High temperature mortality of Wolbachia impacts the sex ratio of the parasitoid Ooencyrtus mirus (Hymenoptera: Encyrtidae).

Background: Wolbachia bacteria are estimated to occur in more than half of all insect species. In Hymenoptera, Wolbachia often manipulates its host's reproduction to its own advantage. Wolbachia is likely the reason that males are rare in the uniparental Ooencyrtus mirus Triapitsyn & Power (Hymenoptera: Encyrtidae). The likelihood of producing male offspring can be increased by giving mothers a continuous supply of Bagrada hilaris (Burmeister) (Heteroptera: Pentatomidae) host eggs to parasitize for 2-3 weeks, by feeding the parents antibiotics, or by rearing parent wasps at high temperatures; all variables that have been shown to correlate with depleting Wolbachia titers in other organisms. The purpose of the current study was to determine whether thelytoky in O. mirus is due to Wolbachia, and if so, at what time in development the sex change occurs. We also wished to determine if Wolbachia removal results in the production of intersexes, as in some other hymenopterans. Finally, mating behavior was observed to see if and where it breaks down as a result of the species becoming thelytokous. Methods: Females were collected from parental lines of O. mirus reared at 26, 30, 31, 32, 33, 34, and 36 °C. The offspring of these females were reared at 26 °C, and their sex-ratio was determined. In a subsequent experiment, the parental generation was switched between 26 °C and 36 °C during development to narrow down the critical period at which changes occurred that subsequently affected the sex-ratio of their offspring. Results: The sex ratio was male biased in the offspring of O. mirus parents reared at 34 °C and 36 °C (high temperatures), even if the offspring themselves were reared at 26 °C. The constant temperature at which the percentage of males started to increase after two generations was 31 °C (10% males), rising to 39% males at 33 °C, and 100% males at 34 °C and 36 °C. Lasting more than 2 days, the critical period for the change toward a male biased sex ratio was during the second half of the parent's development. Molecular diagnostic assays confirmed that O. mirus females contain Wolbachia and males do not. Examination of preserved males and male-female pairs under a dissecting microscope showed no signs of intersex characters. Observation of the mating behavior of live O. mirus showed that males initiate courtship by drumming their antennae on a female's antennae, but after a few seconds, the females typically turn and walk away. However, a few instances of possible copulation were noted. Conclusions: As hypothesized, the results indicated that thelytoky in O. mirus is likely mediated by Wolbachia bacteria. To maximize the population growth rate without generating males, the best temperature for mass rearing this species is 30 °C.

Trypanosomatids Associated in the Alimentary Canal of Bagrada hilaris (Hemiptera: Pentatomidae).

Bagrada hilaris (Burmeister) is an invasive pest of economically important crops in the United States. During physiological investigations of B. hilaris, a flagellated protozoan was discovered in the alimentary canal of many specimens. This manuscript characterizes the morphology and molecular identification of the trypanosomatid, which appears similar to trypanosomatids identified in other stink bug species. It has been identified as a species in the Blastocrithidia genus based on morphological characteristics and molecular analyses.

Pre-oviposition Period and Immature Development of Maconellicoccus hirsutus (Hemiptera: Pseudococcidae) on Cucurbita moschata 'Black Futsu' Squash.

The developmental time of pink hibiscus mealybug, Maconellicoccus hirsutus (Green), immatures was investigated on the host plant Cucurbita moschata Duchesne ex Poiret variety 'Black Futsu.' Because host plant species influences developmental rates of M. hirsutus, understanding the life history of this specific host plant has implications for the mass rearing protocols of its natural enemy, Anagyrus callidus Triapitsyn, Andreason and Perring, currently being released in California, United States. Fruit from 'Black Futsu' squash were infested with first instar pink hibiscus mealybug and kept at 26.6 ± 2°C, 50 ± 10% RH, and 0:24 (L:D) h photoperiod for the duration of the experiment. Every 24 h the life stages of pink hibiscus mealybug individuals on the squash were recorded. After adult eclosion, observations of adult females continued until the first eggs hatched, which revealed an average pre-oviposition period of 7.2 ± 0.1 d and an average length of the egg stage of 7.0 ± 0.0 d. The average developmental times for both sexes were similar from the egg stage through the second instar. Third instar females took nearly twice as long (7.2 d) to develop into adults as did third instar males. However, females have just three immature instars while males have four. The males spent an average of 4.5 ± 0.3 d as third instars and 4.8 ± 0.4 d as fourth instars before developing into winged adults. On average, female immature developmental time was 27.8 ± 0.2 d from egg to adult and male developmental time was 29.4 ± 0.2 d from egg to adult. The implications of these results on rearing A. callidus are discussed.

