Australian garden insects with Denis Crawford
My latest YouTube video: “Control Cabbage White Butterflies with nets”. This is a follow-up to the previous video which dispelled the myth of controlling cabbage white butterfly with white plastic butterfly mimics.
In this video I show how easy it is to set up a net on a frame to protect some broccoli seedlings. I also talk about why there are so many cabbage white butterflies around at the moment.
Last night the Horticultural Media Association of Australia (HMAA) awards night (the ‘Laurels’) were held on Facebook Live. This article “Nullius in verba” won the Laurel in the Technical Category. The article was originally published in 2018 in Hort Journal Australia. Here it is again in its entirety, with some external links that should appear in blue.
——————————————-
Scientific facts often get lost among all the opinions, ‘alternative facts’, hyberbole, and ‘fake news’ of the digital age. This month’s Pest Files is dedicated to separating the facts from the myths.
Let’s start with something simple – the cabbage white butterfly (Pieris rapae) whose caterpillars are voracious munchers of brassica plants (kale, cabbage, broccoli, etc.). Many gardening magazines and blogs, and even some radio and TV gardening shows, reckon female P. rapae won’t lay their eggs when other females are present. The theory is that these butterflies are territorial and will avoid each other so there is little or no competition between their offspring. To protect your crop all you have to do is place a plastic white butterfly mimic amongst your brassica plants – or so the story goes.
Insects are ectothermic meaning they don’t generate their own body heat, and rely on external sources to regulate their body temperature. Freezing temperatures are life threatening to many insects, so how do they survive winter?
One July morning I went down to my vegetable garden to see how the plants had survived the deep freeze (-3°C) of the night before. I wasn’t surprised to find my brassicas were covered in ice crystals, but I didn’t expect to find a cabbage white butterfly (Pieris rapae) larva also encrusted in ice. I decided to keep an eye on it, so after the day warmed up a bit I revisited the garden to find the caterpillar happily munching on the plant. How did it do it?
