Hello, I have potted Key lime trees and a Meyer Lemon about 5 years old that have scale. They were fine until this past winter indoors when I noticed it. I did try the 1 % horticultural oil solution spray on a single plant in May once the plants were moved outside. The plant was sprayed at night, but after a few days, the leaves and green stems appeared lighter and somewhat mottled in colour and not healthy looking. The other citrus in the exact same location look fine, except for the scale. I marked a branch on a different tree just recently and sprayed only that branch and the same thing occurred within a couple of days. I will try and get a picture, but obviously the oil has caused this. Should I try a different type of oil or treatment? Maybe reduce the strength further. I want to avoid damaging the plants further, but would like to eliminate the scale. The label says Concentrated Horticultural Oil Insect Spray. Contents :Mineral Oil 97% thanks, Mike
You say you sprayed them once you moved them outside- it sounds to me like the damage that was caused (especially a mottled leaf appearance) was from spraying the plant in the sun, or right before it got very sunny. Small water droplets act like magnifying glasses on leaves, and burn them in the sun, or even under a hot light.
This link might help. It is certainly working for me. I had an enormous outbreak of scale inside my enclosed tropical atrium and it is now almost totally eradicated in under two months: http://www.botanicalgarden.ubc.ca/forums/showthread.php?t=37387&highlight=natural+scale I have no association with this company other than the fact I have purchased these critters twice!
I use Safer Insecticidal Concentrate Soap. For all my pest problems. I may need to spray a few times. "No big deal". I get a few leaf eaters in the early summer, but they back off after eating the untreated leaves, Brown Scale is the biggest problem in the fall this works great.
I did spray the plants at night and out of the sunlight. The sun may have been out the next day, but I did not spray them in the sunlight. I'm not sure what to try next. thanks, Mike
Horticultural oils, that are sprayed in the late evening (or at night) it does not matter if the following day is hot and sunny. Horticultural oil correctly applied, I have personally never seen or heard of a tree suffering any type of damage. In fact many people use oils as leaf shine on house plants. What was the trade name of the product you used? Without pictures to see, I doubt that any real damage was done. - Millet
Just a note. I sprayed with oils for over three years trying to kill scale and their eggs. It never worked. They always came back.
Below is an link to an overview that will help give more incite into scale. Scale Management Guidelines--UC IPM First order of business is identify the scale insect that is a problem and then determine a means to get rid of it. Our approach to attacking a scale indoors in the home, in a greenhouse or even in an enclosed atrium can and may differ somewhat as the use of certain beneficial insects indoors may require containment, which some home growers may not be able to achieve. With oil sprays indoors to be effective we want coverage on both the faces and the undersides of the leaves. Some of the armored scale may not be adequately eradicated even with one or a few timely horticultural oil sprays. A ground based approach may also be needed in that some of the armored scale can live and overwinter in the soil (University of Florida/IFAS EDIS). We can knock scale down one year and they can be right back the next, if we are not fully aware of which scale we are dealing with. Jim
Scale is always a huge battle to get rid of- if the oil didnt work, i'd try using it in a heavy concentration than recommended in the bottle. If that doesnt work, try mixing 2 table spoons of mild dish detergent with every gallon of oil mixture. This breaks the surface tension of the water, and helps drown the buggers. If THAT doesnt work...I'd say those parasites are your best bet, short of scrubbing the whole tree by hand (which i've done plenty of times)
That certainly may work. In my case, I had scale in a controlled environment inside a private botanical garden. The garden is filled with natural rain forest animals and very rare exotic plants. Oils kill many of the desirable entities inside that atrium. Many public gardens refuse to use such treatments preferring to use natural controls. I found these natural control insects on the advice of a highly qualified botanist! Although everyone prefers to ignore my posts on several threads regarding these natural insects control methods. THEY WORK! They are not inexpensive but again, They work! My garden is now virtually scale free. The insect is a beetle known scientifically as Lindorus lopanthae. Read about it here: http://www.rinconvitova.com/Scale control.htm
I agree that natural predators are the best way to go when possible, but there are times when no predators are available or the time it would take to get them is too long. I have bought lady bugs and mantis, and I try to protect my assasin bugs and lacewings when I can. My main use of oil is to control leaf miners and I only spray it on new growth.
I've purchased up to 5000 lady bugs with zero success on scale at any one time. Lindorus lopanthae works! Delivery has always been at least the second day by Fed Ex and/or UPS. This company is the largest and only producer of this beetle. All others buy from them.
Photopro says........'They (scale) always came back'. The fact that scale comes back has nothing what so ever to do with horticultural oils, nor would it have anything to do with ANY TYPE of eradication program or eradication chemical. An oil spray cannot control future generations of scale not yet present, that will attack at a later date. One major benefit of properly used Horticultural Oils, is that they DO NOT kill beneficial insects, therefore many public botanical gardens actually do use horticultural sprays as one part of a pest control program. Presently, horticultural oils are the number one control of scale in every citrus growing nation world wide, so they must work for someone. If you think that oil sprays do not work for you, than please use whatever you feel comfortable with. Take care, and the best to your trees. - Millet
Photopro, why would you purchase Lady Bugs, for the control of scale. Scale is not on the Lady bugs diet, therefore Lady Bugs, are not interested in scale in the least. - Millet
I was told horticultural oil, when used in a more concentrated form as a dormant oil, would defoliate a plant.
