Get Rid of Pesky Hornworms, Caterpillars and Grubs–the Organic Way!

Spring has spring and bugs are emerging.  I recently spotted a hummingbird moth in my garden and then discovered grubs while planting bulbs later that day.  These two innocent looking bugs are actually very destructive.  Luckily, they can be easily eliminated with completely organic, non-toxic and animal-safe products.

Tomato Hornworms and Caterpillars — Vicious and Disgusting

''Manduca quinquemaculata'' adult female taken by Shawn Hanrahan at the Texas A&M Insect Collection in College Station, TexasHummingbird moths are beautiful, but their larva is the damaging Tomato Hornworm (Manduca quinquemaculata) caterpillar.  Hornworms can demolish a crop of tomato/eggplant/pepper plants overnight.  Their color makes them hard to see until the damage is catastrophic.  I once thought that the only way to control hornworms (without toxic pesticides) was to hand-pick them off the plants.  Unfortunately, hand-picking is not effective when plants are large and mature.  Unless you have an active control strategy, you will never be ahead of the battle once the first eggs are laid.

Skip Ahead to Organic Options for Controlling Hornworms

White Grubs – Background

Various white grubs

And then come the white grubs.  They are often found curled up in a little ball when you are digging.  They are usually around 1 inch long and about 1/4″-3/8″ in diameter.  These white colored grubs are the larvae of several kinds of beetles.  The beetles lay their eggs in the late summer and the hatched larvae burrows in the soil to feed on any roots they can find.  Depending on the species, they will spend upwards of 4 years underground.  The grubs can damage any plant you have including flowers, vegetables, trees, lawns, shruubs and more.  If you find a single grub, I can assure you there are probably many more.

Skip Ahead to Organic Options for Controlling Grubs

Organic Options for Grubs, Caterpillars and Hornworms

Tomato Hornworms (and any other caterpillar pests)

In the past you could wait for another bug/bird to eat them or you could hand-pick them off your plants.  Both methods will not kill 100% of the hornworms and will leave some behind.  I believe it helps to use a reactive and preventive approach for hornworms.  Basically, kill the ones you can and kill any new ones before they inflict large amounts of damage.

Luckily, there is a bacterial pathogen that will kill nearly any caterpillar, known as Bacillus thuringiensis (BT).  BT is a naturally-occurring bacterial disease of caterpillar-like insects.  It is non-toxic for humans and animals and can be used up until the date of harvest.  I have used the Bonide BT Concentrate because it is certified organic, works fast and is cost-effective.  I spray down my garden every week (and after any rainstorm) during hornworm season and rarely find any sign of hornworms.  BT will not harm beneficial insects including bees, butterflies, praying mantises, spiders, ladybugs, etc.  And BONUS….you can also use BT to kill tentworms and all other caterpillar pests.

I personally use and recommend the following for organic hornworm control:

Bonide ThuricideSolo 419 2-Liter One-Hand Pressure Sprayer

 

 

 

 

 

 

White Grubs

There are only a few non-chemical methods to control white grubs.  The first is soil cultivation (tilling) in the fall and spring.  It will kill some of the grubs, however it will still leave some burrowed underground.  Tilling is also not an option in many flower beds, raised gardens, lawns, near trees or in no-till gardens.

The second option is an organic and pathogenic bacteria, known as “milky spore” or Paenibacillus popilliae.  This bacteria is a disease of white grubs and rapidly kills white grubs when ingested.  When applied, the milky spores in the soil are swallowed by the grubs, and then rapidly reproduce inside of the grub.  This continues for 1-3 weeks until the grub dies.  Once the grub dies, millions of new spores are released into the soil–spreading the disease to more grubs.

Milky spore is not harmful to beneficial insects, bees, birds, pets or humans.  It also performs well in very cold and dry regions.  And BONUS — Most people only need to apply it one time because most spores remain in the soil for up to 20 years!

Application is easy.  I mix the appropriate amount of milky spore powder with dried coffee grounds (fine sand will work too) and then use a hand-spreader to apply it to the infested area.  Make sure you water it in thoroughly after application.  I apply milky spore in August, when the grubs are closer to the surface and feeding–but it can be applied any time of the year.

