Population Dynamics Of Spider Mites Research Articles

ИНСТРУМЕНТАЛЬНЫЙ ЭКОНОМИЧЕСКИЙ УРОВЕНЬ ПОВРЕЖДЕННОСТИ И ЭКОНОМИЧЕСКИЙ ПОРОГ ВРЕДОНОСНОСТИ ПОПУЛЯЦИЙ ПАУТИННОГО КЛЕЩА НА ЗЕМЛЯНИКЕ

Spider mites of the genus Tetranychus are universally one of the significant pests that damage garden strawberries and many other crops. One of the important problems of the pest population management is to be able to identify the thresholds of this pest, which, when feeding, causes a change in the color of plant leaves. Since it is very difficult to determine visually the level of leaf damage by spider mites, the authors of the study turned to the previously substantiated instrumental method for assessing damage using the relative electron transport rate (rETR) based on chlorophyll fluorescence detection in the leaf. Instrumental thresholds of pest damage were calculated: the economic injury level (EIL) and the economic threshold (ET). Studies were carried out in the laboratory on the leaves of strawberry grown in conteiners at temperature of 22 ± 2°C, relative humidity of 75 ± 10%, photoperiod (L : D) 16:8 h, as well as on the experimental plot of the strawberry plantation of JSC “Lenin Sovkhoz” (Moscow region); registration of the population dynamics of spider mites on the leaves being made. At the same time, using the JUNIOR-PAM fluorimeter (Heinz Walz, Germany), the dynamics of chlorophyll fluorescence in the leaves of the control (without mites) and experimental (damaged by mites) variants were measured. As a result, two varieties of industrial strawberries obtained a range of variation of the numerical physiological index, expressed in terms of the ratio of rETRmax between the experimental and control variants, equal to 1.4–2.0 conventional units, which corresponded to the economic injury level (EIL) of strawberry leaves. The latter trait was comparable to the same parameter obtained in the laboratory – 1.6. The economic threshold (ET), which signals the beginning of pesticide treatments, if it is reasonably expected that the number of pests will reach or exceed the value of EIL, also expressed in terms of the ratio of rETRmax between the experimental and control variants, turned out to be equal to 1.1–1.2 conventional units. The authors recommend using the proposed instrumental criteria for the harmfulness of the Atlantic spider mite on strawberries. We believe that this approach can be applied to other species of spider mites, as well as sucking insects.

No influence on population dynamics of spider mites in cotton fields of intercropping with walnut, a poor-quality host

Intercropping is a common agricultural practice used to improve crop yields and profits; however, the intercrop species and its quality as a host for the main crop's key pests can affect the pests' population dynamics under intercropping conditions. Fruit trees - cotton intercropping systems are commonly applied in Xinjiang of China, and previous studies have confirmed that intercropping of cotton with species (e.g., jujube and apple) that are good spider mite hosts can increase the spider mite density in cotton. In this study, the effect of intercropping cotton with walnut, which is a poor host for the key spider mite pest Tetranychus truncatus, was examined. For this spider mite, feeding on walnut leads to significantly longer development time for larvae + nymphs and a short oviposition period which leads to a lower total fecundity, lower survival rate and lower intrinsic growth rate (rm) compared to cotton. Correspondingly, in the two-year, multiple-scale field study, we found that the population dynamics of spider mites in cotton did not significantly differ in the field plots between a walnut-cotton intercropping system and monocultural cotton. Similar trends of spider mite density were also observed in commercial fields. Based on previous work and the current study on fruit tree-cotton intercropping systems, we concluded that while intercropping cotton with intercrop species that are suitable spider mite hosts increase the spider mite population in intercropped cotton, the use of a poor host plant such as walnut has no significant effect on spider mites populations in cotton. Hence, our study results improved the understanding of pest management and monitoring in intercropped cotton systems.

Effect of salt stress on secondary metabolites of cotton and biological characteristics and detoxification enzyme activity of cotton spider mites

