Tetranychus Turkestani Ugarov Research Articles

Asymmetric reproductive interference between two closely related spider mites: Tetranychus urticae and T. turkestani (Acari: Tetranychidae)

Tetranychus turkestani Ugarov and Nikolskii and Tetranychus urticae Koch RF (red form) (Acari: Tetranychidae) are closely related species. Previously, the two species were found in separate agricultural habitats in Israel. Here, additional collections were undertaken and mixed populations of the two species were found. Manipulation experiments were conducted in order to test whether sexual interactions occur when T. turkestani and T. urticae RF share the same host. Interspecific crosses showed that the two species are capable of producing viable F(1) females, but that these females are sterile as their F(2) eggs failed to hatch. This indicates a post-zygotic reproductive barrier, supporting the current placement of T. turkestani as a separate taxon. Mating behavior parameters revealed that males of both species courted virgin conspecific and heterospecific females at the same rate and readily tried to copulate with them. Female mate recognition seemed to be more reliable in T. turkestani than in T. urticae RF as the number of copulations was significantly higher and their duration significantly shorter in the T. turkestani interspecific (T. turkestani female x T. urticae RF male) as compared to the intraspecific crosses, a phenomenon not observed in T. urticae RF. In mixed cultures, a significant reduction in female production was observed for T. urticae RF but not for T. turkestani, suggesting an asymmetric reproductive interference effect in favor of T. turkestani. The long term outcome of this effect is yet to be determined since additional reproductive factors such as oviposition rate and progeny survival to adulthood may reduce the probability of demographic displacement of one species by the other in overlapping niches.

Functional and Numerical Responses of Stethorus gilvifrons Mulsant Feeding on Strawberry Spider Mite, Tetranychus turkestani Ugarov and Nikolski

Laboratory experiments were conducted to measure the functional and numerical responses of Stethorus gilvifrons Mulsant feeding on Tetranychus turkestani Ugarov and Nikolski. Adult ladybirds were isolated singly for 24 h in 8 cm petri dishes with either 4, 8, 12, 24, 48 or 96 adult females of T. turkestani. Results showed a typical type 3 functional response, with up to 65.2 preys attacked when 96 preys were provided. The rate of attack and handling time were 0.0012 and 0.415 (days), respectively. The number of eggs deposited by the predator depended on the density of the prey; up to maximum of 223.6 eggs female(-1) at prey density of 96 spider mites were recorded. No eggs were laid at densities of 4 and 8 prey/arena.

Life-history of predatory mites Neoseiulus californicus and Phytoseiulus persimilis (Acari: Phytoseiidae) on four spider mite species as prey, with special reference to Tetranychus evansi (Acari: Tetranychidae)

The commercially available strains of Phytoseiulus persimilis Athias-Henriot, the biological control agent of Tetranychus urticae Koch, perform poorly in the Western Mediterranean, probably because they are not well adapted to local climatic conditions. For that reason, efforts are being focused on the development of a biological control programme using native phytoseiid mites. Four species of red spider mites can be found in vegetable crops in eastern Spain: T. urticae , Tetranychus turkestani Ugarov and Nikolski, Tetranychus ludeni Zacher and the recently introduced Tetranychus evansi Baker and Pritchard. To evaluate their potential role as biological control agents, the present study evaluates the life-history of local populations of Neoseiulus californicus (McGregor) and P. persimilis when fed on T. urticae , T. turkestani , T. evansi , and T. ludeni in the laboratory. Results indicate that N. californicus and P. persimilis are able to feed and complete their development on the four tested red spider mite species. The predators may exhibit a particularly high capacity for population increase when fed on T. urticae , T. turkestani , and T. ludeni , thus may be able to provide effective control of these species in the field. When fed T . evansi , however, predator performance was poor; significant increase in development and preoviposition times, and a reduction in oviposition period and fecundity were recorded. The resultant low capacity for population growth suggests poor ability of the two tested predators to suppress T. evansi populations on commercial crops. It is unlikely therefore that P. persimilis and N. californicus , now being widely used to control T. urticae in greenhouse crops in Central Europe, will be able to halt any spread of T. evansi to greenhouse crops in temperate areas.

