Efficacy of Fungicides Applied for Protectant and Curative Activity Against Myrtle Rust

Myrtle rust, caused by the pathogen Austropuccinia psidii, affects species of the Myrtaceae, many of which are endemic to Australia and New Zealand. Originating from South America, A. psidii is now present in both countries, necessitating effective chemical control for disease management. Using an artificial inoculation protocol, the efficacy of eight fungicides (tebuconazole/trifloxystrobin, cyproconazole/azoxystrobin, fosetyl aluminum, triforine, triadimenol, oxycarboxin, copper, and tebuconazole) applied as curative or protectant treatments was tested on two native New Zealand species (Lophomyrtus × ralphii and Metrosideros excelsa). The impacts of rate (×2), frequency (single or double), and timing (pre- or postinfection) of fungicide application were investigated. Overall, the most effective fungicides tested across both species were those that included a demethylation inhibitor and strobilurin mix, notably tebuconazole/trifloxystrobin (Scorpio) and cyproconazole/azoxystrobin (Amistar Xtra). These fungicides significantly reduced infection of host plants relative to the water control. Timing of application significantly affected bioefficacy, with applications made 7 days before inoculation or 7 days after inoculation being generally the most effective. The rate of fungicide application was not significant for both host species, with few interaction terms showing overall significance. Key findings from this study will set the foundation for further fungicide bioefficacy research conducted to evaluate formulations and adjuvant mixtures, determine suitable application methods for enhanced retention and coverage, and derive optimum application time for effective protection of native and exotic Myrtaceae species in New Zealand.

Effect of dose and adjuvant on uptake of triclopyr and dicamba into Pinus contorta needles

Management of dense infestations of wilding Pinus contorta in New Zealand requires high doses of herbicides; 18 kg active ingredient (a.i.) ha^-1 triclopyr and 5 kg a.i. ha^-1 dicamba are used in combination with a complex mix of adjuvants (methylated seed oil, non-ionic surfactant and ammonium sulfate) and other active ingredients. From the perspective of cost and environmental impact there is a need to reduce the complexity of this tank mix and the rates of active ingredients. Using radiolabelled herbicides, this study evaluated the effect of dose and adjuvants (crop oils, non-ionic surfactants, and organosilicones) on needle injury and uptake of triclopyr and dicamba into P. contorta needles at 24 hr or 7 days after treatment (DAT). The uptake of triclopyr decreased significantly with increasing concentration (0.75%-6%) resulting in the highest uptake dose at the equivalent of 18 kg a.i. ha^-1 triclopyr at 7 DAT. When applied at 18 kg a.i. ha^-1, none of the adjuvants tested significantly increased the uptake of triclopyr (applied as Grazon^®), with ~50% uptake occurring at 7 DAT. The uptake of dicamba (applied as Kamba^® at 5 kg a.i. and 10 kg a.i. ha^-1) was significantly affected by dose and adjuvants. The uptake of dicamba applied at 5 kg a.i. ha^-1 was low at 7 DAT with no adjuvant (31%); however, use of a methylated seed oil doubled the uptake. When triclopyr and dicamba were applied together, there was no evidence that either active ingredient negatively affected uptake of the other, with triclopyr enhancing uptake of dicamba. These results show potential to reduce the amount of herbicide used for conifer control without compromising efficacy.

Swath pattern analysis from a multi-rotor unmanned aerial vehicle configured for pesticide application

BACKGROUND

Although unmanned aerial vehicles (UAVs) are increasingly used to deliver small-scale aerial pesticide applications, there remains uncertainty over their efficiency in terms of uniformity of spray deposition and their application efficiency. Consequently, a field study was designed to quantify factors influencing the uniformity of spray deposition from a multi-rotor UAV that is operated commercially in New Zealand. Two sampling systems for measuring spray deposition, a continuous horizontal string and steel plates placed on the ground were compared.

RESULTS

The spray deposit distribution characteristics and calculated lane separation values (distance between flight lines that produces a maximum coefficient of variation of 30% for spray deposits) were strongly influenced by wind speed, nozzle position, release height, ground speed and droplet size. Lane separation values ranged from 1 to > 5 m. Swath distribution parameters (spread and position of peak deposition) derived from plates were not significantly different from those derived from string. However, total deposition on strings relative to plates increased with small droplets. Reducing plate sampling intensity from 0.25 m intervals to 0.5 m and even 1.0 m had only a minor effect on estimates of swath parameter values.

