If you see weeds and wonder if it is Hydrilla the following "quick test" was taken from a previous post.

Hydrilla is often confused with the native Elodea or the non-native Egeria. Hydrilla has one or more teeth on the underside of the midrib, neither Elodea nor Egeria have these midrib teeth. The teeth make Hydrilla feel rough when drawn through your hand from base to tip. ~ Texas A & M.

I'll admit I don't know one water weed from another......just ticks me off when they stick on my lures !....lol    I'll have to be more observant into the future.
 
What's amazing is how resilient some water weeds are! They completely drained a small lake in our town, dug it out deeper, refilled it and it's already half choked up with weeds a few years later.....unreal.      

Learned something new, did not realize there are two variant forms of Hydrilla, the more I learn the more I learn that I do not know.
 
Hydrilla: Ask the Expert James Balyszak  /  Cornell University Cooperative Extention
CCE Invasive Species Program
 
Q: How effective is drawdown as a control technique for Hydrilla and what depth is recommended in order to completely eliminate populations? Does the effectiveness depend on snowfall and winter temperatures?
A: For drawdown to be effective, the soil temperatures and sediment need to experience a hard freeze to affect the hydrilla tubers. Drawing down the water will expose the sediment to air temperatures, which must fall below freezing for a semi-extended time. Snow cover will act to insulate the exposed sediment, which can reduce drawdown effectiveness.
Q: How did hydrilla get to the U.S.? Where is it from?
A: Hydrilla first arrived in the U.S. in Florida in the late 1950’s through the aquarium trade. An aquarium was most likely dumped into a local waterway, and from there hydrilla spread throughout Florida and beyond. The strain of hydrilla in the southern states (dioecious hydrilla) originated in Sri Lanka.
The strain of hydrilla found in the northern climates (monoecious hydrilla), originated in Korea, and has the ability to withstand colder environments. While we cannot pinpoint the exact cause of infestation, there are several possibilities. Transport of hydrilla fragments on a boat/trailer/equipment from an infested water body is the most likely cause. An illegal aquarium dumping is also a possibility. Unfortunately, hydrilla was discovered after the infestation had become established, so it is nearly impossible to determine the original cause of the infestation.

Old Dog- I will check out the northwest corner of the causeway this summer. For Bennett Bay- I'm assuming you are referring to the small bay that Bennett Run flows into just south of the spillway between the spillway, Hartstown Road and Fries Road? We treated the Phragmites in that area this past September. I noticed the bay was full of lotus but didn't see any hydrilla. Let me know if you are referring to a different area.

What time of year do they treat Hydrilla at Pymy ? How many times also?  Does the treatment chemical affect any fish or other aquatic life at all ?   

I'm like the Captain, really don't know one from another, just weeds.  But I do have a couple questions as well.  One, wayyyy back when, probably thirty years or better, there was a huge downturn in the perch population.  Not only numbers, but size as well.  Pymie used to have fantastic perch fishing in regards to very large specimens being caught.  11 and 12 inch perch were not uncommon.  Rumor back then was they treated the weeds and it really decimated the perch population.  Do you believe there was any truth to that, or was it even possible?
The other question I have is a bay that I used to launch my boat in, As you approach the spillway it would be on the left (southwest?) side of the road.  You have to exit the bay under the old railway bridge to enter the main lake.  I used to use that bay all year, even though it's nothing more than a sandy beach, but now by May it is choked full of what looks like lily pads!  What caused that?  Same with many areas all throughout the northend.  I assume the nitrogen rich run off from the farms had something to do with this, but how/what are the plans to contain  or reverse it?

Captain Hook- For 2016 we used two different herbicides to treat the hydrilla. Sonar (fluridone) is granular and required three treatments starting when growth first starts in from the tubers. In 2016 it was once in June, once in July and once in August.  Aquathol (endothall) is liquid injection and is a one time treatment. We did one treatment in July. Both are labeled specifically for hydrilla and showed differing strengths and weaknesses.  While they can impact other vascular plants in the treatment area, there are zero water use restrictions for drinking, fishing, swimming, or livestock/pet consumption at the concentrations used.
 
Opsman- The "lily pads" you are seeing are American Lotus. Though native to the US, the species first appeared in Pymatuning in the late 90's and quickly became invasive causing access issues to mooring areas and launches. The park attempted using the weed harvester to control and found it to be ineffective. We now selectively treat certain areas to keep navigation channels open. As far as perch populations, speaking with the other assistant manager here, we believe it was due to a few factors. I can say that the herbicide treatments that were done should have absolutely not had any impact to the perch. More likely that was the time that walleye and crappie were really getting established. The perch simply couldn't compete. Also perch tend to like deeper water than what Pymatuning Lake can provide.

Even tho it doesn't affect the fish, it does affect where the fish will be. Weedbeds that had produced great catches of gills and crappies for numerous years were practically devoid of the beds that were normally there last season. I did manage to find some areas that still held bedding gills but not nearly the numbers of years past. I'll adapt to where the fish move too. Just hope it doesn't turn out like Shenango is, with very few weed beds for the bigger gills to spawn in.

Now if ducks and geese eat those Hydrilla plants at Pymy and fly over to Mosquito Lake and deposit their droppings there, are those seeds or whatever capable of spreading ? 
 
Shenango had good weeds when it was first flooded......no more.

 Waterfowl spread all kinds ov stuff, ain't gonna stop it from spreading. Buddy dug a hole last spring in yard & filled with water for frogs. By end ov summer full of minnies from birds.
 
crappy