Study shows indigenous vegetable capable of defeating deadly pests

A farmer tends her managu in a farm in Kimende, Kiambu County. FILE PHOTO | NATION MEDIA GROUP

What you need to know:

  • The plant, according to researchers from the International Centre of Insect Physiology and Ecology (Icipe), has the ability to defend itself against major pests like the tomato red spider mite, making farming it cost friendly.
  • Findings show a distinctive defence strategy in this plant based on opposing roles, with the leaf fragrance acting as an attractant, while the stinking odours defend the plant against certain insect behaviours, such as egg laying.
  • The tomato spider mite (Tetranychus evansi) causes serious damage, significantly hindering the production of African nightshade and other crops that are members of the family

African nightshade (managu or osuga) has a unique ability to defend itself against pests and diseases, a new study has shown.

The plant, according to researchers from the International Centre of Insect Physiology and Ecology (Icipe), has the ability to defend itself against major pests like the tomato red spider mite, making farming it cost friendly.

To protect itself, the study says, that managu develops a sweet smelling mixture of compounds on its leaves that are capable of fooling spider mites by attracting them to the plant.

“We found that when the mites reach the leaf’s surface, the “small hairs” on the leaf, trap the pests, hindering their further movement,” said Dr Lucy Kananu, lead author of the study.

“The disturbance caused by the mites on the leaf surface causes the succulent lobes of these hairs to crack. The cracked lobes then release secretions that contain foul-smelling chemicals that prevent the pests from laying eggs, thereby breaking their reproduction cycle,” she explained in a paper published in the current issue of the PLoS ONE journal.

DISTINCTIVE DEFENCE STRATEGY

Dr Kananu said past studies had demonstrated that while plants use various defence systems against pest attack, pests can overcome these defences, for instance by avoiding or suppressing them.

“Our findings show a distinctive defence strategy in this plant based on opposing roles, with the leaf fragrance acting as an attractant, while the stinking odours defend the plant against certain insect behaviours, such as egg laying. In effect the pest is lured to a ‘dead-end’ in its life cycle,” she added.

The findings are a fascinating discovery, given the growing attention on the vital role that indigenous vegetables can play in improving the nutritional security of many African households.

In Kenya, African nightshade is consumed widely and known variously by different communities. At the Coast, it is referred to as mnavu (Kiswahili), managu (Kikuyu), namasaka (Luhya), and osuga (Luo). It is an excellent source of protein, iron, vitamin A, iodine and zinc.

The tomato spider mite (Tetranychus evansi) causes serious damage, significantly hindering the production of African nightshade and other crops that are members of the family (tomato, potato, eggplant and tobacco and weeds like black nightshade, bitter apple and wild gooseberry).