One of things that is often said about organic gardening is that by not using pesticides a garden reaches a state of balance where predators reduce or even eliminate damage from pests. This does not happen over night and sometimes weather or other changes cause the balance between pests and predators to shift.
This year, 2010, has been difficult. Following the long cold winter came a long cool spring which held back many plants and weakened others. In our garden broadbeans were very slow to establish and growth has been limited. Now (mid July) they are growing well but are stunted.
Until now we have never had much of a problem with blackfly (aphids) but this year they are quite bad. That poses a dilemma. Should they be sprayed with an organic bug killer or should we accept some damage and wait for the predators to restore the balance? Spraying with anything risks killing friends as well as pests so might do more harm than good.
I was undecided until today. Close examination showed that patches of aphids were dead and mouldy; then I spotted the cause! There were many ladybirds (ladybugs in the US) and larvae were clearly visible. They are ugly and at first sight you would think there were the sort of thing you do not want in your garden but if you have aphids they are your best friend because: “Typically, Ladybugs (Hippodamia convergens) eat over 5,000 Aphids and other soft-bodied pests during their one-year lifetime.” [From: http://www.naturescontrol.com/aphid.html accessed 09/07/1010]
Last year we had no aphids and no ladybirds. This year we have lots of both so I hope the ladybirds breed well and take care of the aphids!
Also, forget the advice that all you need to do is to pinch out the tops of broadbeans to avoid aphids; they will attack stems and pods.
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All photographs © Colin Shaw 2010. Do not reproduce in any form on web sites or on/in any other media without written permission.