Re-collection and identity of Ooencyrtus californicus (Hymenoptera: Encyrtidae), and its new synonym, Ooencyrtus lucidus.

Girault (1917) very briefly described and diagnosed the encyrtid wasp species Ooencyrtus californicus Girault (Hymenoptera: Encyrtidae) with the following limited data (p. 22): "Sacramento, California, from bug eggs on Pinus sabiniana, September". The first author examined its two syntypes, poorly mounted on a slide, of which only parts of the four antennae and a slightly damaged fore wing remain (Triapitsyn et al. 2020). They concluded that this species was better considered a nomen dubium until fresh specimens could be collected from the same host plant in or near the type locality. In July 2019, an effort was made to re-collect O. californicus from foothill (or gray) pine, Pinus sabiniana (Pinaceae), in the Oakhurst area of Madera County, California, USA, where this pine is abundant, but no specimens were captured. At the same time, a very similar insect was collected from sentinel eggs of the invasive stink bug Bagrada hilaris (Burmeister) in Riverside, California. This insect was cultured in the laboratory as part of a B. hilaris biological control program. Due to the poor preservation of the type specimens and in the absence of genetic evidence, it was impossible to positively and properly attribute specimens of this newly collected parasitoid to O. californicus. Therefore, to provide a much needed scientific name for this native egg parasitoid, it was described as Ooencyrtus lucidus Triapitsyn Ganjisaffar in Triapitsyn et al. (2020). The two nominal species were separated based on minor differences in the proportions of the scape, pedicel, and first funicular segment of the female antenna (Triapitsyn et al. 2020). John S. Noyes, world expert on Encyrtidae and one of the reviewers of Triapitsyn et al. (2020), disagreed with the erection of O. lucidus as a new taxon based on the morphological similarities of the female antenna with that of O. californicus, so the description was published with the understanding that the two might be conspecific. But to settle this one way or another new specimens of O. californicus had to be collected to allow morphological and molecular analyses.

Effects of Parasitoid Age, Host Egg Age, and Host Egg Freezing on Reproductive Success of Ooencyrtus mirus (Hymenoptera: Encyrtidae) on Bagrada hilaris (Hemiptera: Pentatomidae) Eggs.

Bagrada hilaris (Burmeister) is a serious pest on brassica crops in many regions throughout the world. As part of our efforts to enhance biological control, we have been studying an egg parasitoid that was collected from B. hilaris eggs found on brassica plant debris in Pakistan. This species has recently been described as Ooencyrtus mirus Triapitsyn & Power. A major component of rearing biological control agents is understanding the relationship among host egg age, parasitoid age, and reproductive success. To this end, we used a factorial design to evaluate all combinations of host egg ages 0-5 d and parasitoid ages 0-11 d. The results showed that the best combinations are 0- to 1-d-old host eggs with 3- to 10-d-old parasitoids. A further study using frozen host eggs showed that O. mirus can reproduce as successfully on frozen B. hilaris eggs as on fresh ones.

Evaluation of the Physiological Host Range for the Parasitoid Ooencyrtus mirus, a Potential Biocontrol Agent of Bagrada hilaris.

