Short-range dispersal of recently emerged males and females of Bactrocera tryoni (Froggatt) (Diptera: Tephritidae) monitored by sticky sphere traps baited with protein and Lynfield traps baited with cue-lure

Dispersal of immature male and female Queensland fruit fly, Bactrocera tryoni (Froggatt) (Diptera: Tephritidae), was assessed over a period of 1 week from a single release point on three separate occasions using an array of Lynfield traps baited with cue-lure and odouriferous yellow or black sticky spheres baited with food lure (protein autolysate). Lynfield traps recaptured males; yellow or black spheres recaptured both sexes in approximately equal proportions, although at a much lower rate. As a percentage of the recapture rate for males by Lynfield traps, the mean recapture rate for yellow spheres ranged from 1.0% to 7.5% for males and 0.7% to 4.0% for females, whereas the recapture rates for black spheres ranged from 0.4% to 3.6% and 0.6% to 1.8%, respectively. The rate of recapture of sterile male flies was greater than that of unsterilised flies; this may have been due to a faster maturation rate in sterile males or because a greater proportion of them remained within the trap array rather than dispersing. There was no significant trend in recapture rate with distance from the release point to the edge of the array (88 m), except in the case of females on sticky traps where no trend was detected between 19 and 88 m. These results lend support to assumptions made about the distribution of males and females with respect to the minimum breeding density of fruit fly propagules invading a fly-free zone, and the method chosen to distribute sterile B. tryoni for the sterile insect technique.7 page(s

Modification of host finding and oviposition behaviour of the citrus leafminer, Phyllocnistis citrella, by horticultural mineral oil

Horticultural mineral oil (HMO) deposits affect postlanding searching behaviour and contact evaluation of oviposition substrates by females of the citrus leafminer, Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae). Both unsprayed and sprayed lemon trees were equally capable of arresting randomly moving female moths by eliciting kinetic responses. The presence of HMO deposits did not affect the approach of female moths to flushes (shoots with immature leaves suitable as oviposition sites), and female moths were equally likely to land on sprayed and unsprayed immature flushes provided mature leaves were not sprayed. The presence of HMO on both the mature leaves and the flushes caused shorter residence and search times within trees and also resulted in fewer immature leaves visited. The HMO-sprayed flushes were also more likely to be rejected for oviposition after contact. Nevertheless, eggs were sometimes deposited on sprayed flushes between residues of the oil droplets

Seasonal dynamics, dispersion, sequential sampling plans and treatment thresholds for the citrus leafminer, Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae), in a mature lemon block in coastal New South Wales, Australia

Abstract Studies of citrus leafminer in a coastal orchard in NSW, Australia indicated that an increase in abundance to about one mine per flush was followed during the midseason flush by a rapid increase in population that was related to an increase in the percentage of leaves infested within flushes and the number of mines per leaf. The fits of frequency distributions and Iwao's patchiness regression indicated that populations were highly contagious initially, and as the exponent k of the negative binomial distribution increased with increasing population density, the distribution approached random. Concurrently, the coefficient of variation of mines per flush (which was strongly related to the proportion of un-infested flushes) decreased to about unity as the proportion of un-infested flushes reached zero and fell further as the number of mines per flush increased. Both numerative and binomial sequential sampling plans were developed using a decision threshold based on 1.2 mines per flush. The binomial sampling plan was based on a closely fitting model of the functional relationship between mean density and proportion of infested flushes. Functional relationships using the parameters determined from Iwao's patchiness regression and Taylor's power law were equally satisfactory, and one based on the negative binomial model also fitted well, but the Poisson model did not. The three best fitting models indicated that a decision threshold of 1.2 mines per flush was equivalent to 50% of flushes infested. From a practical point of view, the transition from 25% infestation of flushes through 50% is so rapid that it may be prudent to take action when the 25% level is reached; otherwise, the 50% may be passed before the crop is checked again. For valuable nursery stock should infestation be detected in spring, it may be advisable to apply prophylactic treatment as the midseason flush starts

Optimum sample size and spatial dispersion of red scale, Aonidiella aurantii on an orange orchard in Australia

