GREASY SPOTS DISEASE ON CITRUS 21/06/2023

GREASY SPOTS DISEASE ON CITRUS 27/05/2022

Citrus is a fruit tree with high economic value. However, pests and diseases are one of the factors that hinder the development and increase production costs. One of the most dangerous diseases on citrus is greasy spot disease. Greasy spot disease is common on citrus grown in tropical and subtropical regions. The disease affects the growth and development of plants, affects yield, quality and reduces commercial value. In our country, citrus greasy spot disease is also often harmful, especially in the Mekong River Delta, however, so far it has not been noticed.

Disease symptoms:

The disease attacks on parts of citrus trees such as leaves, branches, and fruits. However, it usually causes severe damage to mature citrus leaves. Lesions are initially on the underside of leaves, ranging in color from yellow to dark brown, to black, and slightly raised. As the lesions develop, they become darker and a corresponding green spot appears on the upper surface of the leaf. After that, the lesion on the leaf surface also turns yellow, gradually darkens and turns black and greasy dirty. Severely damaged leaves will drop early in the Autumn and Winter, reducing plant vigor and yield.

 

Pathogens and conditions of development:

Citrus greasy spot disease is caused by the Mycosphaerella citri fungus. The disease spreads by wind, by water, etc. The disease usually thrives in tropical areas with a lot of rain, high temperature and humidity > 90%, or cloudy, overcast, lastingly rainy weather In conditions of high density planting, excessive nitrogen fertilization, plants are too green, dense, combined with the garden is shaded by other trees, so it is always humid, etc., the disease is often severe. Therefore, the disease often develops strongly from June to October every year. In the cold winter in the northern provinces, the disease often stops developing.

Highly effective preventive measures:

To manage citrus greasy spot disease, it is necessary to apply a combination of measures that can be applied.

- Planting trees with appropriate density depending on the variety (eg, Giay oranges, the density should be less dense than the sanh oranges).

- Make beds in the East-West direction so that the plants can receive sunlight throughout the day, keeping the garden open and dry.

- Having a good drainage system after rain or irrigation, avoiding stagnant water, will create high humidity in the garden.

- Prune diseased branches before the rainy season, or before the new crop, so that the garden is well ventilated and avoids the garden being dense.

- Fully balanced fertilizer application, not excess nitrogen for healthy plants.

- Use SPC-CAL to ensure adequate supply of Calcium for plants, helping to increase resistance. Calcium also reduces soil acidity and prevents fruit porosity and cracking.

- Use fertilizer TANO-601 to provide necessary micronutrients to increase resistance to pests and diseases, while increasing fruit quality.

- Check the orchard regularly to make sure the disease situation, in order to take timely treatment measures.

- When disease is detected, it should be prevented by one of the following products: CLEARNER 75WP, or DIPOMATE 430SC, or SAIZOLE 5SC, should be combined with SK ENSPRAY 99EC mineral oil to limit penetration. of fungi and prolong the control effect.

 

 

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To prevent, in addition to plowing and burying weed seeds, collecting weed stalks and stumps left after tilling the land to burn, not letting weeds produce seeds in production fields, etc., the use of chemical products is still a measure. optimal because of its ability to thoroughly kill weeds, reduce labor and take advantage of more time than manual weeding.To prepare for the coming Summer-Autumn rice crop, we would like to introduce to you a very new product of Saigon Plant Protection Joint Stock Company, which is Butoxim 5GR. This is a granular product used for spreading by Saigon Plant Protection Joint Stock Company in research, production and distribution.

 

 Miner has the scientific name Phyllocnistis citrella Staint., family Phyllocnistidae, order Lepidoptera. The  miner occurs in many countries in the tropics and subtropics. The main host of the miner is the citrus family - Rutaceae. In addition, the miner also attacks mangosteen and some other plants.

 

Adult is a small planthopper, with a body 2-3 mm long, the whole body is ash gray, slightly greenish, the wings are opaque with many small brown spots.Eggs are oval, 0.3 mm long, have a pointed end and are attached directly to the leaf surface, leaf axils.Larvae are very small, oval in shape, newly hatched are bright yellow. Age 2 and age 3 are in green. Age 4 and age 5 are golden brown and 2 small wing sprouts.

 

Green bugs specialize in the fruit of citrus groups (oranges, tangerines, lemons, grapefruits, kumquats...), some people call them orange bugs, or orange suckers. Their scientific name is Rhynchocoris poseidon or Rhynchocoris humeralis.

 In Vietnam, yellow leaf curl disease is very common on papaya trees, especially the disease is often severe in areas of high and continuous planting, areas with hot and arid climates. The disease has significantly reduced the yield and quality of papaya. Gardens that are infected early when the plants are young may not yield. However, up to now, many gardeners still do not know the cause and how to fix it.

 

 Spider mites are common pests on citrus trees, especially in hot and dry climates that are suitable for spiders to grow and cause severe damage.The group of harmful spiders is usually very small in size, unlike the natural enemy spiders.Spiders have a very short life cycle, high reproductive ability, create many generations in a year, so it is easy to break out into epidemics in a short time.

 

 This group includes species that are generally very small in size, causing damage by sucking plant sap (on leaves, fruits, branches, stems).

There are many species of mealybugs present on the group of Oranges,Tangerines,Grapefruits and Lemons (Citrus), which can be divided into 2 groups:

+ Group of sticky mealybugs with common varieties such as Lepidosaphes, Aonidiella, Coccus and Saissetia.

+ Group of flower mealybugs with common genera and species such as Pseudococcus, Planococcus and Icerya purchasi.

Dry branches and berries disease often appear to be common damage on coffee gardens during the rainy season. The disease causes death of branchs, dry fruit, severely affects the canopy structure and coffee yield if not paid attention to prevention.

  

 Pink disease commonly causes diseases on rubber plantations in the rainy season, especially on garden from 4-8 years old. This year, rubber has to go through a period of severe drought, weakening the tree, so now in tnshe rainy season it is easy to get infected. Therefore, it is necessary to pay attention to good management to avoid affecting the garden.

In recent years, the area of citrus has been expanded because it is a fruit tree with high economic efficiency. However, in order to sell at a high price, not only in quality but consumers also require the external beauty of the fruit, so pest management on citrus is a matter of great concern to farmers. The hot season is a favorable condition for thrips to develop and cause damage, affecting the commercial value of fruit.

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