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%.
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
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
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.
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
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.