Present status of Papaya Mealybug, Paracoccus marginatus Williams and Granara de Willink, in Assam, India, after a decade of its first invasion

Abstract

Abstract Background The North Eastern Region (NER) of India is well known for its rich biodiversity and organic cultivation; however, this is one of the least investigated regions owing to its remoteness. A field study on papaya mealybug (PMB) was conducted to know its present status in Dibrugarh district of Assam, NER India, after its first entry in 2012. Results The pest was initially confined in urban and peri-urban localities in 2012 and has now made its entry even in remote villages too; however, many villages still remain uninfested. PMB has not damaged crops much the way it did in major papaya producing states of India. Out of 217 farmers surveyed, only 31.8% have experienced the infestation of PMB in their crops. The pest has now been recorded in places within an elevation of 98–129 m above MSL. The village homesteads help the pest establish in the ecosystem through natural host shifting. 89.9% farmers adopted either no management practices or applied non-chemical measures. We found the presence of more number of Spalgis immatures in the colonies of PMBs in hibiscus than in papaya. After the first invasion of PMB in Assam, initially it was also worried that the pest might invade tea crop and affect the tea economy of the state; however, no report on PMB infestation on tea crop has been found so far. Conclusions The PMB has acclimatized and established itself in the crop ecosystem of Assam by natural host shifting. The trend of infestation is constant or increasing. No programme on classical biological control of PMB was taken in the farmers’ fields of the state, but there is no hue and cry situation on the crop damage by PMB. High rainfall affected the spread of the pest and predation by Spalgis sp might have resulted in reduction in population. We recorded variable abundance of S. epeus larva in PMB colonies in different host plants based on which we can formulate the bio-control module for PMB. The detailed study on the role of rainfall and natural enemies on population dynamics of PMB is a researchable issue.

Keywords

• NER
• Paracoccus marginatus
• Ape fly
• Spalgis
• Host shifting
• Rainfall