MSc

In coastal states like Kerala, owing to sub-tropical conditions, maintenance of
the quality of the seed during storage has always been a challenge, mostly because the
conditions are highly conducive for the growth and proliferation of storage pests. Use of
insecticides for management of the stored grains is most common, but, the chemical
means of pest management are not advisable in rice as the seeds are often used as food or
feed at the end of the season or on losing viability. Considering the above, a study to assess
the impact of seed protectants on seed quality, longevity and their efficacy against the
storage pests in rice was conducted in the College of Horticulture, Vellanikkara, Thrissur,
during 2019 - 2020.
The experiment was conducted with red kernelled rice variety following a
completely randomized design with three replications and 10 treatments (T1 to T10).
Before treating the seeds, the seed lot was analysed for the seed quality parameters and it
was proved to be of good quality and fit for storage studies. Seed of rice variety Jyothi
was treated separately with seed protectants viz., Neem leaf powder @ 10 g/kg (T1), Neem
seed kernel powder @ 10 g/kg (T2), Sweet flag rhizome powder @ 10 g/kg (T3), Manja
koova rhizome powder @10 g/kg, Panal leaf powder @ 10 g/kg, Spinosad @ 10 ppm,
Diatomaceous earth (T7), Beauveria bassiana @ 1×108 spores.ml-1 (T8), Bacillus
thuringiensis @ 1×108 spores.ml-1 (T9). Untreated seeds (T10) served as control. Both
treated and untreated seeds were dried to ≤12 per cent moisture content and packed in jute
bags. The seed quality parameters like germination, seedling vigour indices, seed moisture
content and insect infestation (number of beetles and larvae, number of infested seeds,
weight of damaged and undamaged seeds) were recorded at the start and subsequently, at
monthly intervals for a period of seven months. Seed microflora was recorded at the start
and end of the storage.
Following treatment with seed protectants, variation in the quality parameters of
seed observed, even before the onset of the storage period. In a few instances, the
parameters remained unchanged after treatment, while in most treatments, a marginal
increase in seed quality was observed. Seeds treated with B. bassiana @ 1×108
spores.ml-1 (T8) had registered the highest germination (%), seed vigour indices (VI-I and
VI-II), length of shoot and root and seedling dry weight, while seed infestation was the
least in diatomaceous earth and neem seed kernel powder. The weight of damaged seed,
the number of infested seed, beetles in 100 g of seed sample were the least in these
treatments. However, a decline in quality was observed in untreated seeds (T10).
Results revealed the existence of significant difference in the impact of various
seed protectants on seed quality and insect infestation related parameters during the
storage period. In both treated and untreated seeds, irrespective of the treatment,
germination, seedling growth (dry weight, length of root and shoot), vigour index- I (VII),
vigour index- II (VI-II), weight of undamaged seeds, decreased significantly over the
storage period. However, the seed moisture content, seed microflora and parameters like
weight of insect damaged seeds, number of beetles, larva and number of infested seeds,
in 100 g of seed samples, increased with increase in storage period. In both treated and
untreated seeds, irrespective of the treatment, germination and vigour index- I (VI-I) and
vigour index- II (VI-II), decreased significantly and progressively over the storage period.
However, there was a significant increase in seed moisture content and seed microflora,
with the increase in storage period.
Seed treatment with B. bassiana resulted in significant enhancement in
germination and seed vigour indices (VI-I and VI-II). The treatment also helped to extend
seed longevity by one month (S6) in comparison with seeds treated with seed protectants
such as neem seed kernel powder, manja koova rhizome powder, panal leaf powder and
B. thuringiensis, as well as untreated seeds. However, in comparison to seeds treated with
B. bassiana, treatment with neem leaf powder, sweet flag rhizome powder, Spinosad and
diatomaceous earth, reduced seed longevity by two months. Considering the date of
harvest, the longevity of B. bassiana treated seed was to 81/2 months, while that of
untreated seeds was 71/2 months. In addition, considering the impact on seed longevity
and seed quality during storage, treatment with neem leaf powder (T1), sweet flag rhizome
powder (T3) and spinosad (T4) and diatomaceous earth (T7) was found disadvantageous
The efficacy of seed protectants against storage pests was also evaluated at
monthly intervals. A significant surge in the insect infestation was observed during the
storage period in both treated and untreated control. The estimates of weight and number
of insect damaged seeds and number of beetles were the least and significantly low in the
treated seeds. Untreated seeds registered the highest insect infestation. Hence, treating
seeds with seed protectants was found advantageous over storing them untreated.
Among the seed protectants used, treating seeds with diatomaceous earth (T7),
neem seed kernel powder (T2) and spinosad (T6) conferred relatively higher protection,
although no significant differences were observed among the treated seeds during the
storage period. However, in spite of its insecticidal efficacy, seed treatment with
diatomaceous earth and spinosad had a negative impact on seed longevity and quality.
The longevity of neem seed kernel powder treated seeds was one month more than that
observed in the diatomaceous earth and spinosad treated seeds.
Although, the insecticidal effect was low, treatment with B. bassaina was
considered the best among the treatments as it had extended the seed longevity the
maximum i.e., by a period of one to two month over all other treatments as well as found
significantly superior to all other treatments in maintaining seed quality during storage.
Seed treatment with neem seed kernel powder was the next best alternative to
B. bassiana. These treatments had exhibited considerable high efficiency in control of
insect population and associated seed damage.
In considerations of the above, the use of entomopathogenic fungi Beaveria
bassiana @ 1×108 spores.ml-1 and the botanical neem seed kernel powder @ 10 g/kg, were
found as the best treatments in reducing the rate of seed deterioration during storage in
rice. Of the two, treatment with neem seed kernel powder @ 10 g/kg accorded better
control of stored pest infestation in rice seeds.