By David Jones, Broad Acre Agronomist

2017 has certainly been a testing year; the arrival of Fall Armyworm, delayed rains and stressed crops, and volatile grain prices all made for a challenging 12 months. But farmers are used to adversity, and I am a firm believer in looking at how we responded and what we can learn for 2018.

Fall Armyworm lessons from 2017

Without doubt the biggest challenge of 2017 was the arrival of Fall Armyworm (FAW). Maize yields were impacted severely and crops lost entirely in worst cases where control measures were too late or inadequate.

A Fall Armyworm larvae found by our agronomist Larsson Chebii back in April

One of the biggest questions I get asked is “will it be a problem next year or is it likely to disappear?” We can say with certainty now that it here to stay at least for a long while, and that we need to get used to fighting it.

Top Tips for Managing Fall Armyworm

Maize is of course the crop most affected, but sorghum, millet, wheat and peas have also been under pressure.

The effect on cob weight of plants infested with FAW. The 5 cobs on the left actually had NO larvae feeding inside them; this is just the effect of the leaf damage alone! The five on the right are from plants with no larvae. A reduction in cob weight of 60%!!!

Don’t forget Cultural Controls

As we as using appropriate insecticides, a number of cultural steps can be taken. Get the crop off to a quick start as early as is sensibly possible depending on moisture and seedbed conditions. As larvae population build up when the first eggs are laid, greater numbers of moths will be airborne, putting far greater pressure on late-sown crops.

In Naivasha this year I saw one larvae on every few plants in the first emerged crop; by April when the last planted crop was at 4 leaf stage I was finding up to 15 on EVERY plant!

Getting the soil structure right, and using appropriate crop nutrition and fertiliser to get the crop away quickly is crucial. Weeds also severely impact on maize more than any other crop, so start clean and keep the crop clean.

The best defence against FAW starts with good establishment

There is a lot to be said for growing shorter, quicker varieties. Although these have a yield penalty, there is a balance to be struck between trying to control FAW in a very tall crop of 691 that is in the ground and vulnerable for 5 weeks later than say Panaar 15 or Pioneer 38. Shorter varieties also allow the final sprayer pass (or knapsack) to be that bit later.Just remember that if using LUMAX herbicide the label states it should NOT be tank mixed with Organophsphate insecticides (acephate, chlorpyrifos, profenofos) – I would allow an interval of at least 7 days to avoid scorch and crop damage.

Another lesson we learnt this year is that despite widespread larval resistance to pyrethroid insecticides such as Lambda-cyhalothrin, the Adult Moth still appears to be susceptible, and has some repellence effect that can last over a week. Do not rely on or over use this, but bear this in mind to keep the moths out of the crop.

Wheat affected

In the last few weeks of the year I have noticed wheat crops being attacked in several parts of the country, as high as 2,200m at Timau. Barley crops far less so at present.

Fall Army Worm 'Hole Punch'

Fall Army Worm ‘Hole Punch’

The tell-tale sign is the ‘hole-punch’ effect in the leaves from where the larvae was feeding in while it was rolled in the stem. Larvae are trickiest to find in wheat and appear to go down to the soil in the morning and shelter in residue on the soil surface.

Very often we could see the damage but the larvae were absent on the plants themselves. Therefore the message is when spraying cereals, spray very early morning or late evening when the larvae will be active and exposed on the upper crop canopy.

I am particularly interested to see whether wider rows and more open varieties (e.g. Kingbird or Farasi) might assist in controlling FAW by allowing greater spray coverage than a very leafy and tillered variety such as Wren or Tai.

What we certainly have noticed is that the worst visible damage is at late tillering through stem extension; I have seen very little larvae feeding on the heads post flowering so far in Kenya although do not be complacent.

Pupae in the soil is also a giveaway and indication of activity; empty cocoons and cold night suggest that the pest is having trouble multiplying and completing its life cycle.

Fall army worm Life Cycle

The later stages of the larvae (3rd instar onwards) are most susceptible to cool temperatures. When night time temperature drops below 9°C we were only finding very small larvae – it appears that they are unable to complete the life cycle so fresh egg lays are from moths that have flown in from elsewhere.

Ultimately 2018 will require good monitoring, a structured insecticide program and crops that are planted well. Although the price of control can easily exceed Ksh 15,000 ($150 USD), maize can still be a reliable and profitable crop for next year.

Introducing Crop Choices®

After choosing the crop in the rotation, selecting the right variety is probably the most important decision a grower will make.

Cropnuts Crop Choices

This is why CropNuts are launching Crop Choices®, Kenya’s first truly independent variety selection guide, based on our own trials data and field experience from our agronomists.

Many countries have a National Variety List or Recommended List, where information about each variety is compiled in an accurate and independent way to allow farmers to easily compare and select varieties based on their own situation and needs.

There is a lot of work involved in observing and trialling the varieties for several crops, but the rewards for selecting the right variety are enormous and can make a big contribution to farm profitability.

Sales material from breeders and seed suppliers just cannot match the power of independent data, which is why CropNuts and AgVenture are collecting this knowledge.

Independent Crop Trials

The rewards for selecting the right variety are enormous and can make a big contribution to farm profitability

The data is available free of charge to customers of the Agronomy Service for a range of crops including wheat, barley and canola, with maize and pulses to be added in due course.

Valuable yield data is already being collected for each variety from our professionally run, fully replicated trials sites like our Timau barley trial pictured, and will be available in early 2018.

Video: Maize Herbicide Trial Tour 2017

Take a short video tour of one of our maize herbicide trials:

Canola Nitrogen and Sulphur Trials Update

Both our trials in Timau and Nakuru looking at the optimum Nitrogen and Sulphur dose rates in Canola are progressing well, and visual responses are very evident. It is important not pre judge this type of work, but the differences between low, medium and high Nitrogen rates in plant colour and crop structure are striking.

Notice below the change in crop colour where more sulphur is added – even though the middle and bottom photos have the same amount of N, it appears as though the crop is unable to fully utilise it without adequate sulphur.

Sulphur Trials

And finally, best wishes to you and your families at Christmas, and a prosperous New Year from all at CropNuts!

About David

 

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.