We identified and evaluated a phytoseiid predator as a biological control agent of multiple spider mites pests that occur in ornamental nurseries. When comparing species, Neoseiulus fallacis (Garman) had a wider prey range than Galendromus occidentalis (Nesbitt), a higher probability of overwintering than Neoseiulus califomicus McGregor and was equally or more effective at suppressing spider mites than either of the other 2 phytoseiids in 4 field tests. To further evaluate N. fallacis we 1) measured prey range when held with 29 ornamental pests or alternative foods under laboratory conditions, 2) tested biological control of spider mites on representative plant species at both small and large spatial scales, 3) developed release and conservation strategies of the predator, and 4) examined the efficacy of the predator in controlling recently introduced pests. Neoseiulus fallacis had greatest survival and reproduction when feeding on spider mites but eriophyid mites, other mites and pollen enhanced survivorship and, in some cases, reproduction. When inoculated into ornamental plants, spider mite suppression was "acceptable" in 81% of small scale tests and-in all large scale tests. Limitations in control occurred in tall, vertical growing plants with little foliar canopy. Inoculation of N. fallacis at low prey densities into apple rootstocks was successful at suppressing Tetranychus urticae Koch and similar to control achieved at moderate prey densities. In small scale banker plant studies, high densities of adult and immature mites of N. fallacis were produced and moved downwind to receiver plants. In field tests with receiver plants placed at greater distances, only N. fallacis adult females readily dispersed to 30 m or more. When comparing overwintering survival of adult females among plant types, N. fallacis survived most on conifers, intermediate on evergreen shrubs and least on herbaceous perennials, deciduous shrubs and shade trees. Covering plants with protective plastic reduced overwintering survival of the predator. Neoseiulus fallacis successfully suppressed the newly introduced pests Panonychus citri (McGregor) and Schizotetranychus celarius (Banks) on Skimmia japonica Thunberg and Sasaella hidaensis (Makino and Uchida), respectively. Initial studies suggest that N. fallacis can be an effective biological control agent of multiple spider mites in low-growing and selected higher-growing ornamental plants. / Graduation date: 2000

The life history, temperature, humidity, and feeding requirements of the phytoseiid predator mite, Typhlodromus americanus Chant and Yoshida-Shaul were tested in the laboratory. Occurance of the mite in the field during different times of the year was investigated as well. Effects of temperature and humidity on egg hatch, the feeding requirements of the larvae, the amount consumed by each life stage, the length of each life stage and suitability of different food sources were investigated in the laboratory. The use of the mite as a biological control agent was evaluated by using the information gained from the laboratory experiments. T. americanus was originally discovered in plantation grown Douglas-fir in western Oregon. Since that time the mite has been found on a number of other hosts throughout North America. The mite is active year round in the Christmas tree plantations of the Willamette Valley in Oregon. The adult is found in or near the one year old bud scars and the eggs are typically deposited there also. Life parameters were measured providing a net reproductive rate of 4.23, a mean generation time of 24.45 days, and an intrinsic rate of increase of 0.059 The intrinsic rate of increase was low when compared to other predator mites and numerical response to prey increase would not be possible with such a low rate. The optimal temperature for the shortest eclosion time (54.4 hr.) and the highest survival (96.4%) was 26��C. The regression of temperature vs. time to hatch gave a 90% R�� with both the slope and intercept significantly different from zero. Humidities above 70% had survival rates over 96% and eclosion rates in the range of 50-58 hours. The relative humidity at which 50% of the population died was 58.6%. The mite was found to feed readily on the pest mite Oligonychus ununguis (spruce spider mite), as well as Tetranychus urticae (two spotted spider mite), and corn, oak, and Douglas-fir pollens. The larval form of the predator mite does not require food to molt to the protonymph, but the protonymph does require food to molt. If water is provided the entire time from egg to death, the protonymph can survive about ten days. Females consumed more Tet. urticae than males in both the immature and adult stages. The T. americanus that were fed corn pollen and Tet. urticae (complete diet) lived for over 115 days. Mites raised on oak and corn pollens did not survive as long (only 70-80 days), and those raised on Douglas-fir pollens did not reach adulthood. Egg production was observed on the complete diet, but not on the diets of pollen. The largest number of eggs were laid around the twelfth day after the molt to adult. Control and management of field conditions to improve habitat for T. americanus will be the best approach for its use as a biological control agent. As it does not respond numerically to prey increase, it will be more effective in a regulatory role to prevent these increases while the prey is at low levels. / Graduation date: 1996