Two-stage sampling and geostatistical teechniques for cost-effective and precise sampling were examined using red scale data that were collected from a commercial orange orchard in Kulnura, Australia in mid-summer, 2004 and 2005. The distribution pattern of red scale on a twig and a fruit well followed the negative binomial, and the degree of aggregation was higher on a fruit than a twig. The analysis of variance and two-stage sampling were used to obtain the suitable sample unit (a leaf, a twig containing two leaves and a 15cm. branch and a fruit in this study) and optimum sample size. A fruit was the most suitable than any other sample units, and a twig was better than a leaf. The optimum sample size for twigs and fruits per tree was 4 twigs (2 leaves and 15cm. branch) and 4 fruits (2 directions), respectively. There was a non-linear relationship between 2 years for the density on 40 fruits of the same tree, because the Spearman rank correlation coefficient (0.84) was much higher than the Pearson's (0.29). The autocorrelation analysis showed that omnidirectional 10cm. apart from each sampled tree was needed to obtain the independent data

To push, pull or push-pull? : a behavioural strategy for protecting small tomato plots from tephritid fruit flies

The protective effects of protein bait spays and oil emulsion sprays against fruit flies (Bactrocera tryoni (Froggatt)) were compared in an experiment with a simple split plot design using tomatoes (Solanum lycopersicum L.) of two varieties. The sprays were then used in a second experimental design based on the 'push-pull' technique that would be relevant to home gardens and village horticulture. Each replicate of each treatment in each of two experiments was represented by a small group of fruiting tomato plants (that represented a small crop in a real garden to be protected by the technique). These were surrounded by other tomato plants (that were stripped of fruit) or by weeds (that represented other food plants or weeds in a real garden). Each category of plant was given either no treatment or imparted with a 'push' or a 'pull' stimulus with a bait spray or an oil spray to act on foraging fruit flies. A simultaneous comparison of all nine possible combinations of these treatments revealed that oil spray applied only to the central plants or to both the central and surrounding plants were two of the three most effective treatments for preventing fruit damage by fruit flies. Bait spray on its own was not always effective and, when paired with oil spray, was no more successful than no treatment paired with oil spray. Another experiment, restricted to combinations of oil spray and no spray, confirmed that plants were best protected by direct application of oil spray and that spraying surrounding plants as well was no better and that spraying surrounding plants alone was worse. These results were related to the small size of each 'crop' and known aspects of fruit fly behaviour

Integrated pest management of two-spotted mite Tetranychus urticae on greenhouse roses using petroleum spray oil and the predatory mite Phytoseiulus persimilis

From 1995 to 1999, four experiments were conducted on greenhouse roses to assess the effectiveness of the nC24 petroleum spray oil (PSO), D-C-Tron Plus, against two-spotted mite, Tetranychus urticae Koch (Acarina: Tetranychidae), and to determine how the oil could be most efficiently and effectively used in combination with the predatory mite Phytoseiulus persimilis Athias-Henriot (Acarina: Phytoseiidae) in an integrated pest management program. The results showed that 0.5% PSO applied fortnightly to roses gave excellent protection from T urticae infestation when the mite population was not already established. However, PSO applied after roses were infested with T. urticae above the economic threshold only stabilised populations without reducing them below that threshold. Populations of P. persimilis in the upper and lower canopies were unchanged after two sprays of PSO at 7-day intervals, and application of PSO to the upper canopy was as effective in controlling T. urticae in the presence of P persimilis as spraying the entire plant. Combining PSO with P. persimilis gave better control of T. urticae than using P. persimilis alone. The most cost-effective use of PSO in the presence of P. persimilis is, therefore, to apply spray only to the upper canopy. This will not affect control of powdery mildew with PSO. Comparison of a control program for T urticae based on the monitored use of synthetic miticides with that based on calendar application of PSO revealed that both gave equally effective control. The benefits of combining PSO and P. persimilis in an integrated pest management program for T. urticae on roses over a program based on synthetic fungicides are discussed

Ant-coccid mutualism in citrus canopies and its effect on natural enemies of red scale, Aonidiella aurantii (Maskell) (Hemiptera: Diaspididae)

