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Mr. Smarty Plants - What are the webs floating in the air? Are they harmful to plants?

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Sunday - October 03, 2010

From: Austin, TX
Region: Southwest
Topic: Pests
Title: What are the webs floating in the air? Are they harmful to plants?
Answered by: Nan Hampton

QUESTION:

Austin, TX has experienced fall weather for the past week..low humidity, nice temps, sunny skies. But long webs are connecting from trees to our plants to the porch. Not on the trunk of the tree like tree lice. Just tons of long webs floating in the air and anchoring on everything:plant and not. What is making them? Harmful to trees and plants? It's not the time of year for web worms or caterpillars. Thanks kindly.

ANSWER:

These are mostly small spiders, each of which has released her/his own string of silk that serves as sort of a balloon or sail to help them fly away on the breeze.  This is their means of dispersing to a new habitat.  Many, but not all, of them are spider hatchlings that are dispersing from their hatching sites to find new territory away from their numerous siblings. Larger spiders can balloon, too, but it takes more silk and more breeze to get and keep them airborne.  Here is a short video from bio-physicist Bob Suter from Vassar College showing spiders launching themselves and explaining how they do this.  Here are links with more information from Purdue University Extension, LiveScience and the Conservation Commission of Missouri.  The webs and spiders aren't harmful to plants.  In fact, if they land on your plants, decide they like their new spot and don't look for the opportunity to relaunch on their gossamer balloons, they will no doubt consume many insects that could be harmful to your plants.

 

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