Thesis (M.S.)--California Polytechnic State University, 2009. / Mode of access: Internet. Title from PDF title page, viewed on March 30, 2009. Major professor: Michael J. Costello, Ph.D. "Presented to the Electrical Engineering Department Faculty of California Polytechnic State University, San Luis Obispo." "In partial fulfillment of the requirements for the degree [of] Master of Science in Agriculture, with specialization in Plant Protection Science." March 2009." Includes bibliographical references (p. 48-54). Will also be available on microfiche.

Three densities of European red mite (ERM) (<i>Panonychus ulmi</i> Koch) and twospotted spider mite (TSM) (<i>Tetranychus urticae</i> (Koch)) were maintained on greenhouse-grown 'Imperial Delicious' apple (<i>Malus domestica</i>) and 'Redhaven' peach (<i>Prunus persica</i>) leaves. As ERM- and TSM-days increased, apple leaf net photosynthesis (Pn), transpiration (Tr) , and chlorophyll content (TCHL) decreased linearly. TSM was more damaging to apple leaf gas exchange than ERM. Apple water use efficiency (WUE) declined similarly with increasing mite-days for both mite species. Apple specific leaf weight (SLW) decreased with ERM-days and increased with TSM-days. Peach Pn, Tr, and TCHL declined linearly for both ERM and TSM. Both mite species were equally damaging to peach leaf gas exchange. Peach WUE decreased with increasing ERM and TSM-days. There was no mite effect on peach SLW. The results from separate apple and peach studies indicate that peach may be more tolerant to mite feeding than apple. / Master of Science

Laboratory experiments were conducted to evaluate Tetranychus urticae Koch dispersal response to fenvalerate and permethrin. A petri dish spider mite trap which allows the partitioning of the dispersal response into spindown and walkoff categories was developed. Fenvalerate induced the more severe dispersal response. A greenhouse experiment was conducted to evaluate Tetranychus urticae oviposition site selection in response to residues of fenvalerate and permethrin, at two levels of residue deposition. When pyrethroid-free leaf surface was available, nearly all eggs were found on the untreated surface, away from the pyrethroid residues. When pyrethroid-free leaf surface was not available, a substantial number of eggs were found suspended by silk threads above the treated surface. The results were found to be in agreement with the general pyrethroid avoidance hypothesis. A series of greenhouse experiments were conducted to evaluate Tetranychus urticae oviposition response following impingement, and contact with residues of fenvalerate and permethrin. In all instances the pyrethroids were found to reduce the number of eggs oviposited. Mites recovered after several days, and oviposition returned to normal. The results did not lend support to the hormoligosis hypothesis of insecticide induced mite outbreaks. Field and greenhouse experiments were conducted to evaluate Tetranychus urticae oviposition response, over time, to soybeans which have received an application of fenvalerate of permethrin. The pyrethroids did not alter the soybeans in a way which improved the quality of the plant as a resource for increased levels of spider mite oviposition. / Master of Science / incomplete_metadata

LD2668 .T4 1954 T64 / Master of Science

No description available.

