There are some common pests on tomatoes and aphids are some of the most voracious, they are able to clone themselves every 20 minutes and even the clones that have been produced come with a built in baby ready to go. So aphids not only clone their children, they do in effect clone their grandchildren. Early in the year they tend to produce all females but as the end of the year approaches they start to produce some males.
The reason for this is that the males can go off and mate with females to start to change the genetic profile a little. This ensures that the species can continue should some unexpected change in environment occur. You can imagine that should the aphids try and survive on cloning alone, with no genetic variation at all, then should some circumstance come along that kills one, then it is obviously going to kill them all. Hence the reason that males of the species have to be retained and why aphids have sex, other than that it wouldn’t be necessary.
When it comes to aphids on tomatoes I can imagine as a keen gardener you are probably thinking ‘shame they thought about that I wouldn’t have to worry about them otherwise’. Unfortunately life is never quite that simple, but never fear, there are a few ways of dealing with aphids and not all of them involve using chemical pesticides.
First of all aphids, commonly known as green-fly or black-fly have a few natural predators. Probably the best known is the Ladybird or Ladybug, which has a very big appetite for aphids and will happily munch their way through whole colonies of aphids, whether they are on tomatoes or any other plant. The good news is that to make this method for controlling aphids easier some companies now specialise in supplying ladybirds in a small plastic tubs, and all you have to do is release them amongst your tomato plants.
The black wasp is another predator of aphids, their assassination techniques are a little more subtle, they simply visit the aphids on the tomato plants and inject a single egg into each aphid. When the egg hatches the larva has a very nice ready meal and proceeds to eat the aphid from the inside out. Wasps like brightly coloured flowers and fruit trees, so if you can plant these in your garden they will be naturally attracted.
The best way to prevent aphids on tomatoes however is prevention. Keep a careful eye on your plants and stop the infestation before it gets started. When there are not too many you can wipe them off between your thumb and finger, squashing then in the process. This is because they are soft bodied and not very robust. It is also because they are soft bodied that they don’t like soap, this tends to cake over their bodies and dry them out. Many people swear by a water and insecticidal soap mix, sprayed onto the aphids before it gets too hot in the sun. This method is probably the most widely used.
Another suggested method for getting rid of them, when they have only just started, is to blast them with a high pressure spray. Not sure I am a fan of that method as I always wonder if you can do more damage than good to your tomato plants, they are after all, not particularly robust themselves, but if you think you can get away with it then it is a suggestion.
The video below has a few suggestions on how to take care of hornworms, caterpillars and your favourite the aphid. Looks very easy!