Friday, July 1, 2022

Dung beetles not new in the north

A northland farmer is as bemused as he is concerned by the fracas around dung beetles being released, having shaken them out of his gumboots for years.

Farming on the edge of Hikurangi Swamp, Greg Martin first noticed the beetles swarming to artificial light, and his boots, in the late 1990s.

“I have put it down to caged trials on them run out of a MAF farm, Spring Flat, around that time. It was like they got them in, and they arrived at our place almost straight away.”

Normally he has to shake the beetles out of his gumboots over spring before going milking.

Given the extremely dry conditions in Northland at present the beetles are evasive, digging deep underground.

It is this digging ability that makes Martin question the wisdom of caged trials.

“When conditions are right they can go down deep. When the cows have been in a paddock the next day you can see where the beetles have been, and have dug down below the pat.”

One concern of public health experts has been the beetle’s ability to dig down and out of caged trials and to fly relatively long distances, possibly carrying diseases with them.

However, it appears the beetles have been around for considerably longer than the mid-90s. Records show the Mexican dung beetles afflicting Martin’s boots were introduced by Ministry of Agriculture and Fisheries scientists in 1958, in Nelson and Northland. The aim was to help reduce fly numbers through the beetles breaking down dung.

The beetle was thought to have died out but a colony was discovered in 1975 at Glenbervie, northeast of Whangarei.

Introduced from Samoa, the beetles’ success appears limited. A study done by Northland entomologist Rod Blank in 1983 reported the Mexican dung beetles had shown little benefit to pastoral agriculture or fly populations.

Supporters of the latest release maintain Australian beetles imported will work faster than their Mexican counterparts. However, concerns have been raised for the same reasons recognised in 1983, that the beetles will not offer effective fly control because New Zealand has few flies that are dung-specific.

Martin said his biggest concern, other than getting the beetles in his boots, was the impact of releasing another foreign insect into NZ when there were already numerous unwanted pests in the country.

Related stories: Public health issue ‘hasn’t been studied’Beetles effective in AustraliaEPA backs dung beetle decisionExperts dump on dung beetleTop medical officer questions beetle safety


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