leaf spot on potatoe leaf

How To Remove Leaf Spot From Strawberries, Tomatoes, Celery And Passion Fruit Using Copperoxychloride Demildex

Leaf spot disease is a problem faced by many commercial growers owing to the pernicious nature of the fungi and bacteria that are responsible for them - combining rapid growth and easy transmission can lead to poorly salable, unhealthy crops if left unchecked and untreated. Copper oxychloride Demildex from African Pegmatite is a highly effective solution, rapidly preventing the reproduction and spread of the organisms responsible.

Leaf spot is a very common plant disease that even the most conscientious gardener is expected to see at least once in their vegetation. They are caused by a wide range of fungal species, as well as, some bacteria. Regardless of what the causative agent is, the prevention and treatment involve about the same practices.


Bacterial Leaf Spot: Tomatoes and Celery

The symptoms of plants affected by bacterial leafspots are numerous, with variable coloration the most common and first noticeable symptom. Infected plants are usually seen with black or brown water-soaked spots on their foliage or in some, a yellow halo which is usually uniform in size. Generally, the spots increase in size and grow into each other in the rainy season or under wet conditions as the case may be. In dry conditions however, the spots appear speckled.

As the spots grow in number, the entire leaf might become yellow, wither and drop from its branch. The most susceptible plants to bacterial leaf spot are members of the Prunus family which include almond, cherry, plum, apricot and peach. The fruit of these trees would usually have spots or sunken brown portions. These aren’t the only crops vulnerable to bacterial leaf spot. Vegetable plants like tomato and pepper crops are also at risk.


For celery, the bacteria responsible for leaf spot is Pseudomonas syringae, with early symptoms being small yellow spots on early leaves. These will enlarge with time and a rusty coloured circle may form around them. Bacterial spot disease in tomatoes is caused by four species of the genus Xanthomonas.


Transmission of both types of bacteria responsible for spot disease is by water - typically most pronounced in times of high humidity and or warmth. Therefore, growth in greenhouses may be more conducive to bacterial transmission, owing to repeated heating and cooling cycles with a moderate humidity level maintained. As with many biological pathogens, those arriving on an already weakened plant will have the most impact. Most concerning for members of genus Xanthomonas is that the bacteria is known for rapid spread, with the pathogen able to transmit to non symptomatic plants over the course of a week from symptomatic plants several metres away.

leaf spot infection
diseased affected leaf

Fungal Leaf Spot: Strawberries and Passion Fruit

Fungal leaf spots on the other hand attack lettuce and some other vegetable crops like (broccoli, cauliflower, tomatoes, peppers and turnips). They are caused by pathogenic fungi. Once the fungi gets into the leaves of the plant, they continue to grow until the leaf tissue is destroyed. Its resulting spots varies in size, from as small as a pinhead spot to one that covers the entire leaf. The dead sections on the leaves of the plants are usually of the colors, tan or reddish, brown or black. In some rare cases, the border of the leaves could turn red or purple. They are generally found in flowering plants and even indoor potted plants.

Leaf spots are most active under moist conditions and warm temperatures, for example, during the summer months. During this period, especially if the plants are being watered by an overhead sprinkling system, there’s just enough moisture to promote infection when the bacteria is either splashed by water or blown on to leaves by wind. Rain and wind are the main culprits for the transmission of the bacteria from plants to plants.

Fungal leaf spot disease is rarely severe enough to cause complete crop failure. However, modest breakouts may cause premature falling of the fruits and excess spots and blemishes to the fruit and leaves can render some of the year’s crop unsellable.


The fungus responsible for leaf spot in passion fruit is Alternaria passiflorae, whereas for strawberries it is caused by Mycosphaerella fragariae. Symptoms on both plant types are similar - spots on the surface of the leaves and larger spots, sometimes even lesions, on stems and stalks. Blemishes and spots to the fruit are not uncommon - it is these which indicate that the disease has taken hold in the plant and prevention strategies are now useless.


Transmission of the two fungi occurs in very similar methods. Both fungi overwinter as mycelium in fallen leaves and are spread to plants in the spring when the weather becomes warmer, with suitable amounts of rain and wind. Disease development for M. fragariae favours cooler daytimes with wetter overnight conditions. Development for A. passiflorae on the other hand is much more pronounced in warm and humid weather, especially where there is a leafy canopy present. Like many other fungal type plant diseases, these capitalise on already weakened plants and those that are at the early stages of their growing seasons.

Effects of Leaf Spot

The Leaf spot disease can have a huge effect on the productivity of plants and their overall well-being. To start with, leaf spot can cause lesions in trees and vegetable plants which in turn causes heavy defoliation as the disease further develops.

It also leads to lower productivity in plants as defoliation of leaves might interrupt the photosynthetic processes of the infected plant.

Leaf spot is generally not harmful to older plants, in younger plants however, the disease can spread really quickly and can make the plants wilt and in more infected plants can die.

leaf spot effects

Prevention and Control

There are a number of preventive measures that growers can apply to prevent the spread of leaf spot in your tomatoes, strawberries, celery and passion fruit gardens. The following are some of them:

Planting resistant varieties: Planting resistant varieties is a very effective way of preventing leaf spot in the aforementioned fruits and vegetables. It is important that you plant resistant varieties of each crop where possible as this will limit, if not completely thwart the development of leaf spot diseases in them.

Husbandry: Pruning your plants or staking them to improve air circulation can go a long way to prevent leaf spot disease, both bacterial and fungal. Improving air circulation starves the causal organism of moisture which it needs for its growth and transmission. While it is important to prune the plants, it is equally as important that only disinfected pruning equipment is used after each cut.

