The Invincible ‘Tea mosquito bug’: A curse for Tea Industry!

 Uddhab Chandra Sarmah

(Senior tea consultant, Solidaridad Asia, retired Executive Director of Warren Tea Limited. He can be reached at ucsarmah@gmail.com)

 The experience of infestations of ‘Tea mosquito bug (Helopeltis theiovora) ‘in the tea industry can be considered a curse to happen almost every year for the past three decades of time, causing an unprecedented loss of the most valuable crop and directly affecting a tremendous loss of revenue earnings at the close of the season. At the same time, the quality degradation of teas largely affects the overall price scenario, also badly creating an imbalance between the cost of production and the sale price of teas, which is finally realized. On the other side, from food safety points of view, the high load of inorganic chemicals used for protection and control of the menace created by these sucking bugs means that the possibility of pesticide residues (MRL) in made teas looms large and has been proven to be a serious concern for every tea consumer.

It has been reported that the crop loss due to pest infestation in tea is estimated to be about over 145 million kg per year, and in revenue, the loss is around Rs 2,800 crore per year, which requires everyone to be aware of the seriousness of the matter.

For the past few decades, along with the other sucking pests, the infestation of tea mosquitoes has exhibited the nature of sucking tender tea shoots and secreting enzymes with toxins by way of puncturing the leaves (stomata) and tender stems of the growing tea shoots. They also paralyse the growth hormones in emerging leaves, causing a complete cessation of new leaf emergence for more than three weeks and destroying the green colouring pigments called ‘chlorophyll, ‘turning the leaf colour totally dark black without any regrowth. For the tea industry, this mosquito infestation of tea bushes severely disrupts production, the value of which is unbelievable. Failure to protect the tea bushes from this insect, especially in the most valuable second flush of each season during the months of May–July, is likely to cause a loss of 30–40% of the revenue income from the tea leaves throughout the year. Farmers are still unaware of these enzymes and toxins that completely shut down the growth of tea leaves and the death of branches.

Regret to mention here that this problem has been occurring almost every year and posing a serious setback for the tea industry not only in producing and making quality tea for both domestic and international markets but also for the most vital factors of food safety in maintaining the Maximum Residue Limits (MRL) of the pesticides used for control of sucking pests like Helopeltis, aphids, Jassids, and others that have been noticed to be gaining resistance to the chemicals used for control over the years of time.

In this article, a roadmap has been prepared, highlighting some ways to mitigate the problems that adhere to the guidelines given by TRA.

Cultural control methods:

Bush sanitation: Regularly remove and destroy the newly emerged spotted leaves and buds of infected tea bushes along with the stems by hand to reduce the number of pests. The sections should be kept clean from weeds all around, including drains, so that mosquitoes cannot take refuge in the weeds.

n Pruning: Following a proper pruning cycle can help in removing the infestation, as the more skiff and UP percent is kept in the hope of a larger quantity of leaves, the more mosquito attacks are observed. The problem gets more aggravated by the ongoing changes in climate in recent times.

n Leaf plucking method: Since tea mosquitoes like to suck sap from young tender soft buds, leaves, and stems, the black plucking method is to be resorted, maintaining 5–6 days of plucking round.

n Shade Management: Proper shade management can help maintain less favourable conditions for tea mosquitoes.

Biological control methods:

n Natural beneficial insects: The presence of natural beneficial insects such as spiders, ants, and some beetles that feed on tea mosquitoes can be provided and encouraged.

n Parasitoids: Use parasitoid wasps that lay eggs on tea mosquito larvae, eventually killing them.

Chemical Control Methods:

n Insecticides: The use of selected PPC-approved systemic insecticides can mainly help control mosquito populations to a great extent. However, care should be taken to avoid excessive use, which can lead to the development of resistance and affect non-target beneficial organisms.

n Spraying techniques and recommended doses for applications: This very important aspect of spraying chemicals is given the least attention, which creates more problems in control.

The location of pests and their targets while spraying requires effective attention to kill the insects.

Using low doses can increase the resistance level of pests.

n Botanical pesticides: Neem oil and other botanical pesticides can be effective and environmentally friendly alternatives.

Integrated Pest Management (IPM): Monitoring: Tea bushes should be monitored regularly for signs of infestation to detect them early and apply appropriate control measures.

n Threshold Level: Implement action thresholds to determine when to take control measures based on pest population levels.

n Combination of methods: Use a combination of cultural, biological, and chemical control methods to effectively manage pest populations.

Methods of rehabilitation:

n Fertilizer: Balanced fertiliser should be applied for the recovery and growth of tea plants.

n Soil management: Ensure proper soil health by maintaining pH levels, organic matter, and adequate moisture.

n Foliar sprays: Use foliar sprays with micronutrients and growth promoting substances to aid the recovery of infested plants.

n Mulching: Mulching can help retain soil moisture and create an environment conducive to root development and plant recovery.

Biostimulants:

n Use biostimulants that can improve plant resilience and recovery. These may include seaweed extracts, humic acids, and amino acid-based products.

n Biostimulants can improve nutrient uptake, increase stress tolerance, and promote overall plant health.

By implementing a holistic approach, combining these approaches can help manage tea mosquito infestations and adjustment by restoring tea bushes.

Unfortunately, neither the TRA nor any other research organization knows yet the name of the toxin injected into the tea bush system in Halopeltis infestation and to test it with some antidote to further control the level of toxicity. The exact chemical composition of the toxin injected by the tea mosquito (Helopeltis theivora) is not well defined in the scientific literature, making it challenging to name a specific toxin.

However, the pest injects a complex mixture of enzymes and toxic compounds that interfere with plant physiological processes, such as growth hormone inhibition and chlorophyll destruction. Thus adopting integrated pest management (IPM) combining cultural, biological, and chemical methods is the most effective strategy. Regular monitoring, timely intervention, and improvement of plant health through balanced nutrition and proper care can reduce damage caused by Helopeltis thivora and help recover tea bushes.

Since specific antidotes for toxins are not available, focusing on overall plant health and resilience through these methods can help manage the impact of the tea mosquito. Considering the gravity of the situation and the frustrations of finding no alternatives to revive the potential crop, there needs to be immediate research on this aspect, either by TRA or agriculture research institutions like ICAR or IARI under the Ministry of Agriculture, India.