Success Neo Insecticide controls diamondback moth in canola

Key Messages

In 2012 two insecticides, each representing a new mode of action, were approved for use against diamondback moth (DBM) in canola. While DBM has been difficult to control with older organophosphates and synthetic pyrethroids, spinetoram (Success™ NEO from Dow AgroSciences) and emamectin benzoate (Affirm^® from Syngenta) are highly effective and with careful management will continue to provide canola growers with cost-effective DBM control for many years.

Background

Diamondback moth (Plutella xylostella) is perhaps the most damaging insect pest of canola in Western Australia. Infestations of plague proportions do not occur every year, but when they do crop losses of up to 80% are recorded. Diamondback moth are universally recognised as having an extraordinary ability to develop resistance to new insecticides, and it is many years since organophosphates, carbamates and synthetic pyrethroids were effective against them in Australia.

Spinetoram, the active ingredient in Success NEO, is a member of the spinosyn family (IRAC Group 5). Spinosyns have formed the basis of IPM-compatible DBM control programmes in vegetable brassicas since the mid-1990s and it is through the combination of efficacy, selectivity to key beneficial insects and grower adherence to insecticide resistance management strategies (IRMSs) that the group is still effective today.

The labelled use rate for DBM in canola is 150 mL/ha, and this rate also controls the secondary canola pests heliothis (Helicoverpa spp.), cabbage white butterfly (Pieris rapae), centre grub (Hellula hydralis) and cabbage cluster caterpillar (Crocidolomia pavonana). Success NEO has no effect on aphids, weevils, slugs, Rutherglen or cluster bugs (Nyssius spp.).

Success NEO must be applied with an adjuvant to assist in the wetting of leaves and stems. Uptake™ oil is preferred but a non-ionic surfactant from a reputable manufacturer is an acceptable alternative.

Success NEO is approved for application from aircraft, with a minimum water rate of 30 L/ha, and from ground-rigs the minimum water rate is 50 L/ha. Whether applying by air or from the ground, higher water rates will always give superior coverage, especially of tall, dense crops.

Honeybees are often present in flowering canola at the same time that DBM need to be controlled. As long as Success is applied when bees are not actively foraging - early in the morning or late afternoon – they should not be adversely affected.

A maximum of two applications of Success NEO may be made per crop. A 14 day harvest withholding period (14 day WHP) should be observed.

Aims

This paper informs advisors and farmers of the recent registration of Success NEO Insecticide for control of DBM in canola. It provides a brief overview of the product and how it should be used safely, effectively and in such a way that insecticide resistance development is averted.

™ Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow.
^® Affirm is the trademark of a Syngenta group company

Method

Small-scale replicated trials were conducted by contract research organisations in Western Australia, South Australia and New South Wales. Trials spanned three different growing seasons and used protocols which varied from season to season with the result that adjuvants, water rates and candidate product use rates were not always consistent between trials.

Success NEO was applied at a range of rates from 42 mL to 150 mL/ha with either Uptake oil or a non-ionic surfactant. Affirm was applied at 300 mL/ha (5.1 g/ha emamectin benzoate) with Agral^® 0.01% v/v, Trojan^® at 30 mL/ha (45 g/ha gamma-cyhalothrin) and Fastac^® Duo at 400 mL/ha (40 g/ha alpha-cypermethrin).

Trials were assessed by counting larvae immediately before application and at intervals following. Larval counts were made using sweep nets and (in one trial) by shaking infested heads over a bucket.

Key:

DAA = days after application

Results

Trial results are summarised in the graph below.

While Trojan and Fastac gave poor control, presumably due to synthetic pyrethroid resistance in the target pest populations, Success NEO and Affirm gave a high level of control of DBM.

In no trial was DBM control complete, and this reflects the difficulty in achieving good coverage in tall, dense crops. Success NEO has a relatively flat dose response from 42 mL/ha to 150 mL/ha, but control was numerically better at the highest rates. It is important that the labelled rate (i.e. 150 mL/ha) be followed to ensure reliable efficacy and just as importantly for insecticide resistance management reasons.

In all six trials, a single insecticide application was made and, given the high degree of control achieved by Success NEO, this is likely to be the only application required commercially in any one season. There are however exceptions where more than one insecticide application may be required, e.g. when DBM populations build up early and in cases of re-infestation. While Success NEO can be applied twice to a canola crop, it is strongly urged that, should more than

^®Agral is a registered trademark of a Syngenta Group company.

^®BS1000 is the Registered Trade Mark of ICI Australia Limited.

^® Trojan is a trademark of Cheminova A/S.

^® Fastac is a trademark of BASF

one DBM spray be made, each is made with an effective product from a different mode of action group.

Because of widespread DBM resistance to organophosphates (Group 1B) and synthetic pyrethroids (Group 3A), the canola grower is limited in choice to Success (Group 5), Affirm (Group 6) and the variably effective Bt products (Group 11C).

Resistance to insecticides is conferred by heritable genes which exist naturally at very low levels in insect populations. When an insecticide from a single chemical group is used repeatedly, insects with the resistance gene for that chemical survive, their progeny inherit the gene and the population becomes increasingly resistant to that chemical group. DBM has a worldwide reputation for developing resistance to just about every insecticide that has been developed – including the widely used organophosphates and synthetic pyrethroids. These particular products have been used repeatedly for many years – either directly targeting DBM or indirectly selecting DBM when the same products are used for control of other pests such as earth mites, aphids, cutworms etc, so development of widespread high-level resistance was inevitable.    

Currently, the genes conferring resistance to spinetoram and emamectin benzoate in DBM populations in WA are at very low levels. To maintain this situation and keep Success and Affirm highly effective in controlling DBM, it is vital that neither product is used repeatedly. By rotating between these two new chemical groups, survivors which may have the resistance gene to the first-applied product will be controlled by an application of the second product which has a different mode of action.  

Another feature of these two new products is their selectivity to beneficial insects (predators and parasitoids). Unlike older products -synthetic pyrethroids in particular - which are highly effective at removing beneficial insects, Success and Affirm are relatively selective and these insects can essentially provide another mode of action against DBM, and provide free-of-charge control of survivors deep below the canopy where sprays may not penetrate.

Key:

All rates expressed as mLs of formulated product per hectare.
3-5 DAA = assessed 3 to 5 days after application

Conclusion

Success™ NEO is a highly effective new insecticide for controlling diamondback moth in canola. In those seasons when more than a single spray application is required, Success NEO should be used in rotation with products with alternative modes of action that also control DBM and are selective to beneficial insects. This will minimise selection for insect resistance and ensure Success NEO remains an effective tool for canola growers in WA for many years to come.

Acknowledgments

The author wishes to thank Dr Greg Baker (SARDI) for supplying trial data generated under GRDC project DAS00094. Thank you to Ms Svetlana Micic (DAFWA) and John Gilmour (Dow AgroSciences) for their valuable feedback and suggestions.

Paper reviewed by J. Gilmour, Dow AgroSciences, Sydney, NSW.