Could the ‘push-pull’ system for control in Africa work on Phelipanche ramosa and Orobanche crenata ?

Mohamed Shrif • Alistair Murdoch • Irene Mueller-Harvey Push-pull habitat management system designed for control of stem borer DESMODIUM NAPIER PUSH PULL PhotobyNjihia, Sam Kenya KARI,

MAIZE Plot sizes: 15 x 15 to 50 x 50 metres Napier Desmodium Maize System developed by Khan and co-workers at ICIPE in Kenya The push-pull strategy in the field

Photo from Francis Muyecko, KARI, Kenya “But my main problem is NOT stem borer, it’s Striga” “And mine is actually Orobanche/ Phelipanche”

SERENDIPITY! Objectives

• To determine whether this ‘push-pull’ control system developed by ICIPE in Western Kenya using Desmodium intortum (Silverleaf) and D. uncinatum (Greenleaf), could be adapted to control Phelipanche and Orobanche • Results here for two Greek seed lots (D1 and D6) of Phelipanche ramosa kindly supplied by Falia • Results not presented today on Orobanche crenata and also for . Experimental system Reading University, 2009/10

Desmodium No Phelipanche ramosa Desmodium

Tube Tube Tomato Upper pots Desmodium Greenleaf or Lower pots Desmodium Silverleaf Host of Striga (Millet), Pea for O.crenata and Tomato for Phelipanche ramosa Shoots of P.ramosa parasitising tomato

Shoots per pot LSD (P=0.05) = 32.80 D6 D1 P. ramosa P. ramosa Silverleaf + D6 Silverleaf Greenleaf + D6 Greenleaf Greenleaf + D1 Greenleaf Silverleaf + D1 Silverleaf Dry weight of shoots of P.ramosa (D1 & D6) parasitising tomato Shoot dry weight per pot , mg LSD (P=0.05) = 4.1 mg D6 D1 P. ramosa P. ramosa Silverleaf + D6 Silverleaf Greenleaf + D6 Greenleaf Greenleaf + D1 Greenleaf Silverleaf + D1 Silverleaf Flavonoid compounds affecting Striga hermonthica HPLC trace • Dual action A. Germination stimulation B. Inhibition of subsequent growth • Overall effects – reduced attachment to host B A – suicidal germination

Inhibition of Germination stimulation subsequent growth

From Pickett, Hamilton, Hooper, Khan and Midega (2010) Ann. Rev. Phytopathol. 2010.48:161- 177 Attachments (in vitro) study using conditioned and GR24-stimulated P. ramosa seeds and Desmodium greenleaf exudates at a range of concentrations So far so good

Now for the bad news! Height, cm, of tomato 14 weeks after planting

LSD, P=0.05 D6 D1 Control Silverleaf Greenleaf P. ramosa P. ramosa Silverleaf + D6 Silverleaf Greenleaf + D6 Greenleaf Greenleaf + D1 Greenleaf Silverleaf + D1 Silverleaf Negative effects of Desmodium and P. ramosa on tomato

Treatment Height Shoot weight Fruit weight Tomato only 120 cm 55 mg 31 mg Desmodium - 19% - 39% - 68% uncinatum (Silverleaf) Desmodium intortum - 21% - 38% - 62% (Greenleaf) P. ramosa seed lot D1 - 25% - 43% - 39% P. ramosa seed lot D1 - 48% - 69% - 36% + Silverleaf P. ramosa seed lot D1 - 36% - 69% - 81 % + Greenleaf

LSD (%) P = 0.05 8 % 13% 6% Conclusions

• Both Desmodium species effectively reduced the number and dry weight of Ph. ramosa shoots parasitising tomato • Ph. ramosa seed lot D1 was affected by the Desmodium more than D6 • Desmodium , however, reduced tomato height and yield

So sorry, the answer to the question posed is yes and no Acknowledgements Our grateful thanks to the government of Libya for a scholarship to Mohamed Shrif To Laurence Hansen and Caroline Hadley for technical assistance ( Environment Laboratory), To Ron Brown (Chemistry& Biochemistry Laboratory) for their technical assistance