Abstract
Phytophagous mites can cause economic losses in many crops, including grapevines. The changes in their population levels may be associated with changes in the predator-prey relationship. Knowledge of the distribution of mites in plants is important for planning sampling strategies and facilitating control decisions. The aims of this study were to (i) evaluate the abundances of Tetranychus urticae (Tetranychidae) and Neoseiulus californicus (Phytoseiidae), and the correlations between them and environmental factors; (ii) determine their distribution on the top, middle, or base strata of the evaluated grapevines (Vitis vinifera, Chardonnay cultivar) and, additionally, report the first occurrence of damage caused by T. urticae in grapevine leaves in the state of Rio Grande do Sul, Southern Brazil. Sixteen samplings were conducted, divided between the 2018 and 2019 seasons. In each sampling, three leaves from the three strata of the plant (top, middle, and base) were collected from 20 plants, totaling 60 leaves per sampling. The predator-prey relationship and their association with environmental variables were evaluated with multivariate correlation, whereas the number of mites per plant leaf strata was compared using a generalized linear mixed model in R software. It was possible to observe the symptoms of damage caused by T. urticae attacks on grapevines in Southern Brazil, characterized by the presence of yellow spots and general yellowing of the vineyard. Our findings indicate that T. urticae and N. californicus individuals are strongly associated with each other regardless of the environmental variables, and such relationship occurs mainly on the lower strata (middle and base leaves) of grapevines. Thus, by taking into account the damage on the leaves of grapevines and the occurrence of T. urticae and N. californicus majorities on specific strata of these vineyards, we suggest that the lower strata of grapevines should be the priority targets for management strategies to control such mites.
Highlights
It is known that grapevines (Vitis vinifera L. [Vitaceae]) may suffer serious damage caused by fungi, nematodes, bacteria, insects, and mites, which attain pest status in regions where they find suitable environmental conditions (Schruft, 1985; Duso & Lillo, 1996)
The average numbers of T. urticae found per plant and per leaf were 18.08 ± 85.38 and 6.03 ± 37.64, respectively
For N. californicus, the average numbers found per plant and per leaf were 3.05 ± 9.24 and 1.02 ± 4.32, respectively
Summary
Cultivated plants are subject to diverse biotic and abiotic stresses. Such stressors may affect the physiology of the plants, which may compromise their productivity. Among the myriad of mite species, the Tetranychidae family is of agricultural importance. Tetranychus urticae Koch, the two-spotted spider mite (TSSM), is the most agriculturally important phytophagous mite, feeding on more than 1,100 plant species and causing economic losses in many crops, including grapevines (Bolland, Gutierrez, & Flechtmann, 1998; Grbić et al, 2011). Biological control is an ecological alternative in organic and conventional farming systems and is very important for integrated pest management (IPM; Baker, Green, & Loker, 2020)
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