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Strengthening integrated crop management research in the Pacific Islands in support of sustainable intensification of high-value crop production

 

The development of high-value crops for domestic consumption and export is considered a priority for economic development and improved livelihoods in most Pacific Island countries. However, pests and diseases, and a lack of improved varieties adapted to local growing conditions, are the major constraints to vegetable production. The project’s broad objective was to build and sustain capacity to develop integrated crop management (ICM) strategies for the sustainable intensification of high-value crop production for export and domestic markets. This was done through improved information sharing: i) by the regular convening of meetings of the project advisory group (PAG) to review project progress and to provide advice on future directions for research and extension activities, ii) field days with farmers (especially in Fiji and Solomon Islands) where new technologies/ crop varieties were demonstrated and iii) the development of a pilot Plant Health Clinic (PHC) program in the Solomon Islands. The PHC program, in which local extension officers were trained as plant doctors, is supported by a mobile app, “Pacific pests and pathogens” that contains 350 fact sheets to aid identification of the most important insect pests and diseases of crops in the Pacific and which also provides management advice. The project focused not only on developing appropriate ICM solutions to some production problems but doing so in a way that the capacity of local collaborators was enhanced. Specifically, the project investigated the regional status of insecticide resistance in the diamondback moth, a notorious pest that is the target of excessive insecticide use throughout the region. Very high levels of resistance to some insecticides were rerecorded (especially in Fiji) and this necessitated the development of an insecticide resistance management (IRM) strategy designed around the biological insecticide, Bacillus thuringiensis (Bt). In collaboration with a local company, a reliable, cost effective Bt product was imported from China and established in the market (prior to the project, this very safe and effective insecticide could not be reliably sourced in the region). The stategy was successfully implemented, resistance levels have declined and evidence to date indicates that Bt is being used sustainably and natural enemy activity in Brassica fields has increased in the absence of broad spectrum insecticides.  In Samoa, research on the interactions between the egg parasitoid Trichogramma chilonis and the large cabbage moth (Crocidolomia pavonana) showed that manipulation of the host plant of an alternative host of the parasitoid could facilitate parasitism of the pest. Further work in Samoa showed that jasmonic acid, an elicitor of plant responses to herbivory, could be used to manipulate pest distributions in the field, offering an exciting possibility that pests and natural enemies could be manipulated in this system for improved biological control.

ICM research also investigated i) improved Solanaceous crop varieties for quality and market potential, and prospects of extending production seasons, ii) disease management/control and a diagnosis protocol for diseases of Solanaceous crops, and iii)) evaluation of soil management practices to promote sustainable soil health. For disease management and control, five plant activators were evaluated for their ability to suppress fungal pathogens; two of the plant activators had broad spectrum control effects on target diseases of tomato and pepper. A field trial in the Solomon Islands also showed low disease severity following the application of a commercial Phosacid systemic fungicide. To improve diagnoses of foliar diseases causing necrosis on tomato and pepper, a molecular assay procedure was developed using Whatman FTA™ cards. The procedure proved effective and diseases of Solanaceous crops from Taiwan, Fiji and the Solomon Islands were consistently identified using three diagnostic methods: microscopy, isolation and the molecular assay. Field trials to evaluate improved varieties of tomato (n=11) and  sweet pepper (n=10) sourced from the WorldVeg genebank in Taiwan were conducted in Fiji, the Solomon Islands, Samoa and Tonga. The trials were completed in Fiji and the Solomon Islands, a total of four open pollinated (OP) tomato varieties (2 in Fiji and 3 in the Solomon Islands) were officially released. For sweet pepper, only one variety was released in the Solomon Islands, while in Fiji, the selection of a variety for official release was delayed. ICM practices evaluated for improved pest and disease management in vegetable production were potting media for tomato seedling production, insect exclusion net, and suitability of protective structures. A long-term soil health trial was also conducted to evaluate soil management practices which included legume rotation and starter solution technology (SST), however, only the legume rotation phase was completed. The good agricultural practices (GAP) and technologies evaluated were also promoted during field days and trainings.