‘Good Morning Garden Doctor,
I live up at UBUD and in our garden there is a very tired looking lemon tree. It was here when we got here but over the past few years it seems to be producing less and less. We’ve had numerous bug infestations lately in the past two years, I think one was a citrus beetle and now it’s full of tiny white bugs. I’ve been spraying white oil, but the bugs just seem to come right back or I can never get rid of them entirely. Once we get rid of one pest another one seems to move in. The tree looks like it’s just hanging on, the new foliage is shrivelled and any lemons that we do get aren’t very good and usually only a few. Should I keep spraying with the white oil or should I try a different pesticide, or just give up? I want to save the tree as it’s an established tree and when we first moved here we had heaps of lemons from it, so many that we made lemonade! Do you have any further advice for lemons and citrus in general? I’m thinking of trying mandarins in the future. Looking forward to hearing back,
Sincerely, Kate.’
You love your lemon tree, but the problem is the bugs do too! There are many types of insects and mites that are common pests of citrus trees. The orange citrus beetle otherwise known as the ‘stink’ bug is one of them, aphids and scale are also common invaders. It definitely sounds like you have a scale infestation which is severely affecting the health of the tree. The scale insects reside on the undersides of the new growth, sucking on the fresh sap and in the process retarding the ability of your plant to grow and produce fruit.
If the scale infestation is severe twigs and branches will be dying back, leaves are shrivelled and falling, and the fruit is stunted if any is produced at all. As the problem your dealing with is unresponsive to pesticide spray then it could be time to take some drastic action and skeletonise the tree – sounds scary doesn’t it but just make sure to do it before Halloween!
Skeleton Pruning
A skeleton prune is simply pruning the tree back to its main limbs so that you are left with the ‘skeleton’ of the plant, in other words a brutal cut back – which in many circles is the go-to option for successfully countering most citrus diseases and pest problems.
With a severe bug infestation, you want to go hard at it, but preferably not back to a stump obviously. At the very least, all of the branches and foliage containing the pests must be removed otherwise they’ll re-infest the new growth. Basically, you need to cut the tree back to its bare bones by removing the canopy. I know it sounds risky, but lemon trees and most other types of citrus usually bounce back hard and grow better after treatment like this. It will most likely be re-invigorated with increased fruit production into the future. For some citrus growers it is a routine course of action undertaken every 10 years or so, whether bug infested or not it gives the tree a new lease on life.
The ideal method of ‘skeletonising’ involves cutting all of the growth back, so that you’re left with a single trunk and strong even spaced branch stumps. Ensure you are using sharp sterile cutting tools – making clean cuts is essential.
Rake up the debris from the lopping and pack it into strong plastic bags sealed tight and left in the sun for a few weeks to kill all the pests, after which time it can be thrown out – but not into the compost.
You will find that soon afterwards the lemon tree responds with lush new vigorous growth. At this point is a critical stage. The tree will require extra water and a constant supply of nutrients to keep pace with the plethora of new shoots sprouting from the skeleton.
Over the next weeks/months the new growth produced can be so dense that it may even be necessary to prune in the centre and thin shoots at the periphery to prevent the tree from becoming overcrowded with foliage. It could take anywhere from one to two years before the lemon tree starts to bear fruit again, but when it does…watch out!
I’m picturing increased yields – a big, juicy constant supply of lemons on a pest free tree, facilitated by the brutal skeleton pruning technique.
Further Tips for General Citrus Care
Citrus will tolerate a range of soils, though most prefer well drained, moderate to slightly acidic soil, pH of 5.5 to 6.5. Citrus will always prefer full sun and a site protected from strong winds. They also need a regular feeding schedule as nutrient rich soil is required for fruit production. Citrus are voracious feeders and they have an insatiable appetite for nutrients and will soak up whatever fertiliser you can send their way. Well-nourished trees will produce high yields, and also develop natural defences to pests and diseases.
All types of citrus require a constant nutrient supply, with a high requirement for trace elements. A regular application of a liquid seaweed fertiliser will supply needed trace elements, otherwise mulch with fresh kelp/ seaweed gathered fresh from the beach. Sprinkle compost around the tree and feed a few times a year with a specially formulated citrus fertiliser. Pelletised chook manure or other animal manures can be also be added to the topsoil over the root zone twice/year. Always water well after fertilising. A consistent supply of nutrients is the key to getting the best out of any citrus – seaweed fertiliser and compost is a requirement at the very least.
Fruit and frequency will also depend on water supply. Too little and the fruit may be small or not appear at all. Water regularly in combination with a free draining soil – they will require least one deep watering weekly for flower bud formation through to fruit set to produce a good crop.
Add mulch for moisture retention and to discourage weeds which will only compete with your tree for water and nutrients. If weeds are left to become over-grown they will invite pests and disease. Never mulch right up to the tree trunk, otherwise collar rot could result – meaning no fruit and probably no tree also!
Hopefully by this time next year I hear that you’ve been making lemonade!
Dr. Kris
Garden Doctor Contact: gardendoctor@hotmail.com
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