Evaluation of the Efficiency of Aqueous Extact of Neem Fruits on Insect Pest of Rice in Rice Agroecosystem of Maga in the Far North Region of Cameroon

The chemical fight against insects pest causes many problems on the biodiversity of ecosystems, destabilizes the trophic level of the ecosystem and has harmful effects on the on health human. Mean while the biological fight using plants extractions can equally play the same role of killing pest, reason why the present study which was carried out in the irrigated perimeters of Maga in the Far North region of Cameroon, have as principal objective to evaluate the aqueous extraction of neem fruit on the insects pest of rice. The specific objectives were to know the biological diversity of insect pest in the irrigated perimeters of Maga, and their repartitioning in the phenological stages, again, to see the effects of the aqueous extractions of the neem fruits on the insects pest per variety and in function of the phenological stages, also to evaluate the damages cause by insects pest during the talling stage in function of the varieties, finally, to evaluate loss cause by the insects pest. The study was made on two rice varieties which were IR46 and NERICA3 in a split plot disposition. The capturing of the insects was done with the help of a sweep net and the identification of the species was done with the help of an entomological buttle, the identification key of insects by Heinrich (1993), Hill (1983), Heinrichs and Barrion (2004) and the families recognition keys by Delvare and Aberlenc (1989).The method of Breniere permited the estimation of loss of output at the talling and harvesting stages of rice caused by the insect pest. The analysis of variance of the result was done using SPSS 20. In the class of insects, twenty two species of insects fall in twenty families divided in seven orders were collected. Among the captured insects, we investigated fourteen insects which were pest. The biological fight have shown an effectiveness in the nursery, talling, and a positive and non negligible effects on the reduction insects pest in the heading and maturation stages and thus has permitted the reduction of damages from insects on the rice plants.


INTRODUCTION 1. Context
Rice (Oryza sativa L.) constitude the most feed aliment in the whole world (Guigaz, 2002). According to FAO, world rice consomation soppose to has risen between 2012 and 2022 at least 1% per year against 1,7% for the years 90-2010. The average consomation per habitat soppose to have increase slightly to 58, 2 kg per person (FAO, 2013). In Africa, rice is produced and consium in 39  Faced with this situation, the populations of these regions are forced to imports in order to meet their needs. While the world paddy rice production is 745709788 tonnes on a surface of 1 647 216 663 ha (FAO, 2013) thus a yield of 4 527,1 kg/ha, Africa has a production of 29

Problem
Improvement and security of agricultural production and the difficulties associated with the insect attacks have pushed researchers and farmers towards the use of synthesis chemical insecticide. But these insecticides have proved its ineffectiveness against certain insect pests, according to Brevault and al. (2007), the whitefly, Bemisia tabaci (Gennadius), and aphid, Aphis gossypii have acquired resistance to organophosphate insecticides characters in Cameroon. In addition these pesticides are extremely stable and persistent in the environment, accumulate in living organisms and food chains, are toxic to humans and animals and cause chronic effects such as dysfunction at the level of the reproductive and immune and endocrine systems, as well as cancers, and are propagated in the environment over long distances to remote locations of the sources of emissions (IOMC, 2002).
Yet there are alternatives to the use of insecticides such as substances of plant origin. Azadirachta indica Juss is a tree in the Meliaceae family, native to India (Formad environment, 2013). It is used and known for its insecticide, fungal properties and medicinal (Huang and al., 1995;Valladares and al., 1999;Carpinella and al., 2002). This tree is present in the far North region of Cameroon, however the use of the aqueous extract of the fruit has never been experienced on insect pest of rice. Yet the work of Kosma and al., (2010) on the properties chemical seeds of neem on nematodes of plantain were effective more, the work of Djile, (2010) bode on the use of neem seed extracts have shown efficiency of the cake of neem on fungal diseases of Cowpea and still the experimental work of Abu Togola, (2010) using oil of neem on insect pests of rice shown very useful.
In view of all this knowing the properties of the neem tree, it is necessary before use of this plant against insect pests, to assess the effectiveness of these substances on insects before using, to see what variety is more efficient, what is its economic significance on two main varieties of rice grown in the far north region of Cameroon in an agroecosystem finally, to see the variety that is best suited for beneficial conclusions can be drawn for food security.

Objectives
The main objective is to assess the effectiveness of the aqueous extract of fruit of neem on insect pests of rice in the rice-growing perimeter of Maga, specifically our work ambition are: -Know the biological diversity of insect pests in the irrigated perimeter of Maga and their distribution by phenological stage.

