Cotton Seed Distributors - Web on Wednesday

Dr Tom Lei, - Research Scientist, CSIRO - Discusses compensation in cotton following pest damage. He has just completed 5 years research on compensation in the cotton industry.

Tom, one of the key things that you spoke about was about compensation and the length of time we’ve got for the crop to compensate. Can you expand on that a little bit?

Yes Adam, what we’ve done in the last few years was to assimilate Helicoverpa damage and throughout a wide range of crop development and especially what we’ve found was that compensation had occurred.

It’s not only in the pre-squaring season, not in the early season only but it happens up to flowering and to perhaps the first full boll, which in this area is about 100 days after sowing and that also coincides with peak LAI (Leaf Area Index) and we’ve done several trials assimilating grub damage up to 6 or 8 per metre and up to first full boll and we’ve found pretty good compensation.

In some years there could be a slight loss of yield at 8 grubs per metre but anything less that that say up to 4, up to 100 days after sowing we’ve found good compensation with minimum delay.

That’s really a key finding I think the fact that you can go out to this 100 days, so at the moment I think growers have got a lot of confidence in the work that’s being done early and now your work is really showing that you can go a lot longer than that and at fairly high levels that you’ve just spoken about. Can you just talk a little bit about the delay if any, and maybe impacts that has on things like fibre quality?

Well firstly about delay, we’ve found that through a variety of trials, not only done in ACI but down in Hillston and up in Kununurra, up to 4-6 grubs per metre damage and the delay invariably came out to be less that 8 days; maximum 7 to 8 days. Quite a lot of them would only have 3 or 4 days of delay and that’s not really significant in terms of statistics to the control.

In terms of fibre quality, obviously that number of days of delay really doesn’t come into play in terms of causing changes in fibre quality in the damage and compensate the crop.

We’ve done one study where we looked at the late bolls that were collected from damaged crops, which were a few days later than the control crop and the late bolls have micronaire values that are slightly lower than the control but still within the industry standard, and so that gave us more confidence about the effect of damage which really is minimum delay and no significant fibre quality effect.

When you looked at different cultivars and different densities, what was the findings there Tom?

Well basically not a lot of differences between cultivars. We looked at a whole variety of cultivars including normal okra leaf, Ingard, Conventional and different sort of determinant type crops and basically no sort of obvious pattern from one year to the next.

They all compensated to the same level and plant density also didn’t make a big difference in terms of how crop compensated from damage and we use densities that varied from 5 plants per metre up to 25, so that’s a fairly wide range and we didn’t find that compensation was effected within that range of plant density.

If we just hypothesize a little bit about our dryland colleagues on skip row and even this year some irrigators with skip row the potential for compensation in that sort of configuration?

Yes, obviously I can only sort of conjecture in terms of how that would impact on compensation because we didn’t do a trial like that but I would think that because you have more space in a skip row situation so that when a crop is damaged it will tend to produce more lateral branches and more leaves so that if you have very high levels of inputs like water and nitrogen, they tend to push the canopy development beyond the optimum level, which may result in yield loss so if you had a skip row, which will allow the excess of canopy to grow into, you might actually retain the yield, perhaps even increase yield in some cases compared to a crop that had just solid configuration.

Would you like to make some comments about the current management and attitude towards compensation and where do you think it could go in the future based on the work that you’ve done?

Yes we’ve started a survey of grower attitudes on compensation and so far we’ve got some responses from a couple of different valleys and the results basically indicate that there is a very strong tendency for growers to rely on compensation.

That reliance obviously declines as the season progresses but they’re still showing fairly strong belief that yield loss is not happening even once flowering begins, so we’re very pleased to see that because they are taking up that sort of message that we are trying to put out in that compensation can happen even later in the crop development but I think with our results we see that compensation is actually even stronger than what they currently perceive it to be so that our work then is to perhaps to send the message out in different ways.

One way is to set up demonstration fields in different valleys and basically show them how compensation can occur with different levels of damage even later in the season and hopefully that will continue the push to convince growers that compensation is important and they should take that into account in their management strategy.

Further Information:  Robert Eveleigh, John Marshall, Craig McDonald or David Kelly