Cotton spider mites (Tetranychus cinnabarinus Boisduvals and T. truncatus Ehara) are important pest of Bt cotton. Abiotic stress, such as salt stress will not only affect the growth and development, but also cause secondary metabolism changes in cotton plants, which may further influence the occurrence of cotton spider mites on the stressed plants. The objective of the present study was to determine the relationships of salt stress with secondary metabolism and cotton spider mite population dynamics. Two transgenic cotton varieties, SCRC28 and K836, currently grown in large areas in saline-alkali land and stressed with varying concentrations of NaCl, were used. The content of gossypol and tannin, two important secondary insect-resistant substances in cotton plants, were determined in cotton leaves stressed along a NaCl gradient. The development, reproduction and detoxification enzyme activity of cotton spider mites were also studied. The results indicated that the gossypol content in SCRC28 and K836 leaves increased by 34.63% and 30.91% with 200 m mol·L−1 of added NaCl, respectively. The tannin content increased by 40.63% and 34.87%. With the increase of salt concentration, the number of mites on salt-stressed cotton decreased compared to controls. The developmental period of cotton spider mites in salt-stressed plants was significantly extended, while the reproductive rate of cotton spider mites was significantly reduced compared to controls. The development duration of the immature stages under the 200 m mol·L−1 NaCl treatments of SCRC28 and K836 increased by 12.84% and 11.94%, relative to the control, respectively. The fecundity of single female feeding on salt-stressed (200 m mol·L−1 NaCl) SCRC28 and K836 reduced by 31.96% and 36.16%, respectively. The CarE activities of cotton spider mite feeding on SCRC28 and K836 with 200 m mol·L−1 NaCl treated were 3.76 and 2.05 fold of the control, respectively; the P450 activities were 2.55 and 5.48 fold of the control, respectively. Correlation analysis indicated that the gossypol and tannin contents in cotton leaves were positively correlated with the CarE activity or P450 activity. Thus, salt stress enhanced secondary metabolism and increased accumulation of secondary metabolites such as gossypol and tannin, which ultimately inhibited the population dynamics of cotton spider mites. Cotton spider mites metabolized gossypol and tannin by increasing the activity of CarE and P450.

Impact of constant versus fluctuating temperatures on the development and life history parameters of Tetranychus urticae (Acari: Tetranychidae).

The impact of daily temperature fluctuations on arthropod life history parameters is inadequately studied compared with the ample amount of research that has been conducted on the effects of constant temperatures. Fluctuating temperatures are likely to be more realistic, as they are ecologically more similar to what these arthropods experience in nature. Here, we compared the impact of 11 constant temperatures that ranged from 10 to 35°C with fluctuating temperatures with the same corresponding mean temperature and an amplitude of 10°C between high (12h) and low (12h) temperatures on the development and life history parameters of Tetranychus urticae under continuous light conditions. No eggs hatched at constant 10°C, whereas 81.5% of eggs successfully completed development at fluctuating 10°C (15/5°C). Egg-to-female adult development was faster under fluctuating temperatures from 12.5 to 27.5°C than under constant temperatures, whereas the opposite trend was observed at >30°C. The lower thermal thresholds (T) were 11.63 and 8.63°C, and thermal constants (K) were 127.81 and 150.69 degree-days for egg-to-female adults at constant and fluctuating temperatures, respectively. The numbers of oviposition days were significantly higher at fluctuating 15°C than at the corresponding constant temperature, whereas the opposite trend was observed from 20 to 30°C. The intrinsic rate of increase (r) was higher at fluctuating than at constant 15°C. The net reproductive rate (R 0) was also higher at fluctuating than at constant 15 and 35°C, but showed an opposite trend at 20 and 25°C. We conclude that fluctuating temperatures should be considered to accurately predict spider mite population dynamics in nature.

Positive association between thrips and spider mites in seedling cotton

Abstract In cotton fields in Texas, spider mites are sporadic pests, whereas thrips are considered as major pests on early stages (before the fourth true leaf stage). Thrips are also important predators of spider mite eggs. In the present study, we tested the hypothesis that the presence of spider mites on seedling cotton may increase the likelihood of the occurrence of thrips. Based on a greenhouse experiment, it was confirmed that seedling cotton was a suitable host for spider mites. Subsequently, we conducted a 2‐year field experiment in which we studied the likelihood of thrips infestation in cotton plants with/without experimental spider mite infestations. Spider mites established better in 2011 (dry and hot season) than in 2010 (rainy and cooler season), and there was a positive association between spider mites on cotton plants and natural thrips infestation. Thus, we showed that the probability of thrips infestation strongly increased with the presence of spider mites. To confirm the proposed hypothesis on a larger scale, a second field experiment was performed, in which one half of a field was infested with spider mites. Weekly sampling of thrips and spider mites showed a two‐fold increase of thrips immatures on plots previously infested with spider mites. The results obtained in the present study emphasize the importance of incorporating spider mite population dynamics into risk assessments of thrips infestation in seedling cotton fields in Texas and elsewhere.

