How to Stop Leaf Curl in Peaches & Nectarines?

Leaf curl is a known issue to many growers of stone fruits like peaches and nectarines, and makes for an unsellable crop if the disease manages to permeate to the fruit. Whilst prevention is better than cure, treatment using copper oxychloride Demildex, available exclusively from African Pegmatite, can alleviate the problem and ensure a healthy, sellable crop every year.

 

Leaf curl is a disease that affects species of plants in the genus Prunus (including peaches, nectarines and other stone fruits) and is caused by a fungus called Taphrina deformans. Leaf curl is one of the most common problems impacting nectarines and peaches. And if left untreated, can destroy the new growth from planted trees. Leaf curl is also known as leaf crinkle.

Leaf curl can lead to off coloured leaves, lesions and other visual deformities - in addition to premature falling of the fruit. All of these factors lead to a less productive crop and also in many cases an unsellable crop. Peaches, nectarines and other related stone fruits are selected by buyers based on appearance. An off colour or misshapen fruit will not be taken up by the commercial buyer, thereby causing financial stress to the grower, in addition to substantial wastage. It is imperative to avoid leaf curl in the first instance. Many commercial growers may benefit from employing agriculture specific fungicides as part of their crop management programmes.

What is Leaf Curl on Stone Fruit/Peaches/Nectarines?

Leaf curl is a problem that usually occurs on the leaves of stone fruit trees. Whenever a grower is witnessing thickened warty texture then this is certain that they are looking at the signs of leaf curl on their tree. It is also obvious when looking at the brightly colored and distorted leaves on the neighbouring infected leaves. However, this disease is quite puzzling too because the peach growers can go years without this disease and not seeing any signs of this problem even if the trees have not been sprayed with chemical treatment. Unfortunately, this disease can suddenly infect many trees in little to no time. Most commonly, this disease affects the plants in a specific moisture environment, with most proliferation and transmission taking place in the spring. Leaf curl in peaches normally occurs in spring when a period of rain lasts more than 10 hours under cool conditions, with typical rainfall levels in excess of 13 mm. The leaf curl infection occurs in any temperature range unlike apple scab and cherry leaf spots, which underscores the need for ongoing management and vigilance. Leaf curl only happens under specific conditions and therefore cannot be considered as an annual threat, however it may be hard to spot at the end of the season owing to its method of overwintering and relative ease of transmission.

leaf curl on plant leaves

What Does it do to Stone Fruit/Peaches/Nectarines?

When it comes to the damage which leaf curl can cause to the stone fruit, it will appear that when nectarines and peaches are sprouting new leaves, these leaves will appear lumpy and thick with a blistered appearance. In many cases, leaf foliage also has the ability to change its color to pink, pale green or even sometimes purple. In addition, occasionally a white bloom can also occur on the leaves of the fruit trees which is an ascal bloom and is related to the reproduction of the fungus (see later). The leaves will brown off over time and in the end, the leaves will begin to fall prematurely. If the plant is flowering, the flowers will also begin to fall. Fruit, when eventually affected, will also fall prematurely and therefore the presence of leaf curl disease will result in a significant loss in the production of the trees and fruit.

Before the falling of the fruit, however, radial pimples and spots are likely to form on the surface of the fruit. These pimples and spots are weak points which may have the potential to allow egress of another disease. It is often stated that a weakened plant is more susceptible to other diseases. Affected fruit may never reach maturity.

Because of how the fungus overwinters (in the bark, predominantly), excellent husbandry, growing best practices and a detailed treatment regimen should be adhered to. A lack of management and treatment will lead leaf curl to continue to affect the trees year after year and will become worse with the passage of time and it can lead to very low yields.

peach tree with leaf curl
leaves with leaf curl

What Causes Leaf Curl?

Leaf curl is caused by the fungus Taphrina deformans. T. deformans is an ascomycete-type fungus, meaning it produces spores sexually via the use of asci. Not limited to just peaches and nectarines, T. deformans will infect all species of the genus Prunus, including apricots, plums, almonds and cherries.

Peach and nectarine leaf curl is a resistant and virulent fungal disease that normally appears on the leaves, flowers, and stone fruit trees in early spring. Even the leaf curls can start long before the emergence of foliage or fruit.

An ascal bloom (from the asci, often white in colour) is present on the surface of the plant leaves. These asci are secreted directly into the plant tissue via lysis breaking through the cuticle primarily on the leaves of the plant. As each ascus contains eight ascospores which themselves give rise to the conidia (spores) - which are released in the early stages of summer.

