|Luckily this snail was exploring the possibilities of compost digestion before deciding to attack my lettuce 'Amaze'. ...Or was it?|
The majority of you reported this is so with the varieties you've been growing this year. This is a top tip, particularly for any wet year which leads to a population explosion of these pesky pests. Resistant varieties particularly mentioned were Red Salad Bowl and Dazzle.
Others said they hadn't noticed any difference, or indeed their slimy populations seemed to prefer red varieties such as Lollo Rosso, so it seems it's not quite as simple as red vs green. @littlesaladco said he'd found sappiness and leaf thickness was important, with the more sappy, thinner leaved varieties being preferred.
During this conversation, I vaguely remembered something I'd studied in A Level biology, where slugs showed an aversion to plants producing compounds from the cyanide family (thankfully not enough to be poisonous to us!). I believe this is what Alys Fowler was referring to at a talk I went to earlier in the year when she mentioned lettuces produce bitter tasting compounds when nibbled. It's a defence mechanism which usually prevents further eating: probably not enough for a wet year like this one with slugs and snails in abundance though :/
Then came the breakthrough. Zoe Lynch came back with a reference showing the presence of anthocyanins in red lettuces might be a key factor. I'm also wondering if these levels are higher in sappier lettuces irrespective of their colour. Of course there may be other factors at play, all contributing to a sliding scale of nicer tasting (probably sweeter) and juiciness, with mainly red at one end (not so palatable) and mainly green (oh so tempting) at the other.
Some saladchatterers said they found red lettuces weren't as nice as green ones, as they tend to be more bitter tasting. It looks like it's not just our pesky pests which have a preference for sweeter tasting, generally greener lettuce ;)
With thanks to Annemieke who originally posted the comment which led to our conversation on #saladchat. Also thanks to the people mentioned above plus @CarlLegge, @CountryGate, @karlasparlour, @maogden, @nicelittleplace, @PatientGarden, @Swanimages, and @wellywoman for joining in the conversation.
I feel the need for some field trials next year :)
NB I also found some other references around this subject if you're interested:
- Predator flower colour preferences on wild radish. The white or yellow flower colour preferred by slugs is thought to be due to these plants having less anthocyanins (recessive gene) than their pink or bronze coloured relatives (dominant gene)
- A rather nicely done school project re slug preference of anthocyanins vs anthoxanthins on pansies