G-MW is still trying to clear irrigation channels that contain residue from the spray, two weeks after the irrigation season was supposed to have started.

The authority says the spray containing Imazapyr was applied in May, June and July.

Some landholders have been supplied with trucked-in supplies of stock and domestic water while they wait for the residue to disappear.

Naring farmer Barry Croke said he saw G-MW spraying weeds in channels near his property in late July.

He said the use of the herbicide so close to the start of the season raised questions about the efficacy of the treatment and the threat of residues.

Instructions for the spray when being used for irrigation channels say: ‘‘If the entire (empty) channel surface is to be treated, delay reuse of the channel for as long as possible (at least six weeks) for Arsenal Xpress to adsorb to soil particles.’’

During routine testing, G-MW detected residual traces of Imazapyr, an active ingredient contained in herbicides used to control the aquatic weed arrowhead, in the water of some treated channels.

‘‘This should have been completed by mid-June at the latest,’’ Mr Croke said.

He was one of dozens of farmers told they could not access water at the start of the season because of the spray residues.

‘‘If you don’t give it time, then the active ingredient will not be fixed in the soil and it will be leached out by the flushing of water.’’

Mr Croke also raised the issue of compensation for being shut out of water deliveries.

‘‘We’re paying our delivery share for access to the system from August to May. I suppose we will still get the bill for access for that whole time.’’

While staff had been keeping him up-to-date on the outcome of testing, he believed the spraying program had been badly managed.

G-MW is continuing to open channels affected by residues but on Monday morning about 300 customers were still affected.

A spokesperson for G-MW said it was expected all customers would have access to water for irrigation and stock and domestic purposes by the end of this week.

‘‘We are working with customers to ensure we’re meeting their water needs.’’

G-MW has not yet commented on questions over whether affected irrigators will be compensated.

The Environment Protection Authority has been advised of the spray issue.

EPA north-east manager Clare Kiely said G-MW had advised EPA of its plan to flush the water from the channels and to contain it in drains until tests for Imazapyr came back clear.

G-MW will then move the water back into its supply channel.

G-MW has sent EPA results of its testing of waterways and EPA is confident the results confirm there will not be any impact on the environment.

‘‘While G-MW has adopted a very prudent and precautionary approach to managing this very low risk issue, EPA will seek the outcomes of G-MW’s internal review of this event to ensure procedures are appropriately revised to prevent the risk of any re-occurrences of this type,’’ Ms Kiely said.

https://www.mmg.com.au/local-news/country-news/authority-cops-spray-over-timing-1.98816