The fungal spores of leaf curl are normally transported by rain and wind onto the nectarine and peach trees as well as in defoliation and debris that surrounds the tree. These spores take shelter throughout their dormancy and the summer period in these areas. These only affect the developing tissues of nectarine during wet and cool days of winter. The spores from T. deformans overwinter on the bark or the buds of newly infected plants.

peach leaf with leaf curl

How to Prevent Leaf Curl?

Although the complete eradication of this disease is challenging, there are some things which can minimise the effects of this disease. It is important to clean up and destroy the fallen leaves on a regular basis to ensure that the fungus finds minimal places to hide and potentially survive the winter. If the disease symptoms are at the early stage then the diseased parts of the trees should be separated to the best of a grower’s ability. Because the persistence of fungi, infections on the diseased parts can grow which will cause even worse damage, and are easily spread.

As part of a treatment and prevention regime, copper oxychloride Demildex can be used for effective leaf curl prevention. Copper oxychloride Demildex is a systemic fungicide that has been proven to work against the fungus T. defrormans and is a preferable choice to avoid the buildup of excess copper in the soil.

It is a preventive treatment best applied as a spray which growers may use in winter before bud bursts or even at the slight appearance of the symptoms of curled leaves. Demildex is recognised as one of the most effective treatments for leaf curl.

What is Copper Oxychloride Demildex?

Copper oxychloride Demildex, produced by, and available exclusively from, African Pegmatite, is one of the most effective fungicides and bactericides that can be used to avoid fungal infections in a whole host plants affected by several fungal diseases, not limited to leaf curl in stone fruits. Cupric fungicides are highly effective in treating various plant diseases, with copper sulfate long being used as a treatment. Although it is a well-known fact that the use of the excess amount of copper can cause problems in all plants as it can lower the production levels, optimally dosed and applied copper oxychloride Demildex is effective at dealing with the fungal infection without inhibiting plant growth or fruit yields.

pristine hanging peaches
peaches

How it is Used to Treat the Problem?

Growers will benefit from simply spraying affected crops on the leaves and stems early in the growing season. Demildex contains approximately 50% copper, which is able to interfere with the enzymatic pathways involved in fungal growth. Additionally, Demildex creates a chemical barrier on the leaf surface which can aid in preventing other infections over extended periods.

Copper oxychloride Demildex is applied in normal conditions at a dosage of up to 0.25 volume% (which equates to 2,500 ppm). This is the equivalent of circa 50% metallic copper. Supplied as a fine, green powder, Demildex contains copper oxychloride at a concentration of 850 g kg-1 and boasts a narrow particle size range - 95% being smaller than 5 μm - and a surface area of 30,000 cm2 g-1 making for easy and rapid solubility, therefore facile uptake.

nectarines
peach cut in half

How it Saves Money in the Long Run by Preventing Problems and Saving Crops?

Undoubtedly, Copper oxychloride Demildex is one of the best solutions which growers can use to treat the problem of leaf curl in stone fruit trees. If leaf curl is allowed to take hold, an unhealthy crop will prevail which can lead to premature dropping of fruit, shedding of leaves and deformed or off colour fruit. As mentioned earlier, non-pristine fruit is less easily sellable.

Most importantly, the Demildex solution is based on a reduced quantity of dicopper chloride trihydroxide which will never affect the productivity of these trees. It means growers are getting a solution that will not cause any severe side effects at all. When taken together, the combination of effects caused by the chemical barrier and by the neutralisation of the fungal pathogen, it can be easily said that Demildex is an effective solution for systemic leaf curl infections. Demildex is both a highly reliable treatment and preventative measure, for the most effective and long-term preservation of idealised stone fruit production.

Notes On The Use Of Copper-Containing Fungicides

Care should be taken during the application of copper based fungicides owing to large quantities of copper being harmful to mammalian and aquatic life. Spraying should be concentrated to the relevant area and sufficient time should elapse between the final round of treatment and harvesting - typically on the order of 14 days. Over treatment and the use of excess copper fungicides is discouraged as this may cause a reduction in crop production.

Summary

  • Leaf curl is a disease caused by the fungus Taphrina deformans, causing discolouration, blotches and curling of the leaves, particularly on stone fruit plants such as nectarines and peaches
  • Should the disease spread to the fruit, it can cause marks to appear on the skin and eventual dropping of the fruit before full maturity
  • Copper oxychloride Demildex is a highly effective antifungal treatment against leaf curl and several other diseases known to the grower
  • Demildex can be used by Commercial growers to ensure a sellable, non-spoiled crop

Copper oxychloride Demildex, from African Pegmatite, is a high performing fungicide developed exclusively for use in agriculture and market gardening. Effective against leaf curl in stone fruits and across many other disease lines, Demildex is the responsible choice for the commercial grower.

copper oxychloride demildex used to treat black spots on roses