Nightmare on elm leaf: zombie virus explodes caterpillars
A “ZOMBIE virus” outbreak is causing caterpillars to explode “like a scene from a horror film”, experts have said.
Members of the public have been warned to stay vigilant and watch for caterpillars in the sun following reports that several have been infected by the baculovirus.
By rewiring the hormones that regulate a caterpillar’s need to moult, the virus forces larvae, which typically avoid sunlight, out from the cover of darkness and on to the stems of plants, where they are rendered powerless. The effect has been observed by scientists in the West Pennine Moors in Lancashire.
While caterpillars typically avoid sunlight and therefore hungry daytime predators, the infected larvae are rendered powerless by the virus, which reprogrammes their hormones and compels them towards a grisly end.
Cases are well-documented in North America, where the Gypsy moth population has been ravaged by the microorganisms, but infestations in Britain have so far been rare.
Although the virus is known to infect other invertebrates, including shrimps and mosquitoes, moths and butterflies are the most common victims, often feeding on plants and vegetation contaminated with microscopic proteins. After entering the insects’ stomachs, the virus quickly mutates and gains control of the host.
They then climb upwards to the top of leaf foliage or trees, where they liquefy and explode, spreading contagious pathogens to other caterpillars.
It is thought that the “oak eggar” moth – a common variety across Europe – has been particularly affected, with caterpillar remains found littered among the branches of heather and bilberry plants on which they feed.
The latest infection comes amid growing concern for the future of native butterfly populations, with three quarters of British species falling into decline over the past 40 years.
During the same period, moth numbers have also nosedived, with once common garden species such as the garden tiger, the V-moth and the spinach teetering on the edge of extinction.
A spokesman for the Wildlife Trust said: “We would ask everyone who sees caterpillars or snails for that matter high up on leaves to report it to us.”