Beneficial arthropods as potential biocontrol candidates of thrips (Thysanoptera: Thripidae) occurring in Tunisian citrus orchards
Thrips are major economic insect pests of citrus worldwide. During the few last years these insects have become serious pests of citrus in Tunisia. The objective of this study was to determine the species of thrips' natural enemies occurring in citrus orchards and assess the effects of manure application on the abundance of soil predatory mites. Sampling of thrips and their natural enemies was performed in citrus orchards in northern Tunisia from 2015 to 2017. Results revealed that (i) the most abundant predatory species found on plant leaves was Chrysoperla carnea representing 40.38% of the total number of natural enemies collected, followed by Coccinella septempunctata (13.57%) and that (ii) the most abundant soil predatory mite was Parasitus americanus representing 43.44% of the total number of predatory mites collected, followed by Stratiolaelaps scimitus, Pachylaelaps imitans and Odontoscirus sp. (9.43%, 6.45% and 5.41%, respectively). Higher population densities of P. americanus and S. scimitus in the soil were directly correlated with decreased thrips' abundance and reduced plant damage. Our findings suggest that manure application significantly affects the abundance of both predatory mites and thrips in the soil. Here we provide first knowledge on natural enemies' action against thrips and their potential use as biocontrol agents in Tunisian citrus orchards.