PANAJI
Cashew, the cash crop of Goa, has started showing a reduction in production, affecting the economy of cashew growers.
The cashew was introduced by the Portuguese from Brazil to control soil erosion in Goa and though the weather here is favourable, the cashew growers are facing many challenges in its cultivation, causing a reduction in yield.
The cashew is largely affected by climatic changes, pests, diseases and the changing lifestyle of people.
PESTS
The Tea mosquito, a pest slightly bigger than the mosquito, infects cashews and sucks sap/juice from the young flush of leaves, flowers and immature nuts. The tissues around the feeding area dry, turn brown and finally black, giving a burnt appearance. This mainly affects flower production, reducing yield by 20-60%.
The Tea mosquito prefers low temperatures and their population grows in such weather, mostly seen during December-January in Goa and affected cashew inflorescence show burning symptoms, which can be seen from a distance. It can be managed by spray of Lambdacyhalothrin (5%EC @0.01%) or Fipronil (5% @ 0.05%) during the emergence of a new flush of leaves and flowers. Biopesticides like Lecaniciliun lecanii (1x108CFU per ml @5gm per lit) suppress the population.
Cashew stem and root borer, a dark brown colour beetle, is a major cause of the reduction by 10% cashew tree population, corresponding to a 10% reduced cashew yield in Goa. This has eventually reduced the cashew population over the years. Their grubs bore into the cashew stem near the soil, causing exudation of gum and frass.
The bark splits, the cashew tree turns pale yellow, wilts and dies. This can be prevented by monitoring the trees for (CSR) infection, removing the affected part of the stem and swabbing the exposed shoots, stems and roots with Imidacloprid (17.8%) or Fipronil (5% @ 2ml/lit water). Spawn of Metarhizium anisopliae /Beauvaria bassiana (1x108CFU per ml @5gm per lit) could be a sustainable approach for the management of CSRB.
Thrips, a tiny insect pest, infects cashews by sucking the sap from the midribs of leaves, leading to silvering of leaves, which later shed. They also infest cashew apples and nuts, which develop corky cracks leading to rotting. Spraying Lambdacyhalothrin (5% EC @0.01%) can manage this pest.
DISEASES
Diseases such as anthracnose, die-back, inflorescence blight affect cashew growth, flowering and fruiting, adding to reduced yield, which can be managed by spray of Mancozeb (@0.1%) or Carbendazim (@ 0.05%) spray.
CLIMATIC CHANGES
The cashews start flowering in cool weather in winter, but the adverse climatic conditions with 3-4 degree rise and variation in temperature as seen in 2023-24 affect flowering.
The unseasonal rain in December-January delays the cashew season and disturbs the flowering and fruiting cycle. Pollination is affected by fluctuations in temperature and humidity and impacts fruit setting.
The difference in day and night temperature affects flowering as cashew flowers are sensitive to a low night temperature of 15 degrees, and high day temperature dries flowers and disturbs their flowering.
CHANGING LIFESTYLE
The changing lifestyle of people made them migrate to urban areas for education, jobs and business neglecting their inherited cashew plantation. The job opportunities in industries and other organisations deviated youth from working in their cashew properties. These factors have also affected the total cashew production in Goa.
CREATING AWARENESS
Experts from the Goa College of Agriculture in collaboration with North Goa Rural Development Agency organise training sessions for cashew growers, SHGs in different villages and talukas of Goa to create awareness on symptoms of pests and diseases in cashews and their management.
[The writer is Dean at the Faculty of Agriculture, Veterinary, Fisheries and Allied Sciences]
