2. Thesis-Introduction to summary - Shodhgangashodhganga.inflibnet.ac.in › bitstream › 10603 › 5673 › 12 › 12... · 2015-12-04 · “Determination of Effective Bait Base

“Determination of Effective Bait Base for Rodent Pests”“Determination of Effective Bait Base for Rodent Pests”“Determination of Effective Bait Base for Rodent Pests”“Determination of Effective Bait Base for Rodent Pests”

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IV. DISCUSSION

4.1 Laboratory Evaluation

In the present study under laboratory conditions the preference of chosen grains (in two

forms viz., Germinated and Non-Germinated) by the rodents were studied with two choice and

multiple choice tests. The rodent pests were also subjected to toxicity tests (acute and chronic

rodenticides under no-choice and choice tests) by using their preferred grains.

4.1.1 Two-choice tests

The germinated cereals and pulses preference over their non-germinated forms and their

mean magnitude of daily consumption by both sexes of different species of rodents viz., B.

bengalensis, M. meltada, M. booduga and R. rattus under two-choice tests were carried out in

the present investigation.

The lesser bandicoot rat (B. bengalensis)

Both sexes of the lesser Bandicoot rat preferred germinated cereals viz., paddy, pearl millet and

ragi to the non-germinated cereals. The differences in consumption of germinated and non-germinated

cereals by both sexes were statistically significant (p < 0.01). The percentage increase in consumption

of germinated paddy, pearl millet and ragi by both sexes of B. bengalensis were 58.55 ± 27.62, 69.94 ±

26.52 and 92.72 ± 16.08, respectively. It is obvious from the results that the germinated pulses were

consumed in greater quantities than the non-germinated. The differences in consumption of the

germinated and non-germinated cereals consumption by both sexes were statistically significant (p <

0.01). The percent increase in consumption of germinated green gram, black gram and Bengal gram by

both sexes of B. bengalensis were 78.68 ± 21.17, 71.03 ± 24.7 and 93.62 ± 10.86, respectively.


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The soft - furred field rat (M. meltada)

The mean germinated grain consumption by both sexes of soft-furred field rat was

(11.54 ± 4.85 g/100g body wt. for paddy); (10.85 ± 4.87 g/100g body wt. for pearl millet) and

(16.40 ± 5.84 g/100g body wt. for ragi). Significant differences (p < 0.01) in grain

consumption between germinated and non-germinated cereals were observed. The percent

increase in consumption of germinated paddy, pearl millet and ragi by both sexes of rats were

42.86 ± 37.49, 81.2 ± 27.16 and 79.59 ± 19.97, respectively. The results clearly indicate that

the germinated pulses were consumed in greater quantities than the non-germinated ones by the

soft-furred field rats. The maximum percentage increase in consumption was noticed in Bengal

gram (94.9 ± 10.39). The differences in consumption between the germinated and non-

germinated pulses were statistically significant (p < 0.01).

The Indian field mouse (M. booduga)

The Indian field mouse preferred germinated cereals over non-germinated cereals.

There were significant differences (p < 0.01) in the consumption of the germinated and non-

germinated cereals by both sexes. The overall mean percent increase in the consumption of

germinated cereals over non-germinated was 88.47 ± 12.18 for paddy, 94.3 ± 10.9 for pearl

millet and 85.09 ±17.83 for ragi. The preferential order of consumption of germinated pulses

by the mice were 33.96 ± 8.45 g/100 g/body weight for green gram 31.13 ± 6.08 g/100g body

weight for black gram, 38.82 ± 6.43 g/100g body weight for Bengal gram. There were

significant differences (p < 0.01) in consumption of germinated and non-germinated pulses by

the mice. The percent increase in consumption of germinated green gram over non-germinated,


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black gram and Bengal gram by both sexes of mice were 90.54 ± 11.24, 83.32 ± 20.72 and

89.12 ± 16.46, respectively.

The House rat (R. rattus)

Both sexes of the house rat preferred germinated cereals viz., paddy, pearl millet and

ragi over the non-germinated cereals. The difference between the germinated and non –

germinated cereals consumption by both sexes was found to be statistically significant (p <

0.01). The percent increase in consumption of germinated paddy, pearl millet and ragi by both

sexes of rat were 86.73 ± 18.99, 86.76 ± 13.19 and 83.71 ± 21.29, respectively. It is obvious

from the results that the germinated pulses were consumed in greater quantities than the non -

germinated ones by R. rattus. The difference between the germinated and non-germinated

pulses consumption by both sexes was found to be statistically significant (p < 0.01). The

percent increase in consumption of germinated green gram, black gram and bengal gram by

both sexes of R. rattus were 77.03 ± 25.08, 83.50 ± 19.85 and 97.50 ± 5.06, respectively.

