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I planted some Fine Wine Weigela shrubs last fall. They seemed to be doing OK over spring then in the summer they took a turn in the wrong direction.

They lost their color and are a light green. Many of the leaves have torn edges. One is doing worse than the other and there's also a siberian iris planted nearby with similar damage to the edges and stunted growth while others do not have that problem.

I first noticed it after a heat spell in the summer. Thought it might be a lack of water but due to the heat but the damaged leaf edges made me think it might be insects. I haven't seen any bugs on the tops or bottoms of the leaves. I sprayed with neem oil just in case.

Here are some pics. I boosted the contrast and sharpness a bit because it's hard to see the plants against the mulch.

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This unwanted grass plant was growing right by the stem of the plant. I pulled it out and inspected the roots. There were a few white round things attached to the roots. I thought they might be grubs but I poked them with a stick and they crumbled into powder. The area has been treated with milky spore disease for grubs if that makes a difference. Here's a picture of the grass roots.

Edit: I think I'm seeing things. This is most likely the perlite from the soil the weigela came in.

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OrganicLawnDIY
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  • I'm a firm believer that insects attack that which is already weak. Likely there is some nutritional element that is missing from the soil which the shrub would like to have. Often in gardens, one section of ground will appear to grow healthier plants than others. Stripe chlorosis of older leaves, mainly between veins, while veins remain green indicates Mg deficiency. Chlorosis starting at leaf tips of older leaves can indicate N deficiency. What is the ph recommended for this plant? – Randy Aug 30 '13 at 16:21
  • pH requirement is 5.8-6.2 which I'll check the soil pH but it should be in that range. Soil was amended with compost and Plant-Tone fertilizer when planting. It's in full sun. Didn't get as much water as it should have during the heat spell and I wasn't doing much in the way of foliar sprays. Since I saw the problem in addition to neem oil I've been spraying with humic acid, seaweed and fish fertilizer as a drench and foliar spray and it seems to be helping at least a little. Should have started spraying before the summer stress. – OrganicLawnDIY Aug 30 '13 at 17:28
  • Yes, without water there is no soil solution which contains the nutrients by which the roots exchange H+ and OH- for other nutrients, but it seems general wilting would be displayed before something so specific as chlorosis of older leaves. Its hard to be sure, but the fact that some plants are suffering while others are not leads me to believe it's not entirely a water issue (unless there is reason to believe one plant gets more water than another). Lack of water could exaggerate an already underlying issue with the plant's compatibility with the soil. – Randy Aug 30 '13 at 18:05
  • Without an accurate soil test, it's hard to be sure the missing peice of the puzzle. You could try an all-purpose, balanced water soluble fertilizer to remedy the situation for now. I'd research this plant to see if it has any particular needs. Also, all the organics you've added could have left the soil a hair on the acid side, which should be temporary while the organics decay. Without a soil test, it's hard to say much for sure. – Randy Aug 30 '13 at 18:09
  • Like you said, "insects attack that which is already weak". The lack of water might have made it a prime target. The location might have been more desirable than other plants. I think I'm going to set up some drip irrigation for next year because this is a hard bed to water when it's hot out. Hopefully it survives. – OrganicLawnDIY Aug 30 '13 at 18:11
  • I took advantage of a sale at ace this spring and stocked up on soaker hose. I need several 100 more feet now with a garden expansion project I'm planning. I wonder if soaker hose can be found in bulk? Anyway, I really like the soaker hose under the mulch. – Randy Aug 30 '13 at 20:22
  • I was originally going to use soak hose but after some reading and contacting one of the manufacturers I learned that soaker hoses don't give even watering. They have less pressure and water flow at the end than at the beginning. The drip tubing that has the emitters in the tubing gives similar watering but with more even coverage. You can purchase that in bulk. – OrganicLawnDIY Aug 31 '13 at 04:21
  • I was wondering how the pressure would workout from beginning to end. I thought about asking in physics. The 250ft I have now seems to be doing ok, but I need to add at least that much more. Instead of running one long 500ft length, I could run two 250ft lengths. Also, it comes in different diameters. Put the smaller diameter at the end for more pressure. – Randy Aug 31 '13 at 14:44
  • Waste of time if you ask me. Why use something that you know will give you inconsistent results that you can't control vs drip emitter line that will give you consistent watering along the whole length for about the same cost. Check out Toro Blue Stripe. – OrganicLawnDIY Sep 02 '13 at 11:47
  • Cost is the main thing. The blue stripe is $1 per emitter and $30 per 100ft of hose. So if I have a plant every 2ft, that's $80 total cost every 100ft instead of $20 for soaker hose. For 500ft, that's $100 vs $400. I'm also not sure I like the emitter dumping water in just one spot. Roots may spread more than the emitter can cover. Also seems like emitters would relieve pressure at beginning which reduces pressure at end, no different than soaker hose. I think the emitter system is better suited for my fruit trees where large distance between plants don't need water. – Randy Sep 02 '13 at 15:29
  • Ah. I see the confusion. There's no need to buy emitters. The drip line I'm talking about already has emitters in the tubing so it functions like a soaker hose. The emitters are pressure regulating so the emitter at the front of the tube puts out the same amount of water as the emitter at the end of the tube provided you don't exceed design length which can be up to 500'. You can combine the emitter tubing and blank tubing where you don't need emitters. I posted some info on what I'm planning on doing on my site if you're interested. – OrganicLawnDIY Sep 02 '13 at 18:01
  • Oh I see now. You should write an article on drip tubing vs soaker hoses. What I need would be similar to what one would design for a corn field. – Randy Sep 02 '13 at 18:26
  • We're getting way off topic. If you search you can find lots of info on the subject and how to design a good drip system. – OrganicLawnDIY Sep 02 '13 at 19:01

