will conduct a second round of tests of the horticultural oil. We are in the process of consulting with cooperators about a second year test of the kaolin clay, given that this product did not provide good control of the pests evaluated. During the second year of the project we will also test sunnhemp for thrips and nematode control.

• Fig. 4. Density of scales on tree trunks
• Fig. 1. Pest density on new leaves
• Fig. 2. Pest density in flowers
• Fig. 3. Pest density on old leaves
• Fig. 6. Total marketable and unmarketable yield
• Fig. 7. Cost to yield ratio by treatment
• Fig. 5. Marketable and unmarketable yield by fruit size

Impacts and Contributions/Outcomes

Papaya farmers rely on extensive and routine chemical pesticide applications to manage these pests. Sustainable pest management methods for reducing damage from these pests are desirable. Results from the first year shows that the oil treatment significantly reduced density of major papaya pests: thrips, papaya mealybug, mites and white peach scale. The oil treatment had the lowest cost to yield ratio, and therefore the most cost effective treatment. The adoption oil sprays as part of a pest management strategy can provide not only control to multiple pests but also an environmentally friendly option for pest control in papaya.

Collaborators: