Montoya, John Edward (2018-08). Evaluating Perennial and Annual Companion Plantings for Pollinator Enhancement of Yield in Small-Scale Vegetable Production. Doctoral Dissertation.
Thesis
Pollination is a key component to obtain proper yield and fruit set in numerous vegetable crops, with the honey bee, Apis mellifera, being their primary pollinator. Honey bee populations in the United States have experienced dramatic declines, exhibiting a loss of 59% of colonies from 1947 to 2005. Likewise, several native bee species have exhibited sustained declines over the past century. We hypothesized that the placement of pollinator-attracting plants near vegetable crops would increase the yield and quality of vegetable crops by attracting a greater frequency and diversity of pollinators. Cucumbers (Cucumis sativus) and habanero pepper (Capsicum chinense) growers have observed increased crop yield by placing bees in close proximity to vegetable crops. However, adding bees may not typically be feasible for small- scale farmers. Limited studies have demonstrated the potential of pollinator-attracting plants to be used as a lure to enhance the visitation of pollinators to adjacent food crops species. This study evaluated the potential of adding pollinator-attracting plants in close proximity to cucumber and habanero plants. Two treatment groups of pollinator-attracting plants were evaluated: perennial companion plantings and interplanted annual companion plants. The perennial treatment group consisted of Phyla nodiflora, Borrichia frutescens, Salvia 'Henry Duelberg', and Eysenhardtia texana. The annual treatment group consisted of Cosmos bipinnatus, Zinnia x marylandica, Borago officinalis and Ocimum basilicum. Yield and fruit quality, in addition to frequency and diversity of pollinator visitations were recorded and analyzed using analysis of variance tests. Significant differences in yield were found among treatment groups with greater yields observed in companion planting treatments, particularly with annual pollinator-attracting species, when compared to control treatments. However, significant differences in fruit quality or size were not found among treatment groups. Significant differences in frequency and diversity of pollinators visiting perennial and annual treatment groups were found among treatment groups with companion planting treatments attracting more pollinators when compared to control treatments. Individual pollinator-attracting plants varied in overall effectiveness and groups of pollinators attracted. Phyla nodiflora, B. officinalis, and O. basilicum were particularly effective for attracting pollinators, whereas Z. x marylandica was very ineffective. Economic sustainability of the system was measured by determining whether investments in pollinator-attracting plants are justified economically in terms of crop yield. Data from our proof-of-concept experiments suggests growers interested in the addition of pollinator-attracting companion plantings should utilize annual pollinator attractants, as they provide an immediate return on investment with a low risk of failure caused by being re-planted each crop cycle and greater flexibility relative to crop selection.