It is understood from the results of the present investigation that all four species of

rodent pests preferred to consume more quantity of both germinated cereals and pulses over

non-germinated forms and the difference between them were statistically significant (p<0.01).

Earlier, Ahmad (1986) studied food preference of B. bengalensis and Rattus rattus

gangutrianus in the laboratory and observed that moist food bait was preferred over dry bait

(grains or flour). The results of the present study are consistent with the previous studies

(Parshad and Nijjar, 1995; Vanitha et al., 1997) in which the germinated grains were found to

be preferred to non-germinated grains. The present study was carried out on the three field

rodent pests one commensal rodent. However, Vanitha et al. (1997) conducted two-choice and


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multiple choice tests on only B. bengalensis and with three grains (paddy, pearl millet and

ragi). The ideal rodenticidal bait should be attractive to the target rodent species and

subsequently it must be induced to eat the bait by virtue of its enhanced flavour, taste and

palatability when compared to other available food (Sridhara and Srihari, 1986).

Earlier studies indicated that food preference of Indian rodents were not only species

specific (Jain et al., 1974), but the same species exhibited diverse preference in dissimilar

habitats (Vasanth Kumar and Khan, 1978). Rodents sample all kinds of food items and exhibit

marked preference for some baits and little preference for others (Barnett and Spencer, 1953;

Barnett, 1956). The results of the present study corroborate these earlier observations. The

choice of bait is influenced by its taste, particle size, texture and nutritional value (Khan, 1974;

Sahni, 1992). Murids in general preferred powdered, small sized and soft food over large and

hard grains (Kamal and Khan, 1977; Ramana and Sood, 1980; Parshad and Jindal, 1991; Sahni,

1992). The preference of germinated grains in the present investigation may be attributed to its

distinct flavour, taste, soft texture and palatability.

Germination has been identified as an inexpensive and effective technology for

improving the quality of legumes by enhancing their digestibility and increasing the content of

amino acids (Chang and Harrold 1988) and reducing the levels of anti-nutrients (Vidal-

Valverde et al., 2002). Sprouting has been reported to be associated with improvement in the

nutritive value of seeds (Badshah et al., 1991; Khattak et al., 2007; Sattar et al., 1995). Several

nutritive factors such as vitamin concentrations and bioavailability of trace elements and

minerals were reported to increase during germination (El-Adawy, 2002; Khattak et al., 2007).

Hence, it may be concluded that the reasons for the higher consumption of germinated cereals


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and pulses in the present study might be due to their flavour, taste, palatability, softness/texture

and nutritional value.

4.1.2 Multiple-choice tests


The mean body weight of both sexes of animals used for the experiments was 134.8 ±

17.16 g. One way analysis of variance based on food consumption by lesser bandicoot rats

revealed significant differences among different types of germinated grains (F5,294 = 16.694, p

= 0.000). Duncan’s multiple range tests on mean consumption of germinated grains showed

three subsets with highest preference for bengal gram, ragi, paddy and pearl millet. However,

the mean intake of the cereal grains differed significantly from green gram and black gram (p <

0.001). Thus, the preference for germinated grains by B. bengalensis was in the order of

Bengal gram ≈ ragi ≈ paddy ≈ pearl millet > green gram > black gram.

The soft-furred field rat (M. meltada)

Food consumption based on one way analysis of variance by both sexes of soft furred

field rats (body weight: mean ± S.D.: 39 ± 8 g) revealed significant differences among different

types of germinated grains (F5, 294 = 16.307, p = 0.000). M. meltada showed the highest

preference for germinated green gram. The mean consumption values of paddy, bengal gram

and pearl millet did not vary significantly as these formed a single subset in Duncan’s multiple

range tests. The analyses revealed ragi and black gram formed the third subset. The order of

food preference for M. meltada was green gram > paddy ≈ Bengal gram ≈ pearl millet > ragi ≈

black gram.


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The results of one way analysis of variance based on food consumption by both sexes

of mice (body weight: mean ± S.D.: 7.93 ± 0.78 g) indicated that there were significant

differences (p < 0.001) among different types of germinated grains (F5, 294 = 12.413, p = 0.000).

