Control of Orobanche (Broomrape) in Tomato and Eggplant

TECHNICAL BULLETIN 196 ISSN 0070-2315

CONTROL OF OROBANCHE (BROOMRAPE) IN TOMATO AND EGGPLANT

N.A. Vouzounis and P.G. Americanos

AGRICULTURAL RESEARCH INSTITUTE MINISTRY OF AGRICULTURE, NATURAL RESOURCES AND THE ENVIRONMENT

NICOSIA CYPRUS

OCTOBER 1998 Editor - in Chief Dr A.P. Mavrogenis, Agricultural Research Institute, Nicosia, Cyprus.

All responsibility for the information in this publication remains with the author(s). The use of trade names does not imply endorsement of or discrimination against any product by the Agricultural Research Institute.

2 CONTROL OF OROBANCHE (BROOMRAPE) IN TOMATO AND EGGPLANT

N.A. Vouzounis and P.G. Americanos

SUMMARY

Broomrape, Orobanche ramosa L. and/or O. aegyptiaca Pers., is a parasitic weed on several crop plants, including tomato (Lycopersicon esculentum Mill.) and eggplant (Sol- anum melongena L.), causing severe crop damage and yield reduction. Broomrape was completely controlled in the field by mulching the soil with black polyethylene sheeting on the day of transplanting tomato and eggplant seedlings. Glyphosate and sulfosate applied twice at 30 to 50 g a.e./ha were also very effective against broomrape but reduced yield of tomato. Despite severe toxicity to eggplants yield was not reduced. Imazaquin applied twice, at 5 to 10 g a.e./ha, was not very effective. Rimsulfuron, applied at 10 to 20 g a.i./ha, reduced broomrape dry weight and number of shoots. It was safe on tomatoes but was toxic to eggplant fruits causing malformation and splitting. Surface application of charcoal (15 g/m2) to the soil had no effect on broomrape infestation, whereas trifluralin incorporation at 900 g a.i./ha prior to planting had insignificant effect.

ΠΕΡΙΛΗΨΗ

Το παρασιτικό ζιζάνιο Οροβάγχη, O. ramosa L., ή το πολύ συγγενικό είδος O. aegyptiaca Pers., µπορεί να προκαλέσει σοβαρές ζηµιές σε φυτά τοµάτας και µελι- τζάνας και να µειώσει σηµαντικά την παραγωγή τους. Η Οροβάγχη καταπολεµή- θηκε αποτελεσµατικά (100%) µε κάλυψη του εδάφους µε µαύρο πλαστικό (0.04 mm) το οποίο εφαρµόστηκε την ηµέρα της φύτευσης των σποροφύτων σε έδαφος µολυσµένο µε το παράσιτο αυτό. ∆ύο ψεκασµοί µε τα ζιζανιοκτόνα γκλάϊφοσεητ ή σάλφοσεητ στις δόσεις 30 ως 50 γρ. δραστικής ουσίας στο εκτάριο σε κάθε ψεκα- σµό, και κυρίως οι πιο ψηλές δόσεις, ήταν πολύ αποτελεσµατικοί εναντίον της Οροβάγχης, αλλά µείωσαν την παραγωγή της τοµάτας και προκάλεσαν σοβαρή ζηµιά στα φυτά της µελιντζάνας χωρίς όµως να επηρεάσουν σηµαντικά την παρα- γωγή. ∆ύο ψεκασµοί µε ιµάζακουϊν 5 ως 10 γρ. δραστικής ουσίας δεν ήταν πολύ αποτελεσµατικοί. Το ριµσούλφουρον 10 ως 20 γρ. δραστικής ουσίας στο εκτάριο µείωσε το ξηρό βάρος και αριθµό βλαστών της Οροβάγχης, δεν επηρέασε τις τοµά- τες, αλλά ήταν τοξικό στις µελιντζάνες στις οποίες προκάλεσε παραµόρφωση και σχίσιµο του καρπού. Η επιφανειακή εφαρµογή ενεργοποιηµένου άνθρακα (15 γρ/ τετρ. µέτρο) στο έδαφος δεν είχε κανένα αποτέλεσµα εναντίον της Οροβάγχης ενώ η ενσωµάτωση τριφλουραλίνης (900 γρ δραστικής ουσίας στο εκτάριο) πριν τη φύτευση είχε µικρό αποτέλεσµα.

