INSECTICIDAL EFFECTS OF STEM BARK POWDER OF AZADIRACHTA INDICA AND LEAF POWDER OF EUCALYPTUS CAMALDULENSIS ON WEEVILS OF STORED MAIZE GRAINS

The insecticidal effects of stem bark powder of Azadirachta indica and leaf powder of Eucalyptus camaldulensis on weevils of stored maize grains was carried out. Four levels: 5.0g, 10.0g, 15.0g and 20.0g of each of the vegetative parts (as treatments) and 0.0g as control were replicated four (4) times, making 36 plots (bottles). These were represented as 36 bottles (kilner jars) each containing 100g of maize, arranged in two separate sets of 16 bottles for each of the vegetative parts. The remaining 4 served as the control, at 0.0g levels. Stem bark powder of Azadirachta indica 5.0, 10.0, 15.0 and 20.0g were introduced into the first set. While the leaf powder of Eucalyptus at 5.0, 10.0, 15.0 and 20.0g were introduced into the second set, followed by vigorous shaking. 30 young adult maize weevils were carefully introduced into each of the bottles and covered with a perforated lid lined with muslin mesh (1.0mm). The bottles and its contents were arranged in a Completely Randomize Design (CRD) for 336 hours (14 days) and 432 hours (18 days) for Eucalyptus and Neem respectively. 10 healthy grains per replicate were sown into polythene pots containing uniform potting mixture of top soil, river sand and cow dung in a ratio of 1:1:1 at the end of the trail. Parameters assessed include mortality, % mortality weight loss, perforation and perforation index (for the insecticidal experiment) and % germination, for the post trail experiments. Result obtained showed a progressive increase in mortality and % mortality, with analysis of variance (ANOVA) not significantly different (P>0.05) at 48 hours after treatment (HAT), but significant (P<0.05) between 96 and 432 HAT. Weight loss, perforation and perforation index were inversely related to the concentrations of the two powder sources, in which cases, the ANOVA of these parameters showed significant different (P<0.05). The % germination obtained did not show much variation despite the significant difference indicated by the ANOVA, thus revealing the preservation potentials of the plant powders.


Introduction
Neem is a fast-growing tree that can reach a height of 15-20 meters (49-66ft), and rarely 35-40meters (115-131ft) it is evergreen, but in severe drought it may shed most or nearly all of its leaves. the branches are wide and spreading, the fairly dense crown is roundish and may reach a diameter of 20-25 meters (66-82ft). the Neem tree is very similar in appearance to its relative, the chinaberry (Melia azedarach). The opposite, pinnate leaves are 20-40 centimeters (7.9-15.7 in) long, with 20 to 30 medium to dark green leaflets about 3-8 centimeters (1.2-3.1 in )long. The terminal leaflets often are missing. The petioles are short. The (white and fragrant) flowers are arranged in more-or less dropping auxiliary panicles which made up to 25 centimeters (9.8 in) long. The inflorescences, which branch up to the third degree, bear from 2500 to 300 flowers. An individual flower is 5-6milimeters (0.20-0.24 in) long and 8-11 millimeters (0.31-0.43in) wide. Protandrous, bisexual flowers and male flowers exist on the same individual tree. Eucalyptus camaldulensis (River Red Gum) is a tree of the genus Eucalyptus. It is familiar and usually seen along water courses right across inland Australia. The tree produces welcomed shade in the extreme temperature and plays an important role in stabilizing river banks. Maize (Zea mays) is one of the major cereal crop produced worldwide. It is a staple food in many countries throughout Africa, Latin America and Asia. Onuk, et al, (2010), noted that maize is one of the most abundant food crops in Nigeria; about 80% is consumed by man and animals while 20% is utilized in variety of industrial processes for production of starch, oil, high fructose, corn sweetener, ethanol, cereal and alkaline, consisting of 71% starch, 9% protein and 4% oil on a dry weight basis. On the same note, Gupta (2011) noted that maize has immense potential to meet food requirement of human population because it has a great significance as human food, animal feed and diversified uses in a large number of industrial products, also that the adoption of improved and sustainable maize technologies holds the key to ensure both sustainability and increased maize production. Despite the importance and uses of maize in Nigeria, it is attacked by various field and storage pest. Maize weevil (Sitophiluszeamays) is a major pest that attack stored maize grains in tropics and temperate regions of the world (Sagheeret al., 2013; Adedire 2001). According to Radha, (2014) the attack of maize weevils may start in the mature crop when the moisture content (MC) of the grain had fallen to 18-20%. Subsequently, infestations in store result from the transfer of infested grain into store or from the pest flying into storage facilities, probably attracted by the odour of the stored grain. In stored maize, heavy infestation of this pest may cause weight losses of as much as 30-40% (Radha, 2014;Ogunsina et al., 2011). Therefore, the objective of this work is to examine the insecticidal effects of stem bark powder of Azadirachta indica and leaf powder of Eucalyptus camaldulensis on weevils of stored maize grains.

