Multi-pronged attack against Fall Army Worm | Sunday Observer

Multi-pronged attack against Fall Army Worm

Pic: Thilak Perera
Pic: Thilak Perera

Research on controlling the spread of the Fall Army Warm (FAW) on crops has been undertaken by many institutions in collaboration with the Department of Agriculture (DoA), and according to studies, the use of insect pheromones to trap the adult male and estimate the density of the pest population has been successful, Professor, Weed Science, University of Peradeniya and Chairman, National Invasive Species Specialists Group of the Ministry of Environment, Buddhi Marambe told Business Observer, in an interview recently.

He said based on initial observations, the DoA recommended 15 pesticides last December, but subsequently reduced only to five.


Q: Has research been undertaken in the country to embark on a program to eliminate the ‘Sena Caterpillar’ menace?

A: Yes, indeed. As the pest is new, research work has been started by many institutes with the Department of agriculture (DoA) as the focal point.

Prof. Buddhi Marambe

Based on the initial observational studies, the DoA recommended 15 pesticides last December, but later reduced only to five.

The use of insect pheromones to trap the adult male and to estimate the pest population densities, has been successful.

Based on the initial screening, DoA has placed orders to import 20,000 pheromone traps. The DoA has also identified four naturally occurring parasitoids and predators who feed on the larvae of FAW and research is under way to check their effectiveness. Based on successful results, these predators can be mass reared for release.

The Ministry of Agriculture has imported a FAW-specific virus from the USA as a biological control agent. Experiments are underway to test its efficacy and persistence of the virus before its release.

These are time consuming studies, and we need to ensure that the bio-control agent will not survive and become another menace after FAW is controlled. A research has been started to investigate the presence of any egg parasites and to see how the adult female can be trapped, which would be a better option than trapping the adult male.

The DoA has also invited all those who have developed their own control measures, especially the locally-produced plant-based pesticides or pest repellents, that they can be scientifically evaluated for their efficacy prior, to any recommendation.

The universities have joined the bandwagon to support the control of the pest. The Faculty of Agriculture (FoA) at the University of Peradeniya (UoP) has initiated a study aiming at rapid and precise identification of FAW using molecular techniques. This is important as many practitioners and even scientists have misidentified the caterpillar on several occasions, claiming that the pest has attacked many other crop species, which was not the case.

Some research carried out at the Uva-Wellassa University has revealed that some locally produced ‘pesticides’ have not killed the caterpillar, but has ‘doped’ it for hours, and the caterpillar becomes active again.

Experiments are on-going to test the efficacy of other locally available techniques on how effectively they can be in overcoming the FAW threat. Basically, no technology is left out, unless proven ineffective. Studies have also been initiated to use electrostatic spraying technology to control the pest in the future.

We have seen that the pest, even enters its pupae stage while being in the maize cob.

The pupae of FAW are usually found on the ground. Scientists, such as Dr. Rohitha Prasantha of the FoA, UoP, have raised the issue of whether the FAW suspends development in an unfavourable environment (Diapause).

These warrant further studies on the life cycle of the pest under Sri Lankan conditions. Surveys are under way to identify the alternative hosts, such as weeds, and to estimate the actual crop losses caused by the pest.

Q: How long would it take the country to completely get rid of the pest which has made inroads into other crops as well?

A: Based on the experience of other countries, the pest has come to stay, and we have to live with it in the future. But this is not to say that we have to give up.

The fight against this invasive alien pest will continue with continuous vigilance. There have been claims that the pest has encroached on to other crops as well. However, apart from the initial impact on sugarcane, the damage to other crop species has not been seen or is minimal.

Q: What are the other crops other than maize that have come under attack by this species?

A: The major host plants that FAW recorded worldwide are maize, millet, sorghum, rice, wheat, and sugarcane. Except for wheat, all other major host crops are economically important crops in Sri Lanka.

The maize crop seems to the preferred host here. We have not found any damage to the rice crops. The alternative crop hosts of FAW are cabbage, beet, groundnut, soybean, onion, cotton, tomato and potato.

We have not found any significant damage by the pest on these crops. The pest prefers grass and other weeds. We need to be vigilant as maize is being harvested. The pest will find refuge in other hosts. Weed control in the fallow land, is thus essential.

Q: What would be the scale of the damage if the country fails to eliminate the pest?

A: The initially estimated loss of maize yield was less than 25%. The recent crop cut survey from the Anuradhapura district revealed that loss of maize yield is about 16%. We still await the overall results.

Thanks to the initiatives by the DoA, other government institutes at National and Provincial, District level, Universities, farming community and others, the FAW population has been brought down to low levels.

The initial application of pesticides (having contact mode of action) has destroyed the early larval stages of the caterpillar. This impact has been supported by other techniques adopted.

If not for such efforts, we would have ended up in a disaster at least in the case of the maize crop, which would be detrimental to the poultry industry because maize is the major source of animal feed.

The continuous use of pesticides may not be the solution, but we have to acknowledge that it is an effective solution to bring down the pest to lower levels during this Maha season, so that other follow up techniques can work.