Caterpillars feed by chewing and ingesting foliage. One feeds voraciously on evergreens until the tree is dead, the other on the new tips of deciduous nut producing trees.
Bagworms; The female can lay up to a thousand eggs at a time which can lead to a huge population on a particular host. They emerge from mid to late May to early June. Cypress trees are the evergreens being the main course, Cedar and Juniper trees and shrubs being side dishes. We have also found them on Maples, Chinese Elms, Box elders, Willows and even Live and Burr Oaks. At infestation levels it warrants the application of pesticides to save the tree and or shrubs, otherwise picking them off, the organic approach is sufficient for control.
Fall Webworms; We have two species of webworms in this area the red headed and the black headed, each have 5 hatchings per growing season and they overlap. The female lays up to 600 eggs that hatch into foliage consuming machines. They begin feeding early in the season around mid May and could be seen all the way up to November. Outbreaks generally coincide with heavy rain and warm sunny days. Webworms feed on the new growth inside the web as they grow larger and more numerous. Hornets and wasps prey on this pest and can be seen shaking the web to coax the worm within range. In most seasons these predators and weather can control populations but as we are seeing this year prey populations are on the down side and pests are taking advantage of this.
It is not recommended to prune out webs or burn webs while in the tree. Upgrade health and vigor of tree by treating with a slow release approved tree fertilizer and systemic medicaments. Proper irrigation is also highly recommended along with tree spraying/trunk inject (specimens) with approved EPA medicaments.
Use only Qualified Certified Arborists who are licensed to prescribe and apply medicaments.