A Tale of Palm scale, Lady Beetles, and Ants.

I think I FINALLY have my palm scale problem under control. I've been fighting it for years. I've learned a good deal about palm scale in the process and thought I might share my experiences. The main points I would like to relate are these: 1. Insecticides other than soap or oils will make scale worse. 2. What ultimately controls scale are predatory insects. 3. It's hard to control scale until you control the scale ranchers, i.e. ants.

My story begins 8 years ago when I built a house out in the country on the northern Gulf Coast. The landscaping which I did mostly myself eventually incorporated about 100 palms. 8 of the palms were hurricane cut Sabal Palmetto. The rest, except for a couple of Meds and Sagos, were Sabal Louisiana. Most of the S. Louisiana were in 1 gallon pots, so they were very small palms when planted (now a few are 8 feet tall).

I don't remember if it was that first summer or the next, but I ran into a problem with Strategus Aloeus, The Ox Beetle. I noticed these quarter sized perfectly round burrows next to my small palms, which later died. I flushed a huge beetle out of one of the burrows with a garden hose. Then I made a big mistake: I poured some Bayer Advantage (Imidacloprid, a systemic insecticide) down the hole. I lost all together more than 20 of the small palms to the beetle. I later found that a prophylactic spraying of Imidacloprid around the base of all the small palms in early summer would prevent attacks from the beetle. Imidadacloprid was saving my little palms.

However, later that summer I started noticing scale on all my palms, not just the small ones I was treating, but also on the big Cabbage Palms. It was severe. However I didn't put 2 and 2 together. I treated the scale with horticultural oil, but continued to spray the insecticide at the base of the small palms. I had an inkling that the imidacloprid might be part of the problem, so I did switch to a non-systemic, which worked almost as well at preventing beetle attacks. The scale, however, would only be temporarily controlled after the oil sprays. It's hard to spray 80 palms, but I was doing it every 2 weeks. As soon as I would stop spraying a few weeks later the scale would be right back.

What was happening is that I was killing the scale predators. What I failed to understand is that it's not possible to control scale with insecticides, oils or soaps. Ask the citrus farmers, they will tell you that. Scale are resistant to most insecticides, and it's very hard to kill them with oils and soaps. What keeps scale under control are predatory insects. Anything that we spray to kill scale kills their predators as well. Oils and soaps only kill the predators that are present at the time of spraying. Other insecticides kill the predators there at the time of spraying, and the ones that visit later. I didn't know it at the time, but the probably the most important predator I have was a coccinellid, a lady beetle, that spends much of it's time in the mulch under the palm. When I was spraying the ground with an insecticide, I was killing this important predator. Also when I was using a systemic insecticide, I was killing every scale predator and parasite.

So I started reading up on scale control. We stopped using insecticides completely. We don't use them anywhere on the property except for Amdro and borate baits to control ants (I'll get to that later), and insecticidal soaps and oils. To stop the beetle attacks, I used rock mulch and barriers around the small palms, and when we did find burrows simply flushed the beetles out with a garden hose. Fortunately at least here, Sabal Louisiana (contrary to what I have read) grows quite rapidly. The only small palms I have left now are the seedlings and I have hundreds of those and some of those are getting big. The beetle generally doesn't attack the big palms and even if it does doesn't hurt them.

So we avoided insecticides, sprayed for scale with Vlock Oil, which I would do initially on every palm starting in late winter, then every 2 weeks for 3 or 4 treatments, and then as needed. I knew ants were involved in protecting the scale so we broadcast Amdro.

2 years ago I attempted to introduce a couple of scale predators, a lady beetle Rhyzobius lophanthae, and a parasitic wasp, Aphytis melinus, which I bought from an online insectary. I'm not sure if either was established. I didn't see a real big difference in my scale problem.

However early last spring (this was I think 3 years after we stopped using insecticides) I could see an improvement in our scale problem and I decided at that point to stop spraying Vlock Oil or anything else and see what happened. Over the course of the summer I did have a few palms get a pretty bad case of scale, but I let it go. Most of my palms were fine. I started seeing these black lady beetles on the worst effected palms. I identified them as Chilocorus stigma, the Twice Stabbed Lady Beetle. Wherever those beetles were I would see scale that looked like it had been chewed up. No matter how bad the scale got on these few palms, I let it go.

I noticed on the palms with scale there were always these tiny ants, only 1 or 2 millimeters long. We had been regularly broadcasting Amdro and it didn't seem to effect these small ants. My wife had these same ants in her vegetable garden, and she found a product called Terro which has a bait in it, Sodium Tetraborate Decahydrate. They are little bait stations that the ants crawl into. They take this bait into the hive, and give it the other ants. The ants can't molt and die. It eliminated her ants.