The Duncan’s multiple range test showed that out of six germinated grains, the experimental

animals preferred ragi, pearl millet and green gram (did not differ significantly) in greater

quantities to other grains. The animal’s second choice was bengal gram. Their least preferred

group of grains was paddy and black gram. Thus, the preferential order of intake of germinated

grains was ragi ≈ pearl millet ≈ green gram > bengal gram > paddy ≈ black gram.


House rats’ (both sexes) food consumption based one way analysis of variance revealed

significant differences among different types of germinated food offered (F5,294 = 14.360, p =

0.000). Duncan’s multiple range tests on mean consumption of germinated grains showed three

subsets with highest preference for pearl millet, bengal gram, ragi and paddy. However, the

mean intake of the afore-said grains differed significantly from green gram and black gram.

Thus, the preference of germinated grains by R. rattus were in the order of pearl millet ≈

bengal gram ≈ ragi ≈ paddy > green gram > black gram.

Three species of field Rodent pests (B. bengalensis, M. meltada and M. booduga)

The results of two way analysis of variance based on food consumption by both sexes

of all the three rodent species (pooled) indicated that there were significant differences among


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different types of germinated grains (F5, 894 = 13.539 p = 0.000). The Duncan’s multiple range

tests showed the mean magnitude of consumption of germinated grains by all the three species

of rodents got categorized into 4 subsets. The results revealed that the highest preference was

for green gram, pearl millet and ragi. The second, third and fourth subsets had paddy, bengal

gram and black gram, respectively. Hence, the preferential order of consumption of food by

the three species of rodents were found to be Green gram ≈ Pearl millet ≈ Ragi > Paddy >

Bengal gram > Black gram.

Although the highest preference by all the three species of field rodent pests was for

green gram, the other three grains i.e., pearl millet, ragi and paddy could also be recommended

as a bait base as these three grains were categorized into the first and second subset in the

Duncan’s multiple range tests. Further, by considering the cost of each of the four types of

grains, any one among them which is the cheapest, could be recommended to be used as a bait

base for the control of all the three species of rodents under field conditions. However, this

requires initially laboratory and later field based trials with rodenticides for making a final

recommendation.

As far as commensal rodents (R. rattus) are concerned the preferences of germinated

grains by them were in the order of pearl millet ≈ bengal gram ≈ ragi ≈ paddy. By considering

the cost of each of the first four types of grains, any one among them which is the cheapest,

could be recommended to be used as a bait base for the control of R. rattus under field

conditions. However, this requires initially laboratory and later field based trials with

rodenticides for making a final recommendation.


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Selection of the most appropriate bait formulation should ideally be made on the basis

of the most palatable formulation available. Although cost also weighs heavily in these

decisions, the primary objective is to eliminate the rodent infestation and failure is likely to

lead to increased long-term costs (Meyer, 1994).

In general, the choice of food may depend on the calorigenic value (Hausmann, 1932),

palatability (Young, 1946) and behavioural components (Barnett, 1956). Certain food items are

sometimes specifically selected because of the energy that they provide (Stenseth, 1977),

especially according to the content of proteins and carbohydrates which can be used (Smythe,

1976).

According to Krishnakumari, (1968) less nourishing foods are accepted if they are

“tasty” with flavours or soft texture. Food selection in rats is determined by factors such as

texture, odour and taste cues (Jackson, 1965; Bullard and Shumake, 1977). In the present study

the germinated grains would have provided soft texture and palatability and hence the rodents

might have preferred them.

4.1.3. Toxicity tests

Based on the results of the present study, the three germinated cereals such as paddy,

pearl millet and ragi, as they are less costlier than the pulses, were used as bait carrier for acute

(2% zinc phosphide) and chronic (bromadiolone 0.005%) toxicity studies and the results

thereof are presented.

Acute Toxicity Tests - No-choice tests:



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The poison consumption by the test animals was found to be high for bait prepared by

using germinated paddy (5.05±1.09 g) and minimum for pearl millet (1.83±0.53 g). The

highest intake of active ingredient (mg/kg) in the test animals were 903.57± 349.54 (Paddy

bait). Cent percent mortality of B. bengalensis was observed on feeding with 2% concentration

of zinc phosphide prepared by using all germinated cereals. Mean hours to death of

experimental animals were 11.80±3.91 (paddy), 4.05±0.55 (pearl millet) and 3.25±0.63 (ragi).


The poison consumption by the test animals was found to be high for bait prepared by

using germinated paddy (2.06±1.1 g) and low for ragi (1.42±0.68 g). The highest intake of

active ingredient (mg/kg) in the test animals was 779.28 ± 385.94 (Paddy bait). Hundred

percent mortality of M. meltada was observed on feeding with 1.5% concentration of zinc

phosphide prepared by using all germinated cereals. Mean hours to death of experimental

animals were 9.10±4.01 (paddy), 6.40±1.95 (pearl millet) and 6.80±2.34 (ragi).