Relative Abundance of Three Species of Spider Mites (Acari: Tetranychidae) on Cotton, as Influenced by Pesticides and Time of Establishment

Cotton, Gossypium hirsutum L., was planted in experimental plots in the west central San Joaquin Valley of California, during two consecutive seasons. Plants were treated with dicofol, methyl parathion, and/or permethrin, to manipulate densities of spider mites, Tetranychus spp., within the plots. Spider mite densities were also modified by inoculative releases of Tetranychus turkestani Ugarov & Nikolski. Several times throughout each season, the relative abundance (i.e., proportion) of each of three spider mite species, Tetranychus urticae Koch, T. pacificus McGregor, and T. turkestani , was determined. In 1982, T. pacificus was the dominant species in all treatments, with a relative abundance of 0.85 in the dicofol plots, and 0.67 in the untreated control. However, T. pacificus was less dominant, and significantly lower in relative abundance in plots treated with methyl parathion (0.53) than in dicofol-treated plots. Conversely, T. turkestani was higher with methyl parathion (0.34) than with dicofol (0.13). In 1983, trends were similar to 1982, although T. urticae was the dominant species in the untreated control, with a relative frequency of 0.49. Permethrin and dicofol had a negative impact on the relative abundance of both T. turkestani and T. urticae . Populations of T. urticae exhibited susceptibility to dicofol, relative to the dicofol resistance of T. pacificus . Early-season inoculative releases of T. turkestani increased the relative abundance of T. turkestani especially in untreated plots. However, late releases were less effective than early releases in promoting the buildup of T. turkestani , relative to the other two species.

Demographic Analysis of Induced Resistance Against Spider Mites (Acari: Tetranychidae) in Cotton

Demographic analyses were conducted of twospotted spider mites, Tetranychus utica Koch, raised on excised leaves of cotton, Gossypium hirsutum L., plants that had been previously damaged by mites, Tetranychus Turkestani Ugarov and Nikolski, or on leaves of undamaged controls. There were no differences in survival or development of individuals reared on leaves of the two treatments. Fecundity of mites was reduced by approximately 50% on excised leaves from plants that had been damaged as cotyledons relative to mites grown on leaves from undamaged control plants. Other workers who have examined the effects of plant conditioning on spider mites also have found this striking effect on fecundity and no effect on survivorship and development. This demographic pattern is consistent with patterns noted when the nutritional quality of the host plant is diminished but inconsistent with patterns caused by changes in the “secondary chemistry” of the host. Adult female mites behaviorally preferred excised leaves of control plants compared with excised leaves of damaged plants. Further work is required before a reliable behavioral assay is available that can be used to determine the chemical nature of induced resistance in cotton.

Isozyme Differentiation of Tetranychus pacificus from T. urticae and T. turkestani (Acari: Tetranychidae) in Laboratory and Field Populations

Cellulose acetate electrophoresis is a simple, rapid technique to distinguish among females of three spider mite species, Tetranychus turkestani Ugarov & Nikolski, T. urticae Koch, and T. pacificus McGregor, found on cotton growing in the San Joaquin Valley, Calif. Phosphoglucose isomerase and malate dehydrogenase separated both laboratory-reared and field-collected samples of T. pacificus from the other two species. Methods for testing the spider mites individually and as a group sample are described. Cellulose acetate electrophoresis was sufficiently precise to detect one T. pacificus in a group sample of 29 T. urticae or T. turkestani . Spider mites collected from almonds responded similarly to those collected from cotton. Est erase enzymes only partially differentiated T. turkestani from T. urticae and T. pacificus .

Laboratory and Field Investigations of Spider Mite (Acari: Tetranychidae) Resistance to the Selective Acaricide Propargite

