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Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae), is an invasive citrus pest in southern California, which secretes honeydew and has the potential to spread a lethal bacterial disease, huanglongbing, of citrus. In urban citrus, Argentine ant, Linepithema humile (Mayr) (Hymenoptera: Formicidae), also an invasive pest, tends honeydew-producing hemipterans. We used field data to determine whether the mutualistic relationship between L. humile and six established species of honeydew producers may hinder or favor the establishment of D. citri and its biological control with Tamarixia radiata (Waterston) (Hymenoptera: Eulophidae) in citrus via competition or mutualism for ants, respectively. In the field, L. humile and D. citri are engaged in a mutualistic relationship. Ants harvest solid honeydew secreted by psyllid nymphs and tended more than 55% of observed D. citri colonies. Linepithema humile displayed a preference hierarchy when tending honeydew producers infesting citrus. It responded equally or less intensively to D. citri than to other honeydew-producing species. Consequently, the mutualism between L. humile and D. citri was affected by the presence of other honeydew-producing species, and the percentage of D. citri colonies tended by L. humile. The number of ants per D. citri colony also decreased as the number of other honeydew producers increased. Diaphorina citri density was also affected by the presence of other honeydew producers. Both colony size and the number of D. citri nymphs counted per tree decreased as the number of other honeydew producers increased. Our results indicate that competition between honeydew producers for the mutualist ant L. humile may hinder the establishment of D. citri by possibly facilitating increased biological control.

Bean thrips, Caliothrips fasciatus, is native to western North America. Once considered a pest of several crops in its native area, its pest status has waned over recent decades. However, due to its habit of aggregating in the navel of navel oranges, bean thrips remains economically important because some countries importing oranges from California have designated it a quarantine pest. Despite continued propagule pressure, bean thrips has never established outside North America. We examined genetic variation in mitochondrial DNA among Californian populations of C. fasciatus and found that potentially two cryptic species are present (supported by Kimura 2-P distances): a common widespread form B and a rarer form A with a very limited distribution. Form B showed strong phylogeographic structure, with many haplotypes having a limited geographic distribution. Inter-population crossing experiments between three geographically isolated populations of form B resulted in the production of some female offspring, indicating a degree of compatibility between these populations of this haplodiploid species. However, substantial outbreeding depression was also detected. A low frequency of offspring production by hetero-population pairs was evidence of pre-mating isolation, while post-mating isolation was also evident in the elevated mortality of fertilized eggs in successful hetero-population crosses. One surprising finding was the total lack of offspring production by virgin females when isolated individually. However, virgin females did produce sons in the presence of other virgin females. A test for the presence of Wolbachia showed that form B was not infected, but that some populations of the rarer form A were.

The sex pheromone of Stenoma catenifer was evaluated in commercial avocado orchards in Guatemala to determine operational parameters, such as optimal lure type, trap height, trap density and estimates of the distances that male moths fly. Of four pheromone dispensers tested, gray and white rubber septa were of equal efficacy, whereas 1-ml low-density polyethylene vials and 2×3-cm polyethylene ziplock bags were least efficacious. The height at which wing traps were hung did not significantly affect the number of adult male S. catenifer captured. For monitoring S. catenifer, these data suggest that the pheromone should be dispensed from gray rubber septa in wing traps hung inside the tree canopy at 1.75 m, a height convenient for trap placement and monitoring. Mark-recapture studies of male S. catenifer indicated that, on average, males flew 67 m in one night. However, it is likely that this is an underestimate of the distance that male moths are capable of flying in a single night. Probabilistic modeling of S. catenifer capture data from different numbers of pheromone traps deployed in seven commercial avocado orchards of varying sizes and infestation levels suggested that 10-13 randomly deployed traps per orchard for a 7-day period are needed to detect at least one male S. catenifer with 90% confidence. These data provide sufficient information to develop effective protocols for using the S. catenifer pheromone to detect and monitor this pest in countries with endemic populations that are exporting fresh avocados, and for quarantine detection and incursion monitoring in countries receiving avocado imports from high risk areas.

The developmental and reproductive biology of a new avocado pest, Scirtothrips perseae Nakahara, was determined in the laboratory at five constant temperatures, 15, 20, 25, 27.5 and 30 degrees C. At 20 degrees C, S. perseae exhibited greatest larval to adult survivorship (41%), and mated females produced a greater proportion of female offspring at this temperature when compared to 15, 25, 27.5 and 30 degrees C. Average lifetime fecundity and preoviposition period was greatest at 15 degrees C at 39.6 eggs per female and 17.6 days, respectively. Jackknifed estimates of net reproduction (Ro), capacity for increase (rc), intrinsic rate of increase (rm), and finite rate of increase (lambda) were all significantly greater at 20 degrees C than corresponding values at 15, 25 and 27.5 degrees C. Population doubling time (Td) was significantly lower at 20 degrees C, indicating S. perseae populations can double 33-71% faster at this temperature in comparison to 15, 25 and 27.5 degrees C. Mean adult longevity decreased with increasing temperature, from a maximum of 52.4 days at 15 degrees C to a minimum of 2.4 days at 30 degrees C. Developmental rates increased linearly with increasing temperatures for eggs and rates were non-linear for development of first and second instar larvae, propupae, pupae, and for egg to adult development. Linear regression and fitting of the modified Logan model to developmental rate data for egg to adult development estimated that 344.8 day degrees were required above a minimum threshold of 6.9 degrees C to complete development. An upper developmental threshold was estimated at 37.6 degrees C with an optimal temperature of 30.5 degrees C for egg to adult development. Unmated females produced only male offspring confirming arrhenotoky in S. perseae.

The suitability of ten diets for the development and reproduction of Franklinothrips orizabensis Johansen, the key natural enemy of Scirtothrips perseae Nakahara, a pest of California grown avocados, was determined in the laboratory. The experimental diets evaluated were: (i) irradiated Ephestia kuehniella Zeller eggs; (ii) irradiated E. kuehniella eggs and avocado pollen; (iii) Tetranychus pacificus McGregor eggs; (iv) T. pacificus eggs and avocado pollen; (v) irradiated E. kuehniella eggs and T. pacificus eggs; (vi) irradiated E. kuehniella eggs, T. pacificus eggs and avocado pollen; (vii) Scirtothrips perseae; (viii) Heliothrips haemorrhoidalis (Bouchè); (ix) avocado pollen; and (x) a young avocado leaf. Franklinothrips orizabensis larvae were unable to develop to adulthood on diets 9 and 10. The remaining eight diets supported complete development of F. orizabensis, but only diets 1, 2, 5, 6, 7 and 8 produced fecund females. On diet 5, F. orizabensis exhibited high larval to adult survivorship (90%), mated females exhibited highest daily and lifetime fecundity, and the progeny of mated females were female biased (53%). Analysis of jackknife estimates of net reproduction (Ro), intrinsic rate of increase (rm), and finite rate of increase (lambda) were all significantly greater for F. orizabensis reared on irradiated E. kuehniella eggs and T. pacificus eggs (i.e. diet 5) than corresponding values for other diets on which female F. orizabensis were able to complete development and reproduce. Incorporation of avocado pollen into diets had an adverse effect on demographic statistics for F. orizabensis, and low quality diets resulted in male biased sex ratios for this predator.