In citrus cultivation, growers often encounter the issue of scars appearing on the fruit surface. Many assume this is due to disease, but that’s not entirely accurate. What exactly causes these scars, and how can they be prevented? Let's find out.
Causes and Prevention of Scars on Citrus Fruit Surfaces
1. Boron Deficiency
Symptoms: The fruit becomes hard and misshapen, with yellowing at the apex. The fruit surface may have reddish-brown scars, and in severe cases, gum droplets may seep from the scars.
Prevention:
-
Mix boron fertilizer with human manure and urine, dig a trench under the tree canopy, apply the mixture, cover with organic fertilizer, and then backfill with soil.
-
Alternatively, mix boron fertilizer with organic fertilizer and apply by deep plowing and soil improvement.
-
Spray a solution of 0.19%-0.2% borax or 0.1% boric acid. In spring, the solution can be applied to the roots or mixed with Bordeaux mixture.
2. Pesticide Damage
Symptoms: Pesticide damage causes irregular water-soaked lesions on the fruit surface, where oil cells in the epidermis rupture and collapse.
Prevention:
-
Use pesticides rationally to avoid damage. Do not mix chemicals if you are unsure about their properties.
-
Alternate the use of different pesticides.
-
Apply pesticides in appropriate weather, preferably on calm, cloudy days, and avoid spraying during midday high temperatures.
3. Thrips
Thrips are particularly harmful to citrus flowers and fruits, causing significant scarring that affects the growth of branches and the appearance of the fruit.
Prevention:
-
Enhance orchard management and conduct timely cleaning to reduce pest population for the following year.
-
Use blue sticky traps in greenhouses to attract and kill thrips. Yellow traps can be used to control aphids, whiteflies, and leaf miners.
-
Spray appropriate pesticides like spinetoram, cyantraniliprole, or thiamethoxam during critical periods such as bud emergence and before and after flowering.
4. Mechanical Injuries
Mechanical injuries occur when wind causes fruit to rub against branches or leaves, creating "wind scars." They can also result from human activities like pruning or spraying, which can scratch young fruit.
Prevention:
-
Plant windbreaks using suitable species such as fir, pine, or camphor trees. Ideally, avoid windy locations when establishing the orchard.
-
Follow proper procedures during manual management to avoid damaging the fruit surface.
Conclusion
Scars on citrus fruit surfaces inevitably reduce their market value. To maximize profits, growers must pay close attention to this issue and implement targeted prevention and treatment strategies effectively.
