The walnut tree can be attacked by insects (fly larvae, aphids, etc.), fungi, and bacteria. Fungal and bacterial walnut diseases are more likely to occur during years with a humid and rainy spring. On this page, we will see how to care for the walnut tree by eliminating and trying to prevent the most common diseases.
Among the fungal diseases that affect walnuts is anthracnose . This disease is caused by Marssonina juglandis and is very common. The symptoms include damaged leaves, shoots and husk, with the appearance of greyish spots that can be more or less large. This fungal disease causes the subsequent death of the affected tissues. If the disease is very deep-rooted , you may see the loss of leaves with consequent repercussions on vegetative activity and poor nut production .
To eliminate this fungal disease of the walnut tree, it is possible to resort to chemical control based on copper preparations (Bordeaux mixture, tribasic sulphate and oxychloride at the doses indicated on the label) with a treatment to be carried out when the leaves fall and a couple of interventions to be done during the spring, when the first grey spots appear. To cure the walnut tree and prevent this fungal disease, it is advisable to carry out all the appropriate pruning .
By thinning out the walnut tree’s crown, you will promote the penetration of light and air circulation, factors that reduce the risk of fungal infections.
Another walnut disease that requires treatment with copper-based preparations is the bacterial disease caused by Xanthomonas campestris yglandis, commonly called ” black spots on walnuts “. This disease manifests itself at the resumption of vegetative growth with the appearance of small, angular oily spots that then cause necrosis of the affected tissues until elongated notches appear that reach the shoots causing them to dry out. This bacterium also affects young fruits, also in this case black spots appear but this time they are located on the apical area of the walnuts (the area opposite the peduncle). The black spots on walnuts are a consequence of the appearance of this disease during flowering. It is through the residue of the stigmas (which is found right in the apical area of the walnuts ) that the infection reaches the kernel causing it to rot.
To cure the walnut tree from this disease it is important to intervene in autumn, when the leaves fall and the buds open. With plants that have entered production, it is also important to intervene when the floral stigmas appear.
Treatments must be carried out with copper salts (Bordeaux mixture, oxychloride, tribasic sulphate… at the doses indicated on the label).
How to care for walnut
To treat the walnut tree and prevent the appearance of various bacterial diseases, it is possible to intervene in the presence of conditions favorable to their development (frequent rains, excessive humidity, etc.) by carrying out a preventive treatment based on copper salts as described above. In any case, it is always advisable to carry out the appropriate thinning pruning and intervene when spots appear on the leaves and on the walnut husk.
