Effects of selected inorganic insecticides and plant extracts on the management of flea beetles on a leafy hibiscus vegetable (“Malakwang”)
Okalebo, Samson Peter
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“Malakwang” is one of indigenous vegetable grown in Northern and Eastern parts of Uganda. However, during the vegetative growth the flea beetles (Podagrica spp.) heavily attack the leaves of the plant and cause more than 50% loss of leaf area and quality.An experiment was conducted during two cropping seasons 2071A and 2017B at National Crop Resource Research Institute (NaCRRI) to assess the effect of selected commercial insecticides and plant extracts on the flea beetle pest population and its damage on Hibiscus spp.(Hibiscus sabdiriffa and Hibiscus cannabinus). The experiment was laid out in a randomized complete block design (RCBD) with nine treatments and three replications. The treatmentshad six inorganic pesticides namely Malathion, Dursban, Pyrinex, Dimethoate, Agrochloridi, Agrophyrifos, and organic pesticides such as plant extract from the Neem tree and Botanical (Black off) were used as a standard check alongside control. The inorganic pesticides had the same rate of application. 3.5ml of Malathion, Dursban, Pyrinex, Dimethoate, Agrochloridi, Agrophyrifos respectively were mixed with 2 liters of water, 300g of fresh Neem leaves were harvested and ground to make a paste then dissolved in 2 liters of water followed by filtering using the sieve, 20ml of Botanical in 2 liters of water and 2 liters of water used for the control. Neem leaves measuring 300gm were crashed and mixed in 2 liters of water. Data was collected oninsect population and level of damage in the morning same day before pesticide application in the afternoon and twice a 14 days interval. The results showed a high pesticides significance (P < 0.001) on pest population with Dimethoate having the least pest population (1.994) and Neem Extract having the highest (3.4245) and the level of damage caused by the flea beetle with Dimethoate having least level of damage (9.7%) and Botanical having the highest (13.0%) in both seasons.The average order of effectiveness for pest population was found to be Dimethoate<Agrochloridi<Agrophyrifos<Dursban<Pyrinex<Malathion< Botanical <Neem Extract<control. The average order for effectiveness in reduction of the level of damage caused by the flea beetles for the two seasons showed that Dimethoate (9.7%) had least level of damage followed by Neem Extract (9.9%), Agrochloridi (10.4%), Agrophyrifos (10.4%), Dursban (10.5%), Pyrinex (11.3%), Malathion (12.4%), and Botanical (13.0%) with the highest level of damage. Lower pest population and level of damage on the Hibiscus spp. on the treated plots indicated the effectiveness of the pesticides. However, Dimethoate was the most effective in controlling the pest population and the level of damage caused by the flea beetles.