Date of Award

Spring 2017


M.S. in Environmental Policy


Professor Gautam Sethi

Second Reader

Professor Jennifer Phillips

Third Reader

Professor Monique Segarra


Sweet Potato is an important staple food crop grown by subsistence farmers in the Solomon Islands. It plays an important food security role and a major source of nutrition and livelihood in the rural areas as well as urban areas in the country. However, the spread of agricultural pests, in particular, the green leaf folder pest (Psara hipponalis), has significantly increased in recent years leaving many smallholder farmers with reduced yields and food insecurity. In this thesis, I reviewed the literature on the common mechanisms used to evaluate the drivers of pest presence and identified the major factors correlated with the presence of sweet potato leaf folder pest in four communities in the Western Province of Solomon Islands. Twenty garden surveys were conducted in each community by researchers from the American Museum of Natural History, with support from the Solomon Island Community Conservation Partnership, the World Vegetable Center and Ecological Solutions Solomon Islands, giving a total of 80 surveys. A structured questionnaire was used and consisted of three categories: pest presence, agrobiodiversity, and the use of cultural controls. Farmers were asked if they had seen the green leaf folder pest in their gardens in the ten days prior to their interview. The assessment of agrobiodiversity in the surveys covered the number of crops grown in the gardens visited. The use of cultural controls included questions on whether farmers use crop mulching, rotation or both activities, and whether farmers apply chemical pesticides in their gardens. Control variables including the presence of Braconid wasps and weather parameters such as temperature, precipitation and relative humidity were also included to evaluate their effect on pest presence.

A probit regression analysis was conducted to test the association between pest presence and climate and farmer-level factors. Practicing a combination of both mulching and crop shifting activities has shown to have the most significant effect in reducing the green leaf folder pest presence. In addition, crop diversification has also played a significant but a lesser role in determining the likelihood of observing the green leaf folder pest in the Solomon Islands. In contrast, the application of chemical pesticides as well as the presence of Braconid wasps did not show any significant effects on the green leaf folder pest in this study. Moreover, among weather variables, precipitation has shown to be the only statistically significant variable correlated with the green leaf folder presence in the Solomon Islands. Based on the findings of this study, the following recommendations can be made: (1) the application of cultural control activities such as using the combination of both mulching and crop shifting should be demonstrated to subsistence farmers to reduce the green leaf folder pest presence, and (2) improved varieties of major food crops such as taro and cassava should be introduced more widely to communities to limit the present of green leaf folder pest.

Access Control

Open Access