EFFECTIVENESS OF THE TRIPLE-LAYER HERMETIC BAG IN CONTROLLING PROSTEPHANUS TUNCATUS (HORN) (COLEOPTERA: BOSTRICHIDAE) AND SITOPHILUS ZEAMAIS (MOT.) (COLEOPTERA: CURCULIONIDAE) ON STORED MAIZE

BY

ANANKWARE PAARECHUGA JACOB

SUPERVISORS: PROF. D. OBENG-OFORI, PROF. K. AFREH-NUAMAH & DR. FATUNBI OLUWOLE.

OUTLINE OF PRESENTATIONINTRODUCTIONJUSTIFICATIONOBJECTIVESFORMS OF HERMERTIC STORAGEMATERIALS AND METHODSLABORATORY EXPERIMENTSRESULTS AND DISCUSSIONCONCLUSIONS AND RECOMMENDATIONS

INTRODUCTION Maize (Zea mais L, from Spanish: maíz after Taíno mahiz) is a

common name for the cereal grass widely grown for food and livestock fodder (Faostat, 2009).

It ranks with wheat and rice as one of the world’s chief grain crops (Anon, 2012). The global production of maize is estimated to be 817 million metric tons annually (Faostat, 2009).

In Sub-Saharan Africa, maize is one of the most important grain staples for agricultural income and caloric intake, accounting for nearly 20% of the plant-based food supply (Jones et al., 2011).

 The current value of maize production in Ghana is approximately US $

400,000,000 a year.

Post-harvest grain storage in Ghana and other developing countries of the world is a major constraint.

INTRODUCTION CONT’DStored maize is attacked by 20 different species of insect pests including the

maize weevil, Sitophilus zeamais (Mot) (Coleoptera: Curculionidae) and the Larger Grain Borer (LGB), Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae).

 Insect pest damage to stored grain results in major economic losses to farmers throughout the world (Obeng-Ofori, 2008).

Millions of rural farmers in Africa produce maize, but completely lack access to post-harvest storage technology. This situation forces small producers to sell their maize at the time of harvest, with the disadvantage of low market prices.

To minimize post-harvest losses of cereals, the Forum for Agricultural Research in Africa (FARA) has developed programs to promote the use of appropriate and effective technologies to support small scale farmers’ in sub-Saharan Africa.

JUSTIFICATIONHermetic storage in metal drums is known to provide good control of all

storage insect pests including the Larger Grain Borer (Giles and Leon, 1974).

However, the high initial cost of drums in some areas and the tendency for

people to use them for other purposes such as water storage limits their use in rural grain storage. Plastic bags provide a cheaper alternative but insects tend to perforate the bags, even if the grain is fumigated initially.

Triple-layer hermetic bags have been used to control cowpea bruchids, Callosobruchus maculatus (F) (Murdock et al., 2003) on cowpea, Dinoderus spp and P. truncatus on cassava chips (Hell et al., 2010) with very promising results.

However, little is known about the effect of the triple layer bags on LGB in stored maize, hence, the need for this research.

OBJECTIVESThe goal of the study was to evaluate the effectiveness of the multi-layer

hermetic bags for the protection of stored maize against infestation by S. zeamais and P. truncatus.

Specific objectives:

Determine the effectiveness of hermetic triple bagging in controlling P. truncatus and S. zeamais;

Assess the percentage viability of the varieties of maize after hermetic storage;

Determine the period for total depletion of oxygen in the triple bags;

Assess the socio-economic benefit of the triple-layer hermetic bag storage technology.

Figure 1: Adult P. truncatus (mag. x100).

Source: Hodges R.J.

Figure 2: Larva of P. truncatusSource: Researcher.

Figure 3: Adult S. zeamais

Source: Maribet and Aurea Central Luzon State University, Philippines.

Source: www.infonet-biovision.org.

HERMETIC STORAGE, ORIGIN & TYPES

What is hermetic storage?

We have three types of hermetic storage, these are;

a) Organic-Hermetic storage

b) Vacuum-Hermetic Fumigation(V-HF)

c) Gas-Hermetic Fumigation (G-HF)

These methods create a low oxygen modified atmosphere which results in 100 % insect mortality of all life stages in a few days to two weeks as well as preventing mold development.

FORMS OF HERMETIC STORAGE

Mega cocoon

TranSafeliner GrainPro Bunker

150 tonne cocoonCocoon beign ffllled

Outdoor storage cocoonTriple-layer

hermetic bag

MATERIALS AND METHODS

Experimental site

Source of maize varieties

Moisture content of maize used in the study

Characteristics of the triple layer hermetic bags used

Culturing of experimental insects

LABORATORY EXPERIMENTSEffectiveness of the triple-layer bag against P. truncatus and S. zeamais

This experiment compared the effectiveness of the triple-layer hermetic bag with two other conventional storage.

Three maize varieties (Obatampa, Abrodenkye and kamangkpong) were divided into three groups, that is, A, B and C, respectively.

Each of these maize samples weighing about 5 kg was put into each triple layer hermetic bag and replicated 3 times.

Fifty (50) unsexed LGBs from the culture were introduced (using camels hair brush) into each of the maize samples.

DETERMINING % DAMAGE, WEIGHT LOSS, MOISTURE CONTENT, AND % GERMINATION

Two different sets of experiments were conducted; each for P. truncatus and S. zeamais.

Each set was sampled after one month (4 weeks), two (8 weeks), three (12 weeks) up to the sixth (24 weeks) month of storage.

At each sampling occasion, the contents of each experimental bag were sieved using a set of USA standard sieve series (Nos. 10 to 35).

