It depends on what you want to use it for. Some problems are made worse by insecticides. Mites are one such problem. There are natural predators for mites that keep them in check, but are killed by such materials. Hence, I would never apply a product unless I had a known problem and this product was the best solution. This is a systemic treatment that is applied with a watering can to the bottom of the plant. It is based on the premise to saturate the earth with toxins in case something troublesome comes along. It ignores the problem it creates by killing parasites and other friendly organisms. Here are some rhododendron pests it is not recommended for in Pennsylvania: Rhododendron Borer, Rhododendron Gall Midge, Rhododendron Stem Borer, Southern Red Mite, and Azalea Stem Borer. Any product that doesn't control mites and does kill their predators can create serious problems. This should only be used for specific problems where it is recommended by your state extension service.

It contains 1% Tebuconazole (fungicide) and 0.2% Imidacloprid (Merit insecticide). If you read the label you will find the following:
Tebuconazole causes liver, spleen, adrenal and/or eye effects and is classified by EPA as a Group C carcinogen.
Imidacloprid causes liver and/or thyroid effects. The combination is highly toxic to aquatic invertebrates. Do not
contaminate surface or ground water by cleaning equipment or disposal of wastes, including equipment wash water. It is not the most toxic material, but it is not benign. I would not be anxious to spread it around my yard.

I don't mean to be an alarmist, just do not treat pesticides like harmless materials which they are not. Always identify pests and follow your state regulations and only use materials that are labeled for that pest in your state.

Here is a link that might be useful: Rhododendron and Azalea Troubleshooting

rhodyman, I appreciate your wise warning. I donÂt use any pesticides (insecticides/fungicides) at all because I just feel they are so dangerous. No plant is worth it to me. I use soap and water on earwigs & other pests, and it kills them instantly. I also use water to wash bugs off of plants. Or, if IÂm feeling really courageous, I will hand-pick the bugs.

If any of my plants were to become infested with anything, and they couldnÂt be saved by my methods, IÂd get rid of the plant before IÂd spray (but, it's never happened because I think nature does a good job on her own). Yes; I realize IÂm an extremist on the no-pesticide stance, but to me, IÂd rather be safe than sorry.

Thanks for the input!

My rhodys have some dying leaves & branches in random places. They're watered so I don't think it's drought.The older ones (8 ft.) had borers, and this spring we cut out all the wood (that had holes) to the main trunk. Some leaves' undersides have a bit of white "webbing" in spots and some black spots that look like what is described as sooty mold. There were a few approx. 1/16" brown specks on some leaves' back that looked like insects dead bodies.

I figured since I don't know what all's ailing them, that Bayer would cover all the bases.

The 8 foot rhodys are at least 30 years old. Could they just be insect/disease prone because they are declining/dying from old age? How long do rhodys live, anyway?

Rhodies will live hundreds of years if kept healthy. Bayer doesn't cover all bases. It doesn't treat Rhododendron Borer, Rhododendron Gall Midge, Rhododendron Stem Borer, Southern Red Mite, and Azalea Stem Borer. It is only a larvacidal soil drench and fungicide. That is all. You need to find the problems and treat the problems. Check your extension agent's recommendations.

ItÂs kind of amazing to me how when a person says something someone else doesnÂt want to seem to hear, that person is just ignored completely  lol! IÂm not saying this to be rude in any way  but there is something unnerving about the thought of someone who doesnÂt really know what theyÂre treating in the first place, to be spraying poisons with a Âwhat the heck, IÂll just kill whatever is there" attitude. Oh well, what can you do?

Sorry if anyone got the impression I was ignoring advice. I thought if I explained my rhody's symptoms they could tell me what the cause is & offer a solution.

PS - I've taken leaves & explained problems to my extension agent before & he was clueless.

The problem is with the mind set that "Bayer would cover all the bases." They want you to think that and to use it regularly, but that is because they want to make money. If you don't need it, don't use it.

Your one problem with dieback this past spring was common in the mid-atlantic area. It hit the hardiest plants the worst. It was caused by the mild but dry winter followed by a severe cold snap. It resulted in much random die back.

You also found borers and took care of that.

You removed the dead parts. That is about all you can do.

Are there any other problems?

Some leaves' undersides have a bit of white "webbing" in spots and some black spots that look like what is described as sooty mold. There were a few approx. 1/16" brown specks on some leaves' back that looked like insects dead bodies. This is what's ailing the 2 yr. old rhody; it doesn't have borers.

In defence of Bayer's product.
It does a great job against black weevil and I have a proof of that.
Untreated shrub
{{gwi:396539}}

and treated
{{gwi:395460}}

After buying several new shrubs being infested by BW (in May you can't see the devil) I took a rule: no matter where you buy rh/azalea, before it goes into ground it must be treated by Buyer T&S.

