Dr David Yeates, the director of the Australian National Insect Collection said there were plenty of reasons for less beetles than usual.

Christmas beetle larvae mostly feed on native plant roots, like eucalyptus, so it's unlikely your gardening has disturbed their life-cycle.

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"They could still be feeling the effects of the drought period we had before the bushfires," he said.

"As we continue to expand our suburbs and build higher-density residential areas it reduces the amount of bushland they have to breed in. They breed more in the bush than suburban gardens."

Dr Yeates said Christmas beetles do come from a c-shaped "curl grub," but so do many other forms of common garden beetle, so don't beat yourself up if you've treated some harshly - you're unlikely to be the cause of beetlegeddeon.

Populations can fluctuate dramatically year to year and location to location, so it's not time to worry about Christmas beetles just yet.

"Their population are patchy," he said.

"If you've noticed a dip it's worth keeping an eye on them next year, but there's no need to ring alarm bells just yet."

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