Southern NSW grain growers should be on the lookout for increased mouse activity, with economic damage at sowing expected in some areas.
Grains Research and Development Corporation (GRDC) monitoring showed mice numbers are on the rise in the southern region of the state, fuelled by ample food and cover following last year’s bumper harvest.
CSIRO researcher Steve Henry said there was already evidence of active burrows on banks around rice crops and in soybeans around Coleambally.
He said it was likely populations would continue to increase in the lead-up to the sowing of this year’s winter crops.
“Given the seasonal conditions, where we have an abundance of food available, growers need to be checking for evidence of active burrows in paddocks,” Mr Henry said.
He said it was vital growers monitored the situation across multiple paddocks, to get an accurate indication of mice activity to inform their management decisions.
“To look for active burrows, I suggest farmers walk about 30 metres in from the edge of the paddock and set a 100 metre (1 metre wide) transect through a crop, following the furrows.
“They should walk slowly along the transect scanning for evidence of mouse burrows, taking note of any burrow that looks active and recording the number of burrows per 100 metre transect, and then repeat across two or four transects.
“If there are more than two to three active burrows per 100 metres, then they have a mouse problem.”
Mr Henry said corn flour could be used to mark potentially active burrows, but the transect should be inspected the next day for signs of activity.
In terms of zinc phosphide baiting, Mr Henry recommended the following:
- Apply bait according to the label;
- Apply baits six weeks prior to sowing if there is sufficient evidence to bait (if planning to bait only once, then bait at sowing);
- Allow at least four to six weeks before re-application of baits to minimise the chance of bait aversion. This allows mice that have previously tried the bait to try it again and also targets news animals in the population that are susceptible to the bait;
- If baiting at sowing, apply directly after sowing (e.g. bait spreader on the back of the seeder). Mice increase foraging activity after sowing because of the soil disturbance. If a novel food is available on the surface they will eat that in preference to digging up the planted seed. Baiting more than 24 hours after sowing will not be as effective;
- Bait over large areas. Encourage neighbours to bait at the same time if they also have a mouse problem. The larger the area treated, the lower the chance of re-invasion post treatment.
Mr Henry encouraged growers and advisers to report and map mouse presence, absence and level of activity using MouseAlert so others could see the scale and extent of localised mouse activity. MouseAlert also provides access to fact sheets about mouse control and forecasts of the likelihood for future high levels of mouse activity in each grain-growing region.
“We need more producers using MouseAlert so that the project can deliver more accurate forecasts of regional changes in mouse numbers,” Mr Henry said.