Biocontrol of Oil Palm Pests Using Metarhizium anisopliae and Beauveria bassiana
Coelaenomenodera lameensis is the main pest of oil palm in West Africa, particularly in Côte d’Ivoire. This species is a leaf miner which, by proliferating, causes enormous damage to oil palm. The aim of this study was to evaluate the effect of the entomopathogenic fungi Metarhizium anisopliae (Met 358 and Met 359) and Beauveria bassiana (Bb 11) on C. lameensis adults. Trials were carried out under controlled infestation on an oil palm plot at the University Jean Lorougnon Guédé in Daloa. Male and female adults were captured and introduced into a muslin-covered cage containing leaflets. Each sex was divided into four batches: a 1st batch treated with Met 358, a 2nd batch treated with Met 359, a 3rd batch treated with Bb 11 and a 4th batch of controls. These adults were sprayed, 48 hours later, at the following concentrations 102; 104; 106; 108; 1010 and 1012 spores/ml for each fungal isolate (Met 358, Met 359 and Bb 11). Three replicates were carried out per treatment for each batch containing 40 adult males and 40 adult females. Concentrations of 1010 and 1012 spores/ml induced mortality rates of up to 100% in less than 7 days with the various fungi. These biopesticides could be an alternative to the abusive use of synthetic insecticides to reduce the damage caused by the pest C. lameensis.
Oil palm, grown for its oleaginous fruit in some twenty countries around the world, is the leading source of vegetable oil, accounting for 39% of vegetable oil production and 66% of marketed oils (Rival, 2020). In 2016, the oil palm sector recorded 65 million tons worldwide, 85% of which was supplied by Malaysia and Indonesia (Rival, 2020). In Côte d’Ivoire, the palm oil sector ranks 4th in the economy. It employs over a million people in the southern part of the forest zone and generates over 400 billion CFA francs in sales (D'Avignon, 2013), with production of 450,000 tons of crude palm oil a year (Cucumel, 2020). Côte d’Ivoire is the 2nd largest producer and 1st largest exporter in Africa. It also ranks 5th worldwide (Cucumel, 2020).
Unfortunately, this crop, at all stages of development, is exposed to numerous phytosanitary problems. These include attacks by several pests, the most important of which is Coelaenomenodera lameensis Berti et Mariau, 1999 (Anougba, 2022). During severe outbreaks, this insect causes extremely serious damage, leading to a drop in production of up to 30- 50% over a period of 2-3 years (Mariau, 2001; Coffi et al., 2012; Tano et al., 2013). Controlling this pest is therefore a necessity.
There are many methods of combating this insect: chemical and biological. Unfortunately, these methods have not yet succeeded in completely eliminating this pest (Kouassi et al., 2020). The massive use of synthetic insecticides creates numerous problems: environmental pollution and consequent human poisoning, the elimination of beneficial insects, the destruction of wildlife and the contamination of groundwater and rivers (HénaultEthier, 2015).
It would therefore be interesting to focus on other equally effective control methods that cause fewer ecotoxicological problems, including biological control of insect pests, which is a safe and environmentally friendly alternative to chemicals worldwide (Lacey et al., 2015). This control involves the use of entomopathogenic fungi to control insect pest populations. They are responsible for infections in many insect species (Aby et al., 2022). Among these entomopathogenic fungi, particularly those belonging to the Metarhizium and Beauveria genera show great promise against insect pests (Mnyone et al., 2009; Lwetoijera et al., 2010; Mnyone et al., 2012).
The aim of this study was to evaluate the effects of the entomopathogenic fungi Metarhizium anisopliae (Met 358 and Met 359) and Beauveria bassiana (Bb 11) on C. lameensis adults.
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