LIMITING INSECT-RELATED COCOA DECLINE IN GHANA; INTEGRATING BIOLOGICAL, COMPUTATIONAL AND SOCIOLOGICAL ELEMENTS
Open Access
- Author:
- Wilkerson, Megan Michaela
- Graduate Program:
- Entomology
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- February 23, 2018
- Committee Members:
- David Hughes, Dissertation Advisor/Co-Advisor
David Hughes, Committee Chair/Co-Chair
Edwin George Rajotte, Committee Member
Nicole Sheree Webster, Committee Member
Shedra Amy Snipes, Outside Member - Keywords:
- Ghana
Cocoa
Entomology
International Agriculture - Abstract:
- Ghana is the world’s second largest producer of cocoa beans. However, farmers are not able to maximize yield potential due to pests and plant diseases that destroy as much as 10- 80% of annual production. The arrival of devastating insect related diseases like black pod (Phytophthora megakarya) and cocoa swollen shoot (Badnavirus) means yield losses can approach 100%. Both diseases are influenced by ant communities. Cocoa ant species form mutualistic networks with honeydew producing mealybugs that supply the majority of their energy food source. In order to safeguard their food source, ants transport soil onto cocoa trees and build tent-like structures to shelter mealybugs. The virus-vector mealybugs are either transported around the cocoa tree by ants, which also protect the mealybugs as they feed. The water mold infects the tree after the ants have transported soils containing infectious spores to the developing pods. The ants do this to form soil tents over the colony of mealybugs feeding on the plant. The transport of disease agents means that ant attendance directly effects cocoa plant fitness. While the occurrence of tent building ant genera, Camponotous, Pheidole and Crematogaster, has a detrimental impact on yields, the presence of a different ant genus, Oecophylla, reduces pod damage by defending trees against pest prevalence. In order to control insect-related decline, farmers should be cognizant of insect dynamics and make decisions based on observations and availability of pest management resources. The ability to manage pests and aid the proliferating of beneficial species is contingent on the farmers’ ecological understanding of the cocoa ecosystem. 90% of farmers correctly implicated pests as responsible for causing holes, dark legions soil on cocoa pods. In addition to having awareness of major cocoa diseases and damage, 61% of farmers were correctly identified pests and beneficial insects. My approach includes testing the efficacy of pesticide alternatives, developing technologies to accurately detect pests and damage, and conduct sociological examinations to uncover the farmers’ ecological knowledge of cocoa insects. Recognizing the shortage of entomological experts to help farmers I also explored the application of machine learning to provide an AI assistant that could automatically identify pests of cocoa. Results from field interviews revealed that 66% of farmers make pest management decisions at the farm level and the majority are cognizant of major yield limiting constraints. Field experiments have shown that cocoa insect populations change overtime and between plantations. The farmers’ perception of cocoa insects directly impacts their management decisions, therefore it is imperative to equip farmers with management alternatives that are less toxic yet as effective as synthetic chemicals. High pressured soapy water has proven to be an effective pesticide replacement that does not require personal protective equipment and reduced the recolonization of virus transmitting mealybugs on 10 cocoa plantations. As a result of these efforts, I aspired to increase the agricultural knowledge and pest management artillery of low yielding cocoa farmers to encourage the adoption of sustainable alternatives to toxic chemicals inputs.