Cultivars of rice
The cultivar of rice used in this study will be Oryza sp. The two varieties of rice used are IR46 and Nerica 3.

The fruits of neem
Neem fruits have been picked up in the town of Maga at the level of the premises of the SEMRY, the collected fruits are those found in the ground below the neem tree, and then they are dried.

Experimental dispositive
Experimental design was a split plot consists of three blocks, divided into basic plots of 7 m x 4 m; in each block, two types of treatments (biological control and control) were applied on two varieties of rice (IR 46 and NERICA 3) with three replicates. The dimensions of each basic plot are 7 m x 4 m, between the basic plots are walkways of 1 m wide and between blocks the aisles of 2 m wide.

Materials for collections of insects
The collection equipment used here is the sweep net. The "sweep net" is a net that is used to collect the insects that live on plants (Goldstyn, 2003). There are different types of nets for the capturing of flight, capture to the ground and mowing, but all consist of three parts: a circle (or RIM), a Pocket (or purse) and a handle. These three parts can be adapted to specific hunts types, for example in the water or in the air. The net used in this study is characterized by the length of his pocket which is approximately twice the diameter of the circle. The diameter of the circle is 40 cm, Pocket about 80 cm and the handle is long (more than 1 m). The Pocket quite finemesh fabric, offers little resistance to air. The net is used to mow by Rapids lateral movements of comes and goes. Insects will be caught using net "sweep net" depending on the case at the rate of 25 double sweeps (50 sweeps) on each of two (02) perpendicular medians in each plot during periods of collections .

ethods 2.1. Obtention of the aqueous extract of neem fruit
The principle of obtaining extracts from seeds of the neem tree has been described since 1975 by Jacobson and Kumar (2003). Extracts from seeds of the neem tree are formed by powder, meal, aqueous and alcoholic seed extracts. The extraction of these substances from seeds of the neem tree can be done in various ways, mechanical and basis of alcoholic compounds such as ethanol and methanol. This principle will be amended to adapt it to our context which is the fruit of aqueous neem extraction

Aqueous extract of the fruit of neem
The fruits of neemier picked up are dried at a temperature of 40 ° C, for two days. We take a quantity of 2 kg of the fruit, grinds it, envelope in a canvas. The canvas is immersed in a container of 5 liter water, immersion lasts one night. Removing water canvas and spins its contents, finally we add the liquid water to have 15 litre of water then we sieve. The aqueous solution obtained is the extract. Before use is added to a wetting agent such as the detergent previously dissolved in water of 5 to 10 mg and everything is thoroughly mixed. The prepared solution is used directly in the following hours.

Application of the aqueous extract of fruit of neem
The application of aqueous extract of seed by spraying on rice plants is performed during an interval of two weeks after the nursery of plants until the last collection of insects in maturity or 0.84 per litre for 28 m 2.

Method of collecting insects 2.4.1. Rhythm of the sampling of insects after the application of the aqueous extract of the fruit of neem by sweep net
On each elementary plot regardless of the treatment applied to the basic plot, the insects will be caught using net "sweep net" depending on the case at the rate of 25 double sweeps (50 sweeps) on each of the parcels elementary so as to cover all the surface by positioning itself on two (02) perpendicular medians in each plot at two week intervals from the fifteenth day after planting or transplanting.

Period of collection of insects
The sampling was carried out on the following four phenological stages of rice: nursery, talling, inflorescence and seed maturation.

Technique of observation and identification of specimens
The keys for the identification of insects from Heinrich (1993), Hill (1983), Heinrichs and Delvare (2004) and the recognition of Delvare and Abbasi families of key (1989) will be used to identify different collected species.

Measurements and data analysis
The larvae, pupae and adults will be counted as the representatives of the strength of the species on each variety, according to variety, from the application of the extract of neem and untreated plots. This allowed us to classify various specimens collected in different orders, families, genera and species and then determine the number of each of these specimens compared with the phenological stages of the plant.
The data used was the Excel software and submitted to statistical analysis using the software SPSS 20. Averages will be compared using ANOVA test to the 5% threshold.