CONCLUSIONS

The potential for precision spraying from UAV platforms has yet to be achieved with improvements required in hardware and software. Further, mechanistic models are needed to quantify how complex interactions among multiple operating and meteorological variables influence spray deposition. © 2019 Society of Chemical Industry.

The Effect of Formulation, Dose, and Adjuvants on Uptake of Phosphite Into Pine Foliage

The aim of this investigation was to determine the effect of dose and adjuvant on uptake of two phosphite products (Phos-A and Phos-B) into Pinus radiata needles. In experiment 1, uptake of 6 kg ha^-1 phosphite, applied as Phos-A, in 100 liters of water, together with an organosilicone superspreader (0.2%), was high (>60%). Uptake at doses greater than 6 kg ha^-1 (12, 15, 18, and 24 kg ha^-1) and applied in volumes less than 100 liters of water (75 and 50 liters) was poor (1 to 30%). Using stability tests and NMR spectroscopy in experiment 2, this appeared to be linked to a concentration dependent reaction resulting in the degradation of the organosilicone adjuvant that facilitated uptake of Phos-A. In experiment 3, uptake of phosphite applied as Phos-B, between 6 and 24 kg ha^-1 in 100 liters of water, was tested alone and with four adjuvants (an organosilicone, alcohol ethoxylate, lecithin, and esterified seed oil). Uptake of Phos-B without any adjuvant was high (>50%) across all doses, indicating the formulation was optimized for P. radiata needles. Uptake of Phos-B increased with concentration up to 72% at 24 kg ha^-1 in 100 liters of water. Symptoms of phytotoxicity were observed at rates of ≥12 kg ha^-1. This study highlighted the effect of formulation, dose, concentration, and adjuvant on the uptake of phosphite into P. radiata needles.

An aerial spot-spraying technique: a pilot study to test a method for pest eradication in urban environments

Background

Pest eradication strategies that use pesticides require application methods that have the lowest environmental and human health impact while maintaining the highest probability of success. This is highly important when eradication takes place in sensitive areas, such as urban or riparian zones. A new aerial application method, the spot-gun, was developed to provide good pesticide coverage on host species while minimising off-target exposure. This type of targeted aerial approach is useful in areas where conventional broadcast aerial spraying was historically used but was not ideal due to the quantity of pesticide hitting non-host species and going off-target. An even distribution of the active component is essential for eradication.

Findings

The spot-gun method was tested and found to provide an even distribution of dye on the adaxial and abaxial leaf surfaces as well as in the top and middle regions in both the inner and outer portions of the canopy. The form of the deposits on the leaf surface was very different from that obtained using a broadcast aerial application with a conventional spray boom.

Conclusions

The distribution results imply that the spot-gun method treatment will provide good efficacy. The implications of the different deposit pattern on efficacy are not known at this stage. This aerial spot-spray method has considerable potential as a tool for targeted aerial application of pesticides to small areas of difficult to reach canopies.

Electronic supplementary material

The online version of this article (doi:10.1186/2193-1801-3-750) contains supplementary material, which is available to authorized users.

Stem injection of a systemic insecticide to control Uraba lugens on urban Lophostemon confertus trees

BACKGROUND

Uraba lugens Walker (Lepidoptera: Nolidae) has the potential to become a serious pest of susceptible forestry and urban trees in New Zealand. Stem injection of insecticides provides a method for the control of U. lugens in public locations where foliar applications are not suitable. Field and laboratory studies were conducted in 2009 and 2010 to determine a dose response profile of U. lugens larvae to acephate injected at 0.0, 0.25, 0.50 and 1.00 g cm(-1) tree diameter measured at breast height (dbh). The concentration of the injected solution varied across years.

RESULTS

The highest mortality (85-100%) of U. lugens larvae occurred at 1.00 g acephate injected cm(-1) dbh. The lower rates (0.25 and 0.50 g acephate cm(-1) ) were more effective in 2010 than in 2009, a factor attributed to the change in volume of injected solution.

CONCLUSION

Systemic injections of acephate at rates above 0.50 g cm(-1) dbh provide a tool for the management of U. lugens in public places. It is recommended that stem injection operations for control of U. lugens larvae be timed to coincide with the emergence of first instars so that larvae are exposed to lethal insecticide doses.