Gardening: Pruning your plants or staking it to improve air circulation can go a long way to prevent leaf spot disease. Improving air circulation starves the causal organism of moisture which it needs for its growth. While it is important to prune the plants, it is equally as important that you use only disinfected pruning equipment after each cut.

Mulching: Having cleaned the plant’s environment, it is now time to use a thick layer of mulch to cover the soil. Mulching the soil will not only tame the aggressive growth of weeds but prevent the disease pathogen from splashing back up onto the leaves of the plant.

Disease-free seeds: Since leaf spot in vegetables is partly spread by the planting of infected seeds or diseased transplants, care must be taken to ensure that these seeds are from a leaf spot free-stock

Isolation: You should isolate infected plants from others before treatment to prevent the spread of the disease.

Tomatoes get sick by late blight

Other preventive measures include:

  • Keeping plants dry. It is recommended that you wet your fruit and vegetable crops in the morning so as to give ample time for the sun to dry the plants before night fall.
  • It is also important that you do not overwater your plants. If you do, you might be encouraging the spread of the disease as its causal organisms thrive best under moist conditions.
  • You should also keep your plants healthy so they are in the right shape to fight fungal invasion and indeed, any other disease. Early intervention and treatment of plants that appear dry or wilting could help them survive leaf spot if infected by it.
  • For indoor plants, care must be taken to water the roots rather than the leaves. You should avoid watering the leaves especially if your potted plant are kept in a warm and humid room.
  • You should keep your plant’s surrounding free from dead leaves and twigs. This is especially true of they have previously been infected by leaf spot from the plant.

In general, sanitation and water management are arguably the most important preventive measures for containing leaf spot disease. For water management, watering in the morning is best practice. You should also increase air spacing between plants by increasing the spacing between them, and perhaps, most importantly is making sure bigger plants are not shading smaller plants or blocking them from getting enough air.

leaf spot


A simple method of control is baking soda solution. Growers can spray the infected plants with a baking soda solution. Since baking soda can burn some plant leaves, growers should only spray a few and then wait for an accompanying reaction. If no reaction is noticed, growers can then proceed to apply every two weeks.

fresh vegetables

Treatment Using Copper-Based Fungicides

Applying copper-based fungicides and sulfur sprays can go a long way in thwarting the spread of leaf spot disease. They do not necessarily kill leaf spot but prevents its spread by stopping the spores from germinating in terms of fungi, and they prevent the replication of organisms for the bacterial cases.

A good copper-based fungicide for this purpose is copper oxychloride Demildex, which is a fungicide used to stop the spread of fungal infection in plants especially in celery, passion fruits, strawberries and tomatoes. It does this by interfering with the enzymes of mycelium and spores, consequently causing damage and forming a chemical envelope to fight against fungal intrusion or attack.

The benefits of copper oxychloride Demildex include:

  • Its excellent manufacturing process ensures a reduction in the volume of copper chloride contained in the end product.
  • It is highly effective with inhibiting and preventing the growth of bacterial and fungal spores in plants.
  • Demildex is extremely soluble in water owing to its high surface area (30,000 cm2 g-1) and small particle size (40% less than 2 μm and 95% smaller than 5 μm).
  • Demildex is purposely designed for agriculture and market gardening, and is supplied as a fine light green powder containing copper oxychloride at a concentration of 850 g kg-1, meaning it is easy to handle and provided at a concentration that will work straight away.

The fungicidal and antibacterial properties of copper oxychloride is down to the copper which slowly dissolves in the moisture present on the plant leaf. This dissolution generally occurs in the presence of weak organic acids, as plant infections take place under moist conditions or rainy periods, a moderate amount of copper gets released onto the plant to either kill or inhibit the growth of fungal spores and micro-organisms. Copper oxychloride Demildex is best applied in the early stages of the growing season, in an aqueous solution at around the 0.25 volume % (2,500 ppm) mark. This represents an equivalent amount of metallic copper of around 50%. Additional applications can be made throughout and even after the growing season has completed - as part of standard watering and fruit/vegetable production best practices.

A note on copper based treatments

Care needs to be taken when using any copper based treatment, including copper oxychloride Demildex. It is important to limit application so that excess copper is not allowed to build up in the soil and or runoff into water supplies. Copper is toxic to aquatic life. Excess copper levels in soils can lead to productivity reductions in many plants. When spraying, special care should be taken to avoid ingestion. A time period not less than 14 days should be left between the final spraying of a copper based fungicide/bactericide and harvesting.


  • Spots on fruiting plants can be caused by either fungal or bacterial means
  • Fungal spot disease, affecting strawberries and passion fruit, is caused by the fungi Alternaria passiflorae and Mycosphaerella fragariae respectively
  • Bacterial spot disease, affecting celery and tomatoes, is caused by the Pseudomonas syringae and four species of the genus Xanthomonas respectively
  • Both diseases are transmitted in similar ways, with good plant husbandry and a clear adherence to commercial growing best practices being essential
  • In only the most extreme cases does spot disease cause complete crop failure - but even modest cases can cause premature falling of fruit, a generally unhealthy plant or visually displeasing examples which are difficult to sell
  • Treatment using copper oxychloride Demildex is effective at preventing the growth, transmission and spread of the fungi and or the bacteria responsible for spot diseases in the fruiting plants mentioned here and many others

Copper oxychloride Demildex is a purposely designed copper based treatment for plants suffering from bacteria and fungus-cased spot diseases. Highly effective even in modest applications Demildex can help prevent a wasted crop - and is available exclusively from African Pegmatite.

copper oxychloride demildex used to treat black spots on roses