Chemicals, Vegetables

The looming threat of the deadly tomato leafminer

Pakistan is fortunate to be among the lucky few countries with a limited number of highly destructive pests and diseases. Nevertheless, it is currently threatened by the Tuta absoluta, a deadly pest that predominantly attacks tomato crops.

Tuta absoluta is known as the South American Tomato Leafminer. Though native to South America, it travelled from Chile to Spain in 2006. It has also managed to spread in Europe, the Mediterranean and Central and South Africa.

It arrived in India in 2014 and was reported in Nepal in 2016. Defying quarantine barriers, it managed to enter Bangladesh, Iran, Turkey and the Middle East. In a nutshell, we can easily say the menace is knocking on our door and bent upon entering Pakistan. If, defying plant quarantine barriers, the Tuta absoluta enters the country; it will be disastrous for local tomato growers.

Literature review has suggested that the Tuta absoluta arrived in Turkey in 2010 but in the absence of a tomato crop it shifted to potato, causing huge economic losses. Besides potato, its alternate host plants are egg plants, datura, chenopodium and many species of Solanaceae.

If, defying plant quarantine barriers, the Tuta absoluta enters the country, it will be disastrous for local tomato growers

The adaptable nature of the pest is extremely alarming as an abundance of alternate host plant species will make it difficult to control once it enters into the country. Entry could be from any country Pakistan imports tomatoes from whenever a shortage occurs.

The Tuta absoluta is a micro Lepidoptera. The adult moth has a grey brown colour and is about six millimetres in size. The moth has a life cycle of 29 to 30 days depending upon temperature. Under favourable climatic conditions 8 to 10 generations can occur in a single year. The female can lay 260 eggs in her entire life.

The larva feeds voraciously upon tomato plants producing large galleries in leaves, burrowing stalks and consuming terminal buds and green and ripe fruits. The pest is capable of causing devastation to the entire crop with 100 per cent yield loss.

Although there are several pesticides which are used as a foliar spray to control the tomato leafminer, but because of the peculiar nature and high fecundity rate of this pest frequent sprays are required that are neither cost effective nor safe.

However, the use of sex pheromones has proven to be effective in suppressing the Tuta absoluta population and keeping it within the economic threshold. In India “Pest Control of India” provide lures (pheromones) to farmers for control of this potent pest.

Since prevention is better than cure, the Federal Department of Plant Protection Karachi, under Ministry of National Food Security and Research Islamabad, which is maintaining the Plant Quarantine Regulatory Service in the country must keep a vigilant watch on imports of tomato consignments from India and Iran (Pakistan’s major import countries for the fruit) and also a watch on passengers coming from Gulf countries who maybe carrying tomatoes. In case of Tuto absoluto infestation consignments should be confiscated and destroyed.

At present, pheromones that provide safe and effective control of tomato leafminer as well as Pink Bollworm of cotton are very costly, beyond the means of financially constrained growers. It is suggested that federal government provide an adequate subsidy on pheromones.

The impact of alien or exotic pests in a country can be gauged from the Banana Bunchy Top Disease (BBTD) introduced in Pakistan in late 1989. Initially this very virus disease appeared on banana plantations in a small pocket in Ghorabari, district Thatta.

Despite the fact that BBTD was an exotic disease no effort was made for its eradication, or any quarantine measures were taken to restrict its spread in other banana growing areas. As a result the deadly menace managed to spread in the entire banana growing areas of the country causing an annual loss of millions of rupees.

By: Mohammad Zayauddin