Are Woody Galls on Citrus Tree Trunks Harmful?

 

Citrus vein enation (CVEV), also known as woody gall, is a viral disease which affects various lemon and lime trees and citrus rootstocks. This disease is caused by the CVE virus, a luteovirus which is transmitted by aphids, including the black citrus aphid (Toxoptera citricidus), cotton aphid (Aphis gossypii), and green peach aphid (Myzus persicae).

The disease is endemic throughout cooler climates and spreads more easily in such locations because damage from many species of aphids is greatest when temperatures are relatively cool, around 18-25 °C (65–80 °F) . It’s rarely found in warmer regions with higher temperatures.

Note, these woody galls on citrus tree trunk are not related to the more common citrus galls found on young branches which are caused by the citrus gall wasp pest.


Inside a woody gall, no wasp larvae or other pests can be seen inside because this disorder is caused by the woody gall virus.

 

Symptoms of Woody Gall

This disease causes enations (small bumps, overgrowth or thickening) in the underside leaf veins of sour orange (Citrus × aurantium), and woody galls (rough swellings) on the trunks or rootstocks of acid lime syn. Egyptian lime (Citrus aurantifolia Christm. Swingle), rough lemon (Citrus jambhiri Lush), Rangpur lime ((Citrus X limonia Osbeck), and Volkamer lemon (Citrus volkameriana).

Most citrus varieties do not show any symptoms when infected by the CVE virus, but the disease is readily transmitted by aphids from affected citrus trees whether symptoms are visible or not.

The woody galls usually form on the trunk, but can also form on branches, and they typically form near thorns, or around where the tree has been wounded in some way.

Vein enations on the leaves are not easy to spot, and are relatively rare in orchards, but when they do occur they are are found mostly on the vigorous new growth of young lemon trees or young sour orange seedlings in plant production nurseries where they’re being grown.

 

Impact of Woody Gall on Citrus Trees

The galls formed by the CVE virus do not affect older, established trees, nor do they cause any decline in their productivity, so the disease has no economic impact for orchards.

It’s very common for woody galls to form at the bud union on rough lemon rootstocks in some instances, but usually the damage appears to be minor. Young trees budded to rough lemon seedling rootstock have showed decline only when severe galling occurs.

 

How to Control Woody Gall

The citrus vein enation virus (CVEV) is a graft-transmissible diseases of citrus, the virus spreads from infected plant propagation material when young citrus trees are grafted.

This disease can best be controlled by:

  • avoiding susceptible rootstock varieties
  • using budwood from disease-free sources
  • protect budwood source trees from aphids

Essentially, the main control is prevention when trees are very young, and this is more of a concern for production nurseries that graft trees, as they desire to produce healthy, disease-free trees for sale.

If mature trees become affected, which can happen after aphid attack, there is no need for concern, the damage is only cosmetic. The trees may not look the best, but no action is necessary because the trees will still fruit and the quality of the fruit is unaffected.

 

Other articles on citrus problems and how to fix them:

 

References

  • UC Davis College of Agricultural and Environmental Sciences – Citrus growing in Afghanistan, Kitren Glozer and Louise Ferguson
  • University of California Division of Agriculture and Natural Resources, Statewide Integrated Pest Management Program – Citrus:
    Diseases and Disorders of Limbs, Trunks, and Roots
  • University of Florida – Some Disease Problems of Citrus Rootstock, E. C. Calavan 
  • International Organization of Citrus Virologists, Food And Agriculture Organization of The United Nations, Rome, 1991 – Graft-transmissible diseases of citrus, Handbook for detection and diagnosis of graft-transmissible diseases of citrus
  • Control of Plant Virus Diseases, Richard F. Lee, in Advances in Virus Research, 2015

About Angelo (admin)

Angelo Eliades is a presenter, trainer, writer, permaculture consultant, urban permaculture pioneer and food forest specialist.
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