INTRODUCTION the Mediterranean and Asia but also in more temperate areas such as Eastern Europe, Tomato, Lycopersicon esculentum Mill., where it is one of the most serious problems and eggplant, Solanum melongena L., are in- in vegetable crops (Pieterse, 1979; Saghir fested by broomrape, i.e Orobanche ramosa and Dastgheib, 1978). All species produce a L., or O. aegyptica Pers., or both. The two very large number of tiny seeds which re- species (often confused taxa) are widespread main viable for many years, germinating in the Mediterranean region (Musselman, only in the presence of a suitable host. A sin- 1986, 1987). Generally, Orobanche species gle plant of Orobanche can produce over parasitise a large number of hosts of the fam- 100.000 seeds which can survive in the field ilies Solanaceae, Fabaceae and Brasicaceae for up to 20 years (Gold, et al., 1976). (Chater and Webb, 1972; Kasasian, 1971; Hence, the control of Orobanche species is Saghir and Dastgheib, 1978). Orobanche very difficult. Control has been attempted thrives in the hot climate of the Middle East, through the use of trap crops (Krishnamurty 3 et al., 1977), germination stimulants (Ed- were also included. The sprays for the first wards et al., 1973; Saghir; 1979, 1986), soil four herbicides were repeated after 15 days. solarization (Jacobsohn et al., 1980; Sauer- Trifluralin was incorporated in the soil prior born and Saxena, 1987; Abu-Irmaileh, to planting. Activated charcoal was surface 1991), rotations, selection of resistant varie- applied and irrigated in. Black plastic sheet- ties (Petzoldt and Sneyd, 1986) and chemical ing was laid down on the date of planting. methods including fumigation with methyl Herbicide application was made with a knap- bromide, metham-sodium and dazomet, that sack sprayer fitted with a flat fan nozzle. directly kill the seeds in the soil. Fumigation, Spray volume was 500 l/ha. Plot size was however, is tedious and expensive (Ramaiah, 5.0x1.0 m with treatments arranged in a ran- 1987). A more economical method, i.e. ap- domised complete block design with four plication of low rates of glyphosate was first replications. Approximately two and four reported by Kasasian (1973) with broad- weeks after the second application of herbi- beans. Since then there have been several re- cides the crops were inspected for symptoms ports on the successful use of this herbicide of toxicity. A few days before harvest began, in leguminous crops against O. crenata Orobanche was collected from a 5-m length (Schmitt et al., 1979; Americanos, 1983; Ar- of the row in each plot. The number of jona-Berral et al., 1984; Mesa-Garcia and shoots and the dry weight of the parasite Garcia Torres, 1985), but also against other were determined. Plots covered with black species of Orobanche, including O. cernua plastic sheet were sampled for Orobanche at Loefl. in sunflower (Castejon et al., 1987), the end of the harvesting period after the O. ramosa L. in tobacco (Lolas, 1986), O. plastic was removed. Treatment effects on aegyptiaca in celery (Jacobsohn and Levy, crop yield were examined only in one year 1986; Americanos, 1991) and in cabbage and are, therefore, only indicative. The data (Americanos and Vouzounis, 1995). Glypho- were analysed using analysis of variance sate application, however, is often phytotox- methods. ic (Mesa-Garcia et al., 1984; Mesa-Garcia and Vasquez-Cobo, 1985). More recently, RESULTS AND DISCUSSION imidazolinones have given promising results against O. crenata in both pre- and post- In the first two years of the trials (1993/ emergence applications to broadbeans (Gar- 94), infestation of Orobanche was heavy, cia-Torres and Lopez-Granados, 1991). To- and glyphosate, imazaquin and sulfosate ap- mato is one of the main hosts of O. ramosa plied on both tomato and eggplant crops (Musselman, 1980; Parker, 1986). In Cyprus, were effective against the parasite, signifi- it infests not only tomato but also eggplant. cantly reducing its dry weight and number of The present work concerns the use of shoots. The reduction was more marked for herbicides and soil mulching with polyethy- glyphosate and sulfosate, being over 50% lene sheeting to control Orobanche in tomato (compared to control) for the first two rates and eggplant crops. of both herbicides, reaching 85% for the highest rate in both crops (Tables 1 and 2). MATERIALS AND METHODS In the 1995 and 1996 trials, the highest rates of glyphosate and sulfosate were again very Eight trials, four with tomato and four effective against Orobanche but the erratic with eggplant crops, were conducted in distribution of the parasite did not always al- fields known to be infested with Orobanche, low differences to reach significant levels. from 1993 to 1996. Seedlings of both crops Imazaquin had a significant effect in only were planted in April in rows 1.20 m apart, two cases. In similar studies, Kotoula-Syka with 0.80 m spacing in the row, and were ir- and Eleftherohorinos (1991) found imaza- rigated with drippers. When the plants had quin ineffective. Yield data were collected produced their first flower cluster, they were only in 1996. The high rate of glyphosate sprayed with various rates of the herbicides and sulfosate reduced the yield of tomato, glyphosate, imazaquin or sulfosate, while in while the yield of eggplants was not affect- the trials of 1995 and 1996 rimsulfuron, tri- ed. However, in the 1995 trials both herbi- fluralin, activated charcoal and soil mulching cides completely destroyed eggplants (Table with black polyethylene sheeting (0.04 mm) 2). Similar glyphosate rates or even higher