Assessment of losses due to insects at harvest time
The methodology for this evaluation is that of Breniere (1982).
Fifteen days before the beginning of the harvest, we take 20 clumps of rice on each elementary parcel to examine. Sampling is done randomly. To do this, we simply stretch a rope with knots spaced all across the rice fields of 2 m, removed the nearest clump of each node. All stems carrying panicles are separated from each other, until we get a total of 200 stems (stop at this number). We opens then each stem with a penknife, and are classified in: -panicles without attacks from borers in the stem: n1; -panicles with attacks of borers in the stem (insects present or not): n2.
After threshing of grains of each batch, we get: -p1, weight of n1.
On the same location, estimate the number of panicles per square metre. To do this, we uses a rigid framework of 1 m² asked to randomly on the ground (do ten repetitions to get an average value). The following formula expresses with a fairly good approximation (by weight of grain per hectare) loss due to attacks by Drillers from the heading P= Weight loss of the grain in ha n1=Panicles without attack of borers in stems ; n2=Panicles with attack of borers in stems; (insects present or not); p1= Weight of n1; p2= Weight of n2; N= Numbers of panicles in m 2 This data can then be converted into monetary value. There will be care in category n1, stems whose tassels would be altered by causes other than Drillers (blast to the neck for example). If their number is not too important, the benefit expected by the fight against the Drillers would be reduced even. Note that this method of calculation does not take account of losses (dead hearts) during tillering. Because of these inaccuracies, this assessment -is usually the actual loss. It can therefore be regarded as a minimum usable for the study of the profitability of the fight. The method is quite laborious but without difficulty.

Assessment of damage from insects during talling
To achieve this, it was noted on each parcel: -Nt: average number of fruiting stems / m2 control plots; -N: average number of fruiting stems per meter square plots. These values are obtained by averaging a few surveys (at least five) conducted at random in each plot using a rigid framework of 1 m². If, on the other hand, surveys intended for the assessment of the loss of harvest due to the stem borers after tillering was conducted (using the above method) on plots of couples, the formula indicates the loss before bolting: Pa= n1= Numbers of stems without attack of borers p1= Weight of grains of n1 Pa= Loss of harvest cause by insects before heading. Applied to each control plot, this formula is used to calculate the average value of Pa of all couples (treated plots and untreated) representative of the rice-growing perimeter. The expected results will be reliable if the area concerned is relatively homogeneous and if found not in the presence of certain pests that are characterized by heterogeneous infestations: sampling, then, is more really representative of reality. All of this is generally feasible in situations of strongly framed rice which has begu n investments (irrigated) requiring the guarantee of high productivity.

III. RESULTS, ANALYS IS AND DISCUSSIONS 1. Biological diversity of insects in the paddy field of Maga 1.1. Inventory of the biodiversity of insects and classification
The Table 1 show the species collected in our experimental plot in the irrigated perimeter of Maga. Table 1 presents the species collected in our experimental plot in the irrigated perimeter of Maga, Classes, orders, families, genera species classification and along with their status.

Inventory of insects captured in different phenological stages and classification
The Table 2 show the inventory in different stages shows that insect pests vary in richness (number of species), in abundance (number of each species), based on different stages. This table shows the number of insects captured on control plots, rice varieties IR46 and NERICA 3 nursery depending on their class, order, family, genus and species. The insects captured at the nursery stage vary in numbers and species. They are spread over 4 orders and 8 families of Diptera, the order that has the most species, and the most abundant species is Glyphodera mantis.
At the nursery stage, the plants has characteristic of being very young and has well developed leaves bodies which promotes the development of phytophagous insects as defoliators insects and sucking biting of the leaves and it is what will justify the presence of Diptera pests and bugs. The table 3 shows the number of ins ects captured on control plots, rice varieties IR46 and NERICA3 during talling.  At the talling stage insect pests that we have captured, we divided them into 4 orders, 9 families and 9 species. At the talling stage the plants are young, well developed, bushy so insects grow best because the environ is conducive for their outbreak. So, defoliating, biting and sucking phytophagous insects belonging to the orders of Diptera and hemipteran especially develops. According to Grist and al., (1969), Hemiptera Nephotettix sp were indeed recognized as vectors of serious diseases of Tungro, Yellow dwarf and the Grassy Stunt Virus including the extension seems to expand with the development of highly productive varieties and high talling. The table 4 shows the number of insects captured on control plots, rice varieties IR46 and NERICA3 in heading stage. At the heading stage we caught 11 species of insect pests in 5 orders and 11 families the order Diptera was dominant and abundant. Insects caught in this stage are defoliators and also sucking biting, we note the presence of a grain pest, Stenocoris clariformis At the heading stage the plant has the characteristics of tillering but the difference of the output of the panicle is warranting that they are almost of the same type of insect pests and paniculaire initiation the granivores call where the presence of Stenocoris clariformis. The table 5 shows the number of insects captured on control plots, rice varieties IR46 and nerica 3 at the stage maturite. At the maturity stage we captured 10 species of insects. Divided in 3 levels and 9 families, insect pests are less abundant and are of sucking biting of seeds which are dominate.
The mature stage is marked by the senescence of leaves and stems. Insects are struggling to feed on the foliage for insects phylophages, also on the stem to stem borers. But the training and seed development promotes granivores insect outbreaks of the justifying the increase in species of Hemiptera much.

