By Emilie Demard
Mites are pests of economic importance in traditional groves and citrus under protective screen (CUPS).
Results from a two-year survey in CUPS at the Indian River Research and Education Center (IRREC) in Fort Pierce, Florida, showed that the citrus rust mite and the citrus red mite populations can reach high levels resulting in leaf and fruit damage. Increases in the number of citrus red mites were noticed in winter (January–February), early summer (June), and fall (September–October) in CUPS. Rust mites reached high abundances on fruit from June to September.
Several acaricides such as pyridaben, fenbutatin oxide and abamectin significantly reduced the mite populations, providing short-term control.
While chemical control provides fast results, it can negatively affect the population of beneficial arthropods. Specifically, predatory mites from the family Phytoseiidae (also called phytoseiid mites) are important natural enemies of small sucking insects (thrips, aphids, whiteflies) and pest mites. Studies show that phytoseiid abundance increases in spring (February–March), in both CUPS and traditional groves, when citrus trees are blooming. Pollen is an important alternative food for these predators since it provides proteins to females that are used for egg production.
Scouting with a hand lens to evaluate pest mite densities and to check the presence and abundance of predatory mites is essential before scheduling any pesticide applications. Phytoseiids (see photo) are usually white, yellowish or brown reddish depending on the prey they feed upon. They are 0.2 to 0.6 millimeters long with four pairs of legs and usually move faster than pest mites.
If growers are concerned about managing for mites and want to include beneficial mites in their management programs, spraying materials that are toxic to mites should be avoided from February to March when phytoseiid populations are high. In traditional groves with a conventional pest management program, a peak of phytoseiids during spring were noticed when no pesticide applications were scheduled. However, in CUPS, results showed that phytoseiid abundances significantly decreased after abamectin, pyridaben and fenbutatin oxide applications.
Finally, phytoseiids use groundcover to shelter from unfavorable conditions, reproduce and find alternative food (such as alternative prey, pollen and sugary plant secretions). The presence of groundcover surrounding citrus groves or within tree rows may benefit the development and maintenance of phytoseiid populations when pest mites are scarce in the canopy. In the IRREC CUPS, the floor is covered with a black tarp that prevents the establishment of groundcover. While this cultural practice does not prevent the occurrence of phytoseiids, it can affect the species assemblage since the relative abundance of phytoseiid species was different between CUPS and open-air systems.
Emilie Demard (email@example.com) is a postdoctoral researcher at the University of Florida Institute of Food and Agricultural Sciences Citrus Research and Education Center in Lake Alfred.
Share this Post