This presentation covers about important biotic factors that are responsible for grain spoilage,its growing conditions and effect on grains

1. C
BIOTIC FACTORS IN GRAIN STORAGE
By;
K.Vinitha
M.Tech FPE
2018694619

2. Introduction
• Biotic factors, can be described as any living component that affects another organism, or shapes
the ecosystem.
• In a storage ecosystem, several biotic and abiotic factors interact to cause damages to the stored
grains.
• Biotic factors like insects, rodents, fungi, mites and abiotic factors like inappropriate temperature
and moisture cause degradation in quality.
• The insects, mites and the microorganisms that attack stored grains and the stored grain itself
constitute the biotic factors of the storage system

3. INSECTS
• One third of the world grain crop is lost each year during storage. (Much of this is due to
insect attack.)
• Many grain insects preferentially eat out grain embryos - reduces the protein content of feed
grain and lowers the percentage of seed germination .
• Grain insects are divided into primary and secondary grain insect pests
• Important grain pests are
• Sitophilus oryzae L. (Rice weevil). They attack cereals like rice and cereal products such as
paste, flour and biscuits
• Sitophilus zeamais (Maize weevil). They attack maize, sorghum and other cereals.

4. • The optimum temperatures for most insect species range between 25
and 32°C.
• At temperatures below 14°C and above 42°C, the rate of development
is reduced
• Most storage pests will die at temperatures below 5°C and above 45°C.
• The optimum relative humidity for most species is around 70%,
• Minimum (RH) 25 - 40%
• Maximum (RH) 80 - 100%.
Contd..

5. Rice weevil: Sitophilus oryzae
Both the adults and the grubs cause damage. The
developing larva lives and feeds inside the grain
causing irregular holes of 1.5 mm diameter on grains of
rice, sorghum, wheat, barley, maize.
Lesser grain borer: Rhyzopertha dominica
The adults and grubs bore into the grains feed and
reduce them to mere shells with many irregular
holes. The adults are powerful fliers and migrate
from one godown to another, causing fresh
infestation

6. Khapra beetle: Trogoderma granarium
The greatest damage is done in summer . The grubs
eat the grain near the embryo or at any other weak
point and from there proceed inwards. They usually
confine themselves to the upper 50 cm layer of
grains in a heap or to the periphery in a sack of
grains.
Rust-red flour beetle (Tribolium castaneum)
Mainly attacks milled grain products. Adults and larvae feed
only on the grain dust and broken kernels and do not attack the
undamaged whole kernels. Infestation leads to constant and
unpleasant smell of the rice
The white larvae bore into the kernels and eat
the inside. Mature larvae eat the outer portion
of the grain, leaves only a thin layer of the
outer seed coat . Adults damage only the
surface layer of bulk-stored grain.
Angoumois Grain Moth (Sitatroga cerealella

7. RODENTS
• Rats and mice have been estimated to damage 3-5 % of the world cereal crops in common.
• Rodents prefer feeds mainly on the embryo -causes damage to the nutritional value and
germination ability of seeds.
• Diseases can be transferred to humans by rodents –includes typhoid, paratyphoid, and
scabies.
• Three species of rodents are major spoilage factor of stored products:
• Rattus rattus (Black rat)
• Rattus norvegieus (Brown rat)
• Mus musculus (House mouse)

8. Contd..
• Rodents consume cereal crops and damage sacks and building structures.
• Rats consume about 25 gm of food per day and mice eat approximately 3-4 gm per day.
• Contaminates much great portion of the grain with their hairs, pathogenic agents and
excretions .
• Produce leaking out of damaged bags or storage containers
• Bag stacks collapsing due to damage to the lower layers

9. Fungi
• Storage fungi are usually not present to any serious extent before harvest .
• Small quantities of spores of storage fungi present on spilled grain present in harvest, handling
and storage equipment or structures, under improper storage conditions – inoculum increases
rapidly leading to significant problems.
• Many spoilage fungi cause loss of germination in seed grains, discolouration and darkening of
the grains, reduction in protein content, musty odours, and changes in fatty acid profiles and
other constituents of the grains
• The most common storage fungi are species of Aspergillus and Penicillium.
• When grain moisture rises to 16 to 18% in corn and 15 to 17% in soybeans, – results in
aflatoxin production

10. Bacteria:
Contd…
Development of storage fungi in stored grain is influenced by
• Moisture content of the stored grain
• Temperature of the stored grain (4-10°c fungi grows slowly, 21-25°c grows rapidly)
• Condition of the grain going into storage,
• Length of time the is grain stored
• Amount of insect and mite activity in the grain
The bacterial species that occur commonly on grain are generally non-pathogenic, sometimes
contamination with bacterial pathogens such as Salmonella, Escherichia coli and Bacillus cereus can
occur.
This may occur during harvesting, but more often is a result of poor hygiene in road or rail trucks during
transportation, or poor pest control during storage.

11. Mites
• Mites, the tiny (<1-mm size) arthropods, occur in grains both in tropical
and temperate regions.
• The moisture content of the grain is the critical factor for their survival.
• They multiply rapidly in damp and moldy grain at low temperatures.
• In heavy infestation, mites impart a characteristic odor owing to their lipid
secretions.
• Consumes the germ part of the grains and disseminate storage fungi and bacteria
• Causes dermatitis and allergies in humans.
• Mites in stored grain may be either saprophytic (e.g., Acarus siro and Typophagus
putrescentiae), parasitic, or predatory (Pyemotes spp., Cheyletus spp).

12. BIRDS
• Losses result from direct feeding and from contamination by their droppings and feathers.
• Their activity starts immediately after harvest, during threshing and drying and during storage,
particularly in bag-storage in developing countries.
• The birds also have a role in bringing grain insects and microflora into grain stores .
• Major pests are the pigeons (Columba livia ) feed on the spillage and the sparrow (Passer
domesticus).
• Other opportunistic grain feeders such as parrots, doves, and weavers are of local importance.
spillages are often inevitable.