Mice Activity Threatening Winter Crop Establishment

Currently mouse numbers are moderate/high in a band across SE South Australia and NW Victoria with numbers expected to peak at sowing of winter crops in Southern Australia. Mice can cause significant crop damage, loss of livestock feed/fodder, contamination of stored grain and spread of disease. Mice have continued to breed in strong numbers through this year’s summer/Autumn period. This is a result of good spring and summer rains and having grain left in the paddocks offering a quality feed source enabling mice to breed. We have seen similar years like this like back in 2016/2017 season following strong summer rains, with 2011 being the last official mice ‘plague’ year. In each of these years we have received good summer rains and had grain on the ground generally from storm damage, frosting or allowed volunteers to re-establish and set seed.

Figure 1. March 2020 approximate mice location and relative abundance according to the GRDC ‘Monitoring of Mouse Populations Across Australia’ project.

 

Mice have the ability to cause significant economic loss if not controlled. Growers should actively monitor mouse activity through chew cards or burrow counts to determine management. To determine active burrow threshold simply walk in 100m x 1m straight transect along the sowing furrow and count the number of burrows that look active. Repeat the process across 2-4 transects and if there are more then 2-3 active burrows per 100m then threshold has been reached. Mouse chew cards are also a good way of tracking mouse activity. The 10 x 10cm pre-soaked canola/linseed oil cards should be set at night, pegged down and spaced 10m apart in the paddock. Thresholds are as follows; <10 squares per card eaten = low to moderate activity, >10 squares per card eaten = Moderate to high activity and >20 squares per card eaten = high to very high mouse activity.

Figure 2. Mouse chew cards used for monitoring activity (L) and an active mice hole observed out in the paddock (R).

 

We are currently seeing isolated areas of high activity in SW Victoria in paddocks that had good summer rain, grain on the ground and generally paddocks that were burnt late. If a paddock has a combination of these factors a thorough check is recommended. Peak mice activity is generally at night, this will provide the most accurate representation of activity. Damage has already been observed in early April sown canola and winter wheat crops. Please refer to the below management recommendations for mouse control prior to sowing your crops this season.

  1. Paddock Monitoring; Monitor for mice numbers prior to sowing; active burrow counts & mouse chew cards.

  2. Reduce ground cover and food source; Strategic tillage to burry food source, burning stubble residue and livestock grazing to reduce risk.

  3. Baiting with Zinc Phosphide; Products such as Mouseoff 2.5% ZP applied at label rate 1kg/ha to achieve even coverage of 2-3 grain/m2.

  4. Manage over large areas; Coordinating management with neighbours to reduce chance or reinvasion

 

Please consult with your Western AG agronomist today if you suspect your crops may be at risk of mice damage. As always being proactive rather then reactive is the best form of management!

Article produced by - Brendan Smith, Western AG Ballarat

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