English edition

Part 4-1

⑦ Longhorn beetle

👉 What is Longhorn Beetle?

Adults appear in May - September. Bite the bark, mainly pierce the main trunk below 60 cm above the ground to lay eggs. The larvae eat the inside of the trees, and since it puts out wood chips and feces from the hole of the tree, it can be said that it is easy to discover. Larvae take 2 years to adult. Larvae become pupae in trees.

👉 Damage to the longhorn beetle

Larvae (commonly known as Teppoumushi) keeps eating under the bark in trees. As a result, trunks and branches become hollows, they may break or die. Adults harm the soft bark of a new treetop, which may cause branches to die. Damage to young trees is great, and many trees besides citrus are harmed.

👉 Removal method 

If you find an adult, you kill it. Also, if a branch or trunk has a round scratch, crush the egg because the possibility of the egg laying part is high. If a hole opens in a branch or a trunk, and the wood chips etc. are squirting, there is a possibility that there are larvae, so we insert a wire etc. and kill it.

When using medicine, spray EMP emulsion and benica water-soluble material etc. from the middle of June to the middle of July when spawning begins. Scatter to the main trunk within 70 cm from the ground. In addition, wrapping palm fibers or newspapers around the trunk of 30 to 40 cm from the ground, it is also effective to prevent adult egg laying.

⑧ Thrips

👉 What is Thrips

Even adults are small and 1-2 millimeters tall. Thrips repeats occurrence around 10 times a year. Larvae and adults suck juice of new buds, new leaves, flowers and fruit. Thrips occur frequently during high temperature and dryness in summer. So many thrips are born in a short period of time. Thrips prefers to inflict soft parts of plants.

👉 Damage to thrips

Thrips enter the flower and suck the juice. Buds are also targeted. As a result, the flowers do not flower, they become brown and wither. Moreover, the color may come out white. Leaves do not spread when thrips parasitize on sprouts. Fruits may have small spots on the skin. It may be like a scab. Be careful about virus mediation. At first glance, it is similar to the damage of spider mite, so to distinguish it we will check the insect.

👉 Removal method

In the visible phase, the medicine will show its effect, but if it gets into the flowers etc, the effect will be small. Pick up thrips and dispose of it. Thrips suck the juice mainly on the back of the leaves, so spray the medicine on the back of the leaves. You can also capture thrips by gluing a blue adhesive tape around the tree. You can prevent intrusion of thrips by sticking light reflection film etc around the tree.

5、Disease of the lemon

① Melanose

👉 Symptom

I see it in the period when it rains around June to September. Even in the high temperature period around August and the temperature falling after November, the spreading speed is slow. Bacteria of Melanose that live in the soil bounce back with rain and water and get stuck to the leaves on the bottom to infect them. It is also called early blight or black stars disease. When rain continues, Symptom frequently occurs. As the number of leaves decreases, the force of tree growth is weaken and flowers bloom less easily. It can be said that any fruit tree catch this disease. It is a disease that is particularly prone to young branches and leaves.

👉 Workaround

Immediately remove the diseased leaves, and also remove the falling leaves. I will wipe the medicine about every 3 days, about 3 to 4 times.

If all the leaves have fallen without correcting Melanose, organize the withered, thin, small branches and cut lightly the branches. It is effective to remove sick leaves that fell to the ground and give a lot of potash fertilizer. 

If sprout comes out after removing sick leaves, preventive medicine is sprayed to prevent recurrence. In the case of potted plants it is also effective to evacuate to a place not exposed to rain. It is also good to sterilize the ground surface. 

👉 Points to watch out for

a Clean the dead leaves and branches so that they do not fall on the root of the tree. 

 Water the roots
of the trees so that branches and leaves do not get wet.

 Make sure that the tree does not hit the rain.

 To prevent water from bouncing, lay multiple sheets etc.

 If it finds out the occurrence, remove it, sprinkle the medicine to prevent spreading.

 Do not make fertilizer run out.

 Do not apply more nitrogen fertilizer at one time.

👉 An effective fungicide

 Aerosol                         ; Ortran C, Benica DX etc.

 Spraying agent           ; Benica X Spray etc.

 Before it occurs          ; Daconille 1000 etc.

 Early stage of onset  ; Supple emulsion etc.        

② Xanthomonas campestris pv. citri

👉 Symptom

Xanthomonas campestris pv. citri prefers low temperature and it infects by rain and wind. It is a disease that occurs against a wide range of things, such as fruits, flowers and branches. Sometimes lesion spots are formed on the spring leaves, the center becoming cork and becoming rough. The surroundings are accompanied by a yellow blur. Especially, if a branch has a wound, it infects from there. On the branches of summer and autumn, Xanthomonas campestris pv. citri frequently occurs on the edible traces of Citrus leafminer (Ekakimushi).

