Push-pull technology

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Push-pull technology is a method for biological pest control . Plants with a repellent effect are used within the culture, while those with an attractive effect are used to drive the insects away from the useful plants (push) or to attract (pull) them.

development

The infestation by stem borer , a relative of the European European corn borer , leads to considerable crop losses for small farmers in East Africa. Other problems are the parasitic striga and the low nutrient content of tropical soils. Pesticides and fertilizers are unaffordable for subsistence farmers . To combat the stem borer, push-pull technology was developed at the International Center of Insect Physiology and Ecology (ICIPE) under the direction of Hans Rudolf Herren in collaboration with the Kenyan Agriculture Research Institute (KARI) and Rothamsted Experimental Station . It was discovered thatDesmodium ( Desmodium adscendens ) not only repels the stem borer moths, but also kills the Striga.

Mode of action

Desmodium as a repellent is planted between the rows of crops , while napier grass ( Pennisetum purpureum ) is planted as a "trap" in a belt around the field. The stem borer moths are lured away from the grain to the napier grass in order to lay their eggs there and not on the leaves of the grain. Repulsive as well as attractive effects are based on so-called volatile , volatile organic compounds ( VOC , abbreviation for volatile organic compounds), which the insects use for orientation and for finding the host plant . Napier grass as well as desmodium are perennial and can easily persist for more than ten years. Once the grain has been harvested, the rows of grain are chopped or plowed, while the rows of desmodium and napier grass are merely cut back before being re-sown.

Combating the stem borer

While the Desmodium ejects volatile, the stem borer repel, the napier grass produces a volatile mix similar to that of the grain. However, in much larger quantities than is the case with grain, so that the female stem borer lays her eggs preferably on the leaves of the Napier grass. When the hatching larvae attempt to penetrate the stem of the grass, the grass produces a slimy substance that kills the pest .

Combating Striga

The parasitic striga germinates when the seed senses the presence of so-called root exudates given off by the corn roots. As a result, it attaches itself to these and removes sugar from the corn plant . The Desmodium produces root exudates, which also stimulate the germination of the Striga seed, but at the same time also substances that kill the germ immediately. This not only prevents the seeds from developing, but also actively removes them from the soil. This is important because a single Striga plant produces up to 20,000 seeds that remain viable in the soil for up to 20 years.

Improvement of soil fertility

Like all legumes , Desmodium can organically bind atmospheric nitrogen and thus make it available for its growth and that of the surrounding plants. Research at ICIPE found that the amount of nitrogen released is pretty much what corn needs for optimal growth. In addition, the dying leaves and roots of desmodium add organic material to the soil , which promotes soil organisms and increases the availability of nutrients.

Supply of cattle feed

Napier grass is very fast growing and grows up to four meters high. Parts of the napier grass belt can be harvested without affecting the protective function and are used as fodder. Desmodium can also be used as fodder if it is cut back after harvest. The mixture of the two plants is nutrient-rich and is available in the dry season when other food sources dry up.

Other positive effects

The soil is protected from erosion by the soil cover of the Desmodium . In addition, the increased shade inhibits evaporation and the water retention is improved. The seeds of the Desmodium can be harvested and sold. The proceeds of 600 Kenya shillings (around 6.50 euros per kilogram) are a welcome source of cash.

Individual evidence

  1. ^ A b Khan ZR, Hassanali A, Khamis TM, Overholt WA, Hooper AM, Pickett JA, Wadhams LJ, Woodcock CM. 2002. Control of the witchweed, Striga hermonthica, by intercropping with Desmodium spp., And the mechanism defined as allelopathic. Journal of Chemical Ecology 28: 1871-1885.
  2. ↑ pers. Come. Western Seeds Company

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