1.2.. Population dynamics  Population dynamics of insects on the IR46 varieties
The figure 1 shows the dynamics of insect phenological stages. Fig.1

: Curve of the dynamics population of insects on the IR46 variety
The curve of insect pests has almost the shape of a Bell, the size of the population of insects at the talling stage has the highest number followed by the heading and the nursery, insect pests are more numerous than the predators except at the end of maturity where the predators are more numerous than insect pests. Insect pests are more numerous at the tillering stage because at this stage the plant is young and well developed. Combined with climatic factors this stage promotes the overgrowth of insect pests , at the nursery stage pests such as stem borers are in the larval stage which makes a very difficult conditions for their capture by the sweep net.

Evaluation of the aqueous extract of neem fruit on rice variety
The curve of pest insects in the shape of a Bell (figure 2), she believed from the nursery until the tillering reaches an optimum and decreases to the maturation. This means that throughout the growth of the rice, the population of insects varies according to the phenological stages and varieties. Tillering is the stage or insects are more likely followed by the heading, nursery and finally maturation. The curve of Predatory insects believes slowly. The nerica3 variety has more bugs than the variety IR46 no matter the phenological stages. The variation of the insects throughout the growth of rice can be explained because each phenological stage has a peculiarity and involves some specific insects, and play on their density in relation to the ecological environment. During the talling stage the plant are bushy well-developed, phytophagous insects like defoliators of leaf sucking biting, and also of stem borers are present in abundance. The duration of this status and the ecological conditions for the development of insects can explain significant outbreak of insects in this stage. During the heading stage, the quality and quantity of SAP contained in the leaves and parts of the plants declines, leaves are sparse and poor quality this justifies the decline in population during this stage. The maturity stage is marked by the senescence of leaves and stems so insects do feed on the vegetative parts of the plant, the maturity stage is especially marked by advanced defoliation and senescence. All this helps to reduced numbers of insect pests, the abundance of predators in this stage can be explained by the effect that the maturity stage coincides with the arrival of rains which promotes the Tettigonidae outbreaks. Given this dynamic of insects from the rice phenological stage we realize that insects have much more visited the heading, nursery and talling stage and it more on during talling, nurseries and early heading stages that should be considered to fight against insect pests. In mature climatic conditions may favour the outbreak of insect predators.

Assessment of the effect of the aqueous extract of the fruit of the neem on insects of rice  Nursery
The figure 3 shows the diagram of the strength of insects, collected in the different treatments by the variety at the nursery stage.

Fig.3: Effect of biopesticide in the nursery
One notes that the number of insect pests on the control is larger, than the number of insect pests on plots treated with aqueous neem fruit extract regardless of the variety of rice. On the threshold of 5% biological treatment is significant for the variety IR46 compared with control IR46, and organic NERICA3 treatment is significant as compared to the nerica3 control. This means that the treatment has been effective insect pests affect hard rice by hunting and by inhibiting food intake. Jacobson (1984), demonstrates the inhibition of food intake of the flea beetle of Podagrica uniforma and development of larvae of the beetle and the Epilarchnacrysoelina melon lemon Papiliode modocus.
 Talling Figure 4 shows the diagram of the strength of insects, collected in the different treatments by variety at the tillering stage.
IR1: control IR46, IR3: Treatment of IR46 with aqueous extract of neem seeds, N1 control NERICA3, N3: treatment of NERICA 3 with aqueous extract of neem seeds Numerically the number of insect pests on witnesses is larger, than the number of insect pests on plots treated with aqueous neem fruit extract regardless of the variety of rice. On the threshold of 5% biological treatment of Nerica is significant on the control Nerica treatment and IR46 biological treatment has a positive effect on insects from the control of IR46. The insecticidal action of the aqueous extract of neem fruit had an effect on insects pest by reducing their numbers on treated plots according to Gaby (1997) the action of the neem tree is at least 100 species of pests including rice leafhoppers, flies etc...
 Heading The figure 5 shows the diagram of the strength of insects, collected in the different treatments by variety at the heading stage. IR1: control IR46, IR3: Treatment of IR46 with aqueous extract of neem seeds, N1 control NERICA3, N3: treatment of NERICA 3 with aqueous extract of neem seeds Fig. 5: Effect of biopesticide in heading On the threshold of 5% biological treatments had effects on control the action of the aqueous extract of neem on insects, it is not significant because the dose was not sufficient at this point or Sunshine which quickly denatured the product during heading.

