The Sena pest problem


By Dr Upatissa Pethiyagoda

Former Director, CRI)

Thousands of poor farmers and perhaps half a million dependents among them, are facing a devastating predicament in the shape of The Sena Pest. Thousands of farm crop acres have been heavily damaged by this latest peril, and many more are under dire threat. Dry Zone farmers are only now painfully recovering from years of drought, floods, shortages of fertilizer, and aggravated by meaningless and ill-informed banning of necessary inputs (Glyphosate being the outstanding example). As usual "Wasa Wisa Nethi Krushikarma" "Waga Sangramaya" and other such ridiculous slogans substitute for competent technical guidance and sensible planning. The financial cost must be enormous. Meanwhile, those whose business it is to look after the welfare of the Farming Community are busy with their political games. Personal well- being, pillage of public money and "ceremonials" of no use, are the priorities of the privileged. What the taxpayers and a cowed public are treated to, can only be described as "Ponderous Trivialities"; this is an Oxymoron (not restricted to those who have been at Oxford but who still remain Morons).

In the early seventies, coconut plantations could have been devastated by the "Coconut Leaf Miner", (Promecotheca cumingi), if not for timely action led by Dr Colvin. R. de Silva, who was then the Minister of Plantations - a person of great intelligence and a brilliant minister, the likes of whom we were not blessed with in his successors – despite what we were led to believe would be "Scientific" Cabinets. This was mentioned in The Opinion page article of 10 January, under the pen-name of "Punchi Bandara ", who was clearly a person who was in a high position in the Ministry at the time! I myself had the opportunity to see this effort at close quarters – although it is more than 35 years since I left my intimate contact with the CRI who played a great role in this epic operation and ask to be excused if my recollections now are blurred in detail. The "Sena" infestation is much more complex, but the lessons learnt at that time are still worthy of emulation.

The current pestilence has implications which make this pest much more complicated than the "Cumingi" problem. While the host range of PC was confined to coconut, the Sanaa Caterpillar is reported to attack more than 100 crops besides Maize and Kurakkan. The adult moth is reported to be capable of being carried up to a 100 kilometers in wind currents. Also the cultivations are largely those of small farmers whose livelihoods are solely reliant on their small farms, who have already suffered greatly by climatic disasters. Their voices are not as powerful as the plantation sector, but their distress is palpable. Many lessons learnt from the Cumingi exercise still cover important principles, which I shall try to portray.

All available entomological expertise and talents were harnessed – other Crop-related Institutes (TRI, CRI and "Minor crops") Universities, Department of Agriculture, quarantine, Museum entomologists etc. This meant that officials from diverse organizations were drawn to several activities through release from their usual jobs. The group was chaired by Minister Dr. Colvin, whose legal talents and professionalism were there to monitor progress and provide legal assurance for the team to operate in unconventional ways. For example, the movement of any parts of coconut was actively prohibited from the infested areas (for example, the woven baskets traditionally used to transport rambutan) and authority to prevent any possible entry of the pest, which was known to originate from suspect areas. Interestingly, the embargo covered plants such as Orchids. Since the epicentres were close to airports, the possible entry by "Hitch Hikers" on arriving planes was hard to prevent. Trains were another possible vehicle strengthened by the observation that infestations were commonly close to train stations – Mount Lavinia, Moratuwa, Kalutara, Benthota, Dodanduwa and Galle. Experimental work was done in premises rented in Havelock Town rather than at Lunuwila, which has coconut plantations. The activity was akin to a military campaign! This helped to prevent unwitting spread to new areas. The adult beetles were attracted by lights. Parasites of the beetle were brought in from Indonesia and Singapore. The hyper- parasites of the larva (notably Paediobis parvulus) gave spectacular and immediate results which helped in containing the pest and within months the parasite was reduced to a few areas. This is a good thing as they could serve as nuclei for combating any minor entries. I can now confess that a minor incident in the Katunayake area was met by a spectacular show of competence, with a mock "fire-fighting" type operation. This quelled any likely public criticism of the CRI as happened when the original incident occurred. This was hailed as a timely intervention. It was quite cheap because the spray was merely water, as the scientists were convinced that the natural panic was unfounded as the mild problem would be wiped out by natural enemies!

The lead role was logically assigned to the CRI. It would be invidious to name any individuals, as it was truly a co-operative, team exercise. However, I have to make special mention of the CRI, which consequently developed an outstanding capability in its "Crop Protection Division".

For many reasons, there has to be a thorough study of published literature to draw on experience elsewhere when confronted with similar problems. Much information could be garnered by considering experience with the related "Late Army worm". With today’s communication advances, this would be relatively easy (by trolling the Internet). This will avoid any need to "re-invent the wheel". The fact that the pest has long been known in many countries and situations, means that a wealth of information already exists.

Considering the severity and wide incidence of this pest, chemical control will be impractical and hazardous. Given the huge expense that this will entail, means that "Biological Control" is virtually the sole option. This would necessarily be slower, and less "spectacular" than spraying pesticides but has proven to be an effective, safer and longer lasting. This makes it by far the most sensible approach.

Here again, the CRI has vast experience and success in several instances. Cumingii, Black Beetle, Red Weevil and the weed Eupatorium are noteworthy, while the mite (Sinh. "Maita") has been more recalcitrant. The facilities and experience in rearing parasitic agents means that the CRI is well equipped but it may not be wise for it to assume the lead role but rather it could offer help by providing facilities. Even if similar insectories are needed, the cost would be comparatively modest.

The lifecycle of the Pest must be established first in order to identify the most vulnerable stages and to plan the best strategy. In the present case it will probably be the caterpillar (or Grub) that is the best stage to attack. In the case of the Coconut Leaf-miner, the larval (and most damaging Miner) stage was the best, while egg parasites, although known, were not as effective and the adult stage was even less amenable. The best options will be special to individual cases. Thus for Black Beetle, Pheromones (hormonal Sex attractrants) are the best. In the case of the "Shot Hole Borer" the approach was to attack the fungal symbiont. Thus, the possibility of there being natural parasites (hyper-parasites) must first be explored. In a novel approach, the Philippines ran a "Beauty contest" where the ballot paper was a Black Beetle grub. Hopeful young bucks ensured a successful poll! In the late seventies, a sudden invasion by locusts caused panic among people in the Hingula area. Much like the "Sena "case, the pest devastated many crops in home gardens. As the plague was detected early and thus was relatively localized, a heavy application of insecticide was warranted and was very successful. Our entomologists would be the best to chart a suitable strategy.

In the case of Cumingi International assistance by the FAO was provided in the form of an assigned Biocontrol Specialist, vehicles and funds to obtain parasites that had been identified as useful in places as distant as Indonesia and Singapore. In the case of "Sena" its wide geographical occurrence ought to provide many opportunities for collaboration and there could be many institutions that will assist. We fervently hope that some method will be identified, although it could not meet the present need for a swift remedy. It will at least help as an insurance against future invasions. Ideally, it is a balance of the hyper parasite and the pest is the best.

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