Reports have been gathering recently about Fall Army Worm, a potentially devastating pest of Maize which has been sweeping from West Africa, down to the South of the continent and now towards us here in Kenya.
Originally a pest of the southern states of the US, Fall Army Worm is a small larvae laid by the adult moth, which completes its lifecycle in the growing maize plant and causes significant yield damage and often total crop loss. Early leaf damage can be mistake for hail damage.
Farmers caught off guard
The adult moths are spread by the wind and can travel significant distances to infest new crops, often catching growers off guard. While maize is the principal host, the larvae can survive on Soybeans and other grasses between seasons.
The most significant damage is done late in the crops life, when the larger final stage of the larvae’s life cycle is completed and its appetite is at its greatest. This coincides with tussling and cob formation, damage to which serious affects yield, and control with insecticides at these late stages is very poor once the larvae move into the shelter of the developing cob.
Burning crop residues and stubble will not control the Fall Army Worm, as the primary cause of infestation is the arrival of the adult moth, rather than the emergence of juvenile larvae.
Crop monitoring is crucial
Accurately timed insecticides early in the crop’s life when larvae have been identified is crucial. Even if populations appear low for several weeks, the feeding rate increases exponentially as the larvae mature. Selection of an effective chemical is vital, to provide rapid control whilst leaving beneficial predators such as Parasitic Wasps to provide suppression of further larvae attacks.
Unlike Common Army Worm, the Fall Army Worm often occurs in patches across a field, so thorough crop inspection is vital to spot early infestations. Larvae feed during the day so are relatively easy to spot, but they can be confused with similar species. If in doubt send your CropNuts agronomist a WhatsApp photo for identification and further advice.