The thelytokous egg parasitoid Ooencyrtus mirus Triapitsyn and Power (Hymenoptera: Encyrtidae) was recovered from brassica plant debris in Pakistan in an effort to find a biological control agent of the invasive bug Bagrada hilaris (Burmeister) (Heteroptera: Pentatomidae) in North America. As the first step in determining the overall host range of this parasitoid, adult females were exposed to the eggs of eight alternate pentatomid host species, two non-pentatomid heteropterans, and two lepidopterans, in choice and no-choice tests. Although O. mirus was more successful on B. hilaris than the other species in terms of the number of the eggs laid, the number of emerged progeny, and the developmental time of the progeny, it was able to reproduce on all of the alternate hosts except for one of the lepidopterans, whose eggs appeared too small for this parasitoid. The results show O. mirus to be a generalist parasitoid species with a preference for B. hilaris. The results also indicate that there is a linear relationship between the mean body length of O. mirus females and the mean host egg weight with an adjusted R 2 of 0.90. The implications of this study on the release of O. mirus for the control of B. hilaris are discussed.

Effect of Temperature on the Survival and Developmental Rate of Immature Ooencyrtus mirus (Hymenoptera: Encyrtidae).

Bagrada hilaris (Burmeister) is an invasive pest of cole crops in the southwestern United States. To find potential biocontrol agents of B. hilaris, three egg parasitoids were imported from Pakistan, including Ooencyrtus mirus, a recently described uniparental species. We investigated the effect of temperature on survival and developmental rate in O. mirus from egg to adult. At 14 and 16°C, no adults emerged unless the immatures were transferred later to a warmer temperature. At constant 18°C, a low percentage emerged, but again more emerged if the immatures were transferred to a warmer temperature. Survival ranged from 80 to 96% at 20-37°C and did not differ significantly among these temperatures. No adults emerged at 38°C. Regardless of the amount of time the parasitized eggs were held at 14 and 16°C, the developmental times after returning the eggs to 26°C were similar, suggesting a quiescence process rather than simply slow development. At higher temperatures, the developmental rate increased linearly from 18 to 36°C and then declined at 37°C. The Wang model provided the best fit of the data and estimated a lower developmental threshold at 13.0°C, an optimal temperature at 35.6°C, and an upper developmental threshold of 38.3°C. The thermal constant for total immature development is 168.4 degree-days. The results show 36°C to be the best temperature for rearing O. mirus, and that O. mirus-parasitized eggs can be stored at 14°C for months without losing viability. These are crucial data to consider when mass rearing this biological control agent.

Life History Evaluation of Ooencyrtus lucidus, a Newly Described Egg Parasitoid of Bagrada hilaris.

Ooencyrtus lucidus Triapitsyn & Ganjisaffar (Hymenoptera: Encyrtidae) was recently recovered from fresh sentinel eggs of Bagrada hilaris (Burmeister) (Hemiptera: Pentatomidae) in California. In the present study, life history traits of O. lucidus were studied at 26 ± 0 . 5 ∘ C, 40 ± 10 % RH, and a photoperiod of 14 L: 10 D hours. Results showed that 95.2% of the parasitized eggs yielded successful emergence of adults. The total immature developmental time was 14.27 and 13.95 days for females and males, respectively. The sex ratio of O. lucidus was 0.5 (females/offspring). Mated females laid on average 6.0 eggs per day and 222.7 eggs during their mean ovipositional period of 37.3 days. There was no significant difference in reproduction parameters between mated and non-mated females. The net reproductive rate ( R 0 ) was 103.8 females/female/generation, the intrinsic rate of increase ( r m ) was 0.171 females/female/day, the finite rate of increase ( λ ) was 1.187 population multiplication/day, the mean generation time (T) was 27.1 days, and the doubling time (DT) was 4.0 days. The highest longevity was observed in mated and non-mated females fed with honey, and they lived for 70.8 and 70.1 days, respectively. Providing females with host eggs in addition to honey, reduced their longevity by 24% in mated and 28% in non-mated individuals. Non-mated females and males deprived of honey only lived for 3.5 and 2.5 days after emergence, respectively. Our results indicate that O. lucidus has sufficient life history traits to make it a promising egg parasitoid for the biological control of B. hilaris.

On the origin of Anagyrus callidus (Hymenoptera: Encyrtidae), a parasitoid of pink hibiscus mealybug Maconellicoccus hirsutus (Hemiptera: Pseudococcidae).

