Holometabolous nature of Fall armyworm (Spodoptera frugiperda): The secret of its susceptibility to control, management

Fall armyworm (Spodoptera frugiperda) is an invasive alien insect pest in Nigeria. It is first reported in Africa in Nigeria in 2016. Since then, it has spread to over 40 African countries and Asia.

However, its effect on agricultural production has been worrisome. Various control and management strategies have been proposed by farmers and agricultural researchers. Most of the control methods have resulted in other problems such as environmental and public health issues because of the use of pesticides.

However, insects have been divided into two due to their life stages. Some insects are hemimetabolous. Hemimetabolous insects are the insects that undergo incomplete metamorphosis. The eggs hatch into nymphs. These nymphs look very much like adults.  After some moultings they become full grown adults. However, the holometabolous insects are different. Their eggs hatch into larva and the larva change into pupa and pupa turn into adults. The hemimetabolous insects have incomplete metamorphosis while holometabolous insects have complete metamorphosis.  Holometabolous have four life stages, which is egg, larva, pupa and imago or adult.

Fall armyworm is a holometabolous insect, hence it has complete metamorphosis. The different life stages make it susceptible and hence allow possibility of easy management than hemimetabolous insects. Fall armyworm normally pupates in soil, therefore proper soil tillage like ploughing and harrowing can reduce the menace of fall armyworm. Also in small holders farms, the eggs of fall armyworm can be collected and destroyed. The eggs are normally laid on underside of the leaves in batches covered with scales and hair of the moth (fall armyworm is a moth). In the absence of poisonous pesticides, there are several important parasites of eggs and larva of fall armyworm in the order hymenoptera and diptera that can naturally help in managing the fall armyworm. There are also entomopathogenic fungi that can attack the eggs and larvae of fall armyworm. There are also predators of eggs and larvae of fall armyworm in the order hemiptera and Coleopteran found in the farms that naturally attack eggs and larva of fall armyworm.

However, for these farmers’ friends (parasites, predators and entomopathogenic fungi) to be active, the farmer must not use strong poisonous pesticides. Instead farmers can use environmental safe crude extracts and organic substances as pesticides such as the use of bitter leaf (Vernonia amygdalina). Bitter leaf soaked in water for 48 to 96 hours in water will achieve some level of control of Fall armyworm. Also for small holder farmers, the use of appropriate dilution of Rabbit urine with water will achieve some level of control and management of fall armyworm.  The leaves and bark of Camel’s foot tree (monkey bread tree) (Piliostigma thonigii syn  Bauhinnia monandra) soaked in water for 48 to 96 hours will also achieve the control of Fall armyworm. All these are environmentally safe, ecological balanced and allow framers’ friends to also do their jobs in the management of Fall armyworm. This is also economical and health compliant in terms of health safety.

• Dr Timothy Oluwafemi Ajiboye is an Entomologist, a biodiversity conservation expert and a striga management specialist and Principal Investigator of KAFACI Fall armyworm projects in Nigeria. He works at National Centre for Genetic Resources and Biotechnology (NACGRAB) (NABDA centre of Excellence).

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