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