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Hello, this is a question relating to something I’ve noticed in my local area. I’m from South Australia, in the countryside.
Over the last few months I’ve been noticing wide swathes of eucalyptus trees with browning leaves that didn’t produce new growth when the winter rains came; or did, but shortly after the new leaves died as well. Curious, one day on a field trip for something else (I’m an ecology student), I looked closely at some leaves from the affected trees as I walked by. I noticed that they were covered in tiny insect cocoons or eggs. They look like parasites. There are many different shapes of egg, so there isn’t just one species. I’ve also seen swarms of tiny Hemiptera insects (Psyllids?) swarming among the affected leaves, if that helps.
I’ve attached photos so people can get an idea of what I mean. I’m not asking for a species ID necessarily (unless someone already knows), but I’m interested if anyone knows how these outbreaks happen. What influences it the most? Ive heard a lack of underbrush and no small birds can cause a population increase because there’s nothing to eat them. Does temperature and climate play a factor?
And, are the insects actually what is causing the damaged leaves, or are both symptoms of something else, like stress? We’ve just come out of a drought and a dry autumn.
Thank you to anyone who answers. I’m concerned with how large an area has been affected, and any information would be great.