Watch for Bagworms and Fall Web Worm Caterpillars

By Rene' Schmit

July 08, 2010 at 9:22 am  | Mobile Reader | Pring this storyPrint 

Two insect pests that can be quite troublesome during the summer months are bagworms and fall web worm caterpillars.

Bagworms are a common pest to Louisiana conifers especially on cedars, cypress, abrovitae and junipers.  They often go unnoticed due to their hanging, spindle shaped, silk-spun bags that look like miniature plant cones.  The earliest signs of bagworm injury are brown or stressed needles at the tip of branches and a heavy infestation can completely defoliate a conifer plant in a short period of time. 

Bagworms can be controlled by either picking off the bags (on smaller size plants) and destroying them or spraying with orthene, spinosad, carboryl (Sevin) or BT insecticides. 


It is important to spray in late evening or at dusk during the cooler time of day when the bagworms are actively feeding.  Keep in mind that more than one spray application may be necessary to accomplish a complete and effective control.


Fall web worms are out and in large numbers early so they will only get worse if left to forage.  These web building caterpillars infest many types of trees, in particular, sweet gum, pecan, cypress and river birch. 


Fall web worms produce a new generation every thirty days and will remain throughout the summer until either the tree runs out of foliage or the weather cools.  The caterpillars feed continuously and gradually enlarge their webs to encase more foliage as the larvae increase in size. 


Control can be accomplished with spraying carboryl (Sevin), orthene, BT or Malathion.  Add 2 to 3 ounces of a liquid soap to the spray to assure contact with the caterpillars. 
The soap allows the insecticide to cling to the caterpillars and to the webbing therefore reducing the number of sprays needed to manage the population. 


Again, spray in late evening and be sure to always follow label directions.




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