Raspberry Leaves Turning Red (Causes And Solutions)

Seeing red leaves on raspberries is a rare occurrence, so it’s sure to draw attention. 

However, if you want to solve the problem, you must know what caused the leaves to turn differently.

It can be a deficiency of micronutrients, an infectious disease, or a combination of factors. 

If you don’t act quickly, not only will you lose one plant, but you could lose several.

Why Do Raspberries Turn Red in The Spring And Summer?

Several factors can cause red spots on leaves or even redness of the entire leaf, including a lack of phosphorus in the soil, fungal infection, or insect pest damage.

The Soil Lacks Phosphorus

The condition of all parts, not just the leaves, can be affected by the absence of any macro or microelement, and the signs can be similar. 

For example, a lack of these nutrients will show up first on the lower leaves of a raspberry plant, and then it will spread to the stem’s uppermost part. 

Moreover, calcium and boron deficiency shows first at growth points before symptoms appear on more mature branches.

If you want to grow a lot of raspberries, you’ll need a small amount of phosphorus: 6-8 kg per hectare per year. Even though the risk of phosphorus deficiency is low, it exists. 

A reddish-brown spot or the entire petiole may appear on the leaves at any time during the growing season. 

Macronutrient deficiency is the cause of this symptom. The affected leaves will turn black and fall off at this point.

After a month of growth, the buds appear, but their appearance is delayed. In this case, the entire plant turns dark green, and the leaves turn yellow and wither in the fall. Moreover, the plant appears to be covered in rust.

The plant appears to develop normally, with no signs of deficiency in essential nutrients. However, reddish spots on the leaves appear in June due to heat and increased rainfall.

Heavy rains remove soil nutrients like phosphorus from the top layer. Stagnant moisture near the roots also disrupts aeration. You might see similar symptoms when the soil dries out, and nutrients cannot get to the roots.

Fungal Infections

Fungal pathogens persist in the soil, plant debris, on shoots, and in manure, compost, and seeds and can be spread by these means. As on raspberries, some appear as large and small reddish spots on the leaves.

[1] Anthracnose. Early disease symptoms can be seen in late spring and early summer. Small grayish spots with a purplish edge can be clearly seen on the leaf plate’s veins at the edge of the container. 

As the infection progresses, the dots merge into one large one. Diseased leaves eventually turn black and die.

[2] Fungus Didymella applanata is to blame for the raspberry spur blight. So, when it’s rainy or humid outside, the disease is more active, affecting raspberries in the fall, late spring, or June.

Infested plants are ideal for the growth of the fungus, as they are more vulnerable to attack. 

The gall midge insect is the most common companion of the disease. On the other hand, fungus prefers to grow on trees that have been weakened by pests. 

Gall midge is the disease’s most common companion. This disease starts out with purplish spots on the shoots, then moves to the leaves, where it causes blotches of different sizes to appear. Eventually, the leaf dries out and dies.

Insect Infestation makes Raspberry Vulnerable to Diseases

Raspberries’ young leaves and shoots have a delicate structure. As a result, if your raspberry plant isn’t adequately cared for and monitored, it could become a breeding ground for harmful insects. 

Some of the most common pests on raspberries include the stem gall midge, Cane Borers, Aphids, and Spider Mites.

In addition, it is common for anthracnose to accompany the problems, so symptoms of the pest can be mistaken for those of the disease.

What To Do If The Leaves on Raspberries Turn Red And Dry

When you notice red or purple spots on raspberry leaves, the first thing you should do is inspect the bush to determine the cause. 

Insects are the primary cause of disease. So you need to use fungicides and insecticides to treat the infection and protect the bush from pests. Use fungicide if there are no insects present, but a disease exists.

Look for a nutrient deficiency if almost all of the leaves are red. This is because your raspberry needs to be fed with a mineral feeding.

How To Treat Red Spots On Raspberries

Treatment will work if started in time, so inspect the raspberry frequently and act quickly if necessary.

Treatment For Phosphate Deficiency

Phosphorus deficiency can be compensated for during the early growth period (spring-early summer). Still, later in the season, it is difficult to fix. 

In addition, the element’s low mobility in the soil means that it reacts with soil particles to form compounds that plants cannot absorb. As a result, phosphate fertilizer absorption is low, ranging from 15 to 22%.

In acidic soils, phosphorus is best absorbed from water-soluble and citrate-soluble (i.e., soluble in weak acids) forms of fertilizer.

Here are the phosphate fertilizer options and recommended dose:

Important: When fertilizing, keep in mind that phosphorus uptake is linked to nitrogen uptake. So, add Nitrogen to phosphorus fertilizer to increase root absorption capacity.

Fungicides can be used to get rid of the fungus. You should apply fungicide at least 2 weeks before harvest. 

Ensure to spray in the morning or evening, when the weather is calm, and there is no wind.

The interval between sprays is 10-12 days, and the number of treatments (2-6) is determined by the extent of the damage. Alternating the fungicides is recommended for maximum effectiveness.

If more than half of the plants are affected. I’d suggest pulling it up, burning it, and treating the soil with a formalin solution.

Dealing with Insects

Use folk remedies if they don’t work, and then use insecticides if necessary.

A practical method of preventing infection with infections and insect damage is timely prevention, carried out in the spring and fall, with a change of location every 5-7 years.

Perform Sanitary Pruning in Spring

As the snow begins to melt, perform sanitary pruning: cut down the branches that are frozen, sick, or weak. 

Clean the raspberry bush by raking up last year’s leaves and discarding them because they contain larvae, overwintered insects, or disease pathogens. 

When these tasks are completed, the stems are tied up, inspected once more, and fertilizer is applied to the soil (the following calculation is given per square of area):

  • 5-6 kg of organic compost
  • 1:20 solution of chicken manure or 1:10 solution of cow manure – 3-5 liters
  • 50 to 80 grams of superphosphate
  • Sulfate of potassium, 20-40 grams.

After fertilizing, let the soil rest for a few days before spraying with pesticides or fungicides. 

Here is how to do it:

  • Before the buds swell, spray the crown, soil with Bordeaux liquid (1%);
  • For anthracnose prevention, use the sulfur-based fungicides listed in the table above.
  • If there are signs of raspberry gall midge, remove the infected branches. Because it is hard to control this insect with insecticide.

What Should You Do in the Fall for Raspberry?

Clean the raspberry bed after harvesting and leaf fall to prevent pests from making it their home. Sick and damaged branches are cut off after the soil loosens just a bit.

If the branches below have reddish leaves, make a 30 cm furrow from the plant and sprinkle 40 g superphosphate or monocalcium phosphate or between the rows and water.

Do not apply Nitrogen in the fall to not provoke the growth of new shoots. Instead, you can use urea (50 g/10l), zinc sulfate (3 g/1 m²), and manganese sulfate (5 g/1 m²). In addition, I recommend alternate fertilizers – one year, you apply organic fertilizers (e.g., spread organic manure), the following year, use mineral fertilizers.

Suppose you do not ignore the care rules for raspberries, timely pruning, prevention, change of place, feeding. 

In that case, it will not only please a good harvest but also will not force us to take emergency measures to combat the redness of the leaves.

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