The world is a big scarry place at 2 yrs old. I think girls tend to be more affected by it than boys in general.
Our daughter (now 6) stepped on a lady bug. One of the orange ones that sorta sting you. It got between her toes and she REFUSED to walk at grandma and grandpas house for about a year. She would freak out if someone said lady bug...
But whats our son, now almost 4, scared of? right now its BUCKS... And my hubby doesn't make it any better by snorting and yelling buck if boy is out side. But that doesn't stop boy from going out and helping to look for bucks with daddy. lol (I think they are gluttons for punishment)
My little brother was scared to death of an imaginary friend he called "baboom". My hubby got my nephew in laws to fear Yaks... His sister really got on him for that...
My niece in law (currently 11 months) screams EVERY time she sees this odd looking duck puppet... My 11 mo. old son LOVES the same puppet.
If you explain what the purpose is, and don't make a big deal out of it, they usually get over it soon... You've probibly told her things like " the green light helps let mommy know the house is safe... Or the worms make the ground healthy..." It does get better, their fears diminish as they grow in their mental ability to reason. Thats when our fears as moms kick in... So sit back and relax, Enjoy seeing her running around being scared of worms. It won't be too long before you hear the dreaded scentence... " I think he's cute"... AHHHHH!!!