A mango tree infested with mango mealybug.
The mango mealybug (Rastrococus invadens) is an invasive pest outside its native home in Southeast Asia. It threatens mango crops, particularly affecting smallholder farmers. This scale insect pest lowers mango yields and quality, and because it’s a quarantine pest, it can also impact trade.
What is mango mealybug?
The mango mealybug is an insect belonging to the Pseudococcidae, an insect family known for its soft, waxy appearance. Typically white or light yellow, the pests from this family are tiny (about 3 to 5 mm in length) and are often found clustered on the leaves, and fruit of mango trees. They feed by piercing the plant tissue to extract sap. This weakens the plant and, therefore, its production of mangoes through reduced weight and size of fresh mango fruit.
Life cycle and reproduction
Mango mealybugs reproduce rapidly, with females surviving for about 225 days and laying up to 160-200 crawlers during a reproductive period lasting about 200 days. The first instar yellow crawlers hatch into nymphs, which undergo several moults before adulthood. The crawlers tend to stay on the leaf where they were born, and only a few colonize other leaves. Since nymphal development lasts around 28–30 days for both males and females, this causes populations to explode, especially in favourable climatic conditions.
Mango mealybug damage
The damage inflicted by mango mealybugs can be severe and multifaceted:
Mango mealybug produces honeydew that makes tree leaves black and sticky.
Sap feeding
As the mango mealybug feeds on the sap, it extracts vital nutrients from the mango trees, weakening the plants and reducing their overall strength. This can lead to stunted growth, leaf drop, and poor fruit development.
Mango mealybug produces large amounts of honeydew that make the tree’s leaves black and sticky, upon which fungi develop. The resultant thick black layer of sooty mould causes a drastic reduction in the photosynthetic activity in the plants, worsened by the premature drop of mature leaves. During heavy attacks, whole parts of the tree can look blackish in colour. Additionally, the presence of mealybugs makes the plants more susceptible to other pests and diseases, exacerbating the problem.
Fruit quality and reduced yields
Infestations can cause fruits to become discoloured, or drop prematurely. There is also a significant reduction in the weight and size of fresh mango fruit, reflected in the ash content, crude fibre, and reduced sugar levels of both ripe and unripe fruit.
This, of course, means that the quality of the fruit is also often compromised, making it less appealing to consumers, leading to income losses for farmers.
Impact on smallholder farmers
Economic challenges
For smallholder farmers, the impact of mango mealybug infestations is profound. The pest can adversely impact those who rely heavily on mango and citrus fruit to supplement their income. The mango mealybug has been reported to cause 80% of mango yield losses in Ghana and 89% in Benin.
Many farmers in countries like Kenya and Uganda also often rely on mango cultivation as a primary source of income. When pest outbreaks occur, they face reduced yields and increased production costs due to the urgent need for pest management solutions. Farmers can get caught in a cycle of poverty if these solutions fail to control the pest.
Food security concerns
Mangoes are a source of income and a key dietary component for many communities. In times of pest-related crop failures, families may be forced to consume less diverse diets or rely on lower-quality food sources, adversely impacting their health and well-being. This cycle of poverty and food insecurity emphasizes the importance of addressing pest management as a vital aspect of food security.
To combat these challenges, providing smallholder farmers with access to resources and support to manage pests effectively is essential. Strengthening their capacity to sustain crop production improves their economic stability and enhances food security for their communities.
Addressing the threat with integrated pest management solutions
Smallholder farmers can adopt Integrated Pest Management (IPM) strategies to mitigate the impact of mango mealybugs. These include:
Cultural practices: Removing infested material and properly disposing or destroying it when the pest is detected early, preventing the movement of ants that feed mealybugs using insecticidal paint on the tree trunk and maintaining soil health can help reduce mealybug populations.
Biological control: Introducing parasitic wasps from the native home of the pest can provide a sustainable solution to control mealybug populations. The wasps, Gyranusoidea tebygi and Anagyrus mangicola, are effective. A long period may, however, be required before the parasitoid can reach a level to exert effective control. Therefore, experts recommend mass releases in affected areas to hasten this.
Chemical control: The wax covering of mango mealybug renders applying conventionally sprayed insecticides ineffective since the wax is water-repellent. Producers should only expect limited control from this treatment method. Pesticides should be used judiciously to minimize environmental impact.
Farmer education: Training farmers on pest identification, monitoring, and management techniques is crucial for early detection, resulting in effective pest control.
PlantwisePlus and mango mealybug
The mango mealybug has a soft, waxy appearance.
The mango mealybug is more than just a pest. It is a significant threat to the livelihoods of smallholder farmers in low- and lower-middle-income countries. Understanding the biology, ecology and impact of this pest is important for developing effective management strategies.
CABI has already collected data to understand the potential economic impact of this pest in East Africa. This work focused on Burundi (widespread distribution), Uganda (restricted distribution) and Kenya (not present). The evidence note derived from this study will bring to the fore the impacts, in monetary terms, of this pest and inform policy decisions towards the response and management of the pest.
As part of efforts to support mango farmers, PlantwisePlus, working with National Plant Protection authorities, will launch pest risk communication about this pest in Uganda and Kenya. The pest is not present in Kenya, but the risk of invasion is high since it’s already reported in neighbouring Uganda. The primary focus in Uganda is on stopping the spread into new areas outside the hotspot. For Kenya, it’s to prevent entry and arm the farmers with the information to quickly identify and report if the suspected sample is detected and respond to it appropriately.
In West Africa, two parasitoids introduced in the 1980s, Gyranusoidea tebygi and Anagyrus mangicola, successfully controlled the pest. No other interventions were needed. However, in recent years, in some areas, the damage has been high again. In Ghana, CABI is studying the reasons for the resurgence of the mealybug.
Farmers can combat the challenges of mango mealybug by adopting sustainable practices and leveraging community knowledge. This helps to secure their livelihoods and food sources.
More on mangoes from CABI
CABI Book: The mango: botany, production and uses
CABI Pest and Disease Photoguide to Mango disorders
4 mango disorders that can affect yields
CABI trains young service providers to help smallholder mango farmers in Kenya produce quality goods for export
Project launched to improve marketing of pawpaw, mango, avocado and citrus fruits by managing invasive scale insect pests in Eastern Africa
PlantwisePlus gratefully acknowledges the financial support of the Directorate-General for International Cooperation (DGIS), Netherlands; European Commission Directorate General for International Partnerships (INTPA, EU); the Foreign, Commonwealth & Development Office (FCDO), United Kingdom; the Swiss Agency for Development and Cooperation (SDC); and the Australian Centre for International Agricultural Research (ACIAR).
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