Adult insects and grains were collected separately.

After sieving, each grain sample was divided into sub-samples by the cone and quarter method.

These sub-samples were used for the determination of the moisture content, percentage damage, weight loss and the germination potential.

METHODOLOGY CON’T

Determination of percentage damage

The percentage damage was calculated using the formula described by Adams and Schulten (1978), and Duna (2003):

(%) Damaged grains =

ASSESSMENT OF WEIGHT LOSSMaize grain loss bioassay was conducted to determine the damage caused

by P. truncatus and S. zeamais.

The Thousand grain mass (TGM) method described by Boxal (1986) was used to determine dry-weight loss.

The TGM was calculated using the formula:

TGM =

% (weight loss)=

WEIGHT LOSS ASSESSMENT CON’T

Plate 1: A cross-section of the set up after 3 months

Plate 2: Effect of LGB on the polypropylene bags after 6 months

Plate 3: Effect of LGB on the Triple-layer hermetic bags after six months  

Plate 4: Effect of LGB on jute bag after 6 months

DETERMINING VIABILITY AND O2 DEPLETION

The seed viability test was conducted in the laboratory and in the field (using Petri dishes and by sowing in the soil) before and after six months storage.

The viability or germination potential was calculated using the formula:

Germination potential (Gp) =

Where Ng = number of germinated seeds

Nt = total number of seeds in the sample or initial number of seeds in sample

Oxygen depletion was determined with the aid of a GrianPro oxygen analyzer, butterfly needles and Epoxy glue.

SOCIO-ECONOMIC BENEFIT ANALYSIS

This was conducted using the cost-benefit ratio (BCR). BCR is simply the ratio of present worth of project benefits to present worth of project costs.

Mathematically,

B=Benefit in each year of the project

C= Cost in each year of the project

r= Interest (discount) rate

t= 1, 2…n (time of the project life in years)

n= Number of years in the project

Cost (GHȼ) of storage grain loss =

Analysis of results Microsoft Excel 4.0 package was used for all statistical calculations. Where necessary, the data

was transformed using either: (a) for insect count: ×1 = log10 (×) for insect population

(b) for percentages: ×1 = arcsine (P)1/2, where P = ( Brosius, 1988; Lauter and Pincus, 1989).

 

 

RESULTS AND DISCUSSION

Grain damage and weight loss

Hm Poly Jute0

5

10

15

20

25

30

P. truncatus S. zeamais

% W

eigh

t lo

ss

Bag

Figure 10: Percentage weight loss by P. truncatus and S. zeamais on maize stored in 3 different bags.

1 2 3 4 5 60

10

20

30

40

50

60

PolyHmJute

% D

amag

e

Duration (Months)

Figure 11: Grain damage caused by P. truncatus and S. zeamais to maize stored in 3 different containers for varying periods of storage.

MOISTURE CONTENT AND PERCENTAGE GERMINATION

1 2 3 4 5 602468

1012141618

HmJutePoly

Moi

stu

re c

onte

nt

(%)

Sorage duration (months)

Figure 14: Moisture content in the various bags during a 6 month period. 

Hm Poly Jute0

10

20

30

40

50

60

70

P. truncatusS. zeamaisG

erm

inat

ion

(%

)

Bag

Figure 20: Percentage germination of insect infested grain in the various bags

NUMBER OF LIVE INSECTS

Hm Poly Jute0

100

200

300

400

500

600

700

800

900

P. truncatus S. zeamais

N

o. o

f liv

e in

sect

s/k

g gr

ain

Bag

Figure 15: Mean number of live insects after 6 months of maize storage in various bags

1 2 3 4 5 60

50

100

150

200

250

300

350

400

450

P. truncatus, AbroP. truncatus, ObaP. truncatus, KaS. zeamais, AbroS. zeamais, ObaS. zeamais, KaN

o. o

f liv

e in

sect

s/k

g gr

ain

Duration (Months)

Figure 17: Mean number of live insects per maize variety stored for six months.

 DAILY TEMPERATURE, DEW POINT AND RELATIVE HUMIDITY

0 2 4 6 8 10 12 14 16 18 20 220

5

10

15

20

25

P. truncatusS. zeamais

O2 D

eple

tion

rat

e (%

)

Duration of storage (Days)

Figure 23: Oxygen depletion rates in maize infested with P. truncatus and S. zeamais and stored in a triple-layer hermetic bag

CONCLUSION AND RECOMMENDATIONSAll three maize varieties were susceptible to P. truncatus and S. zeamais.

It is possible to protect maize against P. truncatus and S. zeamias using the triple-layer hermetic bag.

The triple-layer hermetic bag is more cost-effective than the jute and polypropylene bags.

Temperature, dew point and relative humidity variations are minimal in triple-layer hermetic bags than in conventional storage.

Water ingress from the surrounding environment is almost absent in triple-layer hermetic bags while jute and polypropylene bags cannot prevent that.

The triple-layer hermetic bag storage could not totally deplete the O2; the least O2 content obtained was 5% after 20 days.

CONCLUSION AND RECOMMENDATIONS CONT’D

The triple-layer hermetic bag has the potential to control P. truncatus and S. zeamais in stored grain.

 

RecommendationsFurther studies should include investigations on effects of climate and

increased temperatures on the effectiveness and longevity of the three layer hermetic bags.

The development of biodegradable triple-layer bags that combines different defense mechanisms.

The high density polypropylene (HDP) bags should be the preferred if available since they have least oxygen permeability.

Knowledge gaps need to be filled to support farmers’ decision in the choice of appropriate storage systems.