Mutualistic relationships between honeydew-producing insects and ants have been widely recognized for several decades. Iridomyrmex rufoniger (Lowne) is the commonest ant species associated with black scale, Saissetia oleae (Olivier), in the citrus orchards of the mid latitudes of coastal New South Wales. Citrus trees with high densities of both red and black scale and high ant activity were identified and the results of excluding ants from half of those trees (using a polybutene band on each trunk) were compared with the results of not excluding ants from the other half. Trees with a low incidence of black scale and ants were also studied. Exclusion of ants from trees was soon followed by collapse of black scale populations because most individuals were asphyxiated by their own honeydew. Also, parasitism of the red scale by Encarsia perniciosi (Tower) and Encarsia citrina Craw was significantly higher than in the control trees over the following year, as was the predation rate on red scale due to three coccinellid predators, Halmus chalybeus (Boisduval), Rhyzobius hirtellus Crotch and Rhyzobius lophanthae (Blaisdell). In contrast, another coccinellid, Orcus australasiae (Boisduval), and a noctuid moth larva, Mataeomera dubia Butler, were seen in low numbers on banded (ant exclusion) trees, probably because of the low availability of their black scale prey, but were significantly higher on control trees apparently because of their invulnerability to ants

Mortality on fruit in citrus orchards caused by naturally occurring enemies of red scale Aonidiella aurantii : relation to spatial distribution of patch density and season

The efficacy of biological control agents depends on the amount of mortality they impose on pests in the field. Quantifying their impact on a pest is critical for guiding decision-making in its management. Here, we quantify the relation of population levels of natural unmanipulated populations of a pest to mortality rates imposed by naturally occurring enemies. Mortality beyond first instar caused by natural enemies of Aonidiella aurantii (Maskell) (Hemiptera: Diaspididae) on fruit was studied in four unsprayed citrus orchards in a warm temperate coastal environment in New South Wales, Australia, over approximately three pest generations in the course of a year. The percentage of hosts on fruit suffering parasitism and predation was usually independent of host density. There was no consistent evidence that one parasitoid influenced another, nor that parasitism and predation rates were related. At the orchard scale, it was apparent that parasitism and predation over a time series were related to current or previous host numbers and could become high enough in relation to fecundity rates to cause pest numbers to decline. Temporal feedback to density could be causing the pest populations to fluctuate between limits at economically sustainable levels given additional mortality of the first instars due to expected rates of dispersal and subsequent pre- and post-settlement failures

Contrasting effects of two pesticides on motile arthropods in a citrus orchard canopy

Multidimensional Scaling (MDS) was used to assess the effects of two different pesticides on non-target motile foliage-dwelling arthropod communities that could be sampled by a portable suction system in a citrus orchard in the coastal region of New South Wales, Australia. Sprays of nC24 horticultural mineral oil (HMO) and an organophosphorous insecticide (methidathion) were applied at the level of whole blocks in the manner pertinent to successful control of (sessile) scale insects. The MDS model produced ordination figures for several sampling times before and after spray applications that showed that any effect of HMO was undetectable but methidathion was disruptive to the sampled motile foliage arthropod community for at least 18 weeks. This was confirmed with ANOVA of arthropod abundance. Thus if sprays were required several times per year it would be desirable to use HMOs to preserve biodiversity

The influence of sublethal deposits of agricultural mineral oil on the functional and numerical responses of Phytoseiulus persimilis (Acari : Phytoseiidae) to its prey, Tetranychus urticae (Acari : Tetranychidae)

Occasional pesticide application in integrated pest management to at least part of a crop requires that any biological control agents must re-invade previously sprayed areas in order that resurgent pests can be constrained. The ability of the phytoseiid predatory mite Phytoseiulus persimilis to feed on adult two-spotted spider mite (TSSM) Tetranychus urticae on excised leaf discs in both control conditions and in a treatment with a sub lethal residue of agricultural mineral oil (AMO) was assessed. The predator exhibited a Type II functional response with the asymptote significantly higher in the AMO conditions due to the fact that the prey grew slower and reached a smaller size in this treatment. In terms of prey volume eaten, the satiation level of the predator was unchanged by the AMO deposits. The numbers of eggs produced by adult P. persimilis females at densities of 4, 8 and 16 TSSM adult females/disc in the control were significantly higher than those in the AMO treatment, but were similar for the higher density levels, 32 and 64 prey per disc. Thus the functional response in terms of volume of prey eaten explained the numerical response in terms of predator eggs produced. The presence of AMO deposits when the prey were at high density had no effect on predator efficiency (volume eaten) but resulted in a lower intake than that in control conditions when there was a greater distance between prey