The Indian Field mouse (M. booduga)

The highest poison consumption by the test animals could be observed for the bait

prepared by using germinated pearl millet (1.95±0.70 g) and lowest for ragi (0.66±0.31 g). The

maximum intake of active ingredient (mg/kg) in the test animals were 4049.19 ± 1349.11

(pearl millet bait). Hundred percent mortality of M. booduga was observed on feeding with

1.5% concentration of zinc phosphide prepared by using two germinated cereals viz., pearl

millet and ragi. Mean hours to death of experimental animals were 5.20±1.29 (pearl millet) and

4.60±1.02 (ragi).


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It is evident from the results that poison consumption by the test animals was found to

be high for the bait prepared by using germinated paddy (5.08±0.71 g) and less for ragi

(1.96±1.09 g). The intake of active ingredient (mg/kg) in the test animals was found to be high

in paddy bait (966.16± 4.57). Cent percent mortality of R. rattus was observed on feeding with

2% concentration of zinc phosphide prepared by using germinated cereals such as paddy and

pearl millet. Hours to death of experimental animals ranged between 4 and 12 hours (paddy;

pearl millet and ragi).

The results of the present study under no-choice tests indicate that cent percent

mortality of test animals (all four species of rodents) on feeding with zinc phosphide baits

mixed with germinated cereals, excepting M. booduga (90% mortality on feeding with zinc

phosphide in germinated paddy) and R. rattus (90% mortality on feeding with zinc phosphide

in germinated ragi).

Acute Toxicity Tests - Choice tests


The experimental animals were found to feed more quantity of plain bait than the

poison bait and the difference between them was found to be statistically significant (p < 0.05;

0.01; 0.001). The intake of active ingredient (mg/kg) was ranged from 0 to 773 in all the three

cereals used in the bait. Cent percent mortality of test animals could be observed only with the

animals fed on the bait prepared by using pearl millet and ragi. Hours to death of experimental

animals ranged between 4 and 18.


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The soft furred field rat (M. meltada)

The experimental animals were found to feed more quantity of poison bait than the

plain bait, however, the difference between them (paddy and ragi) was found to be statistically

insignificant (p > 0.05). The intake of active ingredient (mg/kg) was ranged from 0 to 1500 in

all the three cereals used in the bait. Cent percent mortality of test animals could be observed

only with the animals fed on the bait prepared by using paddy. Hours to death of experimental



Although the experimental animals were found to feed more quantity of poison bait

(paddy, pearl millet and ragi) than the plain bait, insignificant difference was observed between

them (p > 0.05). The intake of active ingredient (mg/kg) was ranged from 204 to 5343 in all the

three cereals used in the bait. Hundred percent mortality of test animals could be observed only

with the animals fed on the bait prepared by using pearl millet. Hours to death of experimental



The experimental animals were found to feed more quantity of plain bait than the

poison bait and the difference between them was found to be statistically significant (p < 0.05-

ragi; p < 0.01-pearl millet). The intake of active ingredient (mg/kg) was ranged from 235 to

1896 in all the three cereals used in the bait. Cent percent mortality of test animals could be

observed with the animals fed on the bait prepared by using all the three cereals. Hours to

death of experimental animals ranged between 4 and 14.


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Under choice tests, cent percent mortality of rodents were observed in B. bengalensis

(fed with germinated prearl millet and ragi bait), M. meltada (fed with germinated paddy bait),

M. booduga (fed with germinated prearl millet bait) and R. rattus (fed with germinated paddy,

prearl millet and ragi bait).

4.1.4 Chronic Toxicity Tests - No-choice tests:


The difference between the poison bait intake on first and second day was found to be

statistically significant for pearl millet and ragi (p<0.01). The highest intake of active

ingredient (mg/kg) in the test animals was 6.61±4.76 on second day of feeding (paddy bait).

Cent percent mortality of B. bengalensis was observed on feeding with 0.005% concentration

of bromadiolone prepared by using all germinated cereals. Mean days to death of experimental

animals were 5.20±2.52 (paddy), 2.10±0.56 (pearl millet) and 3.40±0.84 (ragi).