This year late in February we had a warm week and I sprayed the few severely effected palms with Vlock oil, but left the rest alone. I hit them again in early March, then in late March I started seeing the Coccinellids (lady beetles) come out so I didn't spray again. I noticed the Asian lady beetle, and also Chilocorus stigma. There were many more Chilocorus than last year, and wherever they were the scale was chewed up. We also put out 24 Terro bait stations for ants. Now at the end of April, I haven't sprayed anything for 7 weeks.

Looking around at my palms today I see no ants at all. The palms have a good bit of new growth on them and I can't see any new scale. I'm sure as the season progresses there will be some scale, but I plan to leave it alone. I've found several Chilocorus larvae, and pupae. Hopefully 4 years after I had quit using insecticides, I finally have the problem licked.

So the moral of the story is that if you have a palm scale problem, stop using insecticides. If you have palms and you don't want to get a scale problem that will take several years to get under control, don't use insecticides around your palms. Realize that scale are like cows and ants are the cowboys. Try to take the ants out of the picture without killing your scale predators (the wolves in the analogy). Amdro doesn't seem to be sufficient, but the Terro (Borate, or Boric acid) bait stations seem to be highly effective at least for our ants. Use insecticidal soaps and oils only on palms with severe scale, and try to use it early in the year before the scale predators become active. Look for scale predators. Know what lady beetle larvae and pupae look like (Google coccinellid larva) and take a magnifying glass out with you to look for them as they are quite small. If you see them don't spray at all. They will eventually get the problem under control for you. Good luck with your palms.

Thanks, Ed!

I've noticed the same thing with croton scale on my croton collection. Control the ants & the scale disappears. I even had scale along with tiny ant farmers on an C ernesti-augustii I have as a houseplant. Thanks Ed, good observation!

-Randy

I have had a hugely similar experience here in North Louisiana, although I have just begun going after the ants and am still spraying horticultural oil like crazy. You have accelerated my learning curve with this post and I can't agree more about poison pesticides not affecting scale and whiteflies except to make them poison to beneficial insects. The problem here is I have a horrid problem with palm leaf skeletonizer, and pesticides greatly reduce their appearance - marring damage. I am only spraying for skeletonizers on palm species not affected by scale here... serenoa, butia, and feather palms

Edited May 2, 201511 yr by ryjohn

Heavily mixed Imaclopid mixed with a citrus oil will wipe out scale for me pretty good in one application. I add one other chemical as well but can't remember the name of it. It might be a synergy of the concoction..

But if it doesn't kill it you will have a nightmare infestation on your hands... especially when it comes to cottony cushiony scale on citrus. I mixed per instructions on the package and it hasn't killed scale on any type in my yard

Imidacloprid will kill soft scales, but not hard scales. It will wipe out the only thing that keeps scale under control, i.e. the predators. It might look good for a while, but you're selecting out hard scales and when they've infested your palms, you're going to have a mess on your hands.

Ryjohn you should try the Terro bait stations. My wife got them at Lowe's. It took a couple of weeks but it has completely eliminated the small ants I know had to be tending the scale on my palms. We're in the same climate zone. You're growing feather palms outside? We got down to 12 F last year; all those even CIDP got fried in our neck of the woods. A guy down the road from me has a bunch of CIDP's and they get fried 3 out of 4 winters. Most are still alive after 9 years but they look terrible. Guy next to him lost a huge Fillibusta last winter. Totally dead. Can't beat the cabbage palms for our zone if you ask me.

Some pics of my plams:

http://s16.photobucket.com/user/edaskew/media/sidepond_zpst6zp1xke.jpg.html

http://s16.photobucket.com/user/edaskew/media/path_zpsagfsoiqs.jpg.html

http://s16.photobucket.com/user/edaskew/media/frontside_zps52qap40z.jpg.html

http://s16.photobucket.com/user/edaskew/media/vonmeadow_zpsc7uellho.jpg.html

http://s16.photobucket.com/user/edaskew/media/bigblue_zpsl0ukcyeg.jpg.html

Ed.

I had a similar experience with cicad scale on my sagos, I tried imidocloprid and fipronil systemics and they laughed in my face and proceeded to kill the largest of my seven sagos, one with about five feet of trunk. I was pissed. Thereafter, I sprayed them every other week for two months with mineral oil and they appeared to be dead. Next spring it came back, but relatively trivially. Two apps of mineral oil and gone. This spring I can still see a few bugs on the trunks, none on the leaves, which is a 99.9% improvement from two years ago. I can't see any ant issues, although some nearby Wodyetia (6 of them) are all colonized with small black ants, definitely not fire ants. I'm in the Galveston area so I suspect they're the same ants as you have in LA. I'm starting to believe that I'll never get the scale cured, but hopefully I can keep it beaten down with oil. Meanwhile I'll research the lady bug thing you mentioned. Fortunately, cicad scale doesn't like my true palms.

