Dry spell may alter potato growers’ herbicide strategy this spring

potato ridges in a field

POTATO growers may need to rethink their usual reliance on pre-emergence herbicides this year after a period of dry weather. 

While planting has progressed well thanks to favourable conditions, the dry soils will have a negative impact on the efficacy of the pre-emergence weedkillers typically applied to ridges shortly after planting.

See also: Cover-crop project aims to tackle nematodes in potatoes and daffodils

Corteva Agriscience field technical manager Craig Chisholm says leaving weeds unchecked can reduce yield, slow down harvesting machinery and increase the risk of blight.

“Dry soils can crack or slip down the ridges, disrupting the all-important seal required for optimum efficacy from pre-emergence herbicides.

“As a result, rain or planned irrigation in the next few weeks will stimulate weed growth from the ridge surface and from depth,” Craig says. 

Dry conditions

“Dry conditions in unirrigated fields and disruption to the herbicide ‘barrier’ means that the efficacy of pre-emergence chemistry will be compromised.

“This could well be a year when growers need to think about following up with a post-emergence spray.” 

Titus, containing the active ingredient rimsulfuron, targets key problem weeds and is an “invaluable” tool in a dry season when pre-emergence activity will be negatively affected, Corteva said.


The selective herbicide has been a mainstay of potato growers’ early-season programmes to control a wide range of broadleaf weeds including cleavers, chickweed, redshank, mayweed and oilseed rape volunteers.

Titus has also demonstrated excellent activity on a range of grasses, notably couch.

“The qualities of Titus are well known to UK and Irish potato growers and agronomists and with fewer options available for weed control, it will become an ever-more important tool,” explains Craig.


“Titus should be applied when broad-leaved weeds are small and actively growing, typically cotyledon to four leaves, and grasses pre-tillering (two-to-three leaves), and before crop sheltering can impact herbicide coverage.

“It is suitable for use on all potato varieties excluding seed crops and is compatible with metribuzin, which will further broaden the weed spectrum in potato varieties which are tolerant to post-emergence application.” 

Titus should be applied at 50g/ha when applied alone or 40-50g/ha in mix with metribuzin, and always used with an approved adjuvant.

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