Showing papers by "Jocelyn G. Millar published in 1993"

Host species preference and larval performance in the wood-boring beetlePhoracantha semipunctata F.

Abstract: Adults of the wood-boring beetlePhoracantha semipunctata F. showed variability in their attractiveness to five varieties ofEucalyptus when presented with an array of logs in a natural setting. Logs of two host varieties (E. camaldulensis Dehnhardt and the hybridE. trabutii) attracted two to three times more adult beetles than did logs of other host species (E. cladocalyx F.,E. grandis Hill ex Maiden andE. tereticornis Small). In the field, high oviposition rates byP. semipunctata adults resulted in severe competition among larvae. Larval survivorship was low in field logs ofE. trabutii and high inE. cladocalyx logs, although these hosts were the most and least attractive to the adult beetles, respectively. However, when logs were hand infested at low larval densities, survivorship ofP. semipunctata larvae was highest in logs of bothE. camaldulensis andE. trabutii. These findings suggest that adult beetles in the field were most attracted to those logs ofEucalyptus species that represented the highest quality hosts for their progeny under conditions of reduced larval competition.

Phoracantha semipunctata (Coleoptera: Cerambycidae), a Serious Pest of Eucalyptus in California: Biology and Laboratory-Rearing Procedures

Abstract: Procedures are described for establishing a laboratory colony of the eucalyptus longhorned borer, Phoracantha semipunctata F., and rearing the adult beetles on a continual basis. Adult beetles reared from naturally infested Eucalyptus logs were caged and provided with oviposition substrates (folded sheets of plastic). Techniques for handling and caring for eggs and neonate larvae are discussed. Larvae were individually transferred into shallow incisions in the bark of fresh logs. Total survivorship from neonate larvae to adult was ≈35%. Our procedures yielded an average of 63 adult progeny for every adult female, with a generation time of ≈2 mo during the summer. Beetle colonies were protected from pyemotid mites by dusting rearing logs with sulfur and from ants with granular diazinon. An experiment on adult beetle diet showed that the provision of sucrose water greatly increased longevity and fecundity over a distilled water control, but increasing the concentration of sucrose >5% did not significantly improve beetle performance.

Synergism between chemical attractants and visual cues influencing oviposition of the mosquito,Culex quinquefasciatus (Diptera: Culicidae)

Abstract: Physical factors, such as the color of the oviposition substrate, have seldom been compared with chemical cues in their ability to elicit oviposition behavior in mosquitoes. The role of dyed oviposition waters in attracting ovipositingCulex quinquefasciatus was examined in laboratory experiments. Oviposition waters dyed with ink were found to be significantly attractive to ovipositingCx. quinquefasciatus when compared to distilled water controls. Experiments demonstrated that the mosquitoes were responding to the increased optical density of the dyed oviposition water rather than volatile components of the dye. Ink was also considered in combination with chemical oviposition cues. No comparative data exist on the effect of physical and chemical factors presented together on the oviposition behavior ofCx. quinquefasciatus. Waters dyed with ink acted synergistically with a five-component chemical attractant mixture (3-methylindole, indole, 4-methylphenol, 4-ethylphenol, and phenol) in inducing oviposition in a 2×2 factorial experiment.