Anagyrus callidus Triapitsyn, Andreason Perring (Hymenoptera: Encyrtidae), recently described from southern California, USA and Mexico, is a primary parasitoid of the pink hibiscus mealybug, Maconellicoccus hirsutus (Green) (Hemiptera: Pseudococcidae). This wasp species previously was misidentified as Anagyrus kamali Moursi, which was introduced and released as such in the United States (California and Florida) and Mexico. In this paper, the origin of A. callidus is shown to be from Taiwan, based on differences in the morphology and molecular sequences of voucher specimens of an earlier colony of the misidentified A. kamali from Puerto Rico (released in August 2002 in southern Florida), and specimens that originated in southern Taiwan.

Female Reproductive System Morphology and the Development of a Physiological Age-Grading System for Bagrada hilaris (Hemiptera: Pentatomidae).

In this paper, we describe the morphology of the female Bagrada hilaris (Burmeister) reproductive system and develop a physiological age-grading system related to egg production. The female reproductive system is composed of two meroistic and telotrophic ovaries each containing 5-6 tubular ovarioles. The ovarioles unite into the lateral oviduct which combine to form the common oviduct. The ovarioles are composed of two regions; the distal germarium and the tubular vitellarium which contains maturing follicles. Each follicle is surrounded by a layer of cells; the follicular epithelium. As the follicle passes from the ovariole to the lateral oviducts the follicular epithelial cells slough off and accumulate in the base of the ovarioles and are known as follicular relics. The continuum of ovarian development is divided into two categories: nulliparous ('nonreproducing') and parous ('reproducing'). The nulliparous category is characterized by the absence of follicular relics or eggs in the oviducts as opposed to the parous category where follicular relics and, in many cases, eggs occurred in the oviducts. The nulliparous category is divided further into two stages; N1 and N2 based on ovariole differentiation. The parous category is divided into three stages; P1, P2, and P3, based on the quantity and appearance of follicular relics. Females characterized as P3 produced three times more eggs (79.2 eggs ± 5.7) than females characterized as P1 (27.1 eggs ± 6.0).

Lethal and Sub-Lethal Effects of Insecticides on the Pink Hibiscus Mealybug, Maconellicoccus hirsutus (Hemiptera: Pseudococcidae).

The pink hibiscus mealybug, Maconellicoccus hirsutus (Green) (Hemiptera: Pseudococcidae) is a pest of many plants, and a new problem on dates in California. The effects of seven insecticides and water on different life stages of this mealybug were studied to identify the best material for control. Water did not have any significant effect on mealybugs, but the insecticide treatments significantly affected all life stages tested. The egg hatch rate ranged from 28.5% to 17.2% for spirotetramat, bifenthrin, flupyradifurone, fenpropathrin, and buprofezin treatments, and was lower for sulfoxaflor (2.8%) and acetamiprid (0.1%). Despite high survival of neonate crawlers in the non-treated control and water treatments, 53.1% and 34.6% survived in the spirotetramat and buprofezin treatments, respectively; survival was zero in the other treatments. Spirotetramat and buprofezin caused very low mortality of nymphs in the first day post-treatment, but mortality significantly increased over time and reached 42.8% and 50.6% by day 6, respectively. The other treatments were highly toxic to the nymphs (79.4⁻99.4% on day 6). Insecticides also had a significant effect on the feeding ability of nymphs. By day 6 after treatment, 73.9% to 100% of nymphs treated with different insecticides stopped feeding although they were still alive. Insecticides showed no effect on the mortality of adult females, but the percentages of ovipositing females were significantly reduced (51.1% to 10.6%) in all insecticide treatments, except buprofezin, which was not statistically different from water and the non-treated control. In the process of our studies, we identified abnormalities in the appearance of eggs from females treated with various insecticides, and these aberrant eggs are described.

Reduced Susceptibility of Homalodisca vitripennis (Hemiptera: Cicadellidae) to Commonly Applied Insecticides.

