AGP - Orobanche
 

The problem of Orobanche spp in Africa and Near East

By B.E. Abu-Irmaileh and Ricardo Labrada

 

Problems caused by Orobanche in the countries

Broomrapes (Orobanche spp.)are aggressive root parasitic weeds, which attack strategic food crops, such as legumes and vegetables, and threaten the livelihood of many nations. The continuous spread of Orobanche limits the choice of rotational crops and often force farmers to give up growing the most profitable host crops. Many farmers in the areas infested abandon agriculture altogether, forced to migrate and seek other means of income outside the rural domains.

Heavy Orobanche infestation does not only lead to a complete crop failure, but make field soils Orobanche-sick over a long period of time, preventing the reasonable production of legumes and vegetables in the infested fields for many years to come.  Failure of containing this parasite will be disastrous.

The continuous spread of the parasite in many countries is hastened by the lack of awareness about the biology of the parasite and the possible means of its management among farmers and personnel of the Ministries of Agriculture.

Orobanche crenata Forsk.

A survey on the impact of Orobanche conducted in a FAO Project in 1993 indicated that Orobanche crenata caused 12% losses in faba bean yield in Egypt and Morocco. The spread and the impact of the parasite are increasing ever since. The recent assessment on the impact of Orobanche in another FAO TCP, indicates that an average of 30-40% yield losses in faba bean was due to Orobanche in Egypt and in Morocco.

In Morocco, infestation of Orobanche in legumes progressed from 12% in 1981, 26% in 1994, to 30% in 2001 and  reached 51% in 2003 growing season. The estimated average yield losses due to Orobanche crenata in Morocco was 37.4% in 1998.  

Orobanche crenata infestation in Algeria spreads over 60% of the area in the middle coast and is continuing its spread from the middle zone towards the west. Orobanche ramosa is present in the east and west.

The main Orobanche species in Tunisia include Orobanche crenata, Orobanche foetida and Orobanche ramosa. The available data indicated that about 5 000 ha out of 70 000 ha planted to food legumes suffer from Orobanche infestation. Some farmers replaced food legumes by sunflower and garlic.

Egypt is now becoming an importer of faba bean to meet the dietary demand of the population. Faba bean was abandoned in Upper Egypt due to pest problems, including Orobanche crenata. Orobanche weeds significantly reduce the yields of tomatoes and peas. Its infestation in the newly reclaimed lands is high because of soil and manure transfer from the Wadi, grazing animals, and with water for irrigation. The average yield losses from Orobanche alone account for about 30 % of the total losses caused by all other crop management constraints.

In Ethiopia, the area of tomato production has increased many folds in recent years. However, due to Orobanche problems, some State Farms have had to give up growing tomato. Introduced Orobanche crenata is also a serious problem in areas of faba beans.

Orobanche ramosa L.

In Sudan, a complete failure of production was claimed due to heavy infestations of Orobanche. In fact, it was reported that tomato caning factory (Kariemeh) was closed down in the most suitable areas of tomato production, because farmers abandoned growing tomatoes due to Orobanche ramosa infestations. Orobanche crenata is of recent introduction in Sudan, and its heavy infestation hampered faba bean production in many sites. As faba bean cultivation is limited to specific ecological area, Sudanese officials are eager to halt the impact of this parasite as it can threaten the well being of the Sudanese nation. Faba bean is an essential daily diet in Egypt and Sudan, faba bean is consumed 2-3 times/ day).

In Lebanon, Orobanche parasitic weeds affect several crops, among them potato, tomato, eggplant and faba bean. The fast-spreading parasites namely Orobanche ramosa/eagyptiaca cause heavy yield losses in potato and tomato, while in potato, grown in 150 000 ha and 90% of it irrigated, the parasites are the main pest.   

In Syria, Orobanche accounted for about 5-15% of the total production management constraints facing Agriculture in the country.

The continuing invasion of Orobanche is exacerbated by the lack of knowledge of the farmers as well as the MOA officials about the biology and means of spread of these parasites. Many of the inherent practices spread the parasite. Planting contaminated locally produced seeds, spreading contaminated manure and soil, uncontrolled movement of grazing animals, moving contaminated machinery and lack of proper phytosanitary measures are among the malpractices that encourage the fast spread of Orobanche in many of these countries.  

Orobanche aegyptiaca Pers.
Brief summary of the FAO interregional project TCP/INT/3004

The recent FAO project on Orobanche found that most of the farmers do not apply any kind of control against Orobanche crenata; the nature of the parasitic weed is unknown to them; when infestations are high they plant other crops that are not affected by Orobanche. Some conduct hand weeding but leave the shoots of the parasite in the field. Most of the planting material is contaminated with Orobanche crenata seeds, while grazing animals in infested areas is a normal practice; and rented tractors pass from a farm to another without being cleaned before and by this way the infested soil is moved to clean farms/plots.

Among the control strategies it was seen that in the region Phytomiza fly exists and the insect should be protected using less insecticides in crops affected by Orobanche. It has already been demonstrated of the difficulty to rear this insect. Another possible biocontrol could be the use of specific Fusarium, which requires still more research for its formulation and application in the field .

Preventive measures are also important. Orobanche crenata was introduced in some countries in faba bean seeds infested by the weed seeds. Sometimes the parasite is located in one area of the country and it is relevant to prevent its further spread to other areas. The use of clean crop seeds is essential to contain the movement of the parasite.

In Egypt, tolerant faba bean varieties such as Misr 1 Giza 843, Giza 674, Giza 429 and Misr 2 are effectively used. Unfortunately no tolerant varieties have been found in the other affected countries.

In faba bean the use of glyphosate (40-60 g a.i./ha), applied when the “tuber” of the parasite starts to develop with an interval of 15 days between the applications,  has given good control results. In this case it is important to have the sprayers well calibrated before the application. Farmers in training activities learnt about the subterranean development of Orobanche and applied the herbicide just on time with control above 95%.

In areas of leguminous crops not heavily infested by Orobanche manual weeding at the beginning of flowering

The farmers training carried out in the project through the organization of Farmers Field Schools in the countries gave interesting results.

In addition, it was suggested to focus more on seed bank reduction. The issue on prevention/containment should also part of management.

Regular surveys and mapping are necessary to have better idea of the movement of the parasite in the countries.

Research is needed for generating new technologies and putting them on the ground, and also to validate them in the field. Such a validation can be done in FFS.   

Core Themes