Knowledge of how individual organisms behave in their environment can provide a greater understanding of population dynamics. In a predator-prey system, the choices made by predators when foraging for prey are important aspects of behavior. Particularly in the case of a stage-structured prey population, how the predator selects prey stages once a prey patch has been located can have implications for prey population growth, predator development and fecundity, and predator-prey system dynamics. Predaceous mites of the family Phytoseiidae are important biological control agents of Tetranychus spider mites in agricultural settings worldwide. Phytoseiid species range from specialists that require Tetranychus spider mite prey in order to develop and reproduce to generalist omnivores. In studies with 13 phytoseiid species, specialized species tended to prefer T. urticae eggs as prey or have no prey-stage preference while more generalist species tended to have no prey-stage preference or prey more often on mobile immatures. Further testing with a subset of these species suggested variability among species with regard to genetic and environmental influences on prey-stage preference. The specialist Phytoseiulus persimilis also preferred to forage and oviposit in patches containing egg-biased stage distributions rather than in adjacent mobile immature-biased patches. No benefits to offspring developing in either type of patch were found in terms of developmental time or subsequent adult fecundity. However, the results of both manipulative experiments and nonlinear population models indicated potential benefits of egg-biased predation in terms of current adult female fecundity, a less severe impact of predation on the prey population, and an increased number of predator descendents during the predator-prey interaction. Considering both subjective factors and discriminant analyses, prey-stage preference performed well as an indicator for the ecological classification of phytoseiid species. The classifications of four phytoseiid species occurring on apple in central and eastern Oregon, USA, were evaluated accordingly. / Graduation date: 2004

During summer of 1998 and 1999, 34 and 10 vineyard sites, respectively, were sampled to assess spider mite pests and associated biological control by phytoseiid mites. Vineyards studied spanned five major valleys in western Oregon where grape production occurs. Leaf samples were taken from site perimeters and centers. One leaf was taken every ten meters of border length, five meters inward from the border to prevent wind-biased or extreme edge effects, while 20 leaves were taken at regular intervals from centers. Variables recorded at each site were: plant age, grape variety, chemical spray information and local vegetation occurring in proximity to vineyards. Sites were categorized as either agricultural or riparian based on what surrounding vegetation type was in the majority. Several parametric and non-parametric tests were used to analyze data, including multiple linear regressions using a computer-based genetic algorithm in conjunction with the AIC criterion to pre-select a subset of explanatory variables. Typhlodromus pyri was the predominant phytoseiid mite and Tetranychus urticae was the most abundant tetranychid mite sampled. High levels of T. urticae were found when predator densities were very low, and low levels of T. urticae occurred when predator densities were moderate or high. Phytoseiid densities were highest in June and July, while T. urticae densities were highest from August to September. The latter's densities were significantly higher in vineyards surrounded primarily by agriculture, while phytoseiid densities were not significantly different between the two categories. Predatory phytoseiids had significantly higher densities on vineyard edges, while T. urticae densities were higher in vineyard centers. Caneberry, cherry and grape habitats appeared to be sources of predator immigration, while no vegetation type consistently served as a short-range or nearby immigration source for spider mites. Due to insufficient data, pesticide information was not included in multiple linear regression models, although certain chemicals used in vineyards can potentially impact mite populations. Impacts of surrounding vegetation type, grape variety, regional location, plant age, and presence of other mites on phytoseiid and T. urticae densities are discussed. / Graduation date: 2001

Intra- and interplant movement and dispersal of the predator mites Neoseiulus californicus (McGregor) and Neoseiulus fallacis (Garman) were studied on both lima bean (Phaseolus lunatus L.) and apple (Malus pumila Miller) branch plant systems that were seeded with excess numbers of the spider mite Tetranychus urticae Koch. Individuals of either predator were randomly selected from colonies of well-fed, mixed-age adult females and moved to test plants. When tested separately in each plant system, median leaf positions of N. californicus from the point of release were greater than those of N. fallacis at 1-8 d. A fan placed in front of a common source unit (1x3m) containing T. urticae and near equal densities of both predaceous mites, provided continuous air (wind) to 3 isolated receiver units located 2.5, 5, and 7.5 m downwind. Receiver units consisted of continuous bean foliage with excess T. urticae, but no predators. Wind speeds at the source and each receiver unit averaged 2.2, 0.9, 0.4, and 0.03 m/s respectively. As predators eliminated prey, N. fallacis dispersed earlier at higher prey densities and further downwind than N. californicus, but cumulative densities of each predator in all receiver units were alike after 20 d. Results of both plant movement studies supported the hypothesis that N. californicus has dispersal traits more like those of a generalist predator of spider mites than does N. fallacis. Spatial patterns of dispersal and biological control of pest mites are discussed in relation to predation types within the Phytoseiidae. / Graduation date: 1997