Sorry, if this is going to become combative, I have to bow out. I stand by every single word I wrote. I correspond on a near daily basis with 5 botanists and the curators of two botanical gardens. These professionals check the information on my website for accuracy. Some 200,000 people annually read my site. That number is verified by a website tracking service. But if you or anyone prefers to use oil, feel free.
No one is going to disregard your posts, photopro, in regards to using biological agents that you have found to be successful for you to suppress invading insects. The problem we have in Citrus is that some scale are not easily warded off or even hampered much with the use of biological insects at this time. Granted, in normal growing conditions we may have a percentage kill from natural predators and it is our predator populations that we certainly do not want to kill off. Most of the time I use water jet sprays to liberate the hard to get rid of Yellow scale on my old Meyer Lemon into the air in 100 degree weather. When the scale come back I attack the ant nests in the ground using granulated sugar or better yet crystalline honey that pretty much wipes them out and pretty soon I no longer see the affects of the Yellow scale but they will be back the next year if I keep this method of non pesticide use going indefinitely. What I should spray sometime is the host Grapefruit tree that harbors the Yellow scale and the Citricola scale but since the tree is not mine and adjoins our two properties, I do not feel right about spraying that seedling Marsh Grapefruit that I grew from seed years ago when I know the fruit will be fresh eaten by our neighbors. Millet is correct about horticultural oils which is still the primary method of choice for the soft scales in many Fruit & Nut trees used as a stand alone dormant, pre popcorn, pre full bloom and pre petal fall spray. No one has yet mentioned an insecticide to be mixed in with the horticultural oil. For indoor plants I would advise against using an insecticide unless it was absolutely necessary. For outdoor trees then we have more leg room to maneuver in if we feel the need to use an insecticide such as a low grade, all things considered, organo-phosphate Diazinon along with our Spring oil spray application, which is still used today in many production Fruit & Nut tree orchards out here. Scale are not all created equal such as comparing Oyster scale which can be harbored on several ornamental plants and may not be a problem other than being unsightly. Red scale on Citrus is a whole other matter as a serious outbreak with this insect can kill trees. Effective biological control that will kill a wide array of armored scale as well as soft scale will always be welcomed and preferred by a host of people but one insect will not be specific enough yet to deal with the wide range of scale that can affect the livelihood of the Citrus trees in a production grove setting or even in a greenhouse either. I realize a lot depends on the voracity of the scale but dealing with one scale in a greenhouse with no helper insects generally is easier to contend with than the same scale might be outdoors with ants that can help protect the scale from the predator insects. Jim
Is horticultural oil appropriate for use for plants that stay indoors all the time? Wouldn't the oil remain on the foliage forever because of the lack of rain to wash it off? And wouldn't the oil then eventually capture dust and hold on to it? Does the oil pose a problem for home furnishings? (So many questions!)
Photopro, it is no ones wish to be combative. We appreciate all postings, including yours, and all points of view are appreciated. Do whatever works for you. The difficulty that I see, due to this being a citrus forum, is that we are stating what is a standard method for the control of scale in the CITRUS industry, and also in the fruit industry in general. You are stating various control methods that you have tried in the botanic garden industry. Anyway, we are all grateful for your input. Lastly, I am going to have to spend some time on your web site, as I am sure I will find it quite interesting. Take care. - Millet
Junglekeeper, I have not used oil indoors, but as a chemist, I do not see a problem. It will not last forever, as it will evaporate slowly. It is about the same as mineral oil which is often in lotions. It may increase the dust collecting on leaves a little, but unless it is a very dusty house, it should not be a problem. I would take the tree outside to spray it to avoid getting the overspray on other things.
Thanks for sharing your thoughts, skeet. I get a feeling not many people have used horticultural oil on their houseplants because of similar concerns so feedback based on experience on use in other settings is helpful. I probably should have started a new thread in the pest management forum to cast a wider net.
"I was told horticultural oil, when used in a more concentrated form as a dormant oil, would defoliate a plant." To be honest, i've never even used horticultural oil before, i've always used olive oil and dish soap mixed in water, which works great for me! I offered the suggestion of bumping up the dose a little, based on my experiences with olive oil. I didnt realize this product was an actual chemical, i assumed it was a natural oil. "Is horticultural oil appropriate for use for plants that stay indoors all the time? Wouldn't the oil remain on the foliage forever because of the lack of rain to wash it off?" Junglekeeper, one practice i do and recommend to anyone, is to spray your indoor plants twice a day with a garden-type sprayer, to simulate rain. the plants love the humidity, and it keeps the leaves clean! just a suggestion anyway.
I've been using insecticidal soap and have had success so far. However it does require multiple applications. Since the battle against pests is never over I'm open to other means that could possibly supplement the soap for more stubborn outbreaks. It never hurts to have more tools to work with.
Thanks for all of the ideas everyone. The name of the oil is Green Earth Horticultural Oil by Nu Gro Corporation. If I want a different brand, I will have to look around some more or go to the USA. If the branch I sprayed a few days ago looks ok, I will try a few more with the oil. Mike
