Caterpillar Alert!

gillnurseryProblem Solving, Timely Tips12 Comments

I have had several customers bring me Tussock Moth Caterpillars they found munching on their oak tree leaves.

The creamy white hairs on the caterpillar are long and bristle-like and spread out in tufts down the sides. Two long, sharp black pencil like hairs protrude near the front and rear and these hairs are connected to poison glands, which excrete venom on contact. Contact with the venom may result in itchy irritation.

You can spray your tree with Hi Yield Thuricide Concentrate or Natural Guard Spinosad Hose-end. Both of these products are organic and safe to use on all plants. Thuricide reacts with the cells of the stomach lining of the target pest causing them to not be able to feed within hours of ingesting. Spinosad is a contact kill, but still safe and organic for all plants.

(photo via


12 Comments on “Caterpillar Alert!”

  1. Have noticed green thin caterpillars on bogunvilla. What would be best for this..would a hose on product work?

    1. Dust with Dipel in the early evening. Dipel is harmless to all but caterpillars. No need to pull out the hose, measure, mix, or rinse. Concentrate on the tips, that’s where the caterpillars go first.

    1. Thruricide will not harm ladybugs at all, Spinosad is quick to break down so you would not want to spray on ladybugs, but the area will be safe for them next day or day after.

  2. My oak has obviously already had severe leaf damage unless some of the branches are dead from something else.How long until leaves come back?

  3. Will Thuricide or Spinosad be harmful to birds? So many warblers passing through I wouldn’t want to cause injury or death.

    1. Copied from National Pesticide Information Center
      Can spinosad affect birds, fish, or other wildlife?
      Spinosad is practically non-toxic to moderately toxic to fish depending on the species. It is slightly to moderately toxic to aquatic invertebrates. However, spinosad is very highly toxic to eastern oysters. Spinosad is practically non-toxic to slightly toxic to birds, based on studies with bobwhite quail and mallard ducks. It is moderately toxic to earthworms. Spinosad is very highly toxic to bees. However, evidence suggests that spinosad has little or no effect on honey bees and other beneficial insects after sprays have dried.

    1. Spinosad is an organic with relatively low toxicity and breaks down quickly, but as with most pesticides you should remove their toys and dishes from the area to be treated, and let the treated area dry before letting the dogs out. That said, Confortis Flea Control for dogs and cats is Spinosad in a chewable tablet. Not to say it is good for dogs, but apparently they can tolerate it to the degree prescribed to kill fleas.

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