Lettuce grub - any ideas?

[Nicos]

Sorry, no photos as OH threw it to the chooks before I could call out ‘Bob’s your Uncle’ or anything else tbh!

I pulled a lettuce which was just beginning to bolt and was preparing it in the kitchen sink when I noticed it had a brown , wet, hollow stem.
I put it down to the heat but then on closer examination I noticed a smooth, fat, creamy grub ( about 7mm long by 5mm wide ) closely attached to the outside of the stem but with no obvious access from the outside of the plant.
They may not be connected but I’ve never seen such a fat grub inside a lettuce before and was concerned in case my land might be showing early infestation with anything?
We’ve grown lettuce in the same area for several years now with no problems …could this the start of something new and maybe I should grow them elsewhere?
Its actually the coolest, most shaded part of my sun blasted garden and they’ve never done well elsewhere.

[Plot70]

I bet that grub was the first thing to disappear

[ameno]

Lettuce can get root flies just like cabbages can (although it's not the same species, and they are not nearly as common), and they will sometimes tunnel into the stem, but those proportions you describe make it sound more like a beetle larva than a fly maggot, so I'm not sure.
Did it have a noticeable head? Fly maggots usually do not, and it can be hard to tell which end is the head, whereas beetle larvae almost always do.

As for how it got into the stem, it would have tunnelled in when it was freshly hatched and still tiny, then the tiny entry hole would have healed over, and it when continued to feed and grow inside the stem.
It's like coddling moth larvae in apples. The hole you sometimes see is the exit hole. The entrance hole is tiny and already healed over, making it invisible.

[Nicos]

Couldn’t see a head nope…a fly maggot?…blinking heck , it must have been a big fly!…the maggot was huuuuge!
Interesting, thanks!
I’ll definitely be on the lookout inside the other lettuce. OH is under strict instructions to take a photo next time.