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HomeIssue 27Citrus trees your friends for a century

Citrus trees your friends for a century

By GEOFF MIERS

MANAGING CITRUS – PART ONE

Citrus trees are highly productive, give you a high return for relatively little effort but they do need to be managed properly.

With proper care in managing pest and disease outbreaks, along with providing ample water and food as required, your citrus trees should live for over 50 years.

With citrus currently bursting into bloom and new growth emerging it’s a great time to address pest and disease issues, feeding to boost spring growth and ensure you get good fruit set while also adjusting the amount of water being applied as the temperature starts to climb.

Many trees are still loaded with large quantities of fruit. Navel oranges will start to dry out and go soft so they should be picked with some haste and enjoyed while still full of moisture and flavour. (See photo 1.)

Fruit left on the tree can also impact on the new crop currently forming. The tree will be in bloom with fruitlets currently forming.

Because the navel orange has been hanging on the tree for 10 to 11 months sometimes scale insects and mealy bug can be found on the fruit and attached branches.

If the mealy bug is only on the fruit, simply harvest the fruit, peel and the pest problem is gone. (See photo 2.)

The chances are the mealy bug will have progressed onto the branches supporting the fruit. Either squash with your fingers, jet off with sudden hard squirts of water, spray with white oil or white oil and malathion.

If this approach doesn’t appear to work you may need to treat the tree with a systemic insecticide.

After all fruit has been harvested treat the tree with a systemic insecticide like Confidor as this will travel right through the tree and any insect that sucks on the sap will perish.

Red Californian scale can often be found on the fruit only at this time of the year.

This scale appears as brown, orange or red tiny dots on the fruit. Harvest the fruit, peel and the problem is gone. Otherwise spray with white oil making sure you completely cover the fruit. The white oil will smother the scale insect and it will die.

Valencia oranges are only just reaching full maturity and can be left to hang on the tree for several months. My Valencia orange produces fully ripe fruit from late August through to late December and early January.

Many lemon trees are currently really full of fruit and the crop needs to be thinned with some priority. If the entire crop is left on the tree it is likely the weight will cause the branch to snap. (See photo 3.)

A broken branch can severely impact on the shape of the tree with often quite serious surgery needed to remove the broken branch and reducing the impact of the damage to limit pest and diseases entering the wound. (See photo 4.)

Over time many branches large and small may have been removed from the tree. Poor pruning techniques are often evident where branch stubs are left.

These branch stubs will never produce new growth and should be removed right back to what is called the collar that surrounds the base of the branch.

This poor pruning management can result in the longer term die-back in these branch stubs that can progress down the into the main branch resulting in further die-back. 

When growth occurs from below the graft this new growth needs to be removed. Coming from the root stock graft it is likely to not only be vigorous in growth and outgrow the rest of the tree it will only produce dry, useless fruit at the expense of the rest of the tree.

This regrowth from below the graft will generally have a different leaf form and will have noticeably long thorns. If the regrowth is relatively new you should simply tear off this growth. By tearing it off it is unlikely to regrow back.

If the regrowth has been allowed to grow for some time it will be necessary to cut off or saw off this unwanted growth.

What is required whether using secateurs or a pruning saw you need to cut back to what we term the collar that can be found at the base of the new regrowth branch and the main branch or trunk.

Cutting back to as close as you can to the collar will result in the collar eventually growing over the removed branch sealing the wound completely. Damaging the collar, best described as a swollen ring as the base of the branch will retard or prevent this regrowth.

Once cutting back to the collar I prefer to paint over the wound with a runny mix of copper oxychloride and water to limit the potential for fungal disease to enter the wound before the tree has had a chance to seal the wound.

The same approach is required when dead or pest ridden or diseased branches need to be removed.

PHOTOS: Navel orange in full bloom needs its mature fruit removed • Note cluster of mealy bug on the bottom of the navel orange • Eureka lemon tree fully loaded with fruit with branch hanging down under the strain • Branch on Eureka lemon broken due to weight of fruit. Branch needs to be carefully removed.

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