bugs eating up bushes

Question: please help identify these bugs. they re near the water edge of the lower Poptomac river. spreading quikly over a few day form bush to bush

responder: Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied May 10, 2023, 1:41 PM EDT
response: Hi,  These appear to be a beetle larvae. We do not currently have an entolomologist on our staff team to confirm, but we believe them to be a Baccharis Leaf beetle Larvae. (https://bugguide.net/node/view/77596) They are native and feed on the native Baccharis or Groundselbush plants (assuming that is what is along the water and makes sense that it is).  From Alabama Forestry Commission:  ECOLOGY: The plant is adapted for coastal conditions, it is very resistant to salt spray, flooding, and can tolerate poor sites with low nutrient levels. It does have some wildlife value as small birds will frequently nest in the open branches. It has been used as an ornamental in urban areas around the coast, this is cautioned because the pollen is thought to be allergenic. The seed requires light to germinate so it is often found in open areas. Fence rows, field edges, and disturbed areas such as recently thinned pine stands are especially prone to invasion. The plant may go unnoticed until it blooms in the fall. Baccharis can grow to over 3 feet tall in 2-3 years and will compete for resources that would otherwise be available to crop species in a commercial pine plantation or pasture setting. E. baccharis will readily colonize irrigation ditches and drains because they provide favorable habitat. When E. baccharis is present in natural coastal locations, the baccharis foliage feeding beetle (Trirhabda baccharidis) can reach very high densities. The beetle larva hatch in the fall and can completely defoliate large numbers of E. baccharis. The beetle is rarely observed when the plant colonizes offsite (in a pine plantation for instance). https://forestry.alabama.gov/Pages/Informational/Invasive/PDF/Eastern_Baccharis.pdf Also from USDA (page 2 - right hand column)  https://plants.usda.gov/DocumentLibrary/plantguide/pdf/pg_baha.pdf  Since you are located in Charles County and this is water front, you may want to confirm on your county critical area maps before using anything to treat the larvae. An outbreak of a high population might defoliate plants but like many insect population booms, it probably won't repeat itself too often/regularly as predators will find them and kill-off a number of them. Many insecticides are harmful to aquatic animals so we would not recommend use of any product near water. Given that the beetle is native and the plant is its host, and also that Baccharis is consider almost weedy in many areas, we are assuming that the shrubs will survive either through re-sprouting at the base or may leaf out again.  Let us know if you have further questions about this.  Emily

responder: The Question Asker Replied May 10, 2023, 3:10 PM EDT
response: Thanks. I think you identified it correctly. Would the brush come back better if I trimmed them down. They do normally hold a lot of birds nests.  Anders  On May 10, 2023, at 1:41 PM, Ask Extension <<personal data hidden>> wrote:    ﻿

responder: Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied May 11, 2023, 2:03 PM EDT
response: You may want to wait and trim them after the beetle larvae have moved on, if you don't see any leaves left for them then, you could trim them. You can also do a scratch test and see if the stems and branches are still green. They might flush out new growth if they are.