How often can I spray for aphids?

[little_my]

Okay, so I have a really major aphid infestation in my polytunnel. I've been spraying them off with water, spraying with dilute washing up liquid, shaking them off, squashing them... But they keep coming back stronger than ever (and the ant farmers aren't helping). I'm getting the feeling that for anything to work it's going to have to be repeated a lot more often.

My question is how often I can get away with spraying the plants before I start to get fungal problems ect. I especially worry about the tomatoes which I believe are already at risk during this time of year- also the aubergines and peppers- the aphids are most concentrated on the flowers and young fruit, and I'm worried they'll all get blossom end rot or something...

Any advice would be appreciated.

btw, I'd love to get some predators in, but really cant afford it- I'd still be interested to know if people have had good results with them

thanks!

[Pipsqeak]

Hi little,

Predators work very well in enclosed spaces like your polytunnel, but of course one of the reasons that Aphids thrive in such conditions is because their natural wild predators - Ladybirds & Lacewings in particular - are less easily able to get to them.

The main bought-in Biological control species available for Aphids is a Ladybird too.

There are a few other natural, easily & cheaply made-up plant-based sprays that might be worth trying out. There's an article on Ecocharlie with some spray "recipes" that you might find interesting:

Plant Pests – Ten Top Organic Solutions. « EcoCharlie Blog

I've not tried Rhubarb spray but garlic & chilli definitely work well. We've used both on caterpillar, sawfly and aphids with good results....I guess they have a longer lasting, more residual effect than soap (which smothers the aphids) since they presumably make the foliage unpalatable. I do like the idea of using plants to defend other plants too!