Evaluations of spider mite, Tetranychus spp., susceptibility to propargite, initiated in response to grower concerns about potential resistance in the field, revealed 0- to 42-fold resistance in Tetranychus urticae Koch in a whole-plant residual bioassay. Surveys of spider mites collected from throughout the San Joaquin Valley in June and August 1984 indicated that propargite-resistant phenotypes exist throughout the San Joaquin Valley; 22 of 32 sites sampled in August contained individuals that survived 1,000 ppm in residual bioassays. However, resistant phenotypes were much less common in June than August; only 3 of 23 sites sampled in June had survivors of 1,000 ppm. The shift in susceptibility of populations during the season was shown to result from intraspecific increases in frequency of resistant phenotypes or interspecific shifts in spider mite species abundance, or both. Although resistant phenotypes of T. urticae and Tetranychus pacificus McGregor were discovered, no propargite-resistant Tetranychus turkestani Ugarov and Nikolski were found. Widely differing susceptibilities to propargite exist both within and between T. urticae and T. pacificus populations. A dicofol-resistant laboratory culture of T. urticae originating from the San Joaquin Valley and maintained under pressure for 2 yr possessed a 26-fold resistance to propargite. Although resistance to propargite was discovered in the laboratory, we did not observe diminished performance of propargite in field trials at a location possessing spider mites with up to 45% survivorship of the discriminating concentration of 1,000 ppm propargite.

Spider Mite Species (Acari: Tetranychidae) Response to Propargite: Basis for an Acaricide Resistance Management Program

Spider mites were collected from cotton at 36 locations in the San Joaquin Valley of California, both before propargite had been applied and again late in the season. All populations of Tetranychus turkestani Ugarov & Nikolski, the dominant early season spider mite, were susceptible to propargite. Populations of Tetranychus urticae Koch and Tetranychus pacificus McGregor exhibited a variety of responses from highly susceptible to highly resistant. These levels of resistance were defined by the range and homogeneity of response. Early season T. urticae populations were predominantly susceptible. Late-season collections of T. urticae from the same locations exhibited lower, equal, or increased tolerance to propargite, suggesting instability of resistance. Early and late-season collections of T. pacificus exhibited a consistently higher and narrower range of response to propargite than T. urticae , suggesting a possible natural tolerance to propargite. Field plots demonstrated lack of control with propargite when populations were composed of resistant T. pacificus alone. Cases of multiple resistance to propargite and dicofol were found for both T. urticae and T. pacificus.

Physiological Response of Cotton Plants to Feeding of Three Tetranychus Spider Mite Species (Acari: Tetranychidae)

Laboratory and greenhouse studies with cotton leaves were done with densities (mites per cm2 per day) of 1,2,4,8, and 16 Tetranychus turkestani Ugarov & Nikolski, T. urticae Koch, and T. pacificus McGregor to determine mite density effect on stomatal and mesophyll resistance to water vapor and 14CO2 diffusion and rates of photosynthesis. T. turkestani , by far the most injurious species, caused significant reduction of water vapor diffusion, CO2 uptake, and photosynthetic rate at one mite per cm2 per day compared with the presence of no mites. T. pacificus was somewhat more injurious than T. urticae; significant reduction of the parameters began at two mites per cm2 per day compared with the presence of no mites. The results indicate strongly that T. turkestani has a toxin-induced injury to cotton in comparison with the other two species.

Mites on Soybeans: Moisture and Temperature Relations

Computer analysis of population data for mites, predominantly Tetranychus turkestani Ugarov & Nikolski, in 8 soybean fields during a 7-year period showed a significant correlation with both rainfall and maximum temperature. Rainfall accounted for 51.3% and average maximum temperature for 25.3% of the population variation. Climatological conditions during August appeared to be the most important. Correlation of rainfall totals with mite population for each of the months June through September indicated that August rainfall was most influential. Moreover, of the monthly average maximum temperatures, only those of August were significantly related to peaks of mite abundance. Measurement of soybean leaf temperatures for 2 weeks with electrical monitoring equipment showed that T. turkestani lives under temperature conditions that can fluctuate widely within short periods.

Influence of Phytoseiulus persimilis on Populations of Tetranychus turkestani at the Economic Threshold on Roses123

The predatory mite Phytoseiulus persimilis Athias-Henriot may be maintained and reared in large numbers on potted lima bean plants with the phytophagous mite Tetranychus turkestani Ugarov & Nikolski as the prey (food). Biological control of phytophagous mites on roses was obtained with this predator in tests under green-house conditions. However, the value of this biotic agent for commercial control of mites on roses may be suited best to an integrated pest-management program where supplemental controls are necessary when mite densities reach economic threshold levels.