Nauni University lists dos and dont’s on apple leaf disease

Ambika Sharma

Solan, July 16

The Department of Plant Pathology of Dr YS Parmar University of Horticulture and Forestry, Nauni, today issued an advisory to apple growers to effectively manage the foliar diseases reported from some areas. Alternaria and other fungal species were identified as the primary causal agent of the leaf spot/blight disease based on observed symptoms, besides microscopic observations.

The disease exhibited a widespread distribution, recording variable levels of severity in different orchards of Shimla district — in Kotkhai 0-30%, Jubbal 0-20%, Rohru 0-20%, Chirgaon 0-15%, Theog 0-10% and Chopal 0-4%.

It was observed that farmers following proper need-based sprays of pesticides as per spray schedule depicted minimum disease severity, said a university spokesperson.

Three teams of the scientists from the main campus at Nauni, Krishi Vigyan Kendra (KVK), Shimla; and KVK, Kandaghat, conducted field visits to various apple orchards in Chopal, including Deha, Chambi, Khagna-Roo, Mandal, Deiya, Bhanal and Kiyar; Rohru (Sheikhal, Dhara, Kamoli, Samoli, Karalash, Kharla, Kadiyon) and Kotkhai (Bhadaich, Matlu, Bagi, Sheglta, Ratnari, Panog, Badeiyon, Jashla and Deyorighat); Jubbal (Nandpur, Ruyildhar, Kathasu and Batargalu).

Awareness camps were also organised in Kotkhai, Jubbal and Deha to disseminate information on disease management practices.

Several factors were identified as contributing to the severity of leaf spot disease. This comprised adverse climatic conditions where the combination of less rain (November, 2023 to July 2024) and intermittent rain in June 2024 created an environment conducive to the disease development.

Pest infestations was identified as the other cause. It was found that high mite population contributed to overall tree stress, exacerbating leaf spot disease development.

Non-judicious use

of chemical sprays

Imbalance in crop management in form of non-judicious use of chemical sprays, including the mixing of nutrients, insecticides and fungicides led to phytotoxicity and weakened plant health, increasing susceptibility to disease.

Pre-existing plant stress was identified as another cause as the underlying conditions such as root rot, collar rot and canker weaken tree vigour, making them more susceptible to leaf spot infections.

The university recommends spray of fungicides as the per the schedule given by the Directorate of Horticulture and the university in the apple orchards where these diseases are prevailing.

Additionally, farmers should continuously monitor the status of these leaf spots/blights and need-based application of fungicides should be done as per the recommendations in the spray schedule.

The scientists have advised the farmers to enhance air circulation through proper pruning, remove weeds/grass and infected plant debris from the orchard floor and manage soil moisture levels to reduce disease pressure/stress.

Appropriate fertilisation to promote overall plant health and disease resistance should be undertaken.

Fungicides/insecticides should be used judiciously, adhering to recommended dosages and spray intervals. Rotation of fungicides/insecticides is essential to prevent resistance development. Strictly avoid any unapproved mixing of recommended fungicides with insecticides or nutrients. Repeated spray of any insecticide or fungicide should be avoided advised the farm scientists.

Investigate and implement alternative or complementary management strategies, such as regenerative farming/natural farming practices, to improve soil health, moisture retention, disease/ insect pest and weed control stress farm scientists.

They have also been directed to undertake consistent orchard surveillance which enables early disease detection and timely interventions.

Effective management of root rot, collar rot and canker is essential for overall tree health and disease resistance.