“There’s a revolution brewing and the great thing is that to join, all you have to do is absolutely nothing.”
This was the opening line from Steve Ellis of ADAS, who spoke of the need to re-evaluate our perceptions of pest thresholds when managing crops.
Speaking at the AHDB agronomy conference, Steve explains how over-reliance on chemistry and the development of insecticide resistance, along with a decreasing chemical arsenal, has forced many growers to adopt integrated pest management (IPM) principles when dealing with pest problems.
As readers will know, adhering to pest thresholds before treating a crop is an important pillar of IPM.
However, when looking at pesticide usage, Steve explains how farmers tend to err on the side of caution and treat a crop before the thresholds for aphids, beetles, slugs, caterpillars etc, are reached.
So the question is simple, can smarter thresholds be developed in order to better help farmer decision making on the need to apply a pesticide or not? Well, according to Steve, understanding crop tolerance to pest attack may help growers to do that.
Damage does not equal yield loss
“Just because you see damage, doesn’t mean you’re going to see yield loss,” Steve explains.
In some instances, crops can tolerate more damage than we think.
When is the rite time to increase seed rates or apply slug pellets?
For example, he says oilseed rape (OSR) produces more buds than it needs in order to achieve yield potential. Similarly, wheat produces more tillers than it, in theory, needs.
Steve believes that before even attempting to count the number of pests present in a crop to determine if treatment is needed, growers should first assess the health of the crop.
The health of the crop will determine its ability to incur damage without yield loss, he explains.
While this may be a different form of threshold, it remains a threshold none the less.
Asking the right questions
When challenging the norm and developing these ‘smart thresholds’, there are a number of key questions which need to be asked. For example, when dealing with pollen beetles in OSR, do we know how many buds a single beetle can damage?
A pollen beetle in oilseed rape.
Well, according to work done by the AHDB, an average beetle eats around nine buds.
More and more research is being conducted into this area, Steve remarks.
But in order to determine a new threshold, the level of damage a plant can take before incurring a yield loss needs to be better understood.
This knowledge is readily available according to Steve.
A typical OSR crop needs between 6,000-8,000 pods/m2 in order to achieve full yield potential.
A typical OSR plant can produce up to 200 extra pods per plant, and still achieve the required number of pods/m2. This gives a buffer of 200 pods/plant in which damage can incur without compromising yield.
Are we measuring the right things?
Physically counting the number of pests to determine the threshold can also prove a challenge. Insects can be fast moving, fly away, be weather dependant and the process of counting is time consuming.
So what parameters of the crop can we read to assess how much damage is being incurred by the pest?
In the OSR example, Steve believes that if growers can understand the correlation between loss of green leaf area and the level of pest damage, then that will allow for a speedy indication on whether pests have reached the new threshold, or not, which warrants action.
Smart thresholds in practice
In the case of OSR, research carried out by the AHDB put this to the test.
As mentioned previously, oilseed rape plants produce around 200 more buds than they need in order to achieve their yield potential.
While this figure varies with variety, weather, sowing dates, seed rate etc, the correlation between plant population and excess bud numbers can be used to estimate excess buds. As plant population increases, excess bud numbers decrease.
Assuming that pollen beetles eat nine buds each, once the number of excess buds are known, then a threshold can be calculated.
Assuming a plant population of around 45 plants/m2, then a threshold of around 20 beetles per plant can be calculated.
That level of infestation sounds significantly high but, according to Steve, until that threshold of 20 beetles/plant is reached, the crop will not suffer a yield penalty from those beetles.
How will thresholds evolve?
Steve says that, while there is much more to be done in this area in terms of research, smart thresholds will be developed in a user friendly way, ie something that is convenient and accurate.
Technology will play a role in this, with smart phone apps, sensors and pest development models all playing a part.
Thresholds have long since been part of the farmer’s decision-making process but, arguably, their importance has been reiterated again in recent times.
I have no doubt that in time, given advancements in technology, biological research and an increased understanding of natural predation, much more practical threshold tools will be developed.
At this moment in time however, am I willing to ignore 19 pollen beetles on each of my oilseed rape plants under the assumption that they have not reached levels which will impact on yield? The answer is no.
While the science may be sound, Steve alluded to the fact that there are many other factors which are likely to have an impact on yield and, when that occurs, I’d like to have as many viable pods as possible to help compensate for that.
That said, I do think we’re only scratching the surface in this area and given our likely pesticide free future, now is the time for trial and error.
Read more
Oilseed markets bullish - but will it last?
