Ladybirds - Biological pest control ?
I am rather fond of ladybirds and enjoy seeing them chomping away on aphids which I particularly dislike! I have recently been diappointed in seeing fewer ladybirds despite considerable aphid infestations. Last year I invested in a 'ladybird hotel' to encourage ladybirds to overwinter in my runner bean patch as well as buying some ladybird larvae which I put on my broad bean plants. I can't say that I saw much effect from that - I never saw the larvae again and there didn't seem to be many ladybirds around - certainly none in the ladybird hotel.
Biological pest control seems to be ever increasing in popularity and I have seen more and more outlets selling insect houses, shelters etc. Are we being sucked in by the marketeers? I don't know the answer to that but I did come across this intersting article suggesting ladybirds might not be so effective at tackling major aphid infectations and that buying adult ladybirds for release is a waste of money as they fly away home !!
Ladybirds; they don't make a meal of aphidsby Dr Belinda Clarke
The widely-held theory that ladybirds can control aphids may not be as simple as it appears. Scientists in the School of Biological Sciences at the UEA, part of the Norwich Research Park, have challenged this idea for many years, and have come up with a convincing alternative explanation.
It was in 1888 that ladybirds were first reported as being effective in the biological control of insect pests. And ever since, ladybirds have often been released on to aphid-infested crops in the hope that they would reduce the aphid population.
In many cases, there does appear to be fewer aphids once the ladybirds have been introduced. But as the UEA scientists have discovered, it's not entirely due to the ladybirds' appetite for aphids.
During an aphid infestation, massive numbers of young aphids are produced. The population increases very quickly to a peak, then falls, as winged adults fly away and colonize other plants. After a month or so, the infestation is over.
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I hardly saw any lady birds last year, and haven't seen any yet this year. One thing you have to remember with all biological controls is that for them to survive, there has to be a continuous supply of food- so if your neighbours are all spraying for greenfly, they will lose their ladybirds because there is no food, and yours will become a small isolated colony.
I think biological predators are meant to work quite well in enclosed spaces like greenhouses, but as you say, you can't control them flying away in the open.