Pest management for the glassy-winged sharpshooter, Homalodisca vitripennis Germar (Hemiptera: Cicadellidae), in Kern County, California relies on the application of insecticides. These treatments have contributed to low H. vitripennis field counts since applications were initiated in 2001. However, densities have been high in recent years despite continued management, prompting efforts to evaluate the susceptibility of current populations to insecticides. H. vitripennis adults were subjected to bioassays with five commonly applied insecticides, and the results were compared to baseline toxicities determined in 2002. Two neonicotinoids, imidacloprid and thiamethoxam, were evaluated using systemic uptake bioassays. Contact toxicities of the neonicotinoid acetamiprid and pyrethroids bifenthrin and fenpropathrin were estimated using leaf dip bioassays. Dose-mortality responses were analyzed by probit analysis. For each compound, there was no significant difference in annual LC50 values determined over 2 yr. Compared to baseline toxicities, acetamiprid and bifenthrin were found to be significantly less toxic to H. vitripennis. The LC50 values of these two compounds increased sevenfold and 152-fold, respectively. Tests with the neonicotinoids revealed a trend of decreasing susceptibility levels within each season followed by reversion back to early season LC50 estimates in the following year. In addition, data showed seasonal and site variation in susceptibility to imidacloprid, possibly due to differential applications in nearby fields.

Effects of Temperatures on Immature Development and Survival of the Invasive Stink Bug (Hemiptera: Pentatomidae).

Bagrada hilaris (Burmeister) (Hemiptera: Pentatomidae) is a non-native stink bug that feeds primarily on cole crops and wild mustards. Its invasion into desert agriculture in California and Arizona presents a conundrum between rapid pest development at warm temperatures and severe damage to cool season crops. In this study, the development and survival of B. hilaris were determined at nine constant temperatures (ranging from 20-42°C) when reared on organically grown broccoli florets. Egg hatching was greatly delayed at 20°C, and first instar nymphs did not survive at this temperature. No eggs hatched at 42°C. The highest survival rates (70.0-86.7%) of B. hilaris were observed at temperatures ranging from 24 to 35°C. The total developmental rate of B. hilaris from egg to adult increased from 0.027 to 0.066/d from 24 to 35°C, and then slightly dropped to 0.064/d at 39°C. Based on the linear model, B. hilaris requires 285.4 degree-days to complete its development. The Briere 1 model predicted the lower and upper temperature thresholds as 16.7 and 42.7°C, respectively. The optimal temperature for development (TOpt) was estimated as 36°C. According to the results, B. hilaris is well adapted to warm conditions, and temperatures of 33-39°C are well suited for B. hilaris development. Information from this study helps explain the rapid range expansion of B. hilaris across the southern United States and will be instrumental in predicting future expansion across the rest of the country and in other parts of the world. The relationship between thermal thresholds and invasion dynamics of this pest are discussed.

Allantoin Crystal Formation in Bagrada hilaris (Burmeister) (Heteroptera: Pentatomidae) Females.

Bagrada hilaris is a polyphagous herbivore reported as an invasive pest in the United States. During the course of dissecting Burmeister hilaris unique crystals were observed in both the midgut and oviducts. Crystals were identified using X-ray diffraction techniques. Both acicular (i.e., needle-like, slender, and/or tapered) and cubic (i.e., cube shaped) crystals were observed in six of 75 individuals examined (8.0%). The crystals were mainly observed in females (6.7%), followed by males (1.3%) with no crystals observed in the minimal number of nymphs examined (0%). Crystals of both types were detected in the midgut and lateral oviducts of the females and midgut in males. The acicular crystals often appeared as distinct bundles when present in the midgut and oviducts. Crystals varied in size with the acicular crystals ranging from 0.12 mm to 0.5 mm in length although the cubic crystals ranged in length from 0.25 mm to over 1.0 mm with widths of ∼0.25 mm. The cubic crystals were identified as allantoin although the acicular crystals were most likely dl-allantoin in combination with halite. While allantoin in a soluble form is often found in insect tissues and excreta; being present as a crystal, especially in such a large form, is curious and raises some interesting questions. More research is warranted to further understand mechanisms associated with such crystal formation in B. hilaris and can lead to a better understanding of the excretory process in this species and the role allantoin plays in the elimination of excess nitrogen.

