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Effect of Time of Spray Initiation of Rovral 50 Wp for the Management of Alternaria Blight of Cabbage Seed Crop

Md. Sakhawat hossain
Senior Scientific Officer
Plant Pathology Division, BARI, Gazipur

R. Momotaz
Scientific Officer
Plant Pathology Division, BARI, Gazipur

Abstract/ Executive Summary:

Effect of time of spray initiation of Rovral 50 WP on the incidence of Alternaria blight {Alternaria brassicae (Berk) Sacc. and A. brassicicola (Schew)} and seed yield of cabbage was studied in two successive crop seasons during 2005 – 2007 at the experimental field of Plant Pathology Division, BARI, Gazipur. Fungicide (Rovral 50 WP) spray was initiated at five different dates (i. one week before head incision; ii. at the day of head incision; iii. one week after head incision; iv. two week after head incision v. just after disease onset). Cabbage head was incised on 15 January in both the seasons. Fungicide was sprayed at 12 days interval at 0.2% concentration and was continued up to pod maturity (end of March). Irrespective of the time of spray initiation, Rovral 50 WP gave significant control of Alternaria blight as compare to control and the highest disease control (percent pod infection, number of spot/ pod and PDI of pod spot) was achieved when spray was initiated within one week of head incision (at the day of head incision and one week before and after head incision). The yield contributing characters like per plant pod number, pod length, per pod seed number were enhanced when fungicide spray was initiated at the day of head incision or one week before and after head incision. Seed yield per plant and per hectare was the highest when the Rovral spray was initiated at the day of head incision. Seed infection by Alternaria was more in control treatment and the plots where spray was started two week after head incision and just after disease onset. Good quality higher yield of cabbage seed with lower disease severity and the highest seed germination was obtained from the crop where Rovral spray was initiated at the day of head incision.

Keywords: Spray initiation, Alternaria blight, Cabbage

Location: BARI, Gazipur

Start Date: 01-07-2005

End Date: 30-07-2007

Program Area: Pest Management

Commodity: Cabbage

Objectives:

The present study was undertaken to find out the suitable time of initial spray to obtain maximum yield of good quality cabbage seed with minimum fungicides spray.

Methodology:

The experiment was conducted during the winter season of 2005-2006 and 2006-2007 at the experimental field of Plant Pathology Division, Bangladesh Agricultural Research Institute, Joydebpur, Gazipur. Rovral 50 WP (0.2%) spray was initiated at five different dates viz. one week before head incision, at the day of head incision (January 15), one week after head incision, two weeks after, just after disease onset at 12 days interval and continued up to pod maturity. A control treatment (spaying with plain water) was maintained for comparison. Recommended doses of manure and fertilizers were applied at the time of final bed preparation (Sattar et al. 2005). The experiment was laid out in a Randomized Complete Block Design (RCBD) with three replications. BARI Cabbage-2 (Agradute) was used as planting material and 35 days old seedlings were transplanted in 2 m x 1 m plots maintaining a plant spacing of 50 x 40 cm. Ten seedlings were transplanted in each plot in two rows. The seedlings were watered immediately after transplanting and continued for 3 days to facilitate their establishment. Agronomic practices like weeding, mulching and irrigation were done properly for better crop growth and development. Aphid infestation was controlled by spraying Malathion 57 EC @ 1.5 ml/L.

Five plants from each plot were randomly selected and tagged for data collection. At 70% pod maturity (partial yellowing), data on percent pod infection, number of spot/pod, disease incidence were recorded on the basis of 0-5 scoring scale and percent disease index (PDI) of pod spot was calculated. Number of pod/plant, pod length, number of seed/pod, seed yield per plant and per hectare was recorded just before or after harvest. After harvest the plants of each plot were stacked for 4 days, sun dried and then threshed manually for seed.

Source of Information: Annual Report (2007-08). Plant Pathology Division, BARI, Gazipur 67-69 pp.

Article Link (Online Journal):

Funding Source:

1. Government

Budget:

Total Budget (Tk.) :

Achievement/Findings:

Disease incidence: The lowest percentage of pod infection were recorded in plots where spray was started on one week before in 2005-2006 and just after disease on set in 2006-2007 crop seasons. In 2005-2006 and 2006-2007 crop seasons 100 and 97 percent pod infection was recorded in control plots, respectively. The effects of dates spray starting on spot number were statistically similar and these were significantly low compared to unsprayed control treatment in both the crop seasons. In 2005-2006 crop season, the lowest number of spot/pod was recorded in treatment where spray was started from one week after head incision followed by one week before and at the date of head incision spray. In 2006-2007 crop season the effect of dates spray showed almost similar trend of disease spot/ pod as 2005-2006. In 2005-2006, the significantly lowest and statistically similar PDI of pod spot was recorded on treatments where spray was started at the day of head incision and one week before and after head incision. Starting of Rovral spray at 2 week after head incision and just after disease onset had statistically similar PDI but significantly lower than the control treatment. In 2006-2007 crop season, the lowest PDI was recorded at the day of head incision and one week after head incision.

Yield components and seed yield : In 2005-2006 the largest number of pod/plant was recorded from the treatments where spray was started at the day of head incision followed by one week after and before head incision, respectively and the effect of these three treatments was statistically similar. Effect of other two treatments on pod number was non significant as compare to control. In 2006-2007 the significantly highest number of pod was recorded in treatment where spray was initiated on one week after head incision followed by just after disease onset. However, the effect of other treatments on pod/plant was statistically similar but significantly higher as compare to control. In 2005-2006 crop season, date of starting of fungicide spray had significant effect on pod length and the longest pods were recorded from the treatment where spray initiation occurred at the day of head incision which was statistically similar to one week before and after head incision. In 2006-2007, date of spray initiation did not have significant effect on pod length but the longest pods were harvested from one week before and one week after spraying plots. In 2005-2006, the significantly highest number of seed/pod was obtained from the plot where spray was started at the day of head incision. Number of seed obtained from one and two week after spray starting plots was statistically similar but significantly higher than control plot. However, the effect of one week before and just after disease onset spray treatment did not have significant effect as compare to control treatment. In 2006-2007, the treatments did not have significant effect on number of seed/pod but the highest number of seed/pod was recorded in plots where spray was started at one week after head incision. Starting dates of fungicide spray did not have significant effect on 1000 seed weight in both the cropping seasons. However, comparatively higher 1000 seed weight was recorded from plots starting to spray one week after head incision. The effect of treatment on seed yield/ plant was significant but seed yield/ ha was non significant as compare to control. In 2005-2006, the highest seed yields (per plant and per hectare) were obtained from the plots where spray was started at the day of head incision followed by one week after head incision. In 2006-2007, significantly higher seed yield/ plant was obtained in treatments where spray was initiated at one week after head incision and just after disease onset. The effect of other treatments on seed yield/ plant was non significant as compare to control.

From the results of these studies it may be concluded that for the management of Alternaria blight of cabbage seed crop, 5 – 6 spray of Iprodine starting from the date of head incision or one week after head incision is effective and economically profitable.

Knowledge Management: Report/Proceedings