American army-worm ravages tomatoes in Uganda

Tuta absoluta
Tuta Absoluata appearance on Tomato. Courtesy Photo.

Tomato farmers in parts of the country are battling yet another form of army-worm originating from South America. The small worm, Tuta Absoluta also known asSouth American tomato pin-worm” is said to be ravaging the tomato crop in central parts of the country.

It is also causing yield loss to Irish potatoes in the Kigezi region though it has not caused alarm like the maize ravaging fall army worm.

It rapidly spread to the main tomato growing regions of the Mediterranean and other parts of Europe and now in Uganda, Tanzania, Nigeria, Zambia and other parts of East Africa.

Its presence in Uganda was first confirmed around March 2016 according to the International Journal of Tropical Insect Science. The extent of the damage by Tuta Absoluta is yet to be quantified.

Joshua Sikhu Okonya, a crop entomologist with International Potato Center says the worm causes severe damage to both the potato and tomato crops.

The pests according to studies damages leaves of the plant leading to reduced photosynthesis . It has the potential of causing potential harvest losses up to 50-100 percent in untreated crops.

The Tuta larva pierces into leaves and stems but can also inhabit the tomatoes themselves, making them unfit for consumption and sale.

A female leaf-miner will lay about 260 eggs in a lifetime, which is 30-40 days. The eggs stick to the underside of tomato leaves and stems. After hatching, the larvae will nosh on every part of the plant. When satisfied, they drop to the ground, pupate, and start the whole process over again.

Dr Ambrose Agona, the Director at National Agricultural Research Laboratories also one of the authors of the findings published International Journal of Tropical Insect Science could not be reached for comment.

Reports indicate that the pests have been in Uganda from 2014. A source says they may have come with shipments of potatoes imported for distribution to farmers in Kigezi and Mbale.

Farmers in the affected areas have been frantically spraying insecticides to stave off the assault, but the pest is developing resistance to popular chemicals in these areas, while populations of beneficial insects are being wiped out.

Joshua Okonya, who has studied extensively the pests and pesticide management practices, says it is unlikely that the new pests can be eradicated by pesticides. He says an invasion of this worm just like the fall army worm is irreversible and that is hard to eradicate them.

Okonya says the effectiveness of chemical control is limited due to insect’s nature of damage as well as its rapid capability of development of insecticide resistant strains. He says Tuta absoluta larvae are internal feeders and therefore one cannot effectively control them through application of chemical insecticides

Researchers at International Potato Center in Kenya according to Okonya are finding other means at their disposal to fight it including the use of biological factors.

This pest damage occurs throughout the entire growing cycle of tomatoes. Tuta absoluta has a very high reproduction capability with up to 10-12 generations in year in favorable conditions.

– Uganda Radio Network