In the fields: nice crops but a few worries
“There’s a revolution brewing and the great thing is that to join, all you have to do is absolutely nothing.”
This was the opening line from Steve Ellis of ADAS, who spoke of the need to re-evaluate our perceptions of pest thresholds when managing crops.
Speaking at the AHDB agronomy conference, Steve explains how over-reliance on chemistry and the development of insecticide resistance, along with a decreasing chemical arsenal, has forced many growers to adopt integrated pest management (IPM) principles when dealing with pest problems.
As readers will know, adhering to pest thresholds before treating a crop is an important pillar of IPM.
However, when looking at pesticide usage, Steve explains how farmers tend to err on the side of caution and treat a crop before the thresholds for aphids, beetles, slugs, caterpillars etc, are reached.
So the question is simple, can smarter thresholds be developed in order to better help farmer decision making on the need to apply a pesticide or not? Well, according to Steve, understanding crop tolerance to pest attack may help growers to do that.
Damage does not equal yield loss
“Just because you see damage, doesn’t mean you’re going to see yield loss,” Steve explains.
In some instances, crops can tolerate more damage than we think.
When is the rite time to increase seed rates or apply slug pellets?
For example, he says oilseed rape (OSR) produces more buds than it needs in order to achieve yield potential. Similarly, wheat produces more tillers than it, in theory, needs.
Steve believes that before even attempting to count the number of pests present in a crop to determine if treatment is needed, growers should first assess the health of the crop.
The health of the crop will determine its ability to incur damage without yield loss, he explains.
While this may be a different form of threshold, it remains a threshold none the less.
Asking the right questions
When challenging the norm and developing these ‘smart thresholds’, there are a number of key questions which need to be asked. For example, when dealing with pollen beetles in OSR, do we know how many buds a single beetle can damage?
A pollen beetle in oilseed rape.
Well, according to work done by the AHDB, an average beetle eats around nine buds.
More and more research is being conducted into this area, Steve remarks.
But in order to determine a new threshold, the level of damage a plant can take before incurring a yield loss needs to be better understood.
This knowledge is readily available according to Steve.
A typical OSR crop needs between 6,000-8,000 pods/m2 in order to achieve full yield potential.
A typical OSR plant can produce up to 200 extra pods per plant, and still achieve the required number of pods/m2. This gives a buffer of 200 pods/plant in which damage can incur without compromising yield.
Are we measuring the right things?
Physically counting the number of pests to determine the threshold can also prove a challenge. Insects can be fast moving, fly away, be weather dependant and the process of counting is time consuming.
So what parameters of the crop can we read to assess how much damage is being incurred by the pest?
In the OSR example, Steve believes that if growers can understand the correlation between loss of green leaf area and the level of pest damage, then that will allow for a speedy indication on whether pests have reached the new threshold, or not, which warrants action.
Smart thresholds in practice
In the case of OSR, research carried out by the AHDB put this to the test.
As mentioned previously, oilseed rape plants produce around 200 more buds than they need in order to achieve their yield potential.
While this figure varies with variety, weather, sowing dates, seed rate etc, the correlation between plant population and excess bud numbers can be used to estimate excess buds. As plant population increases, excess bud numbers decrease.
Assuming that pollen beetles eat nine buds each, once the number of excess buds are known, then a threshold can be calculated.
Assuming a plant population of around 45 plants/m2, then a threshold of around 20 beetles per plant can be calculated.
That level of infestation sounds significantly high but, according to Steve, until that threshold of 20 beetles/plant is reached, the crop will not suffer a yield penalty from those beetles.
How will thresholds evolve?
Steve says that, while there is much more to be done in this area in terms of research, smart thresholds will be developed in a user friendly way, ie something that is convenient and accurate.
Technology will play a role in this, with smart phone apps, sensors and pest development models all playing a part.
Thresholds have long since been part of the farmer’s decision-making process but, arguably, their importance has been reiterated again in recent times.
I have no doubt that in time, given advancements in technology, biological research and an increased understanding of natural predation, much more practical threshold tools will be developed.
At this moment in time however, am I willing to ignore 19 pollen beetles on each of my oilseed rape plants under the assumption that they have not reached levels which will impact on yield? The answer is no.
While the science may be sound, Steve alluded to the fact that there are many other factors which are likely to have an impact on yield and, when that occurs, I’d like to have as many viable pods as possible to help compensate for that.
That said, I do think we’re only scratching the surface in this area and given our likely pesticide free future, now is the time for trial and error.
Read more
Oilseed markets bullish - but will it last?
In the fields: nice crops but a few worries
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