Mutual interference between adult females of Galendromus flumenis (Acari: Phytoseiidae) feeding on eggs of Banks grass mite decreases predation efficiency and increases emigration rate.

The Banks grass mite, Oligonychus pratensis (Banks) (Acari: Tetranychidae) causes significant damage to dates in California (USA), if not controlled. Studies are underway to develop biological control strategies against this pest in dates using the predatory mite Galendromus flumenis (Chant) (Acari: Phytoseiidae). In California date gardens, this predator is found in low numbers that are insufficient for the economic suppression of Banks grass mites, and our research aims to understand why it fails to keep up with prey densities. The hypothesis that prey density and predator interference interactively determine the predation efficiency of G. flumenis was tested. In addition, the effect of arena size and prey and predator density manipulations on the emigration rate of the predator was investigated. Our results indicate that the per capita predation rate of G. flumenis decreases steeply with increasing predator density due to mutual interference. Analysis of emigration data considering the arena size and predator numbers showed that the emigration rate of G. flumenis was higher from small arenas, and increased with increasing predator numbers. When emigration data were analyzed using prey and predator densities as independent variables, only the effect of predator density was significant, suggesting that higher predator density increases the emigration rate of G. flumenis. These results contribute to our understanding of the predator-prey interactions, and help in designing strategies for more efficient augmentative releases of G. flumenis.

Biology, Ecology, and Management of an Invasive Stink Bug, Bagrada hilaris, in North America.

The painted bug, Bagrada hilaris, native to eastern and southern Africa and Asia, was detected in California in 2008, and it has spread rapidly throughout several southwestern US states. A polyphagous insect, it is particularly damaging to the billion dollar cole crop industry. B. hilaris frequently causes damage when it migrates to newly planted crops from weedy hosts. Feeding produces circular or star-shaped chlorotic lesions that become necrotic, and infested plants may be distorted. Currently, no reliable sampling methods for B. hilaris exist, nor are there effective natural enemies in the United States. Therefore, management has relied on multiple applications of insecticides and cultural practices such as removal of weedy hosts, destruction of crop residues, timing of planting, and use of transplants. Several pyrethroid and neonicotinoid insecticides are most effective for controlling the insect. Reliable sampling methods and further development of integrated pest management strategies to manage this invasive pest are urgently needed as its range continues to expand.

Evaluation of Bunch Protectors for Preventing Insect Infestation and Preserving Yield and Fruit Quality of Dates, Phoenix dactylifera L.

In experiments comparing conventional date paper wraps with polyester mesh bags, date bunches enclosed in polyester mesh bags had lower insect infestations than dates covered by paper wraps. Carob moth, Ectomyelois ceratoniae (Zeller), infestations of marketable fruit were significantly lower for mesh bags (0.6-3.1%) compared with paper wraps (8.5-15.5%). Other fruit pests [raisin moth, Cadra figulilella (Gregson), and beetles in the family Nitidulidae] were less common than carob moth, and infestation by these insects was consistently lower in fruit protected by mesh bags. Date bunches in mesh bag treatments had a 21-46% net increase in marketable date fruit owing to the fact that the bags prevented marketable dates from falling to the garden floor. The number of abscised kimri fruit was higher in the mesh bag treatment than the paper wrap treatment, yet there were no differences in the incidences of other fruit maladies (black nose, fruit with fungi, shriveled fruit, abscised khalal fruit, infertile fruit, and nonripe fruit). Bunch sanitation, used just prior to bagging and wrapping dates, successfully removed abscised kimri fruit from bunches, which resulted in a significantly lower number of cull dates from one garden, but this response was not present at a second garden. These studies show that mesh bags should be included in an integrated pest management program on dates.

Susceptibility of Bagrada hilaris (Hemiptera: Pentatomidae) to Insecticides in Laboratory and Greenhouse Bioassays.

