AN EVALUATION OF HERBICIDE TREATMENTS FOR THE CONTROL OF Aleclra Vogelii Benth and Striga gesnerioides (Wild) Vatke IN COWPEA (Vigna unguiculata (Li WALP)

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Date
1999-04
Authors
CHIBIYA, PAUL SHINGGU
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Abstract
Seed treatment of acetolactate synthase (ALS) inhibitor herbicides, cinosulfuron and CGA152005 were evaluated for the control of parasitic weeds, Alectra vogelii Benth and Striga gesnerioides (Wild.) Vatke in cowpea (Vigna unguiculata (L.) Walp) at the Institute for Agricultural Research, Ahmadu Bello University, Samaru during the 1994 dry and 1995 wet seasons. The treatments consisted of five cowpea varieties (IT81D-985, SAMPEA 7, SAMPEA 6, IT90K-102-6 and IT89KD-245-1) and 10 herbicide seed treatment, cinosulfuron at 0.05, 0.1, 0.2 and 0.4 and CGA152005 at 0.008, 0.016, 0.032 and 0.064 g/1 including the water soaking and dry planting no herbicide controls. The treatments were laid out in in completely ramdomized design (CRD). In the laboratory and screen house and split plot design in the field varieties were the main plot treatment while the seed treatments were allocated to the sub-plots. The cowpea varieties IT90K- 102-6 and IT81D-985 were susceptible to the herbicide seed treatments evaluated as reflected in depression in seed germination, poor stand establishment as well as high injury and low crop vigour score with and without parasitic weed infestation in the screen house. The nodulation of the cowpea varieties was also lower than the maximum obtained with IT89KD-245-1 with and without parasitic weed infestation in the field. Variety IT90K-102-6 also produced lower leaf dry matter than the maximum produced by SAMPEA 6 in the trials. The variety SAMPEA 6 produced higher cowpea grain yield than SAMPEA 7 and IT81D-985 inspite of high parasitic weed infestation and incidence. Cowpea variety SAMPEA 7 produced the least 1000-grain weight with and without parasitic infestation while IT89KD-245-1 produced the heaviest seeds. Both SAMPEA-7 and SAMPEA 6 supported the highest infestation and incidence of Striga and Alectra in the study. IT89KD-245-1 and IT90K-102-6 however supported lower number of Alectra and incidence than the varieties and IT81D-985. Striga emergence was also delayed on varieties IT81D-985, IT89KD-245-1 and IT90K-102-6 compared with SAMPEA 6 and SAMPEA-7. The seed treatments differentially affected parasitic weed infestation and incidence as well as the vigour, growth and yield of cowpea. CGA152005 at 0.064g/l with Alectra infestation and at 0.032 and 0.064g/l with infestation caused significantly higher injury score of cowpea compared with the lower concentrations and no-herbicide controls. Similarly, the highest ratesr of the two herbicides CGA152005 at 0.064g/l and cinosulfuron at 0.04g/l resulted in lower vigour score than their corresponding low concentrations in the screen house with and without Alectra inoculation. CGA152005 at 0.032 and 0.064g/l also reduced shoot dry weight of cowpea significantly compared with the no-herbicide controls. Similarly the nodulation of cowpea was depressed by cinosulfuron at 0.2 and 0.4g/l and CGA152005 at 0.016 to 0.064g/l with parasitic weed infestation. Under parasitic weed infestation, CGA 152005 at 0.032 and 0.064g/l however produced significantly higher cowpea grain yield than cinosulfuron at 0.05 and 0.1g/l, CGA152005 at 0.008g/l and dry planting control as a result of effective reduction of parasitic weed infestation. Cinosulfuroin at 0.04g/l and the planting of water-soaked seeds also resulted in higher cowpea grain yield than dry planting no-herbicide control. Cinosulfuron at 0.2 and 0.4g/l and CGA152005 at 0.032 and 0.064g/l significantly delayed the emergence of the parasitic weeds in the screen house and field. Alectra/Striga emergence was also delayed by cinosulfuron at 0.4g/l and CGA152005 at 0.064g/l compared with the lower rates while cinosulfuron at 0.2g/l and CGA152005 at 0.032g/l delayed Striga emergence only. The herbicide seed treatments reduced the number of emerged and unemerged Alectra in the screen house and Alectra/Striga shoot infestation and incidence on cowpea in the field. CGA152005 at 0.032 and 0.064g/l caused more effective reduction of infestation than the other herbicide treatments. Yield loss due to the parasitic infestation was 12.7% for SAMPEA 6 to 34.7% for SAMPEA 7. The interactions of varieties and herbicide seed treatments on number of days to 50% flowering without parasitic weed infestation was significant in the trial
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A thesis submitted to the Postgraduate School, Ahmadu Bello University, In Partial Fulfillment of the Requirements for the Degree of Master of Science in Agronomy Department of Agronomy Faculty of Agriculture Ahmadu Bello University Zaria, Nigeria April, 1999
Keywords
EVALUATION,, HERBICIDE,, TREATMENTS,, CONTROL,, Aleclra Vogelii Benth,, Striga gesnerioides (Wild) Vatke, COWPEA,, (Vigna unguiculata (Li WALP).
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