4 Table 1. Effect of treatments on Orobanche ramosa/aegyptiaca and on the yield of tomato (cv. Muril)

Dry weight (g/5-m row) Shoots (no/5-m row) Tomato yield (kg/2 plants) Treatment Rate 1993-94* 1995* 1996* 1995* 1996* 1996

Charcoal (g/m2) 15 -- 136.6a -- 195.2a -- -- Plastic mulch -- -- 0.0d 0.0c 0.0e 0.0d 16.4 Glyphosate (g a.e./ha) 30 220.9bcd 27.0bc 51.0abc 48.5bcd 31.2abcd 4.8 40 246.1bcd 14.0cd 45.1abc 35.5bcde 25.2abcd 6.4 50 70.4e 1.6d 1.9bc 8.5de 2.2cd 2.9 Imazaquin (g a.e./ha) 5 354.9b 53.8b 56.1ab 73.7abc 44.8ab 8.1 7.5 260.4bcd 63.8b 0.7c 102.0abc 0.5d 11.0 10 298.6bc 56.4b 69.0a 88.2abc 49.2ab 10.6 Rimsulfuron (g a.i./ha) 10 -- -- 23.1abc -- 24.0abcd 12.6 15 -- -- 10.1abc -- 11.8abcd 11.2 20 -- -- 24.6abc -- 21.0abcd 13.7 Sulfosate (g a.e./ha) 30 204.0cd 16.7bcd 5.2bc 34.2bcde 9.3bcd 7.3 40 132.7de 9.8cd 2.5bc 17.0cde 3.8bcd 5.2 50 60.7e T 1.7bc T 2.5cd 3.3 Trifluralin(g a.i./ha) 900 -- -- 56.5ab -- 43.3ab 9.2 Untreated control -- 495.9a 54.3b 69.1a 104.2ab 64.5a 12.1

*Data were transformed to 1/(x+0.01)2 before analysis; Means within columns followed by the same letter are not significantly different at P<0.05 based on Duncan’s New Multible Rrange Test; T=complete crop destruction.

Table 2. Effect of treatments on Orobanche ramosa/aegyptiaca and on the yield of eggplant (cv. Bonica)

Dry weight (g/5-m row) Shoots (no/5-m row) Eggplant yield (kg/2 plants) Treatment Rate 1993-94* 1995* 1996* 1995* 1996* 1996

Charcoal (g/m2) 15 -- 116.3a -- 169.0a – – Plastic mulch -- -- 0.0c 0.0b 0.0 c 0.0b 7.9 Glyphosate (g a.e./ha) 30 126.1bcd T 36.0b T 20.0b 4.5 40 125.1bcd T 45.7ab T 25.8b 5.9 50 40.3e T 1.4b T 1.8b 4.9 Imazaquin (g a.e./ha) 5 171.0bc 102.5ab 74.5ab 144.2 ab 41.0ab 4.3 7.5 206.0b 72.9ab 76.8ab 78.7 ab 43.0ab 4.6 10 150.0bcd 51.4b 44.8ab 60.7 b 33.2b 6.6 Rimsulfuron (g a.i./ha) 10 -- -- 0.4b -- 0.3b 1.2 15 -- -- 31.0b -- 25.0b 2.7 20 -- -- 15.4b -- 9.8b 2.3 Sulfosate (g a.e./ha) 30 117.5cd T 33.8b T 38.2ab 5.7 40 76.0de T 4.1b T 3.3b 5.1 50 35.0e T 12.5b T 22.0b 6.3 Trifluralin (g a.i./ha) 900 -- -- 63.9ab -- 41.5ab 4.2 Untreated control -- 285.3a 112.5ab 155.1a 148.0 ab 119.2a 5.1

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