NARO study confirms ash, detergent fight armyworm

Bosco Matsanga, who has been practising maize farming for 10 years in Bukaalu subcounty, Bulambuli district, will never forget the year 2017 when the fall armyworm invaded Uganda and heavily destroyed his maize garden.

“In 2017, I harvested only five bags (500kg) of maize from my two acres, compared to the 20 bags (2,000kg) that I usually get from the same piece of land,” he narrates.

Matsanga added that during the armyworm outbreak in 2017, he ventured into the use of local remedies, such as ash, soil, and detergent to control the pest, but that they were not as effective. According to the UN Food and Agriculture Organisation (FAO) reports, it is estimated that about 450,000 metric tonnes of maize, equivalent to $192m, was lost in the first cropping season of 2017 due to a heavy attack by the armyworm.

This directly affected about 3.6 million Ugandans that depend on maize for a livelihood. However, smallholder farmers like Matsanga may have a sigh of relief after a new study by the National Agricultural Research Laboratories (NARL), Kawanda, an institute under the National Agricultural Research Organisation (NARO) and the International Centre for Insect Physiology and Ecology (ICIPE), have authenticated the potential of local farmers’ management options to eradicate the armyworm in Uganda.

Both laboratory and field trials have demonstrated the use of neem leaf extract among other options like lantana camara (kayukiyuki in Luganda), detergent, ash and soil in the effective control of the maize armyworm larvae. According to the researchers, this provides alternative inexpensive and environmentally friendly armyworm management options for smallholder maize

farmers in Uganda though the use of synthetic pesticides, remains the most popular option.

 DETERGENT MOST EFFECTIVE

 Laboratory research, led by Winnifred Aool, an entomologist at NARL, says the neem leaf extract had the highest repellence with more than 75% of the armyworm larvae moving away from the leaves to the nontreated control, an hour after exposure. This was followed by 72.5% from extracts of lantana camara (kayukiyuki) and 60% from the detergent.

A related study carried out by the same team to assess the effectiveness of the innovations against the armyworm highlights detergent as the most effective option, since it caused 100% death of the larvae in less than 24 hours.

This was followed by ash (80%), neem (10%), and lastly lantana camara (0%). The study further explains that although the armyworm larvae were able to feed on maize treated with neem leaf extract, none of them survived to the next generation, indicating its potential contribution to armyworm management.

ON-FARM FIELD ASSESSMENT

Subsequently, ICIPE conducted an on-farm field-based study under the stewardship of Dr Hailu Girma, the centre country co-ordinator. This study was initiated last year, in the districts of Tororo and Bulambuli, to evaluate the local armyworm control innovations that had been advanced for the laboratory studies but this time, under farmer field conditions.

According to Girma, six treatments that include; neem and lantana camara leaf extracts, detergent, soil, insecticide and water (control) were used in the study. Preliminary findings from the on-farm field study reveal that maize plots treated with insecticide had the lowest magnitude of armyworm damage at 29%, followed by neem (33%), lantana camara (38%), then soil (41%), and detergent (42%) against that of water (47%) across the two districts.

SMALL FARMERS

According to Dr Girma, both the laboratory and field studies demonstrated the importance of locally available materials as control options for armyworm among smallholder farmers that cannot access or afford the recommended pesticides.

Dr Girma was, however, hesitant to recommend any of these methods at the moment, citing the need to carry out more rigorous research, especially in regards to the frequency of application for effective management of armyworm in Uganda.

 OTHER CONTROL METHODS

According to Peter Byaruhanga, an agriculture researcher from Makerere University and farmer in Luwero, inter-cropping cereals, such as maize with legumes like beans may also keep the worm at bay.

“I did it on my farm and realised that the impact went down by between 30-40% when I inter-cropped the maize,” he says. “Use pheromone traps similar to those used to trap fruit flies to monitor the arrival of moths. When you first notice them, look for the distinctive white dot on their fore-wings.

 These traps are now commonly sold in agriculture input stores at as low as sh10,000 each. An acre may require around three traps,” he adds. He advises that early detection is also key. So, look out for larvae and signs of the damage beginning in early crops.

BACKGROUND

According to the Food and Agriculture Organisation 2018 report, about four million farmers in Uganda grow maize, producing four million metric tonnes annually. From the report, maize is also one of the cheapest sources of calories in the country.

The report considers the fall armyworm as an insect pest, native to the tropical and sub-tropical regions of the Americas. “Since its initial report in 2016, the pest has dramatically spread across the sub-Saharan Africa, causing extensive spread damage, particularly to maize. By mid-2017, the armyworm was present in all Uganda’s districts, causing between 15% and 75% yield loss,” says the report.

This story is part of the CABI, SciDev.Net and Robert Bosch Stiftung Script science journalism project