Study Site
The study was carried out in the chemistry laboratory of Binyamin usman polytechnic Hadejia, Jigawa State. It is located 12.45 latitude and 10.4 longitudes and it is situated at elevation 359 meters above sea level in Sudan savannah zone.

Materials
The materials used for the study include maize grains, maize weevils (Sitophiluszeamays), stem bark of Azadirachta indica, leaves of Eucalyptus camaldulensis.

Collection and Preparation of Plant Materials
After collecting both the stem bark of Azadirachta indica and leaves of Eucalyptus camaldulensis in they were shade-dried under free to air for 5 days and were pulverized into fine powder using mortar and pestle, sieved and stored in polythene bags until use.
The fine powder of both plant materials were thoroughly mixed together per 100g of maize grain at different doses of 5.0g, 10.0g, 15.0g and 20.0g while 0.0g/100g served as the control.

Experiment using Stem Bark and Leave Powder of Azadirachta indica and Eucalyptus camaldulensis.
100g of clean and sterilized maize grains were poured into different experimental jars. 5.0g, 10.0g, 15.0g, 20.0g and 0.0g (control) each of both stem bark powder of Azadirachta indica and leaf powder of Eucalyptus camaldulensis were added into each jar and vigorously shaken to ensure thorough mixture of the grains with the plant materials. It was then allowed to settle for 30 minute, after which 30 live adult maize weevils (Sitophiluszeamais) were carefully introduced into each jars. The jars were then covered with perforated lids, lined with muslin mesh of 1.0mm (Chomini, et al. 2006) after which each jar containing the materials were set up in four replicates in a completely randomized design (CRD) in Bupoly chemistry laboratory.

Experimental Duration and Parameters Assessed
The experiment was conducted from 1 st -15 th August, 2019 for Eucalyptus and 1 st -19 th August for Neem. And the parameters assessed include:

Statistical Analysis
The data collected on mortality, percentage mortality, weight loss, perforation and percentage germination were subjected to analysis of variance (ANOVA) to determine their significant.

Mortality and Percentage Mortality
The Thus, at 20/100g as shown by the weevil perforation index (WPI) better grain protection was observed in this trail.
The same pattern is noticed for perforation index of the different levels of the stem bark powder of Azadirachta indica, thereby indicating a significant difference.

Weight Loss
There

Percentage Germination
The effects of the powder of vegetative parts of the test plants did not adversely affect the germination of the treated grains and are therefore significant (P<0.05), the average % germination were 67.5%, 60.0% and 57.5% at 0.0g, 20.0g and 5.0g levels respectively for leaf powder of Eucalyptus and 72.5%, 72.5% and 62.5% at 0.0g, 20.0g and 5.0g levels respectively for stem bark of Neem. This observation is in line with the findings of Chomini, et al. (2010). Their observations showed that treatments of grains with Neem, mahogany bark extract and dried powder of Xylopia fruit did not affect the germination potential of the treated grains. Thus suggesting that the treatments have the potential of preserving the viability integrity of the treated grains.

Conclusion
Following the observations made, it can be concluded that mortality and percentage mortality of maize weevil increase with the levels of plants extracts as well as time of exposure. The perforation and perforation index of the grain were affected by concentrations of vegetative parts of the test plants. This also has influence on the weight loss pattern.