In this edition of Think Agronomy, we explore the current prevalence of Fall Army worm (FAW), how to get your maize planting right, and the early detection signs of copper deficiency in wheat and barley.
Fall Armyworm Update
Fall Armyworm numbers on volunteers maize plants are currently very low in most areas. For me this is a more accurate picture than trapping adult moths, as it actually tells us more about the survival and success of the larvae in the prevailing weather conditions and their ability to complete the lifecycle. Adult moths can migrate over large distances so do not necessarily reflect the likelihood of larvae being able to cause damage in a specific area.
For the few crops that have been planted and are at the four leaf stage already, I am yet to see any larvae. Moths are being caught in traps but in lower numbers than in 2018, so it is important to keep monitoring and be prepared to spray at short notice. I would also advise growers not to neglect Maize Lethal Necrosis Disease (MLND); as the seed treatment wears off around the 3-4 leaf stage growers should be applying an appropriate insecticide, particularly in a continuous maize situation.
Maize Dwarf Mosaic Virus IS prevalent on volunteer plants at higher levels than the past two years, and as one of the component viruses of MLND it should alert us to the possible risk.
Several weeks ago I toured 11 Agrovets through the Rift Valley to obtain seeds for our variety trials; talking to them about maize seed sales in early March, they were fairly optimistic about planting prospects and the area of maize that Kenya could be expecting to plant in 2019.
However last week the mood was much more subdued with the low maize price, lower confidence in the long rains and concerns over Fall Armyworm all cited as reasons when seed sales had been slow. If stocks of seed sitting on Agrovets floors is a visual indication of the (lack of) demand, it is certainly a lot slower than last year.
If we do get late, do not panic but consider the following:
- Do not rush planting if the seedbed is not right; better to wait a few days and establish a crop well, for even and consistent seed placement.
- Spray off before planting! Even if there are just a few tiny weeds, glyphosate them.
- Planting shallow may get plants out of the ground quicker, but below 4cm (1.5”) and the nodal roots do not develop properly.
- Plant populations – if in doubt about how much moisture is in the profile and the forecasts for the rains are not encouraging, aim to establish plant populations on the lower side.
- If conditions are right, apply a pre emergence herbicide – if the rains are patchy this at least means you have some cover. Applying mesotrione + terbuthylazine + metolachlor when the rains have finished and plants are slightly stressed will not help the crop.
- Get the nutrition right to help the crop off to the best start.
Early Copper Deficiency Wheat and barley
Early Copper deficiency symptoms are visible already, particularly on dry, high organic matter soils. Our trials last year showed responses from spraying as early as 2-3 leaf stage with a small dose 150g/ha of Copper.
Water volumes do not need to be high, so this early spray should cover the acres quickly with 50 l/ha being adequate – just ensure appropriate nozzles are used (Green 015 or Yellow 02). I usually follow up with a leaf analysis test at mid tillering to make sure that the plant is ok for copper until the first fungicide and to check for any other low nutrients.
Molybdenum on Pea seed
Last year I looked at the importance of Molybdenum as a seed dressing on peas, and how it – supposedly – can increase nodulation. Several readers kindly got in touch with me to challenge this assertion, which made us slightly despondent about the various pea trials we had in the ground at that time…. and now we have the results of three of these trials which were conducted in Naivasha, and on two different farms around Timau.
ALL three trials showed a very visible increase in nodulation, and two of the trials were taken to yield, both of which showed significant yield increases. Whatever the reason, Molybdenum is clearly a very important nutrient for many of our crops, not least legumes!
Farming for the future requires a change of approach. Monoculture, soil degradation and climate change and soil degradation are threats to the futureof 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.