Significant difference could be observed between the poison bait intake on first and

second day for ragi (p<0.01). The highest intake of active ingredient (mg/kg) in the test

animals was 10.49±3.89 on second day of feeding (paddy bait). Cent percent mortality of M.

meltada was observed only on feeding with 0.005% concentration of bromadiolone prepared

by using germinated ragi bait. Mean days to death of experimental animals were 4.60±2.59

(paddy), 8.50±4.11 (pearl millet) and 8.20±2.29 (ragi) with an overall range of 1-14.


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The Indian Field mouse (M. booduga)

The highest poison consumption by the test animals could be observed for the bait

prepared by using germinated ragi (2.50±0.32 g) and lowest for paddy (1.68±0.26 g). The

difference between the poison bait intake on first and second day was found to be statistically

significant for paddy and pearl millet (p<0.01). The maximum consumption of active

ingredient (mg/kg) in the test animals was 14.89 ± 3.78 (paddy bait). Hundred percent

mortality of M. booduga was observed on feeding with 0.005% concentration of bromadiolone

prepared by using two germinated cereals viz., paddy and ragi. Mean days to death of

experimental animals were 3.60±1.57 (paddy) and 4.40±3.92 (ragi).


It is evident from the results that poison consumption by the test animals was found to

be high for the bait prepared by using germinated paddy (11.46±3.06 g) and less for ragi

(7.18±1.02 g). The observed difference between the poison bait intake on first and second day

was found to be statistically significant for paddy (p<0.05), pearl millet and ragi (p<0.001).

The ingestion of active ingredient (mg/kg) in the test animals was found to be high in paddy

bait (8.19± 3.25). However, cent percent mortality of R. rattus was not observed on feeding

with 0.005% concentration of bromadiolone prepared by using germinated paddy. The baits

prepared by using germinated cereals such as pearl millet and ragi yielded hundred percent

mortality. Days to death of experimental animals ranged between 3 and 14 (paddy; pearl millet

and ragi).

In the no-choice tests, cent percent mortality of rodents could be observed in B.

bengalensis (fed with all germinated cereals bait), M. meltda (fed with germinated ragi bait),


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M. booduga (fed with germinated paddy and ragi bait) and R. rattus (fed with germinated

prearl millet and ragi bait).

Chronic Toxicity Tests - Choice tests


The experimental animals were found to feed more quantity of poison bait than the

plain bait and the difference between them was found to be statistically significant (p < 0.05;

0.01; 0.001). The intake of active ingredient (mg/kg) in the dead rodents was ranged from 0.25

to 5.88 and in the survived animals from 0.25 to 3.60 in all the three cereals used in the bait. A

maximum of ninety percent mortality of test animals could be observed only with the animals

fed on the bait prepared by using pearl millet and ragi. Days to death of experimental animals

ranged between 1 and 11.

The soft furred field rat (M. meltada)

The experimental animals were found to feed significantly more quantity of poison bait

prepared in germinated ragi than the plain bait (p<0.05%) on both days of feeding. The intake

of active ingredient (mg/kg) was ranged from 0.31 to 8.55 in the dead rodents in all the three

cereals used in the bait. Cent percent mortality of test animals could be observed only with the

animals fed on the bait prepared by using pearl millet. Days to death of experimental animals

ranged between 2 and 14.


Insignificant difference was observed between the consumption of poison prepared in

all the cereals and plain bait (p > 0.05) excepting on the first day germinated paddy bait


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consumption (p<0.01) and on the second day germinated pearl millet (p<0.001) bait

consumption. The intake of active ingredient (mg/kg) was ranged from 0.43 to 17.81 in the

dead animals in all the three cereals used in the bait. The observed mortality was 80% for

paddy, 70% each for pearl millet and ragi. Days to death of experimental animals ranged

between 1 and 11.


Definite trend could not be seen in the poison and plain bait consumption by the test

animals and the difference between them was found to be statistically not significant (p >

0.05). The intake of active ingredient (mg/kg) in the dead animals was ranged from 0.73 to

8.69 in all the three cereals used in the bait. The pearl millet and ragi bait produced a maximum

of 90% mortality among the house rats. The paddy bait resulted in sixty percent mortality of

test animals. Days to death of experimental animals ranged between 2 and 14.

The results of the present study that the cent percent mortality of test animals were

observed only with M. meltada fed with bromadiolone bait mixed with germinated pearl millet

under choice tests.

