Cotton Seed Distributors - Web on Wednesday

Greg McNamara (photo), CSD technical officer based at Dalby, discusses the incidence of Fusarium wilt in Darling Downs cotton crops a this season and some of the management research projects being undertaken by CSD.

The levels of Fusarium wilt noticed in cotton fields on the Darling Downs, how would you describe it?

This year the fusarium has been very evident in the crops. In the CSIRO trials the more susceptible lines in there we lost up to 50% of the plant stand first up, and then each irrigation after that we lost another 20% each time. We are still seeing new outbreaks of fusarium happening across the Downs this year even through most of the varieties have an F-Rank of 100 or above, but it is still there and the patches that have been there in the past are still getting a little bit bigger each year.

Why is fusarium that much worse this year compared particularly with last season?

Last season we had 45 cold shock days and but not no wet, whereas this year we have had cool nights but we had the wet weather earlier on in the season. Cool nights combined with wet weather have contributed to the incidence of Fusarium. Steve Allen has shown that in his research that the fusarium infection is a combination of cool weather and wet conditions. This year the fusarium has settled down a little bit later on in the season because we have had a dry finish, we haven’t had rain for virtually the last two months, so the incidence isn’t quite as later in the season.

This season, CSD had got three varieties out in the market place with an F-Rank of roundabout 150 or better, how have they performed in the field?

The varieties that you are talking about are Sicala 45 with an F-Rank of 154, Sicot 14B with an F-Rank of 141 and Sicot F1 with an F-Rrank of 208. Sicala 45 has been the predominant variety grown on the heavily infected areas and its been performing very well with an F-Rank of 154 it can stand up to the fusarium quite well with a good yield and quality. Sicot 14B is a Bollgard alternative and it’s performed quite well to with an F-Rank of 141. There is a paddock of 14B that we have got one of our fusarium ranking trials in and its gone quite well and its really an eye opener to see the different fusaruim rankings in that paddock, ranging from 141 down to 100. And the last variety is Sicot F1 and it’s performed very well on the very heavy fusarium conditions, it’s done very well this year.

CSD has got a number of trials across the Darling Downs and also the MacIntyre looking at fusaruim management practices, a number of these trials are based on the systemic induced resistant product Bion. Can you tell a bit about the trials that are underway on the Downs with Bion?

Bion this year, it’s a combination of work that has been done for virtually the last 4 years. We have been trialing the product for many years looking at the difference of increase in plant stand. This year we have got three main trials with Bion. We have got a small plot trial looking at the rate of application of Bion onto the seed. The rate there ranges from 3 milligrams per kilo of seed up to 12 milligrams per kilo of seed. And out of that we seem to think that probably around about 6 milligrams per kilo of seed is the best option with that.

The second trial, we have is some seed that we had last year with Bion being applied to it so that Bion has been on the seed for about 18 months. We are looking at the difference where the product is still effective after 18 months on that seed compared with Bion that has been applied a month before planting. It seems to be quite well, which is good because it really shows that the shelf life of the Bion on the seed is quite well.

The last trial, we have got Bion that has been on commercial seed through the commercial plant down at Wee Waa. What we have done is got an 8 row planter and we have put 4 boxes of Bion seed in one side, versus non Bion treated seed in the other side and we have done that with a commercial planter full length of field and that will be picked with a commercial picker and go through for yield and quality. And with those there, one of those trials will go through and make modules from the Bion treated seed so it will go right through the commercial gin.

The trials also include some work with foliar zinc application. What’s the rationale behind this trial?

Zinc, it was work that came out of the US that Steve Allen found out when he was over there. They are looking at applying zinc to reduce the amount of fusaric acid that has been produced in the plant which causes some of the symptoms of fusarium. What the rationale behind it is that with higher levels of zinc being applied on the plant, the fusaric acid production is less. So therefore it wouldn’t succumb to fusarium as quickly.

An important part of the work that you are involved in involves the CSIRO fusarium screening of new lines, can you just outline that a little bit what’s happening in that field that year?

What’s involved with the Fusarium Screening trials is we screen up and coming varieties and also progeny row material to assess their fusarium status so we can release the most tolerant material, and use it in our breeding program. We have two sites on the Downs, one at Norwin and one at Pampas. The one at Pampas has got six hectares of progeny row lines, each plot is 10 metres long by one row and there are 4000 of those plots there. We have around 1500 plots in that trial are dedicated to new material, first cross material that comes into the trial and that’s evaluated each year. If there is anything that’s not too bad in that trial they will continue through the trials, out of those they will be selected into their families and continue through the screening process year after year.

It is a similar sort of trial that we have Norwin and same sort of process happens there. We have in those trials Bollgard material, there is Bollgard Roundup material and there is also the new Bollgard Flex and straight Flex lines that will be evaluated for their fusarium status.

Gathering of F-Rank data is obviously an important part of the fusarium program, can you just outline some of your activities in this area?

In gathering the F-rank data, what we do is we take an establishment count at the start of the season, and we take a final count at the end of the season and then we do the stem cuts and the figure that we come up with is the F-rank for that variety. We do that on a number of sites each year so we end up with a number in brackets at the end of the variety name and that is how many trials have been conducted. The idea of it is to give the growers more confidence in the selection of the variety and so that they know what the fusarium status is at the start of the season. Ideally, what we aim for is the number in brackets to be over 10, something like that. Some of the varieties that we have out today have got figures there of about 15 or something like that. Growers should be very confident with the data that comes from that because it shows that the variety fusarium status is fairly stable.

And finally, one of the trials that you are carrying out is called and integrated disease management trial. Just give us a quick outline what’s involved with this particular trial?

The idea of the integrated disease management trial was to use the integrated disease guidelines to formulate best treatment for managing heavily infected fusarium areas. What we have in the trial is Sicot 189, it’s got an F-rank of 100 obviously, and it’s the standard. It was planted on the 7th of October so it was planted in fairly cool conditions, its got no Bion or systemic induced resistance on the seed and it was watered up and exposing it to cool wet conditions which would have bought on fusarium.  

This is a treatment that a lot of growers do use to save one watering. The other IDM treatment, the Integrated Disease Management treatment it is Sicot F1 with a F-rank of 208, its got Bion applied on the seed and planted into pre watered moist soil and then its was planted on the 11th of November. What this should do is get away from the cool wet start with Bion protecting it season long so it should be quite good. We have done establishment counts on that and we will do a final count at the end and then we will do the stem cuts and it should work out that the later treatment should be the better treatment out of the two.

Further Information:  Greg McNamara