 Maturation
The figure 6 shows the diagram of the strength of insects, collected in the different treatments by variety at the maturity stage IR1: control IR46, IR3: Treatment of IR46 with aqueous extract of neem seeds, N1 control NERICA3, N3: treatment of NERICA 3 with aqueous extract of neem seeds The strength of the insect pests on plots of varieties IR46 and NERICA3, is significantly higher compared to plots treated with aqueous extract of fruit of neem in the maturity stage. But on the threshold of 5% biological treatments are not significant. This can be due to climatic conditions which are not conducive to the application of the aqueous extract of neem fruit. Because the maturity stage coincides with the onset of the rains. Jacobson (1997), advocate that the aqueous extract of neem fruit may protect rice during two week to condition that does not rain.
 Effect of the varieties on insects The figure 7 shows diagram of the population of insects on IR46 and NERICA3 varieties

Fig.7: Diagram of the population of insects on IR46 and NERICA3 varieties
Insects are many on the NERICA3 variety IR46 variety but statistical analysis on the threshold of 5% is not significant on the presence of insects on the different varieties.

Assessment of damage during talling
The table 6 presents the average number of fruiting stems per square metre on plots of witness, the average number of fruiting stems per square metre on the treated plots, the weight of grain of n1 and the loss of harvest due to insects acting before bolting. The estimate of damage caused by insects pests before bolting for the control of variety IR46 parcel is Pa = 88, 71 Kg, and for the control of the nerica3 variety plot is Pa = 520, 38 Kg. These results indicate that if rice plant is not treated with the aqueous extract there will be losses due to insect pests before bolting of Pa = 88, 71 Kg for the variety IR46 and Pa = 520, 38 Kg for the variety of rice NERICA3 in this rice agroecosystem. The aqueous extract of neem fruit has a pos itive effect on the yield of rice, in the sense that it prevents insect pests to their devastating actions on rice. The table 7   The fruitful shoots average per square meter is higher for the control compared to the treated plots. This is due to anti parasite and insecticides of the aqueous extract of fruit of neem on borers, which consequently reduces their action on the rice plant by preventing the formation of dead hearts.

Evaluation at the time of harvest of losses due to borers
The figure 8 shows the damage caused by the action of insect borers on the rice plant.

IV.
CONCLUSION Rice (Oryza sativa l.) is the base food of over half of the population of the globe (Guigaz, 2002). But this culture faced many obstacles to its production including attacks from insect pests, control by use of synthetic insecticides and have negative impacts on the biodiversity of the ecosystems and human health yet nature gives us ways to biocontrol through crop protection of crops as the aqueous extract of neem seed against these insects was at issue for us in this study to evaluate the effectiveness of the aqueous extract of fruit of neem on according to variety -To assess losses due to insect borers.
As indicated in this study that there are two classes of arthropods, class Arachnida, and the insecta. The class of Arachnids is represented by an order, two families, and two species of insects, the class of insects is distributed in seven orders, twenty families, and twentyfour species. All species of spiders are predators. Among the captured insects we identified 13comon insect pests, of which four are classified as the fearsome enemies to the cultivation of rice. They registed a damage of up to 100% yield loss, it's Sesamia calamistis, Diopsis sp, Nephottetix nigropictus, Maliarpha separatella . Insect predators include 9 species and parasitoids are numbers 2 species of insects.
The distribution of insect pests by phenological stage varies in abundance in each phenological stage. The most visited stadium by insects is the talling stage. Because at this point the rice plant is well developed and shaped tuft, favourable to the development of insects. The insects were much more abundant on the variety of rice NERICA 3 on the variety of upland rice IR 46.
The aqueous extract of fruit of neem shown to be effective against insects in the nursery and talling stages and had effects on reduction and the action of insects on the rice heading and ripening plant.
The aqueous extract of neem fruit resulted in a reduction of the yield losses caused by insects, and therefore it has improved the yield of rice. Despite to kill insects and reduce the losses caused by them, the aqueous extract of neem seed is more efficient than the use of insecticides synthetic insecticides on insects but contributed enormously to the respect for the environment by decreasing its impact on biodiversity ecosystems.