Disease pressure builds in the south

By Andy Doyle

With mid summer's day now past and winter barley starting to turn, the cyclical nature of the seasons is once again all too evident. I was down in Cork last weekend at the hurling FÅile so I took the chance to look at crops around east and south Cork. And like most other areas this year, crops vary from brilliant to disappointing.

In general, all crops look well at a distance but not all are equally good. Headland damage is evident in many crops from winter wheat to beet. But I saw no fields with bare patches on headlands. Nor did I see any signs of fields being left idle in response to decoupling.

Spring barley

The first spring barley field I stopped at in east Cork looked okay but was disappointing when I looked closer. It had a pale colour and was thin for spring barley. The density was variable as I walked across the tramlines - common in many crops as a result of the variability in early season growth.

This crop was at GS 64 or thereabouts so there is little chance of any improvement at this point. The pale colour was even more worrying because I wonder if it has the reserve to go through a long grain fill period, weather permitting. It just seemed to lack the "vump'' to even fill the existing heads to the maximum but hopefully it will.

There was a fair bit of rhyncho in the crop and some of it was fresh. But it was very obvious that there had been huge rhyncho pressure early on, which had been controlled on the younger foliage. So while there was rhyncho present, it looks like the fungicide(s) has done its job.

The headlands in the crop were poor and variable. No doubt this was related to conditions post planting rather than conditions at planting. However, the big weights of tractor/one-pass combinations may well be partly responsible, especially with the frequent heavy rain this spring.

There were a few wild oats scattered through this crop.

A neighbouring crop showed much more promise. The variety may well have been the same but the yield potential looks much different. This was a very full crop and even looked taller. It was much more uniform also and might not have been affected by the bad spring/early summer weather. There was a bit of headland damage here also but the crop still seemed to show more vigour.

The most visual difference is the darker green colour; it just looks to have much more capability to fill all the grains present. It may have been sown slightly later as this crop is just beginning to flower.

There was a little bit of both rhyncho and net blotch present but nothing to worry about for the moment.

Aphid numbers were beginning to build down in the crop canopy so these might need to be watched in crops still awaiting their second fungicide. Watch sprayed crops also just in case there is a numbers explosion, as Teagasc found advantage in controlling high numbers in the occasional year when they occur.

Another crop of spring barley caught my eye in the glistening sunshine before sunset. This was a very heavy crop and felt a little on the soft side. But it was a very uniform crop again and I wonder if the ground is relatively fresh? This crop had a lot of rhyncho present, both old and fresh lesions.

Looking at some of the different varieties in the Goldcrop trials, most of the unsprayed varieties had a lot of rhyncho present. The definite exceptions were Doyen and Wicket, both of which had only an occasional lesion.

Down in south Cork, I visited an early March sown crop of Doyen with the Bandon Tillage Discussion Group. This was a heavy crop of barley with some speckling on the leaves and a few lesions of rhyncho also.

In general, spring barley crops varied from about GS 37 to GS 65. The later crops had a lot of visible BYDV present.

Winter wheat

The majority of winter wheat crops were obviously late sown after sugar beet and some appeared to be spring sown. Except for headland damage in places, wheat crops looked well. There was certainly some septoria present but not much more than one might expect given the rainfall levels. But what was very visible was significant tipping on the flag leaf that made crops look 'dirty'. This is not septoria but may be a result of the variable weather combined with spray applications.

The first crop of winter wheat I walked into was around GS 73. It was a good crop and looked well except for the tipping. There had been a lot of septoria in the base of the crop where substantial slug damage was also evident.

Interestingly, the septoria was better controlled between the tramtracks than in the rest of the crop.

This might indicate that penetration was an issue with the fungicides, as the area beneath the sprayer is opened up by the brushing movement of spraying and penetration is easier. Where penetration is needed, water volume and nozzle type are important considerations when spraying.

A second crop of winter wheat looked like Claire and was late sown after beet, probably spring sown. Again, the headlands carried damage but the crop looked well at GS 63. There was no septoria present in this crop - yet - but there was a lot of mildew present. Indeed, the mildew was now right up on the flag leaf. While the percentage infection was not very high, it would need to be watched as it could easily jump to the ear.

Down outside Bandon, a crop of mid-November sown Einstein had a lot of septoria present with some mildew also.

The crop looked very tipped but some of this may well have been related to nutrient access or availability because there was a lot of streaky yellowing visible on the flag leaf.

Septoria pressure is very high in the south and the levels got away in this crop because of an extended interval between T1 and T2. The six-week gap just proved too much and the T3 has gone on three weeks after the T2 to help hold any further disease development.

This was a very good crop and looked to have potential. While the odd flag leaf had lots of septoria present, most had only a few specks, which would be akin to the levels of septoria we had to live with 10 years ago before the advent of strobilurins.

Spring wheat

The first crop of spring wheat I visited was fully eared out but not yet starting to flower. There was no disease of consequence present in the crop but it seemed a bit thin. There were some beet bolters present in this (and other crops) but the major weed here by far was wild oats.

There were a huge number of wild oats present and these did not look like they had been sprayed. Wild oats were a feature of many other crops also but some of this may reflect the difficulty in getting good weed kill from a whole range of herbicides this spring.

Septoria and mildew levels were very high in the unsprayed plots in Goldcrop's variety trials. Septoria had come right up onto the flag leaf and mildew was present here also. So there was a fair test of fungicide performance taking place across the region this year.

Sugar beet

Sugar beet crops show the same level of variation as other spring crops this year. Crops vary from the four true-leaf stage up to a few now meeting in the rows. But most are a long way short of this.

There seems to be a lot of variation within most crops also. One early sown crop I walked into had very poor headlands and an awful lot of variation along the row. Good plants could be followed by poor plants for no apparent reason.

Even some of the crops that looked good had this variation present when one walked into the fields. There was evidence of root pest damage on some of these more backward plants but I was not willing to pull up enough of these plants to see if this was the universal cause. But I got the feeding that soil abuse may also have been part of the reason for some of the growth variation.

Establishment itself was also quite variable along the row. This crop had been scuffled recently and this may well freshen it up a bit.

A second crop of beet looked more even but it, again, had variable establishment. It was sown later and may have avoided some of the adverse weather experienced by the first crop. This crop had a good few wild oats present and a scattering of weed beet also. There was also a lot of field speedwell about that looked like they survived the most recent sprays. This crop was sown in drills while the first one was sown on the flat.

Outside of Bandon, I visited a crop that was sown on 6 May. Again, there was lots of variation along the rows and this crop had a long way to go before the foliage would meet.

All the beet crops seemed to have a fair proportion of plants with abnormal leaf growth characteristics.

In the past, we used to say that this might have been a result of grazing by hares or rabbits but in more recent times this problem is put down to mangold fly.

Numbers of this pest were reported to be high in places this spring and this damage may turn out to be significant.