I personally use and recommend the following for organic grub control:

Milky SporeScotts Hand Spreader

 

 

 

 

 

 

Your feedback is appreciated, please leave a comment below with any questions or suggestions you may have!

 

5 thoughts on “Get Rid of Pesky Hornworms, Caterpillars and Grubs–the Organic Way!

  • Harvest McCampbell

    The bad thing abut Bacillus thuringiensis is that it can infect people, and that its toxin, widely known as Bt toxin is also toxic to people. This is primarily a concern of the very young, the elderly, and those with compromised immune systems, as well as farm workers. I do not personally consider using any form of Bt or its toxin to be organic–even though USDA Organic certification allows for it. If you have been following all the research on GMO corn and the fact that many animals will not eat it, and the health hazards uncovered that the industry is trying to hide–it will give you a little clue about this toxin. Much GMO corn is engineered to produce Bt toxin.

    Reply
    • Matt I Am

      Thank you Harvest for your contribution. However, there are no documented cases of human infection by Bacillus thuringiensis. The toxin produced by Bacillus thuringiensis is rapidly metabolized and is not toxic. I cannot speak for the GMO engineered BT toxin, but I would agree it is probably much more potent and dangerous.

      “No complaints were made after eighteen humans ate one gram (g) of commercial B.t. preparation daily for five days, on alternate days. Some inhaled 100 milligrams (mg) of the powder daily, in addition to the dietary dosage (6). Humans who ate one g/day of B.t.k. for three consecutive days were not poisoned or infected.” (Source: U.S. Environmental Protection Agency. 1986. Pesticide fact sheet for Bacillus thuringiensis. Fact sheet no. 93. Office of Pesticide Programs. Washington, DC.)

      “Eight human volunteers ingested 1 g of a Btk (Bacillus thuringiensis subspecies kurstaki) formulation (3×10+9 spores/g of powder) daily for 5 days. Of the eight volunteers, five also inhaled 100 mg of the Btk powder daily for five days. Comprehensive medical examinations immediately before, after, and 4 to 5 weeks later failed to demonstrate any adverse health effects, and all the blood chemistry and urinalysis tests were negative.” (Source: [WHO; Environ Health Criteria 217: Bacillus thuringiensis (1999). Available from, as of June 3, 2010: http://www.inchem.org/pages/ehc.html **PEER REVIEWED**)

      MotherEarthNews even recommends making your own BT using Milk as a culturing medium (Source: http://www.motherearthnews.com/organic-gardening/milk-natural-pesticide-zmaz82mazglo.aspx#axzz2zd5jqPp4)

      Bottom line, the bees, black widows, centipedes and other stinging insects in my garden are much more toxic (potentially lethal) than the readily metabolized toxins produced by this bacteria. There is a risk to everything you do and everything you eat. BT may be too risky for your lifestyle, but it allows me to grow healthy organic tomatoes/peppers/eggplants. I have been eating this produce for years and have never had a single side effect from BT.

      Reply
  • Shelly

    My vegetable garden was decimated this year by zillions of grubs, mostly of the Japanese Beetle variety, but also a few Hornworms. How did I resolve it quickly (which was of utmost necessity by the time I had discovered it, as there were still a few of the 15 tomato plants left that I had started from seeds)? Nematodes. They are the ticket, my friend. Try them!

    Reply
  • nadlou

    Another form of controlling the grubs… chickens!

    Reply
  • Tasha

    Thank you so much! I cannot wait to receive this product! I have had army worm infestation every summer for the past 5 years (well, last year they didn’t really infest as bad), and it drives me crazy. I don’t know why they keep choosing my tree. My neighbor said his tree developed a fungus from them about 2 years ago and he cut his whole tree down, hoping it would grow back recovered. It still hasn’t grown back. I hope my tree doesn’t develop said fungus. Should I spray at the beginning of spring as a preemptive measure? Or, will it just work once eggs have been layed?

    Reply

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