Insect diversity in vineyards, almond orchards, olive orchards, alfalfa fields, and pastures in the San Joaquin Valley of California

Authors: Sisterson, Mark; Dwyer, Donal; Uchima, Sean

Submitted to: Journal of Insect Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/9/2020
Publication Date: 6/19/2020
Citation: Sisterson, M.S., Dwyer, D.P., Uchima, S.Y. 2020. Insect diversity in vineyards, almond orchards, olive orchards, alfalfa fields, and pastures in the San Joaquin Valley of California. Journal of Insect Conservation. Available: https://doi.org/10.1007/s10841-020-00250-2.
DOI: https://doi.org/10.1007/s10841-020-00250-2

Interpretive Summary: Pest insects cause considerable economic loss to agricultural crops. However, some insects benefit agriculture by consuming or parasitizing pest insects or by providing pollination services. While considerable knowledge has been developed for some agriculturally important insects, understanding of the role of many insects commonly found in agricultural areas is limited. In this study, a survey of the insect community found in vineyards, almond orchards, olive orchards, alfalfa fields, and pastures located in the San Joaquin Valley of California was conducted. The most diverse group of insects observed was the Diptera (flies), with an average of 33 families of flies observed per site. In total, flies represented 17% of all captured insects. In almond orchards and vineyards, predaceous flies in the families Empididae, Dolichopodidae, and Syrphidae made up 13% of the natural enemy community. While members of the Empididae, Dolichopodidae, and Syrphidae are known to be predators, little is known about the effects of predaceous flies on pest populations in the San Joaquin Valley of California. Likewise, flies were abundant in almond orchards during bloom. As several of the families of flies observed in almond orchards are known to visit flowers, determining what role (if any) flies play in pollinating almonds is needed. Results will aid researchers in identifying groups of insects that require greater research attention with regards to value in improving crop management.

Technical Abstract: For many agricultural systems, limited data is available on abundance and diversity of insects that are not crop pests or their natural enemies. As recent studies suggest that insect abundance and diversity is declining, there is a need to quantify insect diversity within crop fields to determine what role crop fields play in maintaining diversity. In this study, alfalfa fields, almond orchards, vineyards, olive orchards, and pastures located in the San Joaquin Valley of California were sampled. Ground sweep samples were collected from all five habitats. In addition, foliar beat samples were collected from almond orchards, vineyards, and olive orchards. In total, ~240,000 arthropods were collected with the majority identified to family. Across crops and sampling methods, 20 arthropod orders and 202 insect families were observed. Hemiptera was the most abundant order of insect collected, representing an average of 61% of all arthropods collected. Diptera was the most diverse order of insect collected, with a total of 59 dipteran families observed across crops. Of the 202 insect families observed, 85 were observed in all 5 habitats (42%), whereas 48 families were observed in only one habitat (24%). Families observed in a single habitat were often represented by only a few individuals. Principal component analysis indicated that the communities present in the understory of vine and tree crops were more similar to each other than to the communities observed in pastures or alfalfa fields. Much of the total insect biomass belonged to a few families that included known agricultural pests. In contrast, most of the diversity was made up of families present in low to moderate abundance.