What's eating my dahlia leaves?

lyssa13May 31, 2013

Help! I have two potted dinnerplate dahlia plants that bloomed beautifully when I bought them. However, they are now sad and the leaves are all eaten with holes.

Based on these pictures what do you think it is? What do I do to fix it. And will my plant come back alive once I fix it or is there a chance it's dead?

Help, I'm very much a beginner at this and trying to learn!

Whatever this is hasnt touched anything else in my backyard, just the dahlias!

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Second photo

    Bookmark   May 31, 2013 at 12:35AM
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Oops sorry

    Bookmark   May 31, 2013 at 12:36AM
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Noni Morrison

Slugs! They love young dahlia plants...As long as your tubers are undamaged they should put out new healthy foliage but you need to get rid of the slugs or snails, which ever you have. Use slug bait, or hand pick them off the plants after dark when htey come out to forage.

Bait around your plants with either a non toxic to children and pets slug bait or if that is not an issue, try "Deadline". I have an organic garden so I spray my plants with a mixture of 1/3 household ammonia and 2/3 water. Reapply after rain.

    Bookmark   June 5, 2013 at 10:05AM
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I have never heard ammonia used as a preventative, only direct retaliation on browsing slugs. Have you seen a clear difference between sprayed and not sprayed plants? I like the idea of using ammonia spray instead of or addition to the expensive pellets. Someone on the list recently said that ammonia actually is beneficial for dahlias, too, but I'm not sure how that would be.

Have you had any noticeable decrease in other critter damage as a result of using it as a preventative?

I've heard you can use full or dilute ammonia on trash cans to deter bear, raccoon and opossum from molesting the contents (with varying success, depending on whether the pest has already formed a habit eating your garbage)

I wonder if an ammonia solution might work for nibbling rabbits... I've been using two commercial sprays intermittently (one specifically for baby rabbits), and the bunnies seem to think both tastes like salad dressing.

    Bookmark   June 10, 2013 at 12:35PM
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Noni Morrison

Ammonia IS a high nitrogen fertilizer. The plants love it! I think as long as the odor lingers it works but needs reapplying every few days. And of course the best time to spray it is when the slugs are out enjoying a gourmet feast! But the residue actually will work for a few days if its not raining. Best is to try to capture and dispose of, or poison the slugs before they get to the plant. The two pronged approach as worked well for me.

    Bookmark   June 12, 2013 at 11:01AM
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Interesting... Thanks for your input!

I think I'm going to make my own concoction to spray...
Equal parts Ammonia and commercial rabbit/ deer repellent
Dissolved epson salts (magnesium for plants)
Dish soap (surfacant to get solution to stick, and an earwig/aphid deterrent)
Hot sauce (most the critter deterrent recipes have it in there, so why not)

The growth month of June makes or breaks dahlias, so I figure, give them as much of an advantage I can!

I've heard that an old corn cob soaked in vinegar and lain on the edges of the garden deters critters, too, but I'll pass on that technique for now.

Also, when the plants are grown, trimming bottom leaves off and coating the bottom two inches of the stalk with vasoline helps keep bugs from climbing up to munch on blooms.

    Bookmark   June 12, 2013 at 11:54AM
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I have several plants that look just like the photos. I know that earwigs are eating mine because I go out after dark with a flashlight and have caught them in the act. I dusted mine with Diatomaceous Earth directly on the leafs and on the ground around the stem. I'm still seeing a few but the numbers have been greatly reduced. My original concern was the potential damage the D.E. might do to the plant. After considerable research on the internet it seems D.E. is totally harmless to plants, pets and people. It is even used to dust pets for flea control. Unc

    Bookmark   June 12, 2013 at 12:56PM
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Noni Morrison

By the way, the ammonia spray will kill and defend the plant from aphids too. I first started using it for aphid infestations on my rose bushes.

Now, 10 years laters, following organic principles as much as possible, I have seen NO aphids on my roses this year, but the garden is full of birdsong..

