The role of insect pollinators in avocado production: A global review

Abstract

Insect pollination increases the yield and quality of many crops and therefore, understanding the role of insect pollinators in crop production is necessary to sustainably increase yields. Avocado Persea americana benefits from insect pollination, however, a better understanding of the role of pollinators and their contribution to the production of this globally important crop is needed. In this study, we carried out a systematic literature review and meta-analysis of studies investigating the pollination ecology of avocado to answer the following questions: (a) Are there any research gaps in terms of geographic location or scientific focus? (b) What is the effect of insect pollinators on avocado pollination and production? (c) Which pollinators are the most abundant and effective and how does this vary across location? (d) How can insect pollination be improved for higher yields? (e) What are the current evidence gaps and what should be the focus of future research? Research from many regions of the globe has been published, however, results showed that there is limited information from key avocado producing countries such as Mexico and the Dominican Republic. In most studies, insects were shown to contribute greatly to pollination, fruit set and yield. Honeybees Apis mellifera were important pollinators in many regions due to their efficiency and high abundance, however, many wild pollinators also visited avocado flowers and were the most frequent visitors in over 50% of studies. This study also highlighted the effectiveness of stingless bees (Meliponini) and blow flies (Calliphoridae) as avocado pollinators although, for the majority of flower visitors, there is a lack of data on pollinator efficiency. For optimal yields, growers should ensure a sufficient abundance of pollinators in their orchards either through increasing honeybee hive density or, for a more sustainable approach, by managing wild pollinators through practices that protect or promote natural habitat.

Keywords: Persea americana; avocado; honeybees; insect pollination; managed pollinators; wild pollinators.

FIGURE 1

Number of studies grouped by (a) research theme and (b) country. Forty studies were used for this analysis but, multiple studies contributed to several different themes and two studies were based in two countries. (a) Research theme code: Impact on pollinators (impacts on pollinators of land management or landscape), Honeybee Density (effect of manipulating honeybee density), Effectiveness of Honeybee (effectiveness of honeybees as avocado pollinators), Improving pollination (ways to improve pollination services), Cross‐pollination (cross‐pollination contributions to pollination), Abundance and Efficiency (abundance and efficiency of avocado pollinators) and Insect Contribution (insect contribution to avocado pollination)

FIGURE 2

Forest plot following a random effects model meta‐analysis to compare pollination and production under insect pollination (Experimental) and no insect pollination (Control) treatments in avocado across multiple studies

FIGURE 3

Summary means for pollination and production variables between insect pollination (Open) and no insect pollination (Closed) collected from multiple studies. (a) Average number of fruits set per branch, N = 5 (b) Per cent of flowers pollinated, N = 3 and (c) Average weight per fruit, N = 4

FIGURE 4

Summary of significant positive or non‐significant (NS) results following a vote count comparison across multiple studies comparing insect‐pollinated (Open) and pollinator exclusion treatments (Closed) for the variables fruit set, fruit weight, pollination and yield

FIGURE 5

Relative abundance of pollinators visiting avocado flowers across (a) individual study and (b) grouped by country [Colour figure can be viewed at wileyonlinelibrary.com]

FIGURE 6

Insect groups visiting avocado flowers from 18 studies including (a) the number of studies in which each insect group was observed, (b) the total abundance of each insect group and (c) the overall relative abundance of insect groups across all studies

FIGURE 7

Pollination efficiency of different insect groups including (a) the amount of pollen carried per insect group, (b) the amount of pollen deposition per visit per insect group and (c) the average number of flowers visited per minute per insect group