2 Answers2

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I normally associate that kind of damage with beetles or caterpillars. The leaves have been eaten so much they look like oak leaves! None of the usual pest suspects like scale, mealybug or galls make damage like this so I cannot identify the species. However you can do some quick detective work yourself.

  • Poke around in the mulch at the base of the plant and see if anyone has made a home for themselves. Many pests don't like to go too far for a bite to eat.
  • go out a night with a flashlight and see if the pest is active at night
  • are there any other plants nearby that have similar damage?
  • is there anything on the underside of the leaf. ( a favorite hide out for insects)

Let us know...

Edit: the white stuff on the roots is mycorrhizae which are helping the plant utilize the nutrients in the soil and compost. Not a problem there.

Edit: after your observations that you could not see anything in action you are probably right to assume the cause has moved on. The key to prevention next spring is to make observation a regular part of your gardening. Once a week have a look at the plant and try preventive measures as soon as damage shows up. The presence of a pest one year does not mean they will return next year.

kevinskio
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  • I did see one small brownish round thing on one of the stems but couldn't tell if it was a bug or debris. I've inspected it during the day and at night but haven't seen anything. Haven't checked under the mulch. Will do that soon. There's another weigela nearby that has some but not as much damage and a siberian iris that shows similar marks on the edges that is not doing great. None of the irises I planted flowered but I think that might be a different issue. I have seen a lot of ants in that bed but they seem to just walk past those plants. Wildlife basically squirrels, racoons and skunks. – OrganicLawnDIY Aug 30 '13 at 17:36
  • I checked around the mulch didn't see anything except a little spider. The area was previously lawn and around the root of this some of it popped back up. Pulled most of it before but pulled up a grass plant just now. Thought they were grubs on the roots of it but they were hard and crumbled when poked. Maybe lime, milky spore powder or diatomaceous earth? I think beatles most likely problem for my area. If we can't identify the cause.. what would you recommend to help get the plant back to good health? – OrganicLawnDIY Aug 30 '13 at 18:06
  • I just saw someone post a picture of black vine weevil damage and it looked similar. Did a search for their larvae and saw a similar picture to what I saw. I edited my question to add a picture of the roots of the grass. The larvae wouldn't be dry and crumble when disturbed would they? Probably perlite from the potting mix the weigela came in. Freaking out and seeing things now :) – OrganicLawnDIY Aug 30 '13 at 18:30
  • Checked the plant a few times last night and didn't see any bugs on it or in the soil. Been checking during the day for a few weeks now but haven't seen anything. I think it's safe to assume whatever was eating it is gone now. Any thoughts on what I can do to help it recover and prevent this from happening next year? – OrganicLawnDIY Aug 31 '13 at 14:35
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Root weevil. Very hard to control but beneficial nematodes applied in the fall and again in spring is helpful.

BarkingPig
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