Another very important aspect of prevention of FAW infestations is by maintaining plant diversity on farms. Even if many female moths are flying about, if they don't lay their egg masses on maize plants, or if very young larvae don't 'balloon' onto other maize plants, then the maize won't be infested by FAW.
FAW moths prefer to lay their eggs on maize and sorghum. In large monocultures of maize, the target plants are easy for the female moths to find. However, in mixed agriculture where maize plants are inter-cropped with other crops, such as cowpeas or beans, which are not suitable for the FAW, the hypothesis is that the female FAW will have more difficulty to detect maize plants for oviposition and may miss the target maize plants entirely. This hypothesis of reduced egg laying in mixed-crop systems has yet to be tested in the field in southern Africa, but evidence from farmers in Central America is that when maize is planted together with other crops such as beans and squash (their traditional "milpa" systems), there is less pest pressure from FAW and other crop pests
Agroecologists have documented that polycrops may be effective because of three main reasons or mechanisms:
One possible explanation is that a diversity of plants in the same field confuses FAW, and it is difficult for it to find its preferred host plant (maize), eating less or laying fewer eggs.
Another reason is that the female FAW moth doesn't "like" certain plants because of the chemicals they emit. These volatile compounds are the "push" effect in "push-pull" systems, which "push" pest species away from certain plants while they are "pulled" to others because the plant chemicals make them more attractive. Therfor, planting maize near other plants that "push" FAW moths away is the first step in preventing FAW infestation.
A third possible explanation is that polycropping may provide natural enemies (parasitoids and predators) with resources such as suitable habitat, nectar and water. The natural enemies will therefore be in close proximity to feed on, or parasitize the FAW. We also know that plants that bear flowers for a long period of time, such as many weeds, or some medicinal or condiment plants, do provide nectar to parasitoids and predators of FAW. In Mesoamerica, plants such as Tagetes lucida, Coriandrum, Sonchus olerace, Ruta and onions, attract beneficial insects.
The presence of trees amongst the croplands is also considered important for pest management in many parts of Africa. Trees allow birds to perch, and many birds prey on caterpillar larvae such as the FAW. Trees also provide roosting sites for bats that feed on flying moths. In Africa, many farmers are growing maize in agroforestry systems (MIAF), so it is important to determine if the MIAF plots suffer less FAW attacks than maize grown in a monocrop system. It is certainly important to encourage smallholder farmers to leave the trees standing amongst their fields to support greater biodiversity.