Pest is the major threat for Brassica group. Brassica rapa var. chinensis which is cultivated for commercialization is commonly treated with synthetic chemical pesticides for better crop production. This may due to the low cost and high efficiency of pesticide to keep the insect pest and disease at bay. However, over-dependence and excess use of synthetic chemical pesticide in order to combat insect pest attack and diseases can cause detrimental effect on soil as well as human health and quality of the environment. It can also induce the emergence of “super pest”, secondary pest outbreak and pollutes nearby water resource.
The use of plant extract as biopesticide can be used as an alternative way to combat problems related to crop pests. This method can reduce the impact on environment and human health. A few effective biopesticides can be introduced at the end of this project which implement the synthetic chemical insecticides. Besides saving cost on pesticides, these methods provide easier and safer way of preparing biopesticide. Apart from that, this can reduce the negative impact on environmental health from crop production.
1.4 Objectives
1) To assess the potential of pest repellent plant (PRP) species for managing insect pests in Chinese cabbage (Brassica rapa var. chinensis)
2) To observe the type of insect present in the current location and as a pest for Chinese cabbage
3) To identify which frequency of spray of biopesticide may give optimum result.
Sacred basil (Ocimum basilicum), from the family of Lamiaceae, is an aromatic annual herb and is native to India. It grows up to 1 – 2 feet above the ground and produces plentiful large green leaves. Several studies showed that plant particularly from the family Lamiaceae are most widely used to control insect pest (Lambert et. al., 1985; Morton, 1981; Shaaya, et al., 1997; Lawrence, 1988).According to Zhang et. al. (2009), the essential oils, which were obtained by steam distillation, consist of 29.68% linalool, 21.49% (Z)-cinnamic acid methyl ester, 4.41% cyclohexene, 3.99% α cadinol, 2.27% 2,4-diisopropenyl-1-methyl-1-vinylcyclohexane, 3,5-pyridine-dicarboxylic acid, 2,6-dimethyl-diethyl ester (2.01%), 1.97% β-cubebene, guaia-1(10), 1.58% 11-diene, 1.41% cadinene, 1.36% (E)-cinnamic acid methyl ester and 1.30% of β-guaiene. The essential oils showed significant antifungal activity against some plant pathogenic fungi. Furthermore, 80% mortality was recorded when newly emerged adult beetles (Callosobruchus maculatus) were exposed to 12 hours of fumigation using pure essential oils at a dose of 25 μl/vial (Kieta et. al., 2001). On the other hand, Deshpande and Tiphis (1972) reported that the components methyleinnamate and methylecharicol in essential oil of O. basilicum responsible for insecticidal activity against stored grain insect pests, such as Tribolium castaneum, Sitophilus oryzae, Stagobium paniceum and Bruchidius chinensis. Whereas Ibrahim (2000) discovered that Ocimum basilicum iss capable to reduce the percentage of Faba Bean Beetle Bruchidius incarnatus Boh. eggs hatching besides reduce oviposition. Thus, significantly increases the mortality rate of the insect. Apart from insect repelling properties against insect Allacophora foveicollis, Dube (1989) reported that the dose of 1.5 ml/L of Ocimum basilicum essential oil also showed antifungal properties by completely inhibiting the mycelial growth of 22 species of fungi, including Aspergillus flavus and Aspergillus parasiticus. Similar results were obtained whereby Mycelial growth of the plant pathogenic fungus Botrytis fabae and the rust fungus Uromyces fabaewas have reduced significantly when treated with basil (Ocimum basilicum) oil and its major individual components (Oxenham et. al., 2005).