It is evident from this study that zinc phosphide (2%) mixed with germinated paddy

caused 100% mortality in R. rattus, a short time to mortality, and showed adequately high bait

acceptability. In contrast, the bromadiolone (0.005%) mixed with germinated paddy caused

lower levels of mortality in 2-choice tests, longer time to mortality, but higher bait

acceptability. The results clearly indicated that putting the poisons in the germinated grain has

induced R. rattus to consume greater quantities of bait perhaps due to the bait carrier’s

palatability and texture. Therefore, germinated paddy may be recommended as a bait carrier for


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both zinc phosphide (2%) and bromadiolone (0.005%) poisons for the control of R. rattus.

However, of the two rodenticides, zinc phosphide at 2% concentration may be given priority

over bromadiolone (0.005%) for the control of R. rattus.

Parshad et al. (1985) have reported that in the assessment of brodifacoum poison bait

palatability in choice feeding test, rodent species (namely M. meltada, T. indica and B.

bengalensis) consumed significantly less poison bait than the plain alternative. Similar results

have been reported for Mus musculus (Redfern et al., 1976), T. indica and M. hurrianae

(Mathur and Prakash, 1981). The results of the present study corroborate these earlier results.

4.2 Field evaluation

Based on laboratory evaluation results on acute and chronic toxicity studies, the three

germinated cereals were further evaluated under field conditions in the chosen crop fields

(Samba season paddy crop, Black gram, Sunflower and Cotton) in order to know their efficacy

in bringing down the population of rodents and their depredation to crops at pre-harvest stages.

Samba season Paddy crop (Germinated paddy as a bait carrier)

Three species of rodent pests viz., B. bengalensis, M. meltada and M. booduga

inhibited the crop fields. Of them, in general, B. bengalensis was dominant species followed by

M. meltada and M. booduga. The difference between the pre and post treatment population of

rodents in the zinc phosphide and bromadiolone treated fields in both developmental stages of

the crop was statistically significant (p<0.05; p<0.01; p<0.001) indicating that the utilized

rodenticides apparently reduced all the three species of rodent population. The percentage of

rodent mortality observed in the zinc phosphide treated fields was 68 (Boot leaf stage) and 48


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(Maturation stage). The bromadiolone treated fields had 56% and 69% reduction in population

of rodent pests at boot leaf and maturation stages of the crop, respectively.

Samba season Paddy crop (Germinated pearl millet as a bait carrier)

Both significant (p<0.05; p<0.01; p<0.001) and insignificant (p>0.05) differences could

be observed between the pre and post treatment population of rodents in the zinc phosphide

and bromadiolone treated fields in both developmental stages of the crop. The percentage of

rodent mortality observed in the zinc phosphide treated fields was 60 (Boot leaf stage) and 65

(Maturation stage). The bromadiolone treated fields had 45% and 44% reduction in population

of rodent pests at boot leaf and maturation stages of the crop, respectively.

Samba season Paddy crop (Germinated ragi as a bait carrier)

The difference between the pre and post treatment population of rodents such as B.

bengalensis and M. booduga in the zinc phosphide and bromadiolone treated fields in both

developmental stages of the crop was statistically significant (p<0.05; p<0.01). The percentage

of rodent mortality observed in the zinc phosphide treated fields was found to be 60 for Boot

leaf stage and 69 for Maturation stage. The bromadiolone treated fields reduced 57% and 69%

population of rodent pests at boot leaf and maturation stages of the crop, respectively.

Earlier, Sivaprakasam (1988), Baskaran et al. (1995), Kanakasabai et al. (1995) and

Neelanarayanan (1997; 2008) have already reported the occurrence of these three species of

rodents in different crop fields of Cauvery delta, Tamil Nadu.


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Samba season Paddy crop (Tiller damage reduction at boot leaf stage)

Both rodenticides baits (prepared by using pearl millet and ragi) yielded significant

reduction in rodent depredation in boot leaf developmental stage of the crop (p<0.05; p<0.01).

It is apparent from the results that the percentage of rodent damage reduction / ha when

compared to control fields was observed to be 74 (paddy), 81 (pearl millet) and 30 (ragi) in the

zinc phosphide treated fields; 71 (paddy), 59 (pearl millet) and 49 (ragi) in the bromaddiolone

treated fields.

Samba season Paddy crop (Tiller damage reduction at maturation stage)

In both rodenticides’ baits (prepared by using pearl millet and ragi) used fields

significant damage reduction by rodents at maturation stage of the crop was observed (p<0.05).

It is obvious from the results that the percentage of rodent damage reduction / ha when

compared to control fields were to the tune of 82 (paddy), 84 (pearl millet) and 64 (ragi) in the

zinc phosphide treated fields; 83 (paddy), 83 (pearl millet) and 72 (ragi) in the bromaddiolone

treated fields.

