Was fishing with my son yesterday,he was twitching a worm under the surface.He was catching bass,but also pickeral.The pickeral would break his line.I'm thinking a wire leader might help,but not sure of the size,or will it affect the action of the worm?

Interesting.. A pike never broke me off with braid. I would use a small leader, like the size of your finger. They sell it at Walmart. 

Pickeral like pike or even barracuda have their teeth widely spaced, even still have been cut of with braid umpteen times.  I don't think too heavy a steel leader is needed, I also don't think the lure will be affected.  A number of options, can always buy inexpensive ready made and they work ok.  I make mine with surflon wire and crimps or light "piano" wire using a haywire twist.  Tieable leaders work fine but are more costly.  That all said, if I were fishing with a plastic worm I wouldn't bother with steel.

With plastics, I make some very light steel leaders using tie able wire. I tie one end directly to my hook, and the other to a split ring. I make them about 4 inches long. Tie able wire is tricky to use. It's expensive so you don't want to waste any, and it kinks and curls easily. It takes some practice to tie it without having it curl up on you. It does work. I got tired of having pike bite offs. The loss of tackle was bad enough, but I would have liked to land many of those that got away. I also am not comfortable leaving hooks in the face of fish.

Thanks Scott, you just talked me out of using tieable leaders, lol.  Actually I'm not much of a wire leader user, I take my chances using an ordinary leader.  Some species I fish for wire will reduce the number of strikes, I got off about 25 times in just a few weeks last year, but I caught a ton of fish.

I've always used small wire leaders, usually no more than 6" which were effective against pickerel and pike. I don't think they had a measurable effect on the fishing.

Interesting.. A pike never broke me off with braid. I would use a small leader, like the size of your finger. They sell it at Walmart.

You have been very lucky all it takes is having the braid run across its teeth.....

Get some small diameter leader material that you can tie or heavy fluorocarbon leader material, it's much harder than regular fluoro and should keep them from biting you off a majority of the time. 

You have been very lucky all it takes is having the braid run across its teeth.....

I agree for sure..........

I think the smaller toothy critters may actually have sharper teeth than the larger ones.

Was fishing with my son yesterday,he was twitching a worm under the surface.He was catching bass,but also pickeral.The pickeral would break his line.I'm thinking a wire leader might help,but not sure of the size,or will it affect the action of the worm?

I purchased some of this product in 18 and 25 pound test in 30 foot lengths and am very happy with it so far. Although it may not draw down like line does it does hold its knot and it does not kink. I have been using an Albright Special to join the lines and a Clinch Knot to the hook......

http://www.aquateko.com/Knot_2_Kinky_Titanium_Fishing_Leader_Wire_s/1.htm