👉 Workaround

This disease is a bacterial disease, and in order to prevent it, make sure that the plant does not get exposed to strong rain and wind, while allowing the wind to pass well. In the winter, we will cut away the dead branches and dispose of them. Drugs are not very effective, but the next drugs are sprayed once each before the onset of disease, just before flowering, immediately after flowering, during rainy season, when the typhoon is coming, spray it before it comes.

<Applicable drug>

Bordeaux solution

Copper wettable powder + carbonate lime

Streptomycin agent etc.

③ Elsinoë fawcettii

👉 Symptom

Elsinoë is common in violets and citrus fruits. Initially, a scab scar is formed on the leaves, stems and young branches, and many small white and brown round spots appear. As the spot gradually becomes 2 to 3 mm, the middle becomes scab-like in shape. When the disease progresses, in the case of leaves the spot will break and the hole will open, in the case of the branches it will deform and twist and shrink.

👉 Workaround

Pathogens are a type of filamentous fungus (mold). The scab which can be in the lesion part is the source of the spores. It will pass winter as it is. The temperature is around 22 to 24 ° C, and it is likely to occur if the ventilation is bad. Because it spreads out by rain, we prevent it by vinyl etc. to prevent leaves etc from hitting the rain. In addition, it removes branches and leaves with lesions that are a source of infection, also collects fallen leaves and incinerates it.

Mid to late April (germination period), late May (period when the flowers fall), and middle to late June. This three times, spray the following medicines.

<Applicable drug>

Dithianon wettable powder

Thiophanate methyl wettable powder

Benomyl wettable powder, etc.

④ Gray mold

👉 Symptom

At the beginning, light brown spots like water seems to be formed. After that, spots will grow sharply and rot. As symptoms develop, gray and gray green molds will appear to cover lesions when wet. Gray mold crosses the winter on its plants with mycelium status. At around 20 degrees Celsius, it generates spores at times of heavy rain. Spores are scattered by the wind.

👉 Workaround

If you spread the following medicine before harvest you can prevent the onset.

<Applicable drug>

Thiophanate methyl wettable powder

Benomyl wettable powder

Guazatine liquid medicine etc.

⑤ Cercospora leaf mold

👉 Symptom

Like the soot is covered, the leaves, trunks and branch surfaces become black and dirty. The soot will gradually spread and the coating will cover the entire surface. Breathability and sunshine are poor, prefer a humid environment, Cercospora leaf mold occurs. There is something that happens parasitically on the excretion of sucking pests. And there is something that ingest nutrients directly from plants.

👉 Workaround

It is best not to leave insect pests (such as Coccoidea and aphids) that cause bacteria. Frequent pruning is important because it is likely to occur when breathability or sunshine is bad.

<Applicable drug>

Sumithion emulsion

Ortran wettable powder

Actilic emulsion etc.

👉 Painted Polymita eats it

"Painted Polymita(Kodama Maimai)" which is said to be the world's most beautiful snail eats "Cercospora leaf mold". However, it is difficult to continue to give "Cercospora leaf mold" as a food. In addition, it appeared in Annex I in the Washington Treaty of 2016, it became difficult to import, it seems to be difficult to use as a beneficial insect.

6、Diagnosis due to the symptom

① A leaf is yellow

The leaves slowly turn yellow, and then it falls down, there are cases of leaf lifetime. However, there seems to be a possibility that the roots are damaged.

< Cause yellow leaves >

・ Leaf lifetime

・ Root rot

・ Nutritional deficiency (nitrogen shortage)

・ Water shortage

・ Sunlight is strong

・ The temperature is low

・ Spider mite smoked leaf juice, etc.

We must take measures against each factor. However, once a leaf turns yellow, even if you take measures, there is nothing to return to green again. If you want to return to green, leave a few leaves at the tip and remove other yellow leaves. The young trees of lemon grow branches and leaves well (tree is strong). Sprouts come out relatively soon and only become green leaves.

👉 Roots are damaged

Leaves gradually turn yellow and eventually fall. If the number is small, it is the life span of the leaves, but if there are many, the root may be damaged.

👉 The temperature is low

It gradually withers from the tip and becomes crisp. If it falls below minus 3 ℃ it will be more likely to occur.

👉 Nutritional deficiency (nitrogen deficiency)

The green gradually becomes thin, and when it is terrible it turns yellow as a whole. The cause may have a reason other than just a single element such as nitrogen is missing.

👉 Manganese deficiency etc.

The veins of a leave will yellow. If the condition is bad it will cause abnormal fallen leaves. There is a possibility that the alkalinity of the soil is high.

② The spots of the leaves is yellow

  👉 Five elements of fertilizer

a、Nitrogen (It becomes the basis of the protein necessary for the new organization to grow)

Nitrogen is mainly effective for growing plants. Especially it makes leaves bigger, it is said to be fertilizer for leaves (HAGOE). If it is too much, it will become spindly growth and weak and will be more vulnerable to pests. Growth will be worse if it is not enough. The green becomes thin (it decomposes leaves' proteins and reuses them), the leaves become pale yellow. (It will turn yellow from the lower leaves close to the ground) 

Nitrogen is easy to starve so be careful!

