Beware drought effect on early mildew infected crops

UK - March 27, 2006

Start protecting cereals yield potential now by protecting root development from the effects of early mildew infection before soil moisture deficits reach critical levels advises Dow AgroSciences. 

Cereal root structure development is under pressure this spring from mildew disease and exacerbated by a rainfall shortage.  Drought-stressed crops lose far more yield to mildew, in particular from early infections, than crops with the same level of infection that are not drought stressed.   

Some parts of the UK have recorded their highest early spring soil moisture deficits for many years.  Soil moisture levels are already at least 5 cm below field capacity in many areas, so crops are likely suffer drought without further significant rainfall. 

“The recent dry conditions, followed by an early mildew infection, can significantly reduce cereal root development.  With a poor root structure and a potential spring/summer drought cereals, especially minimal tillage crops, will be at increased risk of foliar disease, lodging and stress.  Crops unable to resist drought will not yield,” says Dow’s technical specialist Liz Tomkinson. 

The bad news is that the root mass cannot recover from early mildew infection.  Root mass reduction starts in spring sown crops almost as soon as mildew infects, which can be from the 2-3-leaf stage.  In winter cereals GS 25-30, usually mid-March to early April, is a critical phase. 

But the good news is it can be prevented with an early mildewicide at the T0/T1 timing such as Fortress (quinoxyfen) from 0.1 to 0.3 l/ha, depending on the susceptibility of the variety and the persistence of control required.  Add a morpholine to remove mildew if more than 5% infection levels are present, or use Orka (quinoxyfen + fenpropimorph). 

Ms Tomkinson advises growers to keep on top of the mildew through the season.  “Wheat plants are very susceptible to the effects of mildew during the phase of rapid growth from GS 30-45. Yield loss from mildew later in the season is mainly as a result of reduced tillers and ear size.  But if conditions are dry at the grain filling stage grain size and weight can also be affected, alongside lower grain proteins because of the retention of sugars and amino acids in diseased leaves,” says Ms Tomkinson.