Orobanche aegyptiaca (Egyptian broomrape)

The symptoms produced by O. aegyptiaca are comparable to those of O. ramosa. There are no very distinctive symptoms but there may be some yellowing and necrosis of the foliage, general weakening of the plant and reduced fruit production.

Phytosanitary Measures

Most countries prohibit entry of major parasitic weed species, including Orobanche spp.

Phytosanitation is aimed at preventing the spread of viable seeds by minimizing the movement of infested soil by farm machinery and vehicles, preventing grazing on infested plant material, treating manure (e.g. composting) and avoiding the use of hay made of Orobanche-infested plants (Jacobsohn, 1984). One should also avoid the use of Orobanche-infested crop seeds.

Cultural Control

Hand-weeding of emerged stems is too late to prevent crop damage but may be worthwhile where infestations are still light, to prevent or reduce future infestations. The stems should immediately be removed from the field to preclude seed shed after pulling.

Trap crops may be used to promote germination of Orobanche seeds in soil, without themselves supporting parasitism, in order to deplete the seed reserve. Examples of trap crops for O. ramosa include flax, Phaseolus bean, sorghum, maize and cucumber (Parker and Riches, 1993). There are few examples of the fully successful use of this principle, but it should be considered in any integrated control approach.

Soil solarization, based on mulching moist soil with polyethylene sheets for several weeks under solar irradiation, can provide excellent levels of control of Orobanche seeds in the upper soil layers where temperatures are high enough (Jacobsohn et al., 1980), and this has been confirmed in a number of studies involving O. ramosa (see Parker and Riches, 1993).

Kebreab and Murdoch (1999) showed that seeds maintained at high mositure and high temperature lose viability relatively rapidly. This could explain the success that has been occasionally reported from prolonged flooding or water-logging (e.g. Mohamed-Ahmed and Drennan, 1994). A period of at least 6 weeks may be needed.

Host-Plant Resistance

Screening of tobacco and tomato varieties against O. ramosa or O. aegyptiaca have demonstrated some variations in susceptibility (see Parker and Riches, 1993; Qasem and Kaswari, 1995) but there are no reports of successful application of these results.

Biological Control

The fly Phytomyza orobanchia has been used for biological control of Orobanche spp. and was effective in the former Soviet Union for decades, using special rearing and inundative release techniques. However, this became less effective due to the spread of hyperparasites (see Kroschel and Klein, 1999, for a detailed review).

O. aegyptiaca is recorded by Holm et al. (1979) as a 'serious' or 'principal' weed in Afghanistan, Arabia, Iran, Jordan and Italy. It is certainly a major problem in many countries of the Middle East and eastern Europe, especially on tomato, tobacco, aubergine and cucurbits. There are reports of 50% yield reduction of watermelon (Panchenko, 1974).