Would genetically modified maize put an end to our Fall Armyworm woes? Let’s explore this intriguing topic
Relentless crop scouting, continual insecticide spraying with rising spray costs, and concerns about the final effects on yield and quality. There is genuine concern about the menace of Fall Armyworm as the maize planting season in Kenya approaches.
One of the most frequent calls that I hear is for Genetically Modified (GM) crops to be introduced to combat the pest and to reduce growing costs and risk of crop failure for farm of all sizes – small holder and large scale alike.
Let us leave aside the ethical debate, but focus on the agronomic question of how effective this tool would potentially be. Would it put an end to our Fall Armyworm woes?
GM insect resistance – to Fall Armyworm, Corn Root Worm, Stalk Borer and Western Bean Cutworm amongst other species – is conferred by the presence of Bacillus thuringiensis (Bt) proteins in the plant which the larvae of the pest consumes and subsequently dies.
Many Bt variants have been developed over the last 20 years and bred into maize varieties in countries such as the United States and Brazil where the Fall Armyworm is prevalent, so we are able to observe their effectiveness over the years to understand how they might perform in conditions in East Africa.
The trend is frankly not encouraging. In recent years Brazil has seen around one third of the total maize crop planted in the traditional main season, and the remaining two thirds in the 2nd season. This has encouraged a continuous ‘green bridge’ of Fall Armyworm, similar to what we experience in Kenya, and has been attributed to increasing the selection pressure and development of resistance. In fact up to 8 generations of Fall Armyworm a year are recorded.
|Trait||Year introduced||Year of first control failure|
|Vip3a||2009||No resistance detected to date|
The major Bt traits effective on Fall Armyworm are listed above, and you can see that most have not endured under Brazilian conditions for more than a few years.
In the United States there is still partial control from some of these traits because of genetic variation in the populations, so it is important to understand that this does not mean that they are totally ineffective. Herculex based on Cry1f for example still provides acceptable control in some lower pressure regions.
However because of their cold winter, Fall Armyworm pressure is usually far lower until the pest moves North towards the major maize producing regions, by which time maize crops are generally larger and more advanced.
Vip3a or ‘Viptera’ is still effective but the pressure for resistance to develop is immense. Refuge areas of non-Bt maize are deliberately planted to allow Fall Armyworm that are NOT resistant to Bt maize to breed and disperse, providing genetic variation in the population. These would be essential if GM was introduced in Kenya, and would have to be well maintained by somebody.
Periodic spraying – probably in the early stages of the crop – would still be a requirement to reduce populations and the likelihood of resistance developing, and the cost of refuge areas would either need to be financed by government or the seed (trait) provider (which one would assume would have to be reflected in the cost of the seed).
So the message is that GM crops definitely do have a strong place agronomically and could reduce the amount of insecticides applied, but they are no silver bullet and managing the resistance threat would need to be well co-ordinated.
*This article is not an endorsement or criticism of GM crops, but an analysis of their likely effectiveness and how they would potentially fit into maize production in Kenya.
Making legume inoculants work
Save on Nitrogen, increase yields, and provide fertility for the following crop. Get legumes inoculated properly from the start…
- Choose the right inoculant for the crop – surprisingly often this is incorrect!
- Ensure the product is stored properly, at the correct temperature. If in doubt ask the person selling it ‘how should I store it?’ If they don’t know the answer, don’t buy it.
- If you are using inoculant for the first time, apply a strip with several times the recommended dose and a strip without (be aware that even tiny amounts of inoculant in the seed pipes etc might contaminate the supposedly untreated strip, giving a false result).
- Record where you did the double strip – next time you come around to that field with the same legume you might want to compare whether the background rhizobium in the soil has made a difference.
- If you are using a liquid kit make sure you do not over mix – UV light can kill bacteria very quickly in a translucent tank.
- Sometimes applying to the seed in small batches is safer – pre mixing a large tank of liquid n-furrow is great until you have a breakdown or a few days wet weather that keeps you off the field. If in doubt, treat it again!
- For the first few runs put a food colouring marker dye in with in-furrow liquid injection – if it’s not going near or preferably under the seed, stop and adjust until it does.
- Remember that following inoculation, even slightly damp seed flows differently to what you may have calibrated your planter with.
- Make sure the seed goes into damp soil; liquid systems especially are useless if the bacteria dry out before the seed germinates. If you must dry plant, a granular clay-based product is preferable.
Farming for the future requires a change of approach. Monoculture, soil degradation and climate change and soil degradation are threats to the future of how we feed the planet. Agventure Ltd set up the Center of Excellence for Crop Rotation to help farmers diversify cropping systems and introduce techniques which have a long-term outlook to improve soil health. The Center of Excellence for Crop Rotation works extensively with Crop Nutrition Laboratory Services Ltd (CropNuts).
Till next time,
David Jones is the Broad Acre Specialist at Crop Nutrition Laboratory Services Ltd. (CROPNUTS). David has a keen interest in soils and no till farming systems where he has undertaken work looking into weed levels and changes in soil structure, and has extensive experience in field trials and in the development of precision farming techniques. In his spare time he enjoys playing rugby.