 Nitrogen becomes nitrate nitrogen due to the action of microorganisms in the soil,

      and it flows away with rain.

 When cow manure compost containing sawdust was applied, when the amount of cow dung

      is small relative to the amount of sawdust, microorganisms ingest nitrogen as food.

As mentioned above, even if 3 elements are applied, nitrogen may be deficient, so be careful.

b、phosphoric acid

Phosphoric acid mainly relates to flowering and fruiting. It is said to be flower fertilizer (HANAGOE) or fruit fertilizer (MIGOE). Too much phosphoric acid will deplete iron, magnesium and zinc. On the other hand, less phosphoric acid causes delayed flowering and fruiting due to poor growth, and fruit quality and yield decrease. Phosphoric acid excess promotes potassium deficiency and induces iron deficiency.


It is said to be root fertilizer (NEGOE) as it mainly relates to root development and adjustment of osmotic pressure within the cell. Because it is easy to flow because of its water solubility, it is effective if you gradually apply it. When the potassium is insufficient, dead leaves and fallen leaves are seen early (it turns yellow from the edge of the leaf and its surroundings), it becomes more susceptible to disease. In addition, the growth of the roots becomes worse, it becomes easy to cause root rot.

d、Calcium (lime)

Calcium mainly works to strengthen the cell wall and strengthen disease resistance of crops. Since the soil of the field gradually tends to be gradually acidic, be sure to mix it according to the acidity (pH) of the soil before planting. If you can keep the soil in a state close to neutrality, the roots are good and you can increase the beneficial bacteria of soil microorganisms. Calcium deficiency seems to occur easily due to excessive nitrogen or lack of water.


It is a substance indispensable for the formation of chlorophyll which synthesizes carbohydrates. If it is insufficient, the generation of chlorophyll decreases and the photosynthesis works worse. It also serves as an active agent for important enzymes in the body. Symptoms of magnesium deficiency are characterized by chlorosis (leaving whitening due to loss of chlorophyll) between leaf veins. In other words, the pulse of the leaf is still green, but the space between the pulse of the leaf and the pulse becomes yellow and it looks like a pattern of a tiger. For magnesium deficiency symptoms, it seems effective to spray magnesium on the leaf face.

Leaves may become yellow due to excess or deficiency of nutrients.

Please refer to the above.

Especially in my lemon trees, yellowing stopped by applying magnesium(dolomitic lime).

I think that it is important to look at the state of the leaves and seek the cause.

👉 About immediate / slow release chemical fertilizer

👉 Lemon leaves turned yellow, so I applied dolomitic lime.

③ Flowers fall (flowers do not bloom)

④ The fruit drops

The following problems are considered as causes of ③ and ④.

👉 Saplings are too young.

 「"It takes a long time for fruit for the first time"

 Please refer to this blog post. 

👉 There is a problem with daily management.

・ Lack of sunshine

  ・ Cold protection measures

  ・ Water shortage / root rot

  ・ Excess or shortage of fertilizer

👉 Nutrition was used too much to grow the branches.

  「It takes a long time for fruit for the first time」

  「Pruning lemon」         See the article.

👉 Lemon could not pollinate.

👉  A biennial bearing.

  Including explanation of Physiological fruit drop (June drop)

👉 I pruned too much.

The reason why flowers and fruits fall are various as described above. In order to respond to it, I would like to observe the condition of lemon trees sufficiently and also to understand what kind of way of raising now. For example, I'd like to confirm "how much did you harvest last year," "When and how much fertilization was done," "how did you prune branches?" etc.

I think that it is difficult to accurately determine the cause, but I would like to respond appropriately by observing and verifying every day. I am planning to record the state of the monthly every month. How many years passed after purchasing seedlings? What is the condition of the lemon tree at that time?

You can observe from various perspectives.

I hope for your reference.

7、Monthly work, monthly record

I try to keep monthly growth record.

I would like to mention here about the work to be done monthly by month.

It is written in Japanese, but if you do not mind, please read it.

"From here" can come in.

Thank you very much for reading

through to the end.

Based on this blog "How to grow lemon"

I would like to continue

verification of lemon cultivation.

I hope to update this blog every time

I can check the results.

If you refer to this blog on occasion,

I am very pleased.

Thank you very much. 


  • この記事を書いた人


■ニックネーム korolemon Lemonを育てています。 子育て奮闘記ならぬ、Lemon育て奮闘記です。 自宅の庭で、ちょとした隙間を見つけて、ちょっとした家庭栽培・・・ 自分で調べた「あれこれ」を実際に自分でやってみて、 どんな結果になるのかの検証です。 奮闘記です。

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