No, I'don have any affiliation with Bayer :-))

Ego,

Neither photo has much of any weevil damage. The distortion and puckering of the leaves you see in the "before" photo could be either chemical damage or Rhododendron Gall Midge, Clinodiplosis rhododendri. Chemical damage should be associated with a chemical application (fertilizer, herbicide, deicing salt, etc.) and should affect more than one plant. The Rhododendron Gall Midge is a native pest of Rhododendron catawbieuse, R. maximum and their many hybrids during the May to October growing season. The larval feeding damage from this fly can cause discoloration and distorted foliage. This damage can appear as in-rolled, twisted leaves that have turned a yellow color. This can be seen on young leaves that have separated from the bud scale. Leaves attacked in the bud stage may die if the injury is severe. Care must be taken to distinguish this pest damage from similarly manifested damage caused by leafhopper injury, chemical injury, leaf-roller activity and aphid feeding. There is no way to undo the damage once it has occurred. Control is effected by applications of insecticides with the bud break stage of rhododendron development. An alternative would be to maintain healthy plants so that they could survive any damage caused by an infestation or to prune newly-infested foliage that contain larvae. Rhododendron Gall Midge damage looks like:
{{gwi:393710}}

Another possibility is the early stages of leaf gall. Enlarged, crabapple-like, green or pinkish galls on young leaves and flowers are caused by Exobasidium Leaf and Flower Gall. The galls become hard and turn white and eventually brown. While very noticeable, these galls will not threaten the health of the plant. This problem is more common during cool and wet spring weather. The first symptoms are swollen or puffy portions on newly expanding leaves, shoots, buds or flowers. The galls range in color from green, to pink or red depending on the part of the plant infected. As these galls age they develop a white surface growth which is a layer of reproductive spores. Eventually the infected tissue will turn brown and shrivel up into hard galls. Fungicides seldom provide control. For best control, start spraying in the early spring with Ferban or Bordeaux. Sanitation and warm dry conditions reduce infestation. It is seldom considered serious. It is most common of evergreen azaleas.

Black Vine Weevil, Otiorhynchus sulcatus, Strawberry Root Weevil, Otiorhynchus ovatus, or Twobanded Japanese Weevil, Callirhopalus bifasciatus chew big notches out of the edges of the leaves. Typical weevil damage looks like:

{{gwi:396542}}

Well, I'm sure now that my dying baby rhody (by your excellent description) has got heavy scale infestations. I don't think there's lacebugs because I'm very familiar with that - my azaleas have had them for the last 30 years, but they don't affect bloom or growth so I just don't do any thing about that. I'll try the oil treatment. That baby rhody is in quite a shady spot. On the older rhodys, I suspect they have borers in the trunk and I understand no insecticide kills them, so I'll just let nature take its course on them. I have my eye on a Hydrangea Paniculata that would be perfect for its spot, hehheh. Anyway, that rhody has been in 16 hr. a day hot sun for 30 summers and I'm surprised it didn't croak years ago.

Rhodyman, not like I want to be overly argumentative since I accept your superiority in all aspects related to the rhododendrons, but...
....in a left lower part of the second picture you may see last year leaves damaged by BW.

Of course, instead of first picture I should of posted this to avoid confusions :-((
{{gwi:396544}}

Ego, The last picture does show weevil damage, no question. It could be any of the following:

Black Vine Weevil (Otiorhynchus sulcatus)
Strawberry Root Weevil (Otiorhynchus ovatus)
Twobanded Japanese Weevil (Callirhopalus bifasciatus)

They do cause leaf damage but they do more damage to the roots. The larva live on the roots. The adults come out at night and chew on the leaves.

However, your second picture does show distorted leaves. That was what I was alerting you to. I would be much more concerned about that in the second picture than any weevil damage in that picture.

The third picture with the weevil damage also looks like you have deer damage. The picture is not detailed enough to show it for sure, but the one stem has been cut off by something.

I have multiple rhodendrons which show the leaf margin damage created by weevils (very like the photograph from Ego in the previous post). I'm wondering if there is anything I can do now (e.g., root drench of a systemic such as Orthene), or if I should wait until April/May. I am in south central PA.

Fortunately, those of us in Pennsylvania have good advice from Penn State:

To effectively manage adults, apply a registered insecticide according to label directions to host plant foliage during late May through June. Optimal timing of an application against the adult stage of this key pest may be achieved by doing the following. In early May place 6-inch by 6-inch boards on top of the mulch beneath several host plants. Pieces of burlap placed loosely around the base of a host plants may be substituted for the boards. During the middle of the day slowly turn over these boards or pieces of burlap. Note when you observe the first adult black vine weevil on the bottom of one of these monitoring surfaces. Because adults (females) need to feed on host foliage for 21-28 days before they’re able to lay eggs, the first foliar application should be made three weeks after detection of the first adult. Since adults do not emerge at the same time, a second foliar spray should be applied according to label directions three weeks after the first one. Spraying foliage in early evening may increase control because adults become active on the host foliage a few hours after sunset.

Applying registered materials according to label directions as soil drenches to container-grown plants from July to mid-October target the larval stage of this pest. The use of beneficial (entomopathogenic) nematodes applied according to label directions may be used to manage the larval stage of this pest in container-grown plants. Be sure to apply water as directed on the product label to the potted plants to be treated with these organisms.

[http://ento.psu.edu/extension/factsheets/black-vine-weevil]

One way to reduce weevil damage is to limit the amount of stems and trunks that touch the ground. They usually should be cut off where they originate. The weevils have to climb up into the rhododendron to get to the leaves. By limiting access points you limit the damage. A sticky trap wrapped around the remaining trunk, or trunks, completes the job.

Yes, the weevils climb up every night and come down during the day. Tanglefoot has proven effective to trap them on their way up or down. The Tanglefoot must cover the entire circumference for a couple inches of any stem coming out of the ground. But, as Mike says, if any leaves or branches are touching the ground or touching other plants that don't have Tanglefoot, the Tanglefoot is not effective. If you have any other plants in the area touching the rhododendrons, they need have tanglefoot on their main stem(s).

Some people go out at night with a flashlight and pick off the weevils. I must admit I don't know many people that persistent. Perhaps some people that like to win cut truss shows.