Himachal: Dr YS Parmar University issues advisory for managing apple foliar disease

Shimla (Himachal Pradesh) [India], July 18 : The department of plant pathology, Dr YS Parmar University of Horticulture and Forestry Nauni, Solan-Himachal Pradesh, has issued an advisory to apple farmers to effectively manage the apple foliar diseases reported from some areas of the state.
Three teams of scientists from, UHF, Nauni, KVK Shimla, and KVK Kandaghat conducted field visits to various apple orchards in Chopal (Deha, Chambi, Khagna -Roo,Mandal, Deiya, Bhanal, Kiyar); Rohru (Sheikhal, Dhara, Kamoli, Samoli, Karalash, Kharla, Kadiyon) and Kotkhai (Bhadaich, Matlu, Bagi, Sheglta, Ratnari, Panog, Badeiyon, Jashla, Deyorighat); Jubbal (Nandpur, Ruyildhar, Kathasu, Batargalu).
The primary objective was to assess the prevalence of Alternaria leaf spot/ blight and other leaf spot diseases, and to conduct awareness camps for farmers, and provide guidance on effective management strategies. Visual assessments of plant health, leaf symptom identification, and disease severity estimation were carried out. Additionally, awareness camps were organized in Kotkhai, Jubbal and Deha to disseminate information on disease management practices.
Alternaria and other fungal species were identified as the primary causal agent of these leaf spot/ blight disease based on observed symptoms and microscopic observations. The disease exhibited a widespread distribution, recording variable levels of average disease severity in different orchards of the district viz, in Kotkhai- 0- 30%, Jubbal- 0-20%, Rohru- 0-20%, Chirgaon- 0-15%, Theog-0-10%, Chopal-0-4 %, however, the farmers following proper need based sprays of pesticides as per spray schedule depicted minimum disease severity. The university has also deputed four new teams to visit other apple growing belts of the state and assess the severity of the disease/ pests.
Several factors were identified as contributing to the severity of leaf spot disease:
Adverse Climatic Conditions: The combination of less rain (November, 2023 to July 2024) and intermittent rainfall in June 2024 created an environment conducive to disease development.
Pest Infestations: High mite populations contributed to overall tree stress, exacerbating leaf spot disease development.
Imbalances in Crop Management: 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: 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 recommended spray 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.