<p><strong>Seasonal population development of spider mites (Acari: Tetranychidae) and their predators in sprayed and unsprayed apple orchards in Van, Turkey*</strong></p>

The aim of this study was to determine the seasonal population dynamics of spider mites [Panonychus ulmi (Koch), Amphitetranychus viennensis (Zacher), Bryobia rubrioculus (Scheuten)] and their natural enemies [Kampimodromus aberrans (Oudemans),Acari, Phytoseiidae; Zetzellia mali (Ewing),Acari, Stigmaeidae; and Stethorus punctillumWeise, Coleoptera, Coccinellidae] on Golden Delicious and Starking Delicious apple cultivars in three apple orchards of Van, Turkey, during 2002–2003. Surveys were carried out weekly from May to November in sprayed and unsprayed apple orchards. The results of study indicated that the population densities of spider mites began to increase generally in early May, reached the maximum level from mid June to lateAugust and persisted until late September in both years. During 2002 the dominant species on both apple cultivars was P. ulmi, whereas in 2003 it was A. viennensis. In this two-year period, the population densities of P. ulmi and A. viennensis reached the maximum level of 318.1 and 427.2 mites per leaf, respectively, in sprayed orchards. In unsprayed orchard, spider mites remained at very low levels because of the presence of K. aberrans which was the only predator of spider mites. On the other hand, in sprayed orchards, although S. punctillum and Z. mali were the most abundant predatory species on spider mites, they could not control them in either apple cultivar and years.

Seasonal distribution and species association among spider mites (Acari: Tetranychidae) and predatory mites (Acari: Phytoseiidae and Acari: Stigmaeidae) in Serbian apple orchards

ABSTRACT Species composition and population dynamics of spider mites (Panonychus ulmi (Acari: Tetranychidae) (Koch) and Tetranychus urticae Koch (Acari: Tetranychidae)) and predaceous mites (Amblyseius andersoni (Chant) (Acari: Phytoseiidae) and Zetzellia mali (Ewing) (Acari: Stigmaeidae)) were studied for eight months each year (March–October) during 2005–2007 at two localities with different intensities of pesticide use. Using Berger–Parker's dominance index and Sorenson's coefficient, the index of dominance and predator–predator, predator–prey, and prey–prey associations were defined among each of these species to determine changes in species compositions and population densities and comprehend the influence of pesticide use in pest management on populations of spider and predatory mites in apple orchards. Sorenson's coefficient helped to measure the intensity of positive, neutral, or negative interspecific associations for each species and Berger–Parker's dominance index clarified the dominance of specific species. During 2005 the dominant species in both localities was P. ulmi, but during 2006–2007 at one locality both species of spider mites showed almost equal dominance. The results of Sorenson's coefficient confirmed that there was significant predator–prey association among P. ulmi and A. andersoni and P. ulmi and Z. mali, and prey–prey association between P. ulmi and T. urticae in both localities. The analysis of the population dynamics showed delayed occurrence of predatory mites compared with the spider mites, from 48 to 106 days for A. andersoni and 91 to 137 days for Z. mali depending on the research period and locality.

Deleterious Effects of Uv-B Radiation on Herbivorous Spider Mites: They Can Avoid It by Remaining on Lower Leaf Surfaces

The herbivorous spider mite Tetranychus urticae usually remains on the lower leaf surfaces of its host plants. Although terrestrial animals are generally thought to be well protected from damage because of UV radiation, insect herbivory frequently increases when solar UV-B (280-315 nm) radiation is attenuated. As UV transmission through leaves is generally low because of the accumulation of compounds that act as selective sunscreens (e.g., phenolics), we hypothesized that T. urticae avoids solar UV-B radiation by staying on lower leaf surfaces. We examined whether artificial UV irradiation and solar UV affected the survival and reproduction of T. urticae and whether staying on lower leaf surfaces was beneficial to their performance under ambient UV radiation. We found that T. urticae was not well protected from UV-B radiation, because artificial UV-B irradiation strongly decreased survivorship and egg production. More importantly; compulsory solar UV irradiation treatments also had lethal effects on T. urticae, whereas the mites could avoid them if they remained on the lower leaf surfaces of their host plants. These results showed that access to habitats protected from sunlight, such as lower leaf surfaces, is likely essential for T. urticae survival under ambient UV-B radiation. The lethal effects of solar UV radiation may also affect the population dynamics of spider mites, and habitat (resource) limitation may increase the probability of interspecific interactions, such as competition and predation. In turn, the occurrence of these interactions in sheltered areas may be associated with observed increases in herbivory under conditions of solar UV-B-attenuation.

