Resistance of New Strawberry Genotypes to the Two-Spotted Spider Mite (Acari: Tetranychidae)

Abstract

The two-spotted spider mite, Tetranychus urticae Koch, is one of the main strawberry pests in Brazil and many other countries. The objective of this study was to compare the resistance of eight strawberry genotypes (‘Albion’, ‘IAC Guarani’, ‘IAC Princesa Isabel’, ‘Oso Grande’, IAC T-0104, IAC 12, IAC 4 and IAC 1.13) to the two-spotted spider mite, by assessing injury level, biological parameters and host preference of the mite. To facilitate the interpretation of the results, leaf trichomes of each genotype were quantified. Thirty days after the artificial infestation of the genotypes with the mite, IAC T-0104, IAC 12 and ‘IAC Princesa Isabel’ showed the lowest injury levels. ‘IAC Princesa Isabel’, IAC 4 and IAC T-0104 were distinguished from other genotypes by the highest mean generation time (T) of the mite, while ‘IAC Guarani’ was distinguished by the lowest T value. Significantly lower values of intrinsic rate of increase (rm), finite rate of increase (λ) and net reproductive rate (Ro) were determined on ‘IAC Princesa Isabel’ and IAC 1.13. The mite showed preference for ‘IAC Guarani’, as inferred by the larger number of females when offered the chance to select the detached host leaflets. Trichome density was highest on IAC 1.13 and lowest on IAC T-0104, IAC 12, ‘Albion’ and ‘Oso Grande’. The results suggested that ‘IAC Princesa Isabel’, IAC T-0104 and IAC 12 are resistant, IAC 4 and IAC 1.13 are moderately resistant, and ‘IAC Guarani’, ‘Oso Grande’ and ‘Albion’ are susceptible to the mite.