White spots on lime tree

[genchan]

Need some advice. I have a lime tree and a few months back, I noticed white tiny rectangular spots appearing on my lime tree. So I cut off the affected branches and rub my hands on the trunk to remove the spots.

It worked and I thought it would be fine but looks like the problem is back. The trunk is covered with the white spots again and the leaves too (underside). Its not moving at all but keep getting more and more.

I have already trimmed it down with two branches left. I am wondering what disease this is, whether its a root disease or surface disease and what I should do.

I have used neem oil couple of times but no effect whatsoever. I am at the verge of unplugging it and replanting with a new lime tree. Or should I cut off the trunk at the base of the soil?...

[genchan]

I think I might have found the answer to my own question.

Euonymus scale!

If it is, then its good to know the problem is not root disease but surface insect. Still I couldn't believe its insect since it doesn't move at all.

What do you think? And how can I control it? I'm thinking pruning is the only choice but I am hoping there's a better way. I read that insecticidal soap is ineffective coz the scales are shielded by wax. Hmm...

[Kisal]

I agree that those are scale insects, but I don't know for sure that Euonymus scale will feed on citrus trees. There are many kinds of scale.

I wouldn't cut off any more of your tree. It's very small as is. I would wipe off all the scale I could see ... perhaps use a magnifying glass to help locate the insects. Then, spray with a solution of 1 part rubbing alcohol to 8 or 10 parts water. That can penetrate the waxy coverings. It should also kill many of the crawlers, i.e. immature insects. You might want to repeat the alcohol spray in about 5 to 7 days, or you could move on to the next step.

After that, I would keep a very close eye on the tree and wipe off any new adults that I noticed. Another way to remove them is to touch each insect with a cotton-tipped swab dipped in rubbing alcohol. Then, I would spray the entire plant every 5 to 7 days with a solution of pure soap and water ... 1 to 2 teaspoons of soap to a quart of water. Be careful not to use a detergent, as it can burn the leaves. The soap solution will kill any crawlers, but it cannot penetrate the waxy coating of the adults, which is why you have to remove those by hand or with a cotton swab dipped in alcohol.

This is all quite a lot of work, of course. You may decide simply to destroy your little tree and replace it with a healthy one. Check all your other plants, because scale insects spread easily from plant to plant.

You can buy ladybird beetles and other predatory insects to protect your plants against pests such as scale. Remember that any sprays will also kill the beneficial insects, so don't use sprays if you release predators on your plants.

[genchan]

Thanks Kisal for your reply.

Ya its really small and the top leaves have been chewed by tiny green grasshoppers.

Over here, there's no rubbing alcohol. There is spirit, normally sold in hardware stores, and methylated spirit sold in local pharmacies. I was told methylated spirit is the same with rubbing alcohol. But did a bit of googling and found out that meth spirit is 95% while rubbing alc is 70%.

So, do you think its okay to use meth spirit? I plan to dip it with swab. Or should I dilute it with water first before dipping with swab?

[Kisal]

Sure, a dilute solution of the methylated spirits should work. Since there is a fairly heavy infestation, you're going to get more of the solution on the plant than if you were dabbing it on just a few bugs. Because of that, I would first mix a solution of 2 part spirits to 1 part water. Then measure out a small amount of that mixture and dilute it further by adding 6 or 8 measures of water. That should give you a mixture that roughly approximates the strength of the suggested "spray-on" rubbing alcohol & water solution. That should be weak enough not to harm the plant, and yet be strong enough to kill the bugs.

If you plan to wipe off as many bugs by hand before using the spirits on the stragglers, it would probably be safe just to do a single dilution of 2 parts spirits to 1 part water.

Check my dilution ratios before you treat your plant, because it's 4 a m. where I am, and I haven't been to bed yet!

[genchan]

Hi. I just noticed that one of my flower plants is attacked by this Euonymus scale and mealy bugs.

Just to double check, is using spirit and soap safe? I mean for fruit trees or edible flower plants, are spirits and soap considered harmful chemicals and bad for health?

[wheelyweb]

Then, I would spray the entire plant every 5 to 7 days with a solution of pure soap and water ... 1 to 2 teaspoons of soap to a quart of water. Be careful not to use a detergent, as it can burn the leaves. The soap solution will kill any crawlers, but it cannot penetrate the waxy coating of the adults, which is why you have to remove those by hand or with a cotton swab dipped in alcohol.

Can you tell me what "pure soap" is? Are there any product names or other clues to help me find it?
Joe

[imafan26]

I have scale on my roses that look a lot like that. They seem to be very insecticide resistant. I have been using imodiclopid on them. It does not control them.

I now use a brush dipped in soapy water to scrub them off. It has been the best control. I do prune off and discard very infested branches.

I have also used horticultural oil to try to kill them. The scrubbing works best.
The horticultural oil, may work a little. It is hard to tell since scale does not fall off after they are dead.

Insecticidal soap alone had no effect. It does not get past the waxy coating.

I'd like to find out if someone has found something more effective. I have been battling this problem for years.