Abundance, diversity and development of thrips (Thysanoptera) on avocados and macadamias in the Levubu region of Limpopo Province, South Africa

Abstract

Some thrips (Thysanoptera) species are presumed to injure avocado and macadamia trees and fruit when feeding as nymphs and adults. We investigated the abundance and species richness of thrips and monitored fruit and nut set and damage on four avocado (Fuerte, Hass, Maluma and Pinkerton) and macadamia (695, 814, 816 and A4) cultivars. Different stages of avocado fruit (1–3, 4–6 and 7–9 cm) or macadamia nut development (closed racemes, nut set, nut size 1–1.5 cm and nut size 3–4 cm) were sampled over two seasons in the Levubu region of Limpopo Province, South Africa. Thrips development on fruit, nuts and leaf flush was recorded to verify the thrips species causing damage. A total of 15 535 thrips were collected during August–January 2020–2021 and 2021–2022. Six thrips morphotypes were identified across macadamia and avocado orchards: Scirtothrips aurantii Faure (Thripidae), Thrips tenellus Trybom (Thripidae), Haplothrips gowdeyi Franklin (Phlaeothripidae), Frankliniella occidentalis Pergande (Thripidae), Megalurothrips sp. (Thripidae) and Caliothrips sp. (Thripidae). Thrips were less abundant in the 2020/2021 season compared to the 2021/2022 season and in avocados than in macadamias. Pinkerton (2020/2021: 4.9 ± 0.8 and 2021/2022: 13.1 ± 0.2) and Fuerte (2020/2021: 6.9 ± 1.3 and 2021/2022: 7.5 ± 0.1) had the highest damage and fruit set per inflorescence in both seasons. Fruit size 1–3 cm had a mean damage of 3.4 ± 0.8 in 2020/2021 and 4.0 ± 0.7 in 2021/2022, 4–6 cm had 5.3 ± 0.9 and 4.7 ± 0.7 in 2021/2022, and 7–9 cm had 5.2 ± 0.9 in 2020/2021 and 5.0 ± 0.8 in 2021/2022. Macadamia cultivars and developmental stages most affected by thrips were dependent on the season. Our results suggest that damage occurs earlier in fruit or nut development, and Fuerte avocados and Macadamia 695 were the least susceptible to thrips damage. S. aurantii larvae developed from all sampled avocado and macadamia tissues and were able to persist until the adult stage, confirming it as the main damaging thrips species of avocado and macadamia in the Levubu region.