Farmers battling pest, diseases, and climate-induced challenges in citrus farming
Yangyel Lhaden
Chitra Kumar, a resident of Jigmechu in Chukha, nostalgically points to the northern forest in his village, reminiscing about the vibrant mandarin orchard that once flourished there in the 1990s. However, a mysterious ailment struck, causing the mandarin trees to die from the top. This affliction swiftly spread, leading to the demise of all mandarin trees within three years.
Until the late 1990s, Jigmechu thrived as a lively mandarin-growing village. The small town boasted a depot where buyers from across the border engaged in the mandarin business. Today, only a few mandarin trees remain, and attempts to replant have proven futile.
The local mandarin is gradually shifting to higher altitudes, causing the disappearance of mandarin among low-altitude growers like Jigmechu, situated at 180 metres above sea level (masl). Mandarin, a vital cash crop grown in 16 dzongkhags, faces challenges such as trees dying due to pests, climate warming prompting a retreat to higher altitudes, and diseases like citrus greening wiping out entire orchards.
Phuntsho Wangdi, Senior Horticulture Supervisor, highlights the current state of mandarin production, stating, “The Mandarin production is good this year, but nationally, both the production of mandarins and the export value have significantly declined.”
In 2021, mandarin production witnessed a decrease of about 40,000 metric tonnes compared to 2006, with around 700,000 fewer mandarin trees in 2021 than in 2006, as per annual agricultural statistics. There were 2,297,364 mandarin trees in 2006 which produced 55,558 metric tonnes of mandarins.
Locals in Jigmechu recall bringing the best mandarin seedlings from across the borders during the period when they noticed their trees dying, leading to the spread of the citrus greening infection.
The citrus psylla, endemic to Bhutan and thriving in warmer climates, acts as the carrier of this devastating disease. Once infected, a mandarin tree slowly dies as the bacterium causes blockage in the nutrient channel, death starts from the top where nutrients are challenging to reach.
Phunsho Wangdi’s visit to Baeyul Kunzang in Chukha in 2008 revealed mandarin orchards stripped bare, resembling damage from a forest fire, due to citrus greening killing all mandarin trees. To control the disease, mandarin trees were chopped, and the land was left bare for five years to break the disease cycle. Resilient grafted mandarin trees were planted in Baeyul Kunzang in 2013 and have now reached the fruiting stage.
While the upward movement of mandarin cultivation is noted in Dagana, with elevation ranging from 180 to 3,800 masl, concerns arise about the impact of climate warming on mandarin farming.
In the 1990s, Tashiding, at a lower altitude than Dagapela and dzong areas, was a prosperous mandarin village. However, lower-altitude mandarins started dying, leading to mandarins thriving in Dagapela and the dzong area.
The mandarin orchard in Tashiding is barren, as mandarin don’t grow well in low altitude areas anymore
Farmers in Dagapela and Khebisa in Dagana express concerns about shifting mandarin orchards and encountering new pests. The upward movement of mandarin is attributed to the scarcity of water during excessive heat. Proper irrigation, orchard management through manure application, and vigilant pest monitoring with timely intervention are seen as crucial to enhance the resilience of mandarins.
“With temperature increasing citrus psylla’s ecology could change and move upwards where Mandarin trees are growing well at higher altitude,” says Phuntsho Wangdi. “However, citrus greening like AIDS is manageable with proper orchard care and timely intervention can suppress the disease without trees dying,” Phuntsho Wangdi said.
In Dagapela, farmers like Phub Tshering have been declaring a fight against mandarin tree challenges, using innovative methods such as applying phenol to collected fruit drops, using concentrated cow urine to combat diseases, and applying manure after harvest. While he successfully revives some trees, attempts to grow new mandarin trees face challenges due to climate changes.
Pests and diseases at Phub Tshering’s orchard
Surendra Raj Joshi, Senior Resilient Livelihoods Specialist with ICIMOD, emphasises the impact of farming at 1.5 degrees Celsius on farmers. Protection of native species like the unique mandarin is crucial, as it faces challenges from climate change. Despite Mandarin not being a priority crop in Bhutan’s draft 13th five-year plan, efforts are made to diversify livelihoods by promoting high-value crops.
“When I visited Bhutan, mandarin was among the top two export commercial crops. Native mandarin of Bhutan and Nepal has distinctive character, like loose skin and good taste, which is sought after in the international market,” Surendra Raj Joshi says. “It is important to protect native species that have unique characteristics which do not face market challenge.”
Nepal
In Nepal, facing similar challenges in citrus farming, Umesh K Acharya, a Senior Horticulture Scientist, notes the doubled production of mandarin in the last 16 years but emphasises the lack of increased productivity per unit area.
Western Nepal reports battles against climate change and new pests, with a new disease called citrus gummosis reported. Vector for citrus greening is reported below 1,200 masl in Nepal.
Umesh K Acharya highlights ecological similarities between Bhutan and Nepal and stresses the importance of knowledge exchange to combat climate-induced challenges. “Fifteen years ago, citrus psylla was reported only below 1,000 masl. The changing climate and ecological shifts could pose a serious threat to our citrus growers.”
Research on growing mandarins with white-fleshed guava in Nepal has shown success in addressing citrus greening disease.
ICIMOD’s project, Green Resilient Agriculture Productive Ecosystems (GRAPE), aims to foster climate-resilient and green economic growth in Sudurpashchim and Karnali provinces. The project explores cost-effective and locally available solutions for agricultural inputs, benefitting farmers in the region.
As both Bhutan and Nepal belong to the Hindu Kush Himalaya, sharing knowledge and resources becomes imperative to combat climate-induced challenges in the agriculture sector.
The focus on protecting native species, implementing innovative solutions, and fostering collaborative efforts is seen as essential to secure the future of mandarin cultivation and ensure the resilience of farmers in the face of climate change.