Arable News

  • Written by: Farmers Guide
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Powdery mildew protection for peas

An EAMU (Extension of Authorisationfor Minor Use), secured for growers by Horticultural Development Company(HDC), has been granted for the use of Microthiol Special (80% w/wsulphur) on vining and combining peas (mapp number 06268). Approval holderCerexagri s.a.
Powdery mildew (Erysiphe pisi) has become a commonly occurring problem in theUK over recent years. The disease develops late in the season,particularly following a period of high daytime temperatures and coolhumid nights.  
The fungus is not seed borne but rests as soil or debris-borne conidia overwinter.  In conditions favouring infection, air borne spores settle ontothe foliage of peas which are approaching pod setting stage andquickly result in a surface film of mycelium and fruiting bodies and cause aslow down of maturity. Severe infection can result in off flavours andtaints of vined or fresh peas.
A significant number of late season peas for processing, fresh market and fordry harvest are very susceptible. And, although there is some varietalresistance in peas, many varieties currently suitable forlater sowing or late maturity are susceptible to a greater or lesserdegree.
Production problems occur when the infection develops during the poddevelopment stage, resulting in crop rejection by the processors and severe podblemishing on fresh market peas, reducing the value and quality. Indry harvest pea, mainly marrowfat types, maturity is delayed and yield lossincurred.
In the past, only Thiovit Jet had off-label approval for powderymildew control in vining and picking peas, although it is no longer beingmarketed, and will become unavailable. Some broad spectrum materials suchas cyproconazole plus chlorothalonil (Alto Elite) will protect againstpowdery mildew in combining peas. However, the interval betweenapplication and harvest is 42 days, too long a period for vining or freshmarket peas.
It is well known that sulphur application prevents infection by powdery mildewin many crops.  The timing of application is critical in peas and shouldbe aimed at the onset of infection at the full flower stage (gs 204). 
To this end, the application of similar 80% sulphur products has been shown tobe beneficial in delaying the onset of infection for the remaining timeof maturation of the fresh market crop, whereas a secondapplication would be necessary for dry harvest peas.
HDC Crop Protection Manager Vivian Powell said, It is part of the HDCs roleto support the needs of growers. The industry had identified a lack of cropprotection products for controlling powdery mildew in peas and we haveworked hard, with the support of PGRO, to obtain this EAMU for growers.
As with all EAMUs, the efficacy and toxicity of the product for which it hasbeen granted has not been assessed and, as such, the user bears the riskin respect of failures concerning efficacy or toxicity. Growersshould be in possession of a copy of the EAMU before use. These can bedownloaded from the HSE web site via their Pesticides Register Database ( 

  • Written by: Farmers Guide
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