Integrating classical biological control with plant health in the urban forest

Abstract: Classical biological control is defined as a process of identification and introduction of natural enemies of pest species for the purpose of reducing the population size of the damaging species. Introduction of a parasitic wasp and a predaceous beetle has reduced populations of the ash whitef ly by 10,00-fold in landscape trees in California. It is hoped that similar introductions of parasitic wasps to control the eucalyptus longhorned borer will be successful in reducing tree mortality. However, choosing the proper species of Eucalyptus for site conditions, proper water management to maintain optimum tree vigor, and proper tree maintenance will reduce the risk of attack by this borer. Plant health care is critical to enhance tree resistance and limit tree susceptibility. The combination of maintaining vigorous tree growth and limiting the number of insect pests in the environment through the action of natural enemies provides a long-term approach to tree protection. Urban forests are unique environments. They are almost entirely artificial and often contain mixes of both endemic and exotic species with high degrees of spatial and species diversity. The understory of the urban forest may be barren as in the case of a parking lot, composed of a single species at a single height as in a turf landscape, or it may be highly varied in height and rich in diversity as in many backyards. Interspersed among the plants, often at regular spacings, are roads and buildings. In addition, plants are often placed at regular distributions within small areas of the landscape (e.g., street trees of one species within a neighborhood), but in irregular patches when observed from the perspective of the entire landscape ecosystem (e.g. many neighborhoods with different street tree species across a large urban area). There is much more public contact with urban forests than commercial or even recreational forests. Consequently, public perception of insect and disease problems in urban trees is often greater and the thresholds for injury are often lower than they are in other types of forests. Urban forests may also receive more water and nutrients, as well as other forms of maintenance than other types of forests because of their monetary, aesthetic, and environmental value. Classical biological control is ideally suited for urban forests (7). DeBach (9) defined biological control as \"the action of parasites, predators, and pathogens in maintaining another organism's density at a lower average than would occur in their absence.\" Biological control by predators, parasites, and pathogens is only one of the types of natural control that exist to lower pest densities, but unlike other control factors such as temperature or humidity, natural enemies frequently are responsive to changes in pest numbers. In addition, predators and parasites have the advantage of mobility, they search for their pest insect hosts and feed or lay eggs on them as they are found. When plant-feeding insects are introduced into new areas without their natural enemies, populations often increase to damaging levels. Introduction of natural enemies reestablishes the relationship between the biological control agents and the herbivore that is used for food. Consequently, the pest populations are often dramatically reduced. The process of introducing exotic natural enemies to regulate populations of pest insects is often referred to as classical biological control. Many of the plant species used in urban forests, particularly in California, are introduced from other areas. Unfortunately, insects that feed on these trees are often also introduced into the area without their natural enemies resulting in aesthetic and economic damage. The use of insecticides is not always the best control strategy because of high levels of public exposure, potential or perceived risk, reduced effectiveness or resistance, frequent need for repeated applications, limited availability of materials, and high costs for effective coverage of large mature trees. However, identification, introduction, and establishment of natural enemies can provide self-sustaining and permanent regulation of pest populations for a 126 Paine et al: Biological Control of Insects relatively low initial cost. Biological control is both compatible and complementary to good tree care practices. Many insect pest problems can be reduced by maintaining vigorously growing trees. Healthy and vigorous trees may be more resistant to insect colonization or may be able to compensate for insect feeding and not suffer as much reduced growth as trees in poor health. However, when pest populations are at very high levels, even well maintained trees can be at risk of damage or death. Biological control acts as an important population regulating factor to limit pest numbers. Establishment of large numbers of healthy trees in urban forests through proper tree selection and maintenance practices in combination with high levels of pest mortality caused by the natural enemies can reduce the insect problems below the damage thresholds with minimal environmental disturbance. The relationship between plant health care and biological control to limit insect problems can be demonstrated in two systems in California. In the first example, the role of an introduced parasite and a predator may be more important for reducing the pest populations. In the second example, tree selection and care may be essential elements critical to the overall success of a biological control-based management program.

Identification and synthesis of a kairomone inducing oviposition by parasitoidAphytis melinus from California red scale covers

Abstract: The parasitoid waspAphytis melinus uses a kairomone from the cover of its scale host, California red scale (Aonidiella aurantii), as an oviposition stimulant. The kairomone was isolated from extracts of scale covers, and identified asO-caffeoyltyrosine by a combination of spectroscopic methods. The kairomone was synthesized, and the synthetic compound was determined to be as active as the chemical isolated from scale covers.