Samba season paddy crop (Cost-benefit ratio of rodenticides)

The difference in the paddy grain yield between control and two rodenticides treated

fields was found to be statistically significant (P < 0.01). Of the two rodenticides used in the

present study for the control of rodent pests, the cost–benefit ratio favoured the zinc phosphide

(1:9 for paddy; 1:11 for pearl millet and 1:4 for ragi) when compared to bromadiolone (1:2 for

paddy; 1:4 for pearl millet and 1:2 for ragi). Thus, it may be suggested that the zinc phosphide

at 2% concentration may be recommended to farming community for adoption in order to


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reduce the tiller damage by rodent pests and consequent yield increase. Further, the germinated

cereals may be suggested as poison bait carrier for rodenticides and the same may be included

in the rodent control programmes of our country. From the results it is evident that application

of both rodenticides did not yield cent percent mortality in the crop field situations. Therefore,

the residual population of rodents in the crop fields (after treatment of acute rodenticide with

any one of the germinated cereals as a bait carrier) may be treated with chronic rodenticide bait

mixed in any one of the germinated cereals and vice versa.

In Pakistan, rat damage to rice is a principal reason why agricultural development has

not spread to some regions (Greaves et al., 1977; Fulk and Akhtar, 1981); B. bengalensis is the

main culprit. Like other species, it cuts tillers but losses are compounded by its habit of storing

food in its burrows. Other common rice-field species are N. indica, M. meltada and Mus spp.,

which appear to eat grain but do not cut down tillers. B. bengalensis responds to the growth of

rice by increasing reproduction (Smiet et al., 1980) in a similar way to R. argentiventer, but M.

meltada maintains a more constant rate, suggesting its presence is less dependent on the rice.

Tiller damage ranged from 10 to 25% in a series of studies in fields not considered especially

heavily infested. In a population of rats of 55 ha-1, 60% of which were B. bengalensis,

damage to tillers indicated yield losses of 2 - 43% (mean 19 %) (Fulk and Akhtar, 1981), and

the application of rat control measures gave a mean yield increase of 21.4% (with only 3.4%

evident tiller damage) (Greaves et al, 1977).

If a lethal dose is not ingested and the rodent recovers, it may develop poison bait

shyness, as well as site shyness that significantly reduce its subsequent susceptibility to any

rodenticide treatments. Achieving 100% elimination of a rodent population using fast-acting

rodenticides is therefore impossible.


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A rodenticide must have three; ideal attributes viz., toxicity, acceptability and safety in

use. The acute poisons are better for giving a quick knockdown, but they have little selectivity

and poor efficacy. They require pre-baiting and rodents exhibit bait shyness for them.

Anticoagulants have advantage as far as efficacy and safety are concerned, but they are slow in

action, more laborious and, hence, treatment cost is comparatively high (Brooks and Rowe

1979; Fitzwater and Prakash 1989; Greaves 1982; Prakash and Mathur, 1987). The results of

the present study are agreeable with these earlier observations. Bromadiolone is generally used

in baits against rats and house mice at 0.005% and was effective in the field against Welsh

resistant rats (Richards, 1981).

Black gram crop (Germinated paddy as a bait carrier)

The following three species of rodent pests viz., B. bengalensis, M. meltada and M.

booduga inhibited the crop fields. Of these, in general, B. bengalensis was dominant species

followed by M. meltada and M. booduga. It is apparent from the results that the population of

B. bengalensis was brought down significantly in both zinc phosphide and bromadiolone

treated fields in both developmental stages of the crop (p<0.05; p<0.01). The percentage of

rodent mortality observed in the zinc phosphide treated fields was 69 for pod formation stage

and 56 for pod maturation stage. The bromadiolone treated fields had 72% and 58% reduction

in population of rodent pests at pod formation and pod maturation stages of the crop,

respectively.

Black gram crop (Germinated paddy as a bait carrier – Pod damage reduction)

Both rodenticides significantly reduced pod damage by rodents in both developmental

stages of the crop (p<0.05%). Zinc phosphide treatment reduced rodent depredation to the tune


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of 67% and 81% during pod formation and pod maturation stages, respectively. Rodent

damage reduction was observed to the tune of 63% and 78% during pod formation and pod

maturation stages, respectively in the bromadiolone treated crop fields.

