Find your 'cold period'
The following information will show you how to locate climate data on the internet, allowing you to find the period of the year when your average daily maximum temperatures are 18°C (H. contortus) or 15°C (T. colubriformis) or below. At these temperatures these worms will have little or no development to infective larvae. Teladorsagia circumcincta and T. vitrinus development continues at temperatures well below these values and grazing management will be less effective.
The Bureau of Meteorology (BOM) web site
A BOM temperature map can be used to show where the daily maximum temperature is on average 18°C or below for the month. Unfortunately, this map is small and low resolution, so it may be difficult to pinpoint your location if you are near a temperature gradient line (isotherm).
- Go to: www.bom.gov.au/jsp/ncc/climate_averages/temperature/index.jsp?maptype=1&period=apr#maps OR go to www.bom.gov.au, then choose: Climate Information, choose: Maps-average conditions, then in the main part of the page choose: Average max, min & mean temperatures.
- Select: Maximum temperature.
- Select month as April (then progressively change and view months through to October).
- Look for the areas coloured pale green to darker green/blue, which have an average maximum of 18°C for the month. Note that the earlier weeks in the first cold month, and the later weeks in the last cold month may not really be 18°C or below, as this is an across-month average.
Weatherzone web site
This site allows you to look up the average monthly maximum temperatures for a particular town.
- Go to: www.weatherzone.com.au.
- Type the name of your closest town into the ‘site search’ box and press enter.
- When the town’s weather information appears, go down to the Almanac (just below the sun and moon times) and select ‘Full climatology’.
- In the top table: ‘Long term climatology’, look for the months that have temperatures of 18°C or less in the row for Mean Maximum (°C). Note that the earlier weeks in the first cold month, and the later weeks in the last cold month may not really be 18°C or below, as this is an across-month average.
- Alternatively, look at the graph (below the tables). Look for the months when the solid red line (mean daily maximum temperature °C) is below 18°C.
NOTE: The temperature of a nearby town may be quite different to the temperature on your farm, where there are long distances or considerable differences in the altitude between them.