It's an excellent study and, in some ways I'm not surprised. I, myself, am no longer raising caterpillars like I used to, because I began wondering about this sort of thing. Nature seems to have gone a bit topsy-turvey in the last couple of years.
Right now (just coming into Spring) in our area of the Bay of Islands, New Zealand (far north) the numbers of aphids are already the greatest I've ever seen. They were so thick on the Swan Plants (milkweed) I was growing, that last week I pulled all the plants out. This coming Summer I'll just plant lots of nectar flowers for the Monarchs and otherwise leave them to it.
Disclaimer: The article below has just been published by the Moths and Butterflies of New Zealand Trust. It is not my article and I have not participated in the research in any way. I am merely passing it on with a view to helping those who care for or raise Monarch Butterflies.
Moths and Butterflies of NZ Trust
07 Sept 2020
If YOU love monarch butterflies we're hoping you won't "love them to death" this summer.
Thanks to an excellent study at the School of Biological Sciences, Victoria University of Wellington, members of the Moths and Butterflies of New Zealand Trust are better equipped to help monarch butterflies this summer. The results are in our Spring magazine, out now.
Dr Phil Lester and Mariana Bulgarella were investigating how many monarch butterflies in NZ carried the parasite Ophryocystis elektroscirrha, commonly referred to as Oe.
This parasite infects monarch butterflies and while it can kill or weaken monarchs it does no harm to anything else. Samples were taken from 408 adult monarchs from locations between Otago and the Far North. This did not hurt the butterflies.
“Surprisingly, almost all butterflies from warmer areas of the country, such as Northland, Auckland, Bay of Plenty and Nelson, carried the parasite Oe,” said Mariana Bulgarella.
“This parasite is absolutely natural. It’s as much a part of the monarch’s environment as fleas are to a dog.”
However, the results from the research has raised one very big concern: people trying to ‘save’ sick monarchs, butterflies heavily infested with Oe, or kept in crowded containers or on unhealthy plants.
“We urge people who love monarchs to remember they’re wildlife, and not pets,” said Jacqui Knight, secretary of the Moths and Butterflies of NZ Trust. “They are cold-blooded and do not ‘suffer’ in the cold. Their wings are waterproof and they can cope with rain.”
“Caterpillars and butterflies know what to do when it’s raining or windy. They don’t need to be raised indoors or kept warm through the winter. They should be left to do what comes naturally.”
We are concerned that by saving unhealthy butterflies people are loving monarchs to death. The fittest will survive and go on to reproduce. It is important that unhealthy butterflies do not reproduce.
“The monarchs have been doing just fine without our help for millions of years,” she said. “While it’s useful to offer some protection against wasps and other predators the current advice, based on scientific evidence, is to raise monarchs in ways that mimic their natural environment. Overcrowded conditions are not seen in nature.”
Check out the FAQ's on the MBNZT website, www.nzbutterflies.org.nz