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Plantwise Factsheets for Farmers
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Sulphur to control powdery mildew in cashew

Recognize the problem

Powdery mildew is a fungal disease which affects the surfaces of shoots, leaves, flowers and fruits of cashew. Symptoms include grey or white dust on the surface of infected plant parts. Heavily affected leaves curl, dry up, and fall. Heavily infected flowers fail to open. Infected nuts become stunted, cracked and rotten, and fall early. The disease can reduce yield by up to 80%.

Background

Powdery mildew occurs mainly during the dry season and less during the wet season. It is spread by wind and can be carried from one season to another through infected, young and densely grown shoots. Chemical products are mainly protectants so they may prevent further spread but only partly control existing infection.

Management

  • Sulphur powder is preferred among other chemicals, because it is effective, locally available, and has a relatively low toxicity (Tanzania blue- label product, WHO toxicity class III)
  • Dusting of Sulphur is advised after observing powdery mildew (whitish powder) on 5-10% of the leaves on each cashew tree
  • Sulphur can be placed into a motorized pesticide mist blower up to a level as per the manufacture`s instruction. 
  • Dusting of Sulphur is done all over the cashew tree early in the morning (6.00-9.00 a.m.) because at this time of day there is enough dew on leaves for the Sulphur powder to stick to
  • The blower operator should move with the wind as he blows, to reduce exposure to the chemical. The operator must wear protective clothing, particularly a mask because the chemical will be everywhere.  Do not re-enter the plantation for at least 1 day.
  • The required rate is usually 1/4 kg per tree (or max 9 kg per acre per season) but rates may differ depending on the product. Please read and follow product label instructions.
  • Sulphur can be applied up to 4 times, the first 3 at intervals of 14 days, and the last one at an interval of 21 days.  Never spray 14 days or less before harvest.
WHO toxicity class I products and Tanzania-red-label-products are not advised. WHO class II and Tanzania-yellow-label-products are not advised in Tanzanian IPM schemes. WHO class III or U and Tanzania-green-label or blue-label-products are preferred. Always double-check with recent list of registered pesticides (MAFC / TPRI).

When using a pesticide, always wear protective clothing and follow the instructions on the product label, such as dosage, timing of application, and pre-harvest interval.

Scientific name(s) > Oidium anacardii

The recommendations in this factsheet are relevant to: Tanzania

Authors: Costantine P. Mboya, Caroline S. Swai, Jubilant Mwangi
DAEO Mkuranga District Council, Tanzania; Ministry of Agriculture, Food Security and Cooperatives MAFC- Extension Services FEU
email: cosmboya@gmail.com, cswai@yahoo.co.uk
Edited by
Plantwise
Created in Tanzania September 2013