Because we have so few lily beetles in our test plots (thanks to our very effective biocontrol agent Tetrastichus setifer) I was only able to find eight adult lily beetles to test for their response to coffee. With so few beetles, I didn't want to risk losing any in an open-garden experiment, so I set up choice tests in plastic bins. Each bin contained a segment of a lily stem "planted" in about two cups of either soil from my garden or used coffee grounds. A beetle was placed in the middle, as shown below:
Lots of gardeners add used coffee grounds to their gardens to improve the texture of the soil. Several readers of this site have suggested that coffee grounds spread around the soil at the base of lilies might also provide an environmentally friendly way to deter lily leaf beetles. While this sounded entirely plausible (insects using their sense of smell to find their host plants might be repelled by any number of odoriferous substances), I always wondered whether the gardeners who swore by this method had actually reduced the populations of the beetle by other means, such as diligently hand picking the eggs, larvae and adults. A couple of days ago, I finally got around to putting the coffee solution to the test. Because we have so few lily beetles in our test plots (thanks to our very effective biocontrol agent Tetrastichus setifer) I was only able to find eight adult lily beetles to test for their response to coffee. With so few beetles, I didn't want to risk losing any in an open-garden experiment, so I set up choice tests in plastic bins. Each bin contained a segment of a lily stem "planted" in about two cups of either soil from my garden or used coffee grounds. A beetle was placed in the middle, as shown below: Five beetles headed straight for the coffee; three ended up on the lily planted in garden soil. When a beetle encountered the coffee, it wasn't in the least deterred, but climbed right up on the mound of grounds and walked across it to the plant. One reader suggested testing fresh coffee. He has a point. The coffee grounds used in my experiment had already had most of the caffeine extracted to make my morning cuppa joe over the past few weeks. Caffeine may, in fact, act as a natural insecticide, so freshly ground coffee might be a much more effective deterrent against incoming beetles. On the other hand, fresh coffee would be a very expensive way to keep lily beetles out of your garden!
8 Comments
5/18/2017 04:58:36 am
Most people drink the coffee in winter and enjoy. Overuse of coffee not good because coffee nature is very hot and it's not good for health. We should drink the coffee, but not daily.
Reply
Elizabeth
10/2/2019 05:28:07 am
I have been battling these beetles by both using coffee grounds which didn’t work and picking them off. Is there a cycle to these beetles. They are destructive and I’m hoping they will move on or die off. Can you suggest anything g
Reply
7/29/2020 07:14:54 am
You have shared a nice article here about the pest control services. Thanks you!
Reply
Ann
8/31/2020 08:45:35 am
I’m wondering if you mix garlic with coffee grinds whether that would be a great deterrent?
Reply
The Rodent
1/3/2021 05:38:55 am
Grew lilies in pots last year. Front garden ones decimated by extensive family of bright red beets despite daily checking and removal of any beets, eggs or poo. Back garden flourished with not even a nibble. Not sure why. I am trying Grazers G4 spray this year, also most will be in back garden. Will report back with any interesting developments.
Reply
suzanne
5/25/2021 12:48:00 pm
My lily plants were already being attacked shortly after emerging so I put fresh garlic in a food processor with water, let sit for a few days, strained the solution into a spray bottle and sprayed the plants. I have not seen a beetle since. The only damage to my plants is the damage prior to being sprayed. I now keep a constant supply of garlic steeped water in my fridge and spray a couple times a week. stinky but environmentally friendly:)
Reply
Maureen
7/28/2021 12:31:14 pm
I used finely chopped garlic with water, let it infuse , also egg shells crushed, with chopped garlic, put eggshells on the top of my plant pot,
Reply
Lilian
5/29/2022 08:54:35 pm
i finally got healthy soil, layers of processed kitchen scraps, eggshells, citrus rind, banana peel, coffee, tea grounds and soil, lilies are coming up healthy in
Reply
Leave a Reply. |
AuthorNaomi Cappuccino was a member of the Department of Biology at Carleton University in Ottawa, Ontario, Canada. She is now retired and no longer updating this site. Archives
June 2021
Categories |