A nursery is having significant damage with the feeding of caterpillars on water lettuce - the aquatic environment makes it difficult (fish) to find an insecticide to use - Is manual removal the only option? The caterpillar appears to be a type of moth. Thanks Steve Powell

Steve.Powell@tn.gov

Answer #2 · Gardenality.com's Answer · Caterpillars are usually a temporary pest. I would suggest removing the plants and putting them in a container filled with water from the pond. Maybe try putting a few of the plants back in the pond in a week or two to see if the caterpillars are gone.)

Answer #3 · Maple Tree's Answer · Hi Steve-This was an interesting question as I enjoy the beautiful foliage of the water lettuce and water hyacinth in my pond every year. Fortunately I have never had a problem with the Water Lettuce Leaf Month or Weevil on my plants. I too did some research and found the only cure for this problem as Brent and Brooks mentioned is removing the caterpillar (Larvae) by hand. This is especially true for those ponds that have fish and other aquatic life. As Brent mentioned you can possibly remove the heavily infested plants from the pond and return them after the larval stage. The larvae stage lasts from 17 to 20 days so returning the plants after this will help to stop or slow the ponds infestation as the adult months do not eat or harm the foliage as the larvae do.

Unfortunately the water lettuce and water hyacinth are considered extremely invasive plants in many of the southern states. The water hyacinth is listed as one of the most productive plants on earth and is considered the world's worst aquatic plant. It forms dense mats that interfere with navigation, recreation, irrigation, and power generation. These mats competitively exclude native submersed and floating-leaved plants. Low oxygen conditions develop beneath water hyacinth mats and the dense floating mats impede water flow and create good breeding conditions for mosquitoes. Water hyacinths are a severe environmental and economic problem in all of the gulf.

The Water Lettuce Leaf Moth and the Water Lettuce Leaf Weevil evidently has been introduced into many areas for biocontrol of water lettuce and water hyacinth. As these are a popular plant for many with ponds it is most likely going to be a problem as these insects will be moving into residential ponds. I'm thinking most likely parks, golf courses, and other sites that enjoy a controlled amount of these plants are being affected also.

Hopefully the nursery's infestation isn't extremely harmful to the plants they have and will survive through this larvae stage of the Water Lettuce Leaf Moth.

John)

Answer #1 · Gardenality.com's Answer · Hi Steve,

I did some extensive research and all I could find was what you had mentioned above....manual removal.

Brooks Wilson)