Monarch butterflies travel very long distances. Since the they have appeared and started colonies in the Eastern states of Australia and they are now in Western Australia, the other side of the country.
Aphid control is essential if you want to grow healthy milkweed plants for monarch butterflies. Here are 10 Ideas to control aphids naturally, and save more milkweed for munching monarch caterpillars. Plant onions and marigolds close to Milkweed.