Field-collected nymphs and adults of Bagrada hilaris (Burmeister) (Hemiptera: Penatatomidae) from three locations were evaluated for susceptibility to insecticides representing 10 classes of insecticide chemistry. Although relative susceptibilities differed between leaf-spray and leaf-dip Petri dish bioassays, consistently low LC50 values were determined for chlorpyrifos, bifenthrin, and lambda-cyhalothrin. Fenpropathrin and methomyl had intermediate values. Susceptibility to dinotefuran varied depending on the bioassay, possibly owing to leaf substrates used in the two bioassays. In soil systemic bioassays, the LC50 value of dinotefuran was significantly greater than that of two other neonicotinoids, imidacloprid and thiamethoxam, and the anthranilic diamide, cyantraniliprole. Mortality and feeding damage of B. hilaris and plant growth on insecticide-treated plants in greenhouse trials were consistent with the laboratory bioassays; the best results were seen with bifenthrin, methomyl, and chlorpyrifos. Mortality to the neonicotinoids was not evident; however, feeding damage and plant growth responses on dinotefuran-treated plants damage were similar to the noninfested control. This highlights the apparent antifeedant properties of dinotefuran that may have prevented adults from injuring broccoli plants after exposure to foliar spray residues. Data presented serve as baseline susceptibilities that can be used to monitor for resistance development in field populations of B. hilaris.

O antigen modulates insect vector acquisition of the bacterial plant pathogen Xylella fastidiosa.

Hemipteran insect vectors transmit the majority of plant pathogens. Acquisition of pathogenic bacteria by these piercing/sucking insects requires intimate associations between the bacterial cells and insect surfaces. Lipopolysaccharide (LPS) is the predominant macromolecule displayed on the cell surface of Gram-negative bacteria and thus mediates bacterial interactions with the environment and potential hosts. We hypothesized that bacterial cell surface properties mediated by LPS would be important in modulating vector-pathogen interactions required for acquisition of the bacterial plant pathogen Xylella fastidiosa, the causative agent of Pierce's disease of grapevines. Utilizing a mutant that produces truncated O antigen (the terminal portion of the LPS molecule), we present results that link this LPS structural alteration to a significant decrease in the attachment of X. fastidiosa to blue-green sharpshooter foreguts. Scanning electron microscopy confirmed that this defect in initial attachment compromised subsequent biofilm formation within vector foreguts, thus impairing pathogen acquisition. We also establish a relationship between O antigen truncation and significant changes in the physiochemical properties of the cell, which in turn affect the dynamics of X. fastidiosa adhesion to the vector foregut. Lastly, we couple measurements of the physiochemical properties of the cell with hydrodynamic fluid shear rates to produce a Comsol model that predicts primary areas of bacterial colonization within blue-green sharpshooter foreguts, and we present experimental data that support the model. These results demonstrate that, in addition to reported protein adhesin-ligand interactions, O antigen is crucial for vector-pathogen interactions, specifically in the acquisition of this destructive agricultural pathogen.

Relationship between temperature and development of Galendromus flumenis (Acari: Phytoseiidae), a predator of Banks grass mite (Acari: Tetranychidae).

The Banks grass mite, Oligonychus pratensis (Banks) (Acari: Tetranychidae), is a serious pest of grains, grasses and dates. In order to develop and optimize biological control strategies against the Banks grass mite, the survival and development of the predator, Galendromus flumenis (Chant) (Acari: Phytoseiidae), at eleven constant temperatures between 12 and 44°C were determined. The survival rates of G. flumenis (67.4-89.5 %) were highest between 26 and 38°C although it developed successfully from egg to adult at temperatures ranging from 18 to 42°C. The lower temperature threshold (T 0 ) and thermal constant (K) for total immature development were 13.3°C and 145.3 degree-days, respectively. The upper temperature threshold was 44.3°C, and the optimal temperature for development was calculated to be 37.5°C. These results indicate that G. flumenis is better adapted to high temperatures than most predators in the Phytoseiidae. In addition, the thermal requirements for total development of G. flumenis was found to be very close to those of O. pratensis which indicates that there should be synchrony between the occurrence of the prey and the predator. Therefore, the lack of predation observed in the field is related to other factors, such as the developmental time between O. pratensis and G. flumenis, or the inability of the predator to establish at the same time, and in the same location, as the prey.