Diseases of garlic and management

Garlic is one of the most economically important crops in the Philippines. It is grown mainly in Ilocos Norte and Occidental Mindoro [Philippines], however, its production significantly decreased over the past decade (BAS, 2011). The decline in local production could be attributed to the reduction in production area of 5,200 hectares in 2000 to 2,500 hectares only in 2010, as well as the deterioration of the quality of planting materials used due to the accumulation of viral diseases through generations of asexual propagation and the presence of other fungal diseases. Virus diseases of garlic are widespread throughout the world can cause enormous loss in yield and quality of crops. Different groups of Allium viruses including Onion yellow dwarf (OYDY) and leek yellow stripe (LYSY) potyvirus. Shallot latent carta virus, and miteborne filamentous allexi viruses have been detected and identified from garlic plantings in different garlic growing areas of Cebu, Benguet, Iloilo, Batangas, Nueva Ecija [Philippines] and IPB [Institute of Plant Breeding], UPLB demo plot in 2014 to early 2016. Serological test confirmed previously reported garlic virus diseases species and the presence of Gar V-C was detected. Viruses disease infection varied with high incidence ranging from 50-90% from garlic fields where the source of planting materials came from farmer's own produced plantings and about 10-20% infection from field which planted tissue cultured planting materials. Viruses occurred in single and or mixed infections in both symptomatic and symptomless garlic plants. Most of the garlic growers are not even familiar with these garlic virus diseases. Symptoms exhibited by these diseases were mistaken by farmers to be caused by other pathogens (i.e fungi and bacteria) or even suspected to be due to nutrient deficiencies with the limited knowledge of the identity and the prevalence of these virus diseases and the unfamiliarity / unawareness of farmers on its existence thus, affecting the productivity of the garlic produce. The key to a sound and successful disease management strategy is the early detection and proper identification of the pathogen causing the disease. Other control measures include the use of cultural, biological and chemical methods and the use of virus free garlic planting materials. Surveys involving a larger number of samples and growing areas has to be conducted to determine the distribution of these diseases. This should also be complemented with the evaluation on the damage caused by these pathogens in single or mixed infections. The high incidence and occurrence of these viruses and other pathogen-causing disease in all surveyed growing areas strengthed the need for a garlic-seed certification program which is essential to ensure the quality of planting materials.