Black gram crop (Cost-benefit ratio of rodenticides)

The difference in the black gram pod yield between control and two rodenticides

treated fields was found to be statistically significant (P < 0.01). The cost of rodent control

operation /ha was Rs.180/- for Zinc phosphide and Rs. 376/- for bromadiolone. The cost-

benefit ratio for this crop was 1:9 for zinc phosphide treated fields and 1:2.50 for bromadiolone

treated fields. Hence, it may be concluded that the zinc phosphide is an economic and effective

rodenticide when compared to bromadiolone. The utilization of zinc phosphide at 2%

concentration with germinated paddy as a bait carrier may be recommended to the farming

community for adoption in their black gram crop fields. Further research work is required on

the efficacy of the other two germinated grains such as pearl millet and ragi as a bait base for

these rodenticides in the black gram crop fields.

Sunflower crop (Germinated paddy as a bait carrier)

Sunflower crop fields were inhabited by B. bengalensis, M. meltada and M. booduga.

Of these, in general, population of B. bengalensis dominated over the other two species. It is

apparent from the results that the population of B. bengalensis, M. meltada and M. booduga

during pre treatment were brought down significantly in the bromadiolone treated fields in both

developmental stages of the crop (p<0.05; p<0.01; p<0.001), however no such difference could

be observed in zinc phosphide treated fields (p>0.05). The percentage of rodent mortality

observed in the zinc phosphide treated fields was 59 for pod formation stage and 42 for pod


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maturation stage. The bromadiolone treated fields had 42% and 46% reduction in population of

rodent pests at pod formation and pod maturation stages of the crop, respectively.

Sunflower crop (Germinated paddy as a bait carrier – Pod damage

reduction)

Both rodenticides significantly reduced pod damage by rodents in the pod maturation

stage of the crop (p<0.05; p<0.01). The rodent damage reduction was to the tune of 58% and

53% in zinc phosphide and bromadiolone treated fields, respectively.

Sunflower crop (Cost-benefit ratio of rodenticides)

Significant differences were observed in the sunflower pod yield between control and two

rodenticides treated fields (P < 0.001). The cost of rodent control operation /ha was Rs.180/-

for zinc phosphide and Rs. 376/- for bromadiolone. The cost-benefit ratio for this crop was 1:2

for zinc phosphide treated fields and 1:0.50 for bromadiolone treated fields. The difference in

cost-benefit ratio is narrow and hence, it may be concluded that the any one of these two

rodenticides with germinated paddy as a bait carrier may be recommended to the farming

community for adoption in their sunflower crop fields. However, further research work is need

to find out the efficacy of the other two germinated grains such as pearl millet and ragi as a bait

base for these rodenticides in the sunflower crop fields.

Cotton crop (Germinated paddy as a bait carrier)

The following four species of rodent pests viz., B. bengalensis, M. meltada, M.

booduga and T. indica were observed in the crop fields. Among them, the B. bengalensis was


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dominant species of this crop field. It is obvious from the results that the population of B.

bengalensis and M. meltada were reduced significantly in zinc phosphide treated fields during

second maturation stage of the crop (p<0.05; p<0.01). The percentage of rodent mortality

observed in the zinc phosphide treated fields was 62 for unripe boll stage and 57 for second

maturation stage. The bromadiolone treated fields had 57% and 65% reduction in population of

rodent pests at unripe boll and second maturation stage of the crop, respectively.

Cotton crop (Germinated paddy as a bait carrier – boll damage reduction)

Both rodenticides application in the cotton crop fields significantly reduced boll

damage by rodents in both developmental stages of the crop (p<0.05%). Zinc phosphide

treatment reduced rodent depredation to the tune of 65% and 75% during unripe boll and

second maturation stages, respectively. Rodent damage reduction was observed to the tune of

67% and 74% during unripe boll and second maturation stages, respectively in the

bromadiolone treated crop fields.

Cotton crop (Cost-benefit ratio of rodenticides)

The difference in the cotton yield between control and two rodenticides treated fields

was found to be statistically insignificant (P > 0.05). The cost of rodent control operation/ha

was Rs.180/- for Zinc phosphide and Rs. 376/- for bromadiolone. The cost-benefit ratio for this

crop was 1:7 for zinc phosphide treated fields and 1:4 for bromadiolone treated fields. Hence, it

may be concluded that the zinc phosphide is comparatively an economic and effective

rodenticide when compared to bromadiolone. The utilization of zinc phosphide at 2%

concentration with germinated paddy as a bait carrier may be recommended to the farming

community for adoption in their cotton crop fields. Further research work is indispensable to


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understand on the efficacy of the other two germinated grains such as pearl millet and ragi as a

bait base for these rodenticides in the cotton crop fields.

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