    Bookmark   June 13, 2013 at 4:22PM
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Lizalily, how did you come to the conclusion of one third ammonia to two thirds water? Did you experiment with stronger solutions and see leaf damage, or were you following someone else's recipe?


    Bookmark   June 15, 2013 at 11:32AM
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Noni Morrison

I was following someone else's recipe from long ago when I used to follow the Cut flower Forum on Garden Web. I tried it, it worked and i like the results. I used this to clear the aphids last year when the ants were farming them on my dahlias.

    Bookmark   June 17, 2013 at 9:29AM
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Thank you! I'll try to stick to that ratio from now on with the ammonia. I used a bit more then 50/50, and think I burned some leaves. No harm done, but I'd hate to burn buds!

My concoction above has been mostly working, but if it rains, all bets are off. I was busy this weekend, and wasn't as viligent spraying twice a day (very rainy here), and a good dozen plants were munched half way down to the ground. Very irritating, watching those cute little tails race away from me. No slug damage (I had baited early on in the season), but I have seen earwig damage since spraying.

    Bookmark   June 17, 2013 at 1:25PM
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I always have problems with slugs, especially early in the dahlias growth cycle from the time they just start coming up til they are a foot tall, but if they make it through that, I don't have any problems with them later when the plants are bigger. I've never seen any slug damage on leaves above about a foot tall.

It's been terrible this year, especially since its raining seemingly 4 days a week or more, like right now! That's made using chemicals or bait almost useless because it either wears off or the baits just disolve. Plus they are growing so slowly due to cooler temps and too much rain, so it seems like they just don't want to grow like they should, and some have died due to rot mainly, but at least 2 were completely stripped bare by slugs forcing me to dig them up and replace them. Thankfully I had many extra tubers stored in pots from last year, so I've been able to replace dead plants.

    Bookmark   June 17, 2013 at 8:22PM
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Two words that will help you, will not over fertilize, will not damage beneficials, and works quite well when done strategically:

Diatomaceous Earth

Kills 'em all. Nothing else needed aside from NORMAL fertilizer (which Ammonia is not - it's very bad). Anything ammoniacal deteriorates your soil condition, and especially when used with frequency.

I've used DE for nearly 2 decades in my veggie and show gardens and little to no problems (that is when I actually do it right lol!)

For pots, I put straw at the top to keep evaporation in check and drastically reduce watering requirements. I sprinkle DE both under and on the straw. I have a set of large buckets I soak my pots in, making sure the water level is below the top of the soil level so as not to wet the DE. The DE scrapes them up when they climb (or ooze) their way in and they're dead the following day. It's crazy how many dead slugs and earwigs I find around the pots. I sometimes have to break out a broom because it looks like a killing zone.

Another way I control them in the veggie garden is to take old plastic containers (i.e. cottage cheese, etc.) and put a couple ounces of vegetable oil and tuna juice in their. Earwigs literally pile up in there - it's disgusting, but makes me laugh inside >:)

Bottom line is the damage has dropped significantly and I'd say that those particular bugs are not problems for me any longer - not that they don't exist. Now, SVB... that's one bug that's pi**ing me off - but a different topic altogether. grr...

Good luck!

This post was edited by gsweater on Fri, Jul 19, 13 at 22:11

    Bookmark   July 19, 2013 at 10:09PM
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salt will kill slugs also but it may harm the plants so be careful

    Bookmark   July 23, 2013 at 10:12PM
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Slugs and snails do NOT like coffee grounds. I place a healthy ring around my dahlia beds along with some crushed egg shell and slugs leave. An organic and safe pellets is Sluggo Plus also gets earwigs but is pricey. I use it only when earwigs attack.

    Bookmark   August 18, 2013 at 7:02PM
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Steve, I was thinking about setting up a coffee ground collection bin (5 gallon bucket) at a gas station and a local coffee shop, and using it on top of the mulch, working it in the soil with leaf compost after the tubers are dug.

What say you? Would the grounds next to the stems and applied heavily do any damage to the blooming dahlias?

    Bookmark   August 20, 2013 at 12:10AM
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