Simulation Modeling of Twospotted Spider Mite Population Dynamics in Apple and Pear Orchards in Korea

Reliable prediction of pest population density plays a critical role in decision making for pest management. For this purpose, a stage-structured simulation model was constructed to predict the population dynamics of twospotted spider mite, Tetranychus urticae Koch in apple and pear orchards. Three external factors influential to spider mite population dynamics in Korean orchard systems are temperature, acaricide and precipitation. Temperature-dependent developmental parameters were mostly derived from experimental measures with a Korean strain of T. urticae. Immature development and adult longevity were fitted to the poikilotherm rate function (modified Sharpe and De-Michele model) with daily mean temperature while its variation and age-specific-oviposition, and -mortality were described by a three-parameter Weibull function relative to physiological age. Acaricidal effect and precipitation effect on T. urticae were expressed as exponential decay. Sensitivity tests and validation process provided good correlations to observed data from apple and pear orchards in a shorter period, but a little deviation in a longer period. Further improvement and implication of simulation model in integrated mite management are discussed.

Effects of chlorpyrifos and sulfur on spider mites (Acari: Tetranychidae) and their natural enemies

In many agricultural systems spider mites are believed to be induced pests, only reaching damaging densities after pesticides decimate predator populations. Wine grapes typically receive two types of pesticides, insecticides and fungicides. Chemicals in either class could impact spider mite densities both directly through spider mite mortality, and indirectly by negatively affecting natural enemies. The impact of a broad-spectrum insecticide (chlorpyrifos) and an inorganic fungicide (sulfur) on mites and their natural enemies was monitored in replicate open-field experiments conducted in an abandoned vineyard in Washington State. In both experiments, chemicals were applied within a 2 × 2 factorial design, allowing assessment of both main and interactive effects of the two chemicals. Following typical management practices on wine grapes in Washington State, we made a single insecticide application early in the season, but repeatedly applied sulfur throughout the season. In the absence of sulfur, chlorpyrifos application led to higher spider mite densities. The main effect of chlorpyrifos appeared to be indirect, perhaps mediated through mortality of generalist phytoseiid mites; generalists appeared to be unable to recover following even a single insecticide application, while there was no evidence for harmful effects of chlorpyrifos on specialist phytoseiid mites. Sulfur had direct suppressive effects on both pest and predatory mites, although in the second experiment the suppressive effect of sulfur on spider mites was weaker when chlorpyrifos was also applied. These field experiments suggest that a complex mix of direct and indirect effects of the two chemicals impacted spider mite population dynamics in our system.

An ecosystem analysis of spider mite outbreaks: physiological stimulation or natural enemy suppression

A simulation model was used to assess the role of several mechanisms proposed to be responsible for spider mite outbreaks on cotton that are typically observed following applications of insecticides. Simulation results were compared to an outbreak that occurred after two pyrethroid applications on cotton in a controlled experiment in the San Joaquin Valley of California. In the model, physiological effects were simulated by increasing spider mite fecundity and decreasing developmental duration, whereas loss of natural enemies was simulated by increasing spider mite age-specific survival. At the levels simulated, survival had the greatest impact on maximum spider mite density, degree days (oD) to maximum density, and cumulative spider mite-oD, whereas fecundity had the least, and developmental duration had an intermediate effect. There were substantial two-way interactions among all three life history parameters, with age-specific survival having the most influence. Survival had the greatest effect on spider mite population dynamics when in combination with short developmental duration. The influence of developmental duration on maximum spider mite density was greater than comparable percentage changes in fecundity, an effect that was more pronounced at high than at low survival. Changing fecundity, developmental duration, or age-specific survival individually did not result in a spider mite outbreak of the magnitude observed in the field. However, changing these three parameters simultaneously, resulted in a simulated maximum density of 8,000/m2, which represents a 12-fold increase over the untreated control, and closely mimicked the previously observed field outbreak. It is proposed that spider mite outbreaks on cotton following insecticide applications are not solely the result of physiological stimulation, but are rather due to several life history parameters being affected simultaneously, with natural enemy-mediated survival having the greatest individual impact. Implications of chemically-induced phenomena affecting spider mite management on cotton are discussed.

Effects of Plant Moisture Stress and Rainfall on Population Dynamics of the Twospotted Spider Mite (Acari: Tetranychidae)

A rainout shelter was used to control soil moisture and rainfall conditions in soybean plots artificially infested with twospotted spider mites, Tetranychus urticae Koch, in 1987 and 1988. Leaf disks were collected to determine the separate and interactive effects of plant water stress and impact energy of rainfall on spider mite population dynamics. In both seasons, spider mites initially colonized lower leaves and dispersed into the upper canopy as populations peaked 3–4 wk later. Precipitation applied with a rainfall simulator was not found to significantly affect mite intensity (mites per leaf area). Significantly greater mite intensities were found in stressed plots on two of six sampling dates in 1987 and in the pooled data of 1988. However, the differences in intensity were slight and may be accounted for, in part, by less total leaf area on the stressed plants. Results did not support the traditional belief that plant stress and the occurrence of heavy, driving rains are important factors in spider mite population dynamics. Rather, other factors associated with drought conditions require consideration to explain spider mite population dynamics in soybean.