A caffeic acid ester mediates host recognition by a parasitic wasp

Abstract: Kairomones are semiochemicals that benefit the receiver but are detrimental to the emitter [1]. One important class of kairomones are the semiochemicals utilized by parasitic Hymenoptera to identify their hosts [2]. For example, Luck and Uygun [3] reported that the parasitoid, Aphytis melinus DeBach (Hymenoptera: Aphelinidae), utilized wateror ethanol-soluble chemicals from covers of the California red scale, Aonidiella aurantii (Maskell) (Homoptera: Diaspididae) and other scale species as oviposition-stimulating kairomones, but no compounds were identified. Here, we show (1) that a previously unknown ester of caffeic acid and tyrosine, O-caffeoyltyrosine, is a major component of the kairomone from California red scale, (2) that A. melinus responds quantitatively to variation in O-caffeoyltyrosine concentration, and (3) that the dose eliciting peak activity by the wasp corresponds with the amount observed in scale covers when scales are most suitable for parasitization by A. melinus. Bioassays were developed based upon the characteristic \"drumming and turning\" behavior of wasps as they investigate scale covers [3] and the tendency of adult females to probe attractive disks with their ovipositors. Bioassays were carried out using measured quantities of extracts and test chemicals applied to filter-paper disks 2 mm in diameter. Treated disks plus a solvent-only control disk were placed in a Petri dish, and the solvent was allowed to evaporate. A female wasp, reared on oleander scale, Aspidiotus nerii Bouch6 [3], was placed in the dish and observed under a dissecting microscope (6 x ) for 10 min. The number of drums and turns and the number of oviposition probes made by each wasp were recorded. Covers of virgin, third-instar scale, the stage most attractive to A. melinus [4-6], were collected by aspiration and placed in 20-ml vials filled with methanol/water (3:1). The vials were placed in an ultrasonic cleaning bath (34 °C) and sonicated for 2 h. The extract was vacuum-filtered and washed with additional methanol/water. Particulates were removed by centrifugation (10 000 g for 20 min). The supernatant was partit ioned three times against chloroform/hexane (3:1) or pure hexane. These nonpolar fractions were biologically inactive. The biologically active aqueous phase was concentrated by rotary evaporation (55°C) to bring the extract to a standardized concentration of i scale-cover equivalent per ~1. The aqueous fraction was acidified with 0.1 ml of 0.075 % trifluoroacetic acid (TFA) in HPLC-grade water and applied to a Cls solid-phase extraction (SPE) column (300 mg, Fisher Scientific) previously equilibrated with 0.075% TFA. The SPE column was eluted by suction using mixtures of 0.075% TFA and acetonitrile starting with 0 % acetonitrile and increasing to 50 % acetonitrile in 5 % increments. Fractions eluted with 20 and 25 % acetonitrile were biologically active. These fractions were combined and concentrated until material started to precipitate. Enough acetonitrile was added to keep all material in solution. The active fractions were purified further by preparative reverse-phase HPLC using a C18 column (Alltech \"Econosil,\" 10 ~tm particle size, 250x10 mm ID) with a Beckman \"Ultrasphere ODS\" guard column (45x4.6 mm ID, 5 ~m particle size) monitoring the effluent at 325 nm. The kairomone, which eluted isocratically in 11 min with 25 % acetonitrile in 0.075% aqueous TFA at 5 ml/min, was collected and concentrated to 1 scale-cover equivalent per ~1. Size exclusion chromatography on polyacrylamide gels (Bio-Gel P4, Bio-Rad Laboratories) showed the molecular weight of the kairomone to be less than 500 Da. Hydrolysis under strongly acidic or weakly basic conditions showed that tyrosine was the only amino acid present in the hydrolysate, but the hydrolysate was biologically inactive. Proton NMR in deuterated methanol, UV spectrometry and mass spectrometry using fast-atom bombardment (FAB) and desorption ionization methods suggested that the kairomone was O-caffeoyltyrosine (Fig. 1). This structure was confirmed by synthesis from caffeic acid and L-tyrosine (Sigma Chemical Co.), and the synthetic material was as active biologically as the natural product (Millar and Hare, in prep.). Although numerous caffeic acid esters occur in plants [7], O-caffeoyltyrosine has not been reported previously. Ncaffeoyltyrosine, the amide of caffeic acid and tyrosine, however, is found in some varieties of coffee beans [8]. Our second objective was to determine how A. melinus responded behaviorally

Establishment and Rearing of Anarsia lineatella (Lepidoptera: Gelechiidae) on a Meridic Diet

Abstract: An improved method for rearing peach twig borer, Anarsia lineatella Zeller, on a lima bean-based diet is described. Two lines of A. lineatella were established successfully using this method. Both lines were comparable with field-collected insects in developmental rate, adult longevity, and pupal weights. Fecundity of one of the lines exceeded published values for wild females after five generations on artificial diet, but fecundity of the other line was considerably reduced, probably as a result of inbreeding depression. Direct observations indicated that moisture on the diet surface was an important factor in the establishment of neonates, with 90% survival achieved under optimum conditions. Crowding was also a mortality factor. At 27 ± 2oC, development from neonate to adult required ≈27.5 d. Virgin adult activity patterns were bimodal, with both sexes being active after onset of scotophase, and with males seeking mates and mating during the last 2 h of the scotophase. Using this method we were able to rear A. lineatella with greater success and with less effort than had been reported previously.