Special Reports/Organic Farming
management of pest insects in stored wheat
By Muhammad Anwar
& Dr Muhammad Ashfaq
FOOD security has always been the most strategic aim of the
nations, worldwide. Food safety is a complementary module
due to losses endured by a number of biotic and abiotic
factors during production, handling and storage. The extent
of such losses depends upon post-harvest management system
and pest control measures.
destructive agents, pest insects play a major role in
post-harvest system of perishable and semi-perishable
agricultural products. Wheat is a staple food of the people
and food security-cum-safety plans include its production
Wheat production fluctuates around 20 million tons which is
enough to accomplish our food, feed, and seed requirements
for few years. By 2010, our wheat requirement will be about
25.5 million tons. Presently, any deficit in domestic
production is compensated with imports.
According to scientists, post-harvest wheat losses range
from 2.5 to 15.3 per cent depending upon the handling and
storage conditions as these are high in private sector due
to the unawareness about pest management protocols and
uncertain storage and marketing system.
Presently, food grains are protected from pest insects by
using synthetic insecticides and fumigants. In early 90’s,
the Punjab Food Department controlled insect pests of
stored-wheat with one tablet of Aluminum Phosphide per cubic
meter volume which now is being done with three tablets for
controlling the resistant strains of insects.
A considerable amount of foreign exchange is spent on the
import of pesticides which can be avoided by utilising our
domestic natural resources. Moreover, Codex Alimentarius
Commission of the WTO recommended organic control of insect
pests to make food products according to the International
Standards Organization. Keeping in view the demands, it was
decided to orientate the research towards organic management
of pest insects in stored wheat and selected local
In the recent past, insecticidal properties including
toxicity, feeding-repellence, surface protection and
oviposition deterrence were confirmed by different
researchers against the insect pests of stored grains in
laboratory studies. Accordingly, oils of these botanicals
were used in the organic control of pest-insects with the
integration of asepsis, disinfestations, and different
packing materials under natural conditions in the
warehouses. This was done to develop an IPM protocol for
safe storage system at farm level by replacing the synthetic
Insect-free jute and cotton bags made from the fabric of
different densities (mesh sizes) were sprayed-over with four
different concentrations from each of the botanical oils and
mixtures in three sets for three storage periods (30, 60 and
90 days) each, with three replications.
Infestation free wheat of new crop was packed in the bags,
treated with different concentrations of test materials to
evaluate their antixenosis and antibiosis. The experimental
units were placed in ventilated warehouses of flourmills
under favourable conditions for the multiplication of stored
The concentrations showing considerable efficacy were tried
as mixtures to note their effects. Absolute data, regarding
mortality, penetration into the treated bags and insect
population build were collected at specified intervals.
After completion of the experiment, rheological tests were
applied to the flour produced from the treated and untreated
wheat to note changes in dough-development and sensory
evaluation of chapatti.
On the analysis of data, different concentrations, storage
periods and packing materials showed a significant effect
upon penetration of insects into the bags and mortality of
insects due to their body contact with botanical oils. The
degree of antixenosis and antibiosis showed a positive
correlation with the concentration of the botanicals but
negative with the storage periods.
Penetration into bags was inversely proportional and insect
mortality directly proportional to the density of packing
materials. Mixture of three botanical oils with 10 per cent
concentration of each gave effective control of the target
insects for two months with a fine cotton cloth packing
which decreased gradually in the third month.
Farinographic studies showed no significant changes in dough
development properties of the flour made from the wheat
stored in bags treated with the botanicals. Moreover,
sensory evaluation proved that there was no distinguishable
taste or taint found in chapatti made from the flour of the
wheat packed in the treated bags.
Recommendations: Farmers can save grain, environment and
capital by using the oil of castor seeds, neem seeds and
rhizomes of sweet flag plant to control insect pests. Oils
should be mixed in equal proportion and sprayed over
jute/cotton bags to be used for packing of cleaned/insect
The mixture may be sprayed with the help of a fine sprayer.
New crop wheat should be spread on metal sheets or cemented
floor in the sun up to the temperatures at 55ºC for about
These sun-heated wheat grains having moisture contents not
more than eight per cent may be packed in treated bags to
get a safe storage for two to three months only. If wheat is
to be stored for more than three months then repeat the
botanical application after every two months. Insect free
new crop wheat with new treated bags and proper sealing can
provide better results.
Moreover, appropriate repair, cleaning and treatment of
godowns/bins are also a supplement for the success of the
suggested insect pests control measure.