Alternative pest control methods ensure the sustainability and yields of paddy farming in Tanjung Karang, finds student Chloe Holley.
PEST CONTROL is a critical part of agriculture because it can impact yield tremendously. But conventional insecticides can devastate the environment. In Tanjung Karang, Selangor, rice planters have turned to biological methods to control pests, a model for farmers everywhere.
(Feature pic: Rice farmers in Selangor are using environment-friendly means to counter pests | Photo by Maureen Beresford)
I visited one such farm in Tanjung Karang last January, as part of a study visit on sustainability in Southeast Asia. I undertook this programme because, as an ecology major, I was intrigued by how other countries approached sustainability and I wanted the opportunity to learn and apply this information to my studies and our own sustainable development in Australia.
We travelled to the rice paddies in Tanjung Karang to observe their sustainable pest control methods. Since the paddies were established in the 1970s, they have relied on pesticides and spent on average USD43 (RM200) every growing season on them.
Flower draw
However, we learned that in recent years, they have switched to using biological control. They now rely on Turnera (Turnera subulata) and sunflowers (Helianthus sp.) to attract the natural enemies of stem borers – one of the most significant pests – away from the rice plants.
It is incredibly important to have a pest management system in the agricultural industry because pests can have drastic impacts on yield. Pests cause the loss of 20—40% of global crop production every year, which can have significant effects on food security around the world.
A Turnera subulata sapling being planted by University of Tasmania students near the rice field (photos by Maureen Beresford)
This is particularly important to rice crops in Malaysia, which supply 73% of their population’s demand for rice. If Malaysian farmers were able to improve their yields, there would be less need for rice imports from Thailand, Vietnam and other countries which make up the remaining 27%, and the country could become self-sufficient.
Biological control has been attempted in many countries over the years, including Australia. Many attempts are often made without proper investigation and without regard for the potential impacts, doing more harm than good.
Cane toad disaster
An infamous example is the cane toad, which was introduced in Queensland, Australia to control the cane beetle population which affected our sugarcane crops. However, the cane toads had no impact on the cane beetle population.
This became one of the biggest ecological disasters in my country because the toads had no natural predators, outcompeted native wildlife and have now spread through almost half of our country. It is only worsening to this day.
Similarly, biological control has been attempted in Malaysia in the past. In the 1950s, the parasitoid Paratheresia claripalpis was introduced to prey on the stem borer Chilo polychrysus, but the attempt was unsuccessful.
However, growing Turnera has been successful in Malaysian agriculture, namely in oil palm plantations. There, it attracts the natural enemies of pests such as parasitoids, increasing the number of these natural enemies, which would then attack the pests. In the same way, they have worked well against paddy pests in the Tanjung Karang rice fields.
Nonetheless, it is important to consider that this is an introduced species from South America and to be wary of the potential ecological impacts that come with non-native species. For example, introduced species have been known to outcompete native species because they can tolerate various environments and are unlikely to have natural predators; some are also toxic and can harm native wildlife.
Following the science
It is certainly a step in the right direction to move away from pesticides, after years of studies have shown the negative effects they can have. Not only can pesticides be detrimental to human and environmental health, they can actually have the opposite effect: increasing pest populations.
Consistent use of pesticides can result in parasitoids developing a natural immunity to them, making them obsolete. Indiscriminate use can also kill off natural enemies of pests that would have helped control their population. In doing so, the pest population could increase without as many predators present in the area.
Some studies have shown that in fields treated with pesticides, the population of eggs and nymphs can increase 100-fold. For example, in Malaysia, frequent use of pesticides has been associated with outbreaks of the brown planthopper (Nilaparvata lugens), a prevalent rice pest.
While biological control seems to work relatively well for the farmers in Tanjung Karang, are there other alternatives that might alleviate pest problems that have co-benefits and avoid the use of introduced species?
As I explored this, I felt distracted by the thought of repeatedly planting vast fields of the same crop for decades. I know that monocultures like those can have many environmental impacts such as depleting soil nutrients, increasing soil-borne pathogens and pest populations; and rice monocultures have even shown higher amounts of heavy metal contamination due to contaminated water and soils.
I started to wonder whether mixed cropping or crop rotations could be beneficial, or even viable, for the area. This method involves changing the crop that is planted to a different crop than the one just harvested. My friends and I did some more research on the topic and found that it is actually quite beneficial as a pest control method as well as having many other benefits.
Longer term pest removal
Crop rotation is a useful pest control method as it removes the habitat and food source of stem borers for an extended period of time. This allows the population to dwindle while another crop is growing so that the next rice-growing season will have fewer pests.
The viability of this method is highly dependent on the types of crop used in between rice seasons but is proven to be much less harmful to the environment than monoculture practices.
Crop rotation has other significant benefits as well such as increasing yield, decreasing pathogens, improving soil nutrients and structure, and improved economic returns for farmers by having more product diversity.
Could crop rotation work in paddy planting in Malaysia? (photo by Chloe Holley)
A study in China found that rotating potato and rice crops was highly beneficial, more so than any of the other crop rotations tested. It generated a higher profit margin, had less heavy metal contamination, better soil quality and – perhaps most importantly – the highest yield of rice.
Legumes were also found to be a good rotating crop due to their nitrogen-fixing properties which can assist in increasing rice yields as well.
There are some issues associated with crop rotation, mostly economic. Does Malaysia have enough of a market for other crops for it to be worthwhile growing them? The farmers in Tanjung Karang have been able to plant rice twice a year; can the benefits of crop rotation outweigh the benefits of generating two yields per year? Does the community have the knowledge or experience to grow and maintain other crops?
These are important considerations to make before alternative methods are implemented.
Useful lessons
Overall, it was incredibly fascinating to observe this method being used in the Malaysian agricultural industry and it is seemingly effective and cost-efficient without causing significant harm to the environment.
I am truly thankful to the communities in Malaysia who allowed us the opportunity to learn from them and took the time to show us their practices. It is encouraging to see smaller communities making more sustainable choices to minimise their impact.
It would be interesting to see what other actions the community in Tanjung Karang could take to further their sustainable development. I hope that farmers in Australia might also make an effort to make sustainable changes to our practices as well.
Chloe Holley is an ecology major at the University of Tasmania. She was in Malaysia as part of the University Global Opportunity Program to study sustainability in Southeast Asia. Macaranga were pleased to moderate a hackathon at the end of the programme. In the hackathon, Chloe Holley, Alyssa Shiel, Atilia Azlan Shah, Maureen Beresford, Molly Hartog, Paige Howard, Stanley Gant and Ty Bowey created a presentation together about the rice paddies at Tanjung Karang, Selangor.
[Edited by SL Wong]
== Update 6/5/24 @7.07pm: We corrected the error in the role played by Turnera and sunflowers – they attract the natural enemies of the pests, not the pests themselves. ==
The views expressed here are those of the author/contributor and do not necessarily represent the views of Macaranga.
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