Potatocrops have enjoyed extremely good growing conditions across most of the UK thisseason providing there has been ample irrigation available and they have beeneffectively protected from the extended periods of extremely high blightpressure.
Asa result, many crops have reached the optimum 80 to 85 mm market-sized tubersseveral weeks ahead of expected. Growers now face the challenge of stoppingfurther tuber growth beneath a vigorous crop canopy, reports Shropshire-basedSyngenta potato specialist, Rob Farrow.
Withthis season’s big crops, an initial Reglone application can quickly burn offthe tops to help manage tuber size more effectively and reliably, he advised.It will also expose the stems for a second application to complete desiccationbefore harvest.
MrFarrow advocated the initial treatment should be applied at a low rate ofone-litre per hectare, which is fully supported by Syngenta, whatever the soilconditions. The follow-up treatment can be tailored at two to four litres perhectare, depending on the remaining stems and green haulm.
Oneof the most frequently asked questions is when do I make the second spray in asequential desiccation programme?.
Fromexperience the temptation is often to go in too quickly. You need to give timefor the leaf canopy to die back and stems begin to go over, especially with bigcrops, he added. In most instances, five to seven days will give betterresults and achieve a more complete kill of haulm with the two-spray Regloneprogramme.
Forbest results the initial treatment in vigorous crops should be applied at400l/ha using the angled Syngenta Potato Nozzle to achieve good coverage andcanopy penetration, highlighted Mr Farrow. The second spray water volume can bereduced to 200 l/ha, again using the angled nozzles for enhanced all roundcoverage of stems.
Thisyears very high blight pressure and widespread reports of infection inunprotected crops, volunteer potatoes and gardens means growers must protecttubers right through to harvest, warned Rob Farrow.
Fortuitously,the Reglone sequential desiccation programme interval also fits with theShirlan blight spray timing at appropriate rates. That enables the inclusion ofeffective tuber blight protection in both desiccation sprays, to minimise therisk of blight spores moving through the soil to infect tubers, he added.
Research has also shown that Reglone does have adirect effect on blight spores. Furthermore, the rapid defoliation and removalof leaf and haulm deprives blight of the green vegetative material on which itdepends, reducing the risk of further development and spore production thatthreatens tuber infection.