Thrips (Thysanoptera) on avocados

In this study, the researcher evaluated the association between plant quality and thrips damage in avocados. The researcher measured soil texture and nutrient levels by taking soil, leaf, and sap samples from avocado orchards in the Levubu region of Limpopo province, South Africa, representing four avocado cultivars (Hass, Fuerte, Maluma, and Pinkerton). From the same orchards, thrips were collected during flowering and early fruit development, and tree height, canopy diameter, foliage density, and fruit drop were measured. The researcher found that the stage and cultivar significantly affected thrips abundance. It was found that there was no difference in thrips abundance between flowering and early fruit development, but the species composition did change. During flowering, the South African citrus thrips, Scirtothrips aurantii Faure, made up 72% of the thrips present on the flowers. This proportion increased to 96% of the individuals on the developing fruit, representing a 33% increase in their relative abundance from flowering to early fruit development. Pinkerton was the most susceptible to thrips infestation and damage among the four cultivars. This cultivar also exhibited the highest fruit drop compared to other cultivars. The principal components analysis was used to reduce the dimensionality of the sap, leaf, and soil elements into principal component scores, and these were used as predictors for thrips abundance on avocados. It was found that measured sap elements were not useful for predicting thrips abundance during flowering and early fruit development. However, the leaf and soil nutrients were significant predictors of thrips abundance during the flowering stage, but the same elements were not predictors of thrips during early fruit development. During the flowering stage, plants with higher leaf sodium (Na), copper (Cu), and dissolved sugar content (Brix) were related to low thrips abundance, and plants with lower sulfur were linked with high thrips abundance. A strong positive correlation between thrips abundance and avocado damage and that fruit drop increased with thrips abundance was found.