Within-Plant Distribution of Two-Spotted Spider Mites, Tetranychus urticae Koch (Acari: Tetranychidae), on Strawberries: Decision of an Optimal Sampling Unit

It is known that two-spotted spider mite (Tetranychus urticae), a major pest of strawberry, is difficult to manage. This study was conducted to determine the optimal sampling unit to increase management efficiency of T. urticae in strawberries. The sampling unit was determined by characterizing within-strawberry distribution of T. urticae and by comparing coefficient of variation (CV) and correlation coefficient (r2) among potential sampling units. There was a significant (p < 0.05) difference in densities within a strawberry according to the leaf age. However, there was no significant difference in its density within a trifoliate leaf. More T. urticae were found on young-fully-opened (moderately old) leaves than on young and old ones. Moreover, these leaves had lower CV and r2 values than others. More specifically, optimal sampling units of T. urticae were fifth, fifth or sixth, and sixth oldest leaves for motiles (immatures and adults), all stages (motiles and eggs), and eggs, respectively. The required sampling number should be determined depending on the density. However, for management purposes, one and two leaflets would be acceptable for eggs and motiles, respectively. By using this small number of suitable sampling unit, the sampling and management for T. urticae in strawberries could be more efficient than before.

The predatory mite Neoseiulus californicus (Acari: Phytoseiidae) does not respond for volatiles of maize infested by Tetranychus urticae (Acari: Tetranychidae)

Among the plants defense mechanisms, the induction and emission of volatile organic compounds, which can be used to attract natural enemies, such predators insects. Although well studied, the induction of plant volatiles that attract natural enemies can vary according to intensity of infestation of herbivores and the species of host plant. We investigated the olfactory behavioral responses of the predatory mite Neoseiulus californicus (McGregor) (Acari: Phytoseiidae) to the volatiles of infested maize (Zea mays) plants by the two-spotted spider mite Tetranychus urticae (Koch, 1836) (Acari: Tetranychidae) in early and advanced infestations. The Bt (Viptera) maize cultivar Impact® was used for tests the behavior of N. californicus. After initial and advanced infestations, the phytophagous mites T. urticae were removed, and the plants were tested using a “Y” olfactometer. The following treatments were evaluated: air vs. air, uninfested plants vs. air, uninfested plants vs. plants infested with 10 females of T. urticae, uninfested plants vs. plants infested with 100 females of T. urticae, uninfested plants vs. plants infested with 200 females of T. urticae and plants infested with 10 vs. plants infested with 200 females of T. urticae. The predatory mite N. californicus did not show preference to the treatments tested, suggesting that maize plants infested by T. urticae do not induce volatiles capable of attracting the predatory mite N. californicus. We concluded that N. californicus is not attracted by maize plants infested by T. urticae.

Biochemical Estimations of Tetranychus urticae Koch Infested Marigold Leaves in Summer and Winter Seasons under Screen House and Field Conditions

Background: African marigolds an important medicinal and ornamental plant is grown throughout the world. The two spotted red spider mite, Tetranychus urticae is one of the most destructive pests of the crop. Methods: Estimation of various minerals and stress measures of T. urticae infested and non infested leaves was performed in two seasons namely summer and winter under both screen house and field conditions. ANOVA was analysed under two factorial Completely Randomized Design. Mite population per leaf was correlated with each biochemical measures and statistical significance of data was analyzed. Result: Significantly lower nitrogen, phosphorous and potassium content was recorded in infested (2.01, 0.307, 1.509% dry weight) leaves as compared to uninfested leaves (2.93, 0.387, 1.874% dry weight) respectively. Summer season reported higher per cent loss in mineral content as compared to the winter season. The content of total phenol and proline was significantly more in infested leaves (18.75 mg/g, 57.07 µ/100 g) as compared to the uninfested leaves (11.42 mg/g and 47.50 µ/100 g). The per cent increase of phenol and proline ranged from (43.90 and 20.81%) in summer and (42.90 and 17.45%) in winter, respectively.

The Tydeoidea (Ereynetidae, Iolinidae, Triophtydeidae and Tydeidae) - An online database in the Wikispecies platform

An online database on the taxonomy of Tydeoidea is described and is available on the Wikispecies platform at https://species.wikimedia.org/wiki/Tydeoidea. It counts 1 324 records or pages, 724 records for the Tydeidae, 334 for the Ereynetidae, 203 for the Iolinidae and 63 for the Triophtydeidae. For each taxon are detailed the parent taxa as well as the child taxa which are listed. A nec subsection lists names of child taxa that are not recommended. Subjective and objective synonymies as well as homonymies are given for each taxon. Notes provide historical aspects of past studies. The type locality and habitat of the name-bearing type and its repository are added for the nominal species-group taxa. Fossil species, species inquirendae and nomina nuda are also reported. References and external links end up a record. Tetranychus viburni Koch is resurrected from synonymy with Tetranychus urticae Koch and placed in Tydeidae; it might be a senior synonym of Tydeus goetzi Schruft. Replacement names are provided for Aureliana and Tydides (homonymy) and for Paratydaeolus clavatus (synonymy).

Deficit Water Irrigation in an Almond Orchard Can Reduce Pest Damage

Irrigated almond orchards in Spain are increasing in acreage, and it is pertinent to study the effect of deficit irrigation on the presence of pests, plant damage, and other arthropod communities. In an orchard examined from 2017 to 2020, arthropods and diseases were studied by visual sampling under two irrigation treatments (T1, control and T2, regulated deficit irrigation (RDI)). Univariate analysis showed no influence of irrigation on the aphid Hyalopterus amygdali (Blanchard) (Hemiptera: Aphididae) population and damage, but Tetranychus urticae Koch (Trombidiformes: Tetranychidae) damage on leaves was significantly less (50–60% reduction in damaged leaf area) in the T2 RDI treatment compared to the full irrigation T1 control in 2019 and 2020. Typhlocybinae (principal species Asymmetrasca decedens (Paoli) (Hemiptera: Cicadellidae)) population was also significantly lower under T2 RDI treatment. Chrysopidae and Phytoseiidae, important groups in the biological control of pests, were not affected by irrigation treatment. The most important diseases observed in the orchard were not, in general, affected by irrigation treatment. The multivariate principal response curves show significant differences between irrigation strategies in 2019 and 2020. In conclusion, irrigation schemes with restricted water use (such as T2 RDI) can help reduce the foliar damage of important pests and the abundance of other secondary pests in almond orchards.