Dioscorea hispida which is also commonly known as “Ubi Gadong” in Malaysia belongs to Dioscoreaceae family. It arise from tuberous roots, and reach a length of several meters. It has trifoliate leaves with hairy and poisonous bulky tuber. White to yellow flesh tuber produces a small yellow flower. They are easily grown near the stream and shady area, simply found in secondary forest (Nashriyah et al., 2010). Different plant parts are used in whitlow, sores, boils and bites of rabbit, jackel or dog (Yusuf et al. 2009). This tuber cannot be consumed raw due to presence of harmful alkaloids in it (Tattiyakul and Naksriarporn, 2010). According to Chanida Palanuvej et al, D. hispida contains water-soluble isoquinuclidine alkaloid, neurotoxic dioscorine with molecular formula (C₁₃H₁₉O₂N), which leads to paralysis of nervous system. However, this tuber can be consumed once it has undergone certain process of removing the toxic alkaloids in proper way (Hudzari et al., 2011a; Muhammad et al., 2012). The toxin from the tuber can be removed by boiling, roasting or soaking in flowing water for 7- 14 days traditionally so that it can consumed safely (Hudzari et al., 2011). Detoxified D. hispida was a staple food for poor rural people those days where they made flour, cakes and porridge out of it. Nevertheless, it is rarely consumed nowadays due to the difficulties of traditional detoxification process. Mlingi (1995) reported that below 10 mg hydrogen cyanide (HCN) per kg body weight is the safe amount of tuber that can be consumed as set by World Health Organization (WHO). Excessive consumption of tuber without further purification may result in cyanide poisoning. It may also lead to lethal effects such as death due to alkaloid intoxication (Andri et al., 2011; Shajeela et al., 2011). Hudzari R. M. (2011) has also came up with automatic alkaloid removal system for Dioscorea hispida to develop a better method compared to the traditional method. On the contrary, these poisonous alkaloids can be used to treat sores of puru and chronic rheumatism by external application (Xinxiang et. al., 2009).
3.1 Germination Test
Seeds will be purchased from Green World. Ten randomly selected seeds were placed on cotton wool and moistened with water daily. All the ten seeds has germinated, showing 100% rate of germination. Thus, these seeds will be chosen to conduct this project.
3.2 Preparation of Soil
The Chinese cabbage will be cultivated using polybags. A mixture of soil consist of top soil, sand and organic compost in the ratio of 3:2:1 will be used. 4 sacks of top soil has been collected from Pasir Akar. Sand will be collected around FBIM area whereas the organic compost will be purchased from Agropolis. After mixing the soil, it will be transferred into respective polybags and followed by seedlings transplantation into the polybags.
3.3 Preparation of Biopesticides
a) Neem (Azadirachta indica) Extract
The Neem leaves were collected from a Neem tree located at Subang Jaya, Selangor. The leaves were washed with water and allowed it to dry at room temperature for one week. About 400 g of Neem leaves will be weighed and soaked for 24 hours in 1 Liter of water. After that, the soaked mixture will be blended and filtered. The filtrate will be used as stock solution.
b) Citronella Grass Oil (Cymbopogon citratus) and Sacred Basil Oil (Ocimum basilicum)
Both of these oils will be purchased online. Add 2 to 3 drops of detergent into 1 Liter of water. This helps to break the water retention and allows oil to be miscible with water. Then, add 2ml of oil into the water. Mix and apply the prepared Citronella Grass Oil and Sacred Basil oil once a week to the crop.
c) Ubi Gadong (Dioscorea hispida) Extract
Ubi gadong was purchased from Pasar Payang. The extract will be prepared in the ratio of 1:3, whereby one portion of Ubi Gadong will be mixed with 3 Liter of water. The skin will be peeled off and cut into small pieces. The Ubi Gadong is then blended in the blender and filtered. The filtrate is then will be used as stock solution.
3.3 Calibration of Hand Sprayer
can apply in a given area, walking with a constant speed.
Walk along the row and spray both above and below the leaves at constant speed. Determine the number of hand-held sprayer will be required to wet upper and bottom part of the leaves. Testing your spraying equipment with water and measure how much it
3.4 Biopesticide Spraying
The treatments will be sprayed both upward and downward direction using a hand-held sprayer until the leaves of Chinese cabbage is completely wet with the treatment. The crop will be irrigated twice a day.The Chinese cabbage will be treated with biopesticides once a week. Insect pest population sampling will be done early in the morning every day.