Effects of herbivory and plant conditioning on the population dynamics of spider mites

Plants vary in their resistance to tetranychid spider mites, and this can have profound effects on spider-mite population dynamics. Such variation can be attributable to many factors. In this review, however, we focus on how previous or concurrent feeding by phytophagous hervivores influences expression of plant resistance to spider mites.Induced resistance is a change in the host plant in response to extrinsic stimuli, resulting in reduced host suitability for the population growth of spider mites. We begin our review by summarizing the different ways in which spider mites and plants interact to produce induced resistance-like phenomena. We then discuss a number of hypotheses which address the mechanisms underlying induced resistance and end by suggesting agricultural applications. Although the potential use of induced resistance to manage spider mites is apparent, progress in this area will depend on a better understanding of the mechanisms involved and their associated costs and benefits to the plant.

Effects of microenvironment on the dynamics of spider-mite populations

The relationship between environmental variables (chiefly temperature and humidity) and the population dynamics of spider mites is reviewed. Both direct effects on the spider mites and indirect effects operating through effects on spider mite natural enemies (mainly phytoseiid mites) are discussed. Factors determining the environmental conditions actually experienced by spider mites (microenvironment) are presented.

An Analytic Model for Description of Temperature Dependent Rate Phenomena in Arthropods 1

A new description of temperature-dependent, rate phenomena was deduced to describe developmental time and ovipositional data for the McDaniel spider mite, Tetranychus mcdanieli McGregor. The derived equation accounted for asymmetry about optimum temperature and was of particular utility for description of systems operating at or above optimum temperatures. Ovipositional and developmental rate functions were used in a temperature-driven, discrete-time, simulation model describing McDaniel spider mite population dynamics. Temperature dependence of the instantaneous population growth rate was determined by fitting the derived rate-temperature function to data generated through simulation at various fixed temperatures. The functional relationship of important population parameters to temperature provided the mechanism for inclusion of phenological effects on mite populations in a synoptic apple pest management model. Two derived functions were fit to several published rate-temperature data sets. Adequacy of description (as indicated by R2 values) indicated general applicability of both functions for description of temperature-controlled, biological processes. Further, it was concluded that the singular perturbation method of matched asymptotes has potentially wide application in ecology, and an Appendix detailing the application of this method is included.

Population Dynamics of Spider Mites and Predators as Influenced by Pesticides for the Control of Late‐Season Cotton Pests

AbstractThe effect of the pesticides, Sevin, Torbidane (Toxaphene/DDT/Methyl parathion), and DDT/Lindane + Endrin was evaluated against spider mites and predators on cotton plants during 1966 and 1967. All the materials tested, stimulated outbreaks of the spider mite, late in the season, and Sevin was responsible for greater mite infestations. The effect of the three pesticides combinations on natural enemies was discussed.ZusammenfassungDie Beeinflussung der Populationsdynamik von Spinnmilben und ihrer Räuber durch Pestizide bei der Bekämpfung von Baumwollschädlingen im SpätsommerIn den Spätsommern 1966 und 1967 wurden die Wirkungen von Sevin sowie Mischungen von Toxaphen + DDT + Parathion und DDT + Lindan + Endrin auf Spinnmilben und ihre Räuber in Baumwollfeldern untersucht. Alle getesteten Mittel förderten die Spinnmilbenvermehrung, am meisten das Sevin. Die Auswirkungen auf die Spinnmilbenfeinde werden diskutiert.

Population Dynamics of Spider Mites Influenced by DDT2

Tetranychus urticae Koeh and T. telarius (L.) exhibit a decided tendency to disperse from crowded colonies. If dense colonies are confined, longevity and oviposition by adults are reduced, and young have less success in maturing. Crowding does not affect hatchability of eggs. Treatment with DDT does not enhance dispersion except at high levels of dosage, and the high levels are toxic, especially to emhryonated eggs and larvae. Emulsified DDT is more toxic than DDT in wettable powder suspension. It is postulated that the outbreaks of spider mites resulting from DDT treatment of crops are the result mainly of: DDT causing dispersion indirectly through the removal of natural enemies, which in turn allows dense local populations to develop. This results in dispersion as a result of crowding, and with dispersion to predator-free surfaces, there follows an increase in the population to economically harmful levels. The terminology used for the species of Tetranychus follows that of Boudreaux and Dosse (1963).