Tldr, I agree that insecticides are counterproductive, oil helps a lot, and I'm looking into natural predators.

BTW Ed, where are you in the motherland (I was born in NOLA, both parents LSU grads). I'm curious about the little black ants. Like I said, my foxtails are swarming with them, yet the trees are thriving so I haven't seen it as a problem. They definitely are not farming scale as the foxies have none, whereas the sagos were covered with cicad scale yet had zero ants. Go figure. I can't see ant control aiding the cicads as they have none, nor can I see it aiding the Wodyetia whereas they have ant colonies but are asymptomatic. Currently I broadcast Amdro for fire ant control, plus I treat the mounds with a Bayer synthetic pyrethrin. It works ok for fire ants but has zero impact on the little black dudes that I think we have in common. The next time a foxie sheds a leaf I'll try to post some pics for you. The shed leaves always have tons of the ants on the trunk side of the leaf. Let me know if it's the same scale farmers that you have in LA. Thanks for posting.

Interesting in that North Louisiana and I think Texas are battling huge scale issues on Crepe Myrtles. And nothing attracts black ants like blooming Crepe Myrtles. I wonder,,,,,,

Also, have to talk about Imidacloprid. I have a mild scale issue on my Magnolias for years. I have resisted Imidaclorpid because of its links to bee decline. I even bought some but could not bring myself to use it, as I want bee hives on my property. You have given me new hope as I not intend to deal with the ants, first.

I've been using Zylam on my palms for scale. I like using horticultural oil, but it only kills what it touches and so doesn't get down in the pleated leaves as they emerge. I started spraying the Zylam in early March and then sprayed again in April. The improvement is dramatic....scale is going away. Zylam should not be sprayed when the palms are near blooming. Usually there will be an outbreak of scale in mid-summer here in Augusta when it is too hot and humid to want to go out and spray everything. I started with the Zylam last summer in spite of the heat. It really works well, but is expensive. Results have been much better than with Imidocloprid.

That makes sense Joseph. The only scale recurrence I've had this spring is on the trunks where I suppose the oil can't penetrate well. I've used the vet version of Zylam, Vectra I believe. It worked great for fleas on my cats! So far this spring my scale problem has been very, very mild. If it worsens I may pay the big bucks for Zylam; I didn't know there was a horticultural version. Thanks for the info!

I'm in south Mississippi, but we're Louisianians both LSU alums. That twice stabbed lady beetle isn't raised commercially. The only scale eating coccinellid that is is rhyzobius. You have scale predators around, if you will avoid insecticides and give them a chance to build up enough of a population to control your scale. I don't think long term any insecticide is going to control scale but ultimately will make the problem worse. Try those terro bait stations for ants. They're not expensive. You'd have to have a magnifying glass to see that these little ants I have are indeed ants. If there are scale there ants around tending them.

The problem here is that the Lady Bugs stop feeding when it gets hot....just as the scale goes nuts. Right now there are plenty of Lady's around, so the Zylam hasn't killed them. Scale seems to be under control for once. I'm going to try the ant baits to see if that helps. We have ants (of all kinds) everywhere.

I had to look up Zylam. It is a neonicotinoid in the same class as imidocloprid. Look for lady beetles in the early morning in mid summer.

Check this out:

http://portlandtribune.com/cr/24-news/155022-massive-bee-die-off-found-in-wilsonville

Interesting conclusions. ...I've noticed scale attacks weak plants. Plants that are vigorous growers rarely have problems. Trachyocarpus seem to be susceptible to scale....I wonder if tne nematodes in my sand weaken them first....and scale insects are then attracted by the weakened palm.

Magnolia scale is so bad on some small trees that the trunks look deformed like elephant man. I have to scrape them off then apply that Bayer systemic. ...seems to be working...just using it for the severe magnolia problem. Will take another look at ant control....got several kinds.

Great subject

My mom told me about Terro probably back in the 80s and we have used it to rid ant colonies that invaded our home on a few occasions. Haven't ever used it outdoors to attack them on plants however. I will say that it's important to place the bait in the direct path of the ants. Our experience was the ants could pass right by it otherwise. Once they find it however, they will signal to others to come munch on it and OMG do they go after it. Inside we found ourself with so many ants I couldn't believe it. Like a moving black sea. We just avoided the area instead of freaking out at the numbers and within 2-4 days I think they were all gone.

As I recall Terro works on "sweet" eating ants. Originally they only had the liquid version that would get placed on strips of cardboard. The little plastic bait traps at least can be placed outdoors easily. We haven't had pets or kids to worry about indoors so the liquid worked well. Can't speak to the plastic bait traps as to whether animals might chew on them, etc.

Good post. I've used common Combat ant bait traps with great success at the base of Sagos and Dwarf Firebush where I've noticed ants infesting. Used coffee grounds spread around the base of the trunk has also been very helpful reducing and eliminating scale for me.