Aphids and Ants
I understand that ants protect/move/farm aphids and I wonder if there
are any effective controls that concentrate on excluding/killing ants? For example, a few weeks ago, I had aphids on my apple tree attended by ants. If I had excluded the ants (greaseband on the trunk?) would that have prevented/reduced the problem? Steve Harris - Cheltenham - Real address steve AT netservs DOT com A useful bit of gardening software at http://www.netservs.com/garden/ |
Aphids and Ants
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Aphids and Ants
In article ,
Tumbleweed wrote: I have watched ants attacking ladybirds near aphids, effectively protecting them. They may not do it deliberately, but if the ants get some benefit from the aphids (why else follow them around) then protecting them in this way would help the ants. OTOH if the aphids gain nothing by being protected from ladybirds and the like, then so much for aphid control by predators or selective spraying. Not at all. It is very common for animals to perform actions that have no useful effect because they had an effect earlier in evolutionary history. I have watched ants walking over ladybird larvae, completely ignoring them. There might not be any evidence that it makes a major difference, but is that because people have done the experiments and observations and seen no relationship, or because no one looked? Some people have done experiments and found no difference. Nobody so far has reported an experiment that detects a difference in the UK. Regards, Nick Maclaren. |
Aphids and Ants
"Nick Maclaren" wrote in message ... In article , Tumbleweed wrote: I have watched ants attacking ladybirds near aphids, effectively protecting them. They may not do it deliberately, but if the ants get some benefit from the aphids (why else follow them around) then protecting them in this way would help the ants. OTOH if the aphids gain nothing by being protected from ladybirds and the like, then so much for aphid control by predators or selective spraying. Not at all. It is very common for animals to perform actions that have no useful effect because they had an effect earlier in evolutionary history. Can you give an example? As people research things more, it often turns out that behaviours or attributes that were thought to be incidental, arent. I have watched ants walking over ladybird larvae, completely ignoring them. But were there any aphids about? :-) And organisms arent perfect, I have watched ants running about and missing small bits of food. That doesnt indicate they dont pick up food. There might not be any evidence that it makes a major difference, but is that because people have done the experiments and observations and seen no relationship, or because no one looked? Some people have done experiments and found no difference. Nobody so far has reported an experiment that detects a difference in the UK. So if I notice ants consistently attacking ladybids&larvae on my apple tree, and the aphids therefore being left alone, should I draw the conclusion that ; a)killing the ants wont help reduce the aphids, or that, b)theories of organic gardening re controlling pests with predators (or more specifically aphids by ladybirds) is bunk? -- Tumbleweed Remove my socks for email address |
Aphids and Ants
In article , "Tumbleweed" writes: | | Not at all. It is very common for animals to perform actions that have | no useful effect because they had an effect earlier in evolutionary | history. | | Can you give an example? As people research things more, it often turns out | that behaviours or attributes that were thought to be incidental, arent. Piranhas attacking something dropped in the water. The grasp reflex of human newborns. If I recall, Gould has other examples. | I have watched ants walking over ladybird larvae, completely ignoring | them. | | But were there any aphids about? :-) And organisms arent perfect, I have | watched ants running about and missing small bits of food. That doesnt | indicate they dont pick up food. Yes, of course. Don't be silly. The ants were 'milking' precisely the aphids that the ladybird larvae were feeding on. And the coexistence went on for a long time. | So if I notice ants consistently attacking ladybids&larvae on my apple tree, | and the aphids therefore being left alone, should I draw the conclusion that | ; | a)killing the ants wont help reduce the aphids, or that, Nobody has so far shown ANY evidence that ants cause an increase in the number or severity of aphid infestations, let alone that killing the ants will reduce the latter. But there HAS been some evidence that (a) is true in at least the majority of cases. | b)theories of organic gardening re controlling pests with predators (or more | specifically aphids by ladybirds) is bunk? Well, I have not seen it work. Ladybirds reproduce fairly slowly and don't eat huge numbers of aphids, so I am unconvinced that they make much difference in controlling infestations. Things aren't as simple as that, because you can also control pests by restricting sources (e.g. I am spraying my philadelphus with soft soap now to protect my broad beans later). Regards, Nick Maclaren. |
Aphids and Ants
On Wed, 19 May 2004 07:08:25 +0100, Tumbleweed wrote:
