The coconut tree (Cocos nucifera) is a member of the palm tree family (Arecaceae) and is known for its versatility of uses, ranging from food to cosmetics. Indonesia is the chief producer of coconut with output of approximately 15,000 million nuts annually1. But, yield and quality of coconut is being reduced because of many reasons including pests e.g. coconut rhinoceros beetle (Oryctes rhinoceros ). This drastic insect pest is causing huge economical losses in Indonesia, which is an alarming situation for farmers. Unfortunately, managing practices of this pest are restricted because of certain factors which are as follows. Coconut palm is not a chief food crop, having lofty stem. Moreover, soil habitat of larvae and its location (usually outside the plantation), therefore; these factors restrain the managing practices. To some extent, farmers control coconut rhinoceros beetle through chemicals but, due to their destructive impacts on environment; application is being prohibited. Hence, experts are switching to biological control. In this regard, fungus Metarhizium anisopliae is most significant which is a soil fungus; causing disease in most insects2,3.
The growth of this fungus is influenced by some factors including pH, temperature, moisture and nutrition. But, because of dry and rainy season of Indonesia the control of O. rhinoceros larvae by utilizing M. anisopliae in dry season can’t be achieved successfully. Conversely, this target can be accomplished in rainy season. Therefore, it is suggested to control the larvae in the rainy season. In addition to fungi, entomopathogenic nematodes (EPN) from families of Steinernematidae and Heterorhabditidae are significant biocontrol agents which act as efficient parasites of insect pests. EPN is being used effectively to manage Order Lepidoptera4,5 and Coleoptera6,7. But; it has not been extensively employed against O. rhinoceros larvae.
Accordingly; Dyah Rini Indriyanti and team conducted a research to assess the efficacy of Metarhizium anisopliae and entomopathogenic nematodes against Oryctes rhinoceros larvae in the rainy season. For this purpose, scientists used 4 level doses of M. anisopliae (MET), 4 level doses of EPN as well as combination of MET and EPN. Seventy two containers were utilized that were positioned in the garden under coconut palm shade. 5kg of organic soil mixed with (MET, EPN and MET+EPN) and ten O. rhinoceros larvae (third instar); were placed in each other container. Afterwards, researchers examined the data through descriptive analysis.
For 8 weeks interval; scientists noted the larval mortality once in a week. Consequently, larval mortality because of MET treatment on 2nd to 7th week was observed. In the meantime, the larval mortality through EPN treatment occurred on 2nd-8th weeks and MET+EPN treatment exhibited larval death on 1st to 5th weeks. Therefore, Dyah and colleagues concluded that mixture of MET and EPN showed a great potential against O. rhinoceros larvae as compare to individual application of MET or EPN. These findings showed that application of two biocontrol agents exhibited synergism effect against O. rhinoceros larvae in the field.
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17 November, 2019