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What is on my hydrangeas? Fungus?

5 years ago

I have about 40 large beautiful blue hydrangeas which are like a hedge in my yard. They are about twenty years old. I have just noticed a strange white blotch on the stems of the plants. Touching the white mark makes them dissolve into almost a powder. I've attached photos. Please help! I would be devastated to loss these beauties. Thanks!

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Comments (8)

Embothrium
5 years ago
Scale insects. Rub them off.
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luis_pr
5 years ago
last modified: 5 years ago
Have you noticed movement? I was thinking that it could a form of scale
(cottony maple leaf scale) that is treatable using Bayer with an active
ingredient called Imidicloprid or insecticidal soaps or insecticidal oils (neem oil).

This pest usually surfaces in late May every year. The cotton acts as a sac where eggs will hatch in the summer. Many of these products will work best when they are applied after the eggs hatch.

You may want to apply those things next year too but start spraying ahead of time. Say 2-4 weeks before you first noticed the problem.... they like to return back home.
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Before you take any drastic steps with your plant try these fungus remedies that are organic. Fungi love wet conditions and overwatering can produce such conditions.The fungi start a rot that invades the roots and then works its way up the plants. Try these sprays before you throw out your plant, but if they don't work then you need to dig up the plant and disinfect the area. Baking Soda This makes a great spray to attack fungi in plants. 2 tablespoons of baking soda 1 gallon water a little vegetable oil Mix ingredients and spray solution on problem areas repeat as necessary. Garlic This plant is known to fight many types of disease causing fungus. It also has repellent qualities to fight other diseases and even insects. 1 garlic bulb 1 quart water. Crush garlic bulb and place in pan of water, bring to a boil, turn off heat. let mixture cool. Strain out Garlic.pour liquid into spray bottle and user on affected areas repeat as necessary. It may be too late to save your plant but these remedies could help you in the future. Good Luck Ena Here is a link that might be useful: home
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Comments (8)
I don't think it is either too much sun or not enuf water - I think what you are looking at is cold damage. Open flowers on any type of bigleaf hydrangea now in the PNW is an indication that the plants are either greenhouse grown or from out of state. And the OP indicates these are NOT greenhouse grown plants. At my nursery, we get a lot of plants from California that are well ahead of our local bloom season - hydrangeas here do not start blooming until the end of June or early July. If they came from out of state, they may have not had sufficient time to become acclimated to our colder climate. And our PNW spring weather has been colder and wetter than normal - a relatively mild frost about a week and half ago nipped all the CA hydrangeas we had on the nursery floor and they ALL have an appearance very similar to the OP's - purplish foliage and crispy flowers and leaves. And while it may be warmer daytime in the WW-Milton-Freewater than it is here in western WA, I'd be willing to bet nighttime temps are still pretty chilly. If it is cold damage, they will come back from that rather easily, although you may need to trim off the damaged portions.
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Comments (2)
Cercospora Leaf Spot. You get brownish and-or purplish spots. Some lesions decay to the point where the leaf ends with a hole. Usually caused by the presence of the fungi and overhead watering; common in the middle of or in late Summer. There are some fungicides that you can use but they are expensive so in my two infected shrubs, I use these practices: water the soil early in the mornings and not the leaves; replace the mulch if the infestation is large; dispose of infected leaves whose affected surface area is large (say 1/3 of the leaf? 1/4?); throw away infected leaves in the trash and not in the compost pile; dispose of the blooms and the dried out leaves in the Fall also in the trash; dispose of plant debris in the trash; do not plant other shrubs nearby to improve air circulation; if using fungicides, start at the first sign of trouble (or as soon as the rainy season starts) as the fungicides only control the issue and do not prevent it. When using fungicides, it is best two use two fungicides with different active ingredients: apply the first one; if the label says to reapply after 7 days, apply the second one instead; if the label of the 2nd one says to reapply after 10 days then after 10 days, apply the first one... and so forth. Here is more info: http://www.aces.edu/pubs/docs/A/ANR-1212/ANR-1212.pdf
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Comments (9)
No, the frost could have damaged them still. The damage can occur when the leaves are still in a leaf bud. Tiny things, almost invisible and hard to distinguish from a flower bud. After leaf out time, the damaged area would have looked normal (just an example), may have dried out, or may have been infected by something (fungus, etc). You can cut the petiole of the worst offenders if they bother you but it is not something that would kill the plant or something that can be undone. Iron deficiency shows up as light green leaves or yellow leaves whose leaf veins remain dark green. Your pictures do not show that symptom. Make sure that the leaves are not getting watered via overhead watering to prevent fungal issues. Also, make sure the plant only gets morning sun (afternoon/evening shade). I could not tell if there was mulch but it will help keep the soil evenly moist and will reduce the number of waterings.
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Embothrium
5 years ago
last modified: 5 years ago
Crushing the adults now would interrupt the annual cycle. There aren't that many present, a utility brush should make short work of them. A lot quicker than all the rigamarole involved with mixing and applying an insecticide.
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NHBabs z4b-5a NH
5 years ago
Imidicloprid is a systemic that will stay in the plant tissues and kill pollinators that visit the flowers. I would try one of the other options first.
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ken_adrian Adrian MI cold Z5
5 years ago
im wondering based on the history provided.. if they turn to dust .. whether this was an issue a year or two back.. and all she is seeing is the mummified remains of an old problem ...

unless you can find active scale.. whats to treat???

hard to tell from the pix.. but the plants might take to a hard rejuvenation pruning .... but that would be a topic for the shrub forum ...

ken
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rhizo_1 (North AL) zone 7
5 years ago
ken, this group of scale insects only bears the white egg sacs when very much alive, active, and bursting with viable eggs.

Gail, since you have forty large plants, you may find it necessary to resort to a systemic pesticide to get this bad infestation under control. You can do this with little impact to foraging pollinators if you apply after the flowers are spent.

But aren't the flowers of Hydrangea macrophylla sterile and completely devoid of anything of interest to bees and butterflies? I just don't remember. But if so, that would make the pesticide issue moot.
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gardengal48 (PNW Z8/9)
5 years ago
There are always some fertile flowers on Hydrangea macrophylla, even the mopheads. They are just not very visible or showy and tend to be obscured by the sterile florets.
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rhizo_1 (North AL) zone 7
5 years ago
Thanks, gg.
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