"Nick Maclaren" wrote in message ... In article , Tumbleweed wrote: I have watched ants attacking ladybirds near aphids, effectively protecting them. They may not do it deliberately, but if the ants get some benefit from the aphids (why else follow them around) then protecting them in this way would help the ants. OTOH if the aphids gain nothing by being protected from ladybirds and the like, then so much for aphid control by predators or selective spraying. Not at all. It is very common for animals to perform actions that have no useful effect because they had an effect earlier in evolutionary history. Can you give an example? As people research things more, it often turns out that behaviours or attributes that were thought to be incidental, arent. I have watched ants walking over ladybird larvae, completely ignoring them. But were there any aphids about? :-) And organisms arent perfect, I have watched ants running about and missing small bits of food. That doesnt indicate they dont pick up food. There might not be any evidence that it makes a major difference, but is that because people have done the experiments and observations and seen no relationship, or because no one looked? Some people have done experiments and found no difference. Nobody so far has reported an experiment that detects a difference in the UK. So if I notice ants consistently attacking ladybids&larvae on my apple tree, and the aphids therefore being left alone, should I draw the conclusion that ; a)killing the ants wont help reduce the aphids, or that, b)theories of organic gardening re controlling pests with predators (or more specifically aphids by ladybirds) is bunk? There's a summary of a paper he http://www.blackwell-synergy.com/lin...d=hvenKPRD9TVh One would *think* that ants protecting aphids would damage the plant more than without ants. In some cases, they could be beneficial, by driving off other herbivores (weevils etc), which would cause more damage. You might also see on some plants, (particularly roses in our garden) a coating of fine earth particles around parts of the stem. Break one open and you'll find the thing full of aphids and ants. Certainly an number of european ant species overwinter aphids and carry them or their eggs out to feeding grounds in the spring. That doesn't meant to say that those plants suffer more or less. -- Tim C. |
Aphids and Ants
On 19 May 2004 07:23:09 GMT, Nick Maclaren wrote:
Piranhas attacking something dropped in the water. Debatable whether that behaviour is useless nowadays. A fair amount of edible dead animals or fruit will fall into the rivers and lakes. The times they get it wrong are more than compensated for by the times they get to the food first. The grasp reflex of human newborns. That's a good one. Also the "diving reflex". If I recall, Gould has other examples. Not one to shy away from controversy, was Gould. Don't rule out the ant/ladybird larvae battles as being started by the larvae They are aggressive hunters and may well have started attacking the ants first. -- Tim C. |
Aphids and Ants
In article m, Tim Challenger "timothy(dot)challenger(at)apk(dot)at" writes: | | There's a summary of a paper he | http://www.blackwell-synergy.com/lin...d=hvenKPRD9TVh | One would *think* that ants protecting aphids would damage the plant more | than without ants. In some cases, they could be beneficial, by driving off | other herbivores (weevils etc), which would cause more damage. Ye gods, just imagine. A treatment to protect broad beans against weevils could be to infect them with aphids .... As Wilde said, the truth is rarely pure and never simple. That could be the motto of ecologists! Regards, Nick Maclaren. |
Aphids and Ants
On 19 May 2004 07:23:09 GMT, Nick Maclaren wrote:
| b)theories of organic gardening re controlling pests with predators (or more | specifically aphids by ladybirds) is bunk? Well, I have not seen it work. Ladybirds reproduce fairly slowly and don't eat huge numbers of aphids, so I am unconvinced that they make much difference in controlling infestations. Things aren't as simple as that, because you can also control pests by restricting sources (e.g. I am spraying my philadelphus with soft soap now to protect my broad beans later). While increasing the number of ladybirds and lacewings surely can't hurt, I bet you'll find that birds take more aphids than ladybirds. Especially when feeding nestlings. Sparrows and blue-tits appear to take a large number. Let's face it, they're bigger, need more food and can scoff a lot more in one mouthful than an army of beetles or lacewing larvae. I've seen values for lacewing larvae of 300 per larva and 5000 per ladybird (adult) advertised (in its life, not per day). That might be a lot for a tiddly little insect but it's peanuts compared to what a tit can polish off. -- Tim C. |
Aphids and Ants
On 19 May 2004 07:54:02 GMT, Nick Maclaren wrote:
In article m, Tim Challenger "timothy(dot)challenger(at)apk(dot)at" writes: | | There's a summary of a paper he | http://www.blackwell-synergy.com/lin...d=hvenKPRD9TVh | One would *think* that ants protecting aphids would damage the plant more | than without ants. In some cases, they could be beneficial, by driving off | other herbivores (weevils etc), which would cause more damage. Ye gods, just imagine. A treatment to protect broad beans against weevils could be to infect them with aphids .... As Wilde said, the truth is rarely pure and never simple. That could be the motto of ecologists! Our motto was: "If there are two theories to explain something, they're probably both right", often changed to: "If there's only one theory to explain something, they're probably both right". -- Tim C. |
Aphids and Ants
Xref: kermit uk.rec.gardening:205707
In article m, Tim Challenger "timothy(dot)challenger(at)apk(dot)at" writes: | | While increasing the number of ladybirds and lacewings surely can't hurt, I | bet you'll find that birds take more aphids than ladybirds. Especially when | feeding nestlings. Sparrows and blue-tits appear to take a large number. | Let's face it, they're bigger, need more food and can scoff a lot more in | one mouthful than an army of beetles or lacewing larvae. Yes. And most aphids reproduce like the THINGS from a 1950s B movie. | I've seen values for lacewing larvae of 300 per larva and 5000 per ladybird | (adult) advertised (in its life, not per day). That might be a lot for a | tiddly little insect but it's peanuts compared to what a tit can polish | off. Yes. The trouble is that 5,000 per annum corresponds to c. 30 per diem, and so you would need one ladybird per infected plant just to keep up. My suspicion is that they are effective primarily at ensuring that there is not too much of a build-up on alternate host plants (often wild ones). Which is definitely not to be sniffed at. As I posted, after having seen a discussion of the alternate host plants of black bean aphid, I am trying the solution of targetting THEM and not the beans! Regards, Nick Maclaren. |
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