3 March 2000

Plenum to close pirimicarb gap?

By Charles Abel

IT kills all aphids, including those resistant to other insecticides, it lasts up to twice as long as alternative products and it is safe to beneficial insects.

Such are the claims for Plenum, the new resistance-busting potato aphicide which Novartis hopes will knock pirimicarb off top spot in the crop. Aphox currently accounts for almost 40% of aphicide use in potatoes.

While kind to beneficials pirimicarb does not control R3 or MACE resistant aphids, a growing problem now confirmed in Kent, Lancashire and the west Midlands as well as the original hot spot around the Wash in Lincolnshire, notes field Novartiss crops manager Michael Tait.

Neither does it control buckthorn aphid, making identification necessary before treatment. And pirimicarbs persistence can vary, particularly in warmer conditions, due to its volatility, he adds.

By contrast Plenums unique mode of action is fully effective against all types of aphid. Although its active ingredient pymetrozine works on a single target site the risk of resistance developing is not high, say Novartis experts.

Limiting use to two early season treatments cuts the risk further. At the 0.6kg/ha rate Plenum offers up to 14 days control, compared with seven from a typical pirimicarb spray, Mr Tait adds. During lower pest pressure rate can be cut to 0.4kg/ha, delivering 10 days of control.

Natural aphid predators such as ladybirds and lacewings are unharmed, reducing the risk of aphid population rebound. "Pyrethroids and carbamates can result in higher aphid numbers later in the season when populations rocket after the aphicides persistence wears off but there are no beneficials in the crop to keep aphid numbers in check," Mr Tait explains.

However, aphid knockdown with Plenum is not rapid. Aphids stop feeding within an hour, preventing direct crop damage, potato leaf roll virus transmission and the transfer of potato virus Y between plants. During the next one to four days, depending on size, the aphid starves to death.

That suits ware and lower grade seed crops, Mr Tait comments. Where virus Y needs avoiding mixing with a pyrethroid should boost repellence, he says.

Truly systemic mobility through the plant means Plenum suits early use, protecting new growth and killing aphids at the base of the crop.

Anticipated farm price per treatment is £15-22.50/ha (£6-9/acre) according to dose. When viewed as cost per day of control that matches pirimicarb, Mr Tait maintains. A typical application of pirimicarb costing £7.50/ha and lasting 5 days costs £1.50/day of control – Plenum at £15/ha lasting for 10 days costs the same, but provides full control between sprays, he says. Sugar beet is unlikely to appear on the label.

owing to an incompatibility between the crop and the active ingredient.

Supplies are pitched to meet widespread use given a typical aphid season, Mr Tait comments.

CUT

For best effects apply Plenum in 200l/ha water using a twin cap jet with the forward nozzle blanked off and a 1004 tip rear-facing. A single hollow cone nozzle is next best. Formulation is water soluble bag for now, a wettable granule version is expected. There is no LERAP requirement.

Harvest interval is currently 55 days, but will drop to 14 in 2001 once the Pesticides Safety Directorate has considered further data, says Mr Tait. Three full rate applications are also expected, plus other crop approvals.

PLENUM APHICIDE

* New mode of action.

* Kind to beneficials.

* Kills all resistant strains.

* 10-14 day persistence.

* Potato approval only.

* No LERAP required.

Pics of Plenum pack (trim tight), aphid + bloke.

Caption:

PLENUMAPHICIDE

&#8226 New mode of action.

&#8226 Kind to beneficials.

&#8226 Kills all resistant strains.

&#8226 10-14 day persistence.

&#8226 Potato approval only.

&#8226 No LERAP required.

Aphids beware… Plenum insecticide kills all aphid types, lasts longer than pirimicarb and does not harm beneficials, says Mike Tait of Novartis (inset).