Occurrence of Whitefly, Bemisia tabaci (Genn.) in Chili, Capsicum frutescens L., at Multan, Pakistan.
The research was conducted to study the occurrence of whitefly, Bemisia tabaci (Genn.), on chili, Capsicum frutescens L., in Multan, Punjab (Pakistan).
In 2007 five chili varieties were planted whereas in 2008 one variety was planted on three different dates. B. tabaci adults were recorded per plant. Whitefly was active during May in both years and did not exceed two adults per plant.
Key words: Whitefly, chilies, Pakistan
Chilies, Capsicum frutescens L., are ingredients of the daily diet of people of Pakistan, India and other Asian countries (Sanyal et al., 2008). They are used as vegetables and as spices for improving the flavour of foods. Green chilies are also consumed; these are rich in vitamin A and C and seeds contain traces of starch (Muthukrishnan et al., 1986). Literature reports different results about the pest status of whitefly, B. tabaci (Genn.), and other insect pests of chilies from different parts of the world. Chilies had been reported as an alternate host of whitefly, B. tabaci in 1930s in Pakistan (Hussain and Trehan, 1933). It has been also argued recently that chilies are important sources of B. tabaci that moves into cotton (Attique et al., 2003; Rafiq et al., 2008) in cotton growing areas of Pakistan.
The Multan district of Punjab, Pakistan has an arid climate and receives mean annual rainfall of about 125mm. The winter season extends from November to February. There is a short spring during March (Amer et al., 2009). Chilies are sown only once in a year in Multan. Chilies are sown as Kharif crop (summer crop) and normally are transplanted from nursery to field in mid February (Iqbal, 2009). There is no judicious application of insecticides in the developing countries. There are no reports in the literature of detailed research on insect pests, their seasonal activity and management on chilies from Multan. The present study was undertaken to determine the occurrence of B. tabaci on different genotypes of chilies and on crops planted at different dates at Multan.
Materials and methods
Experiments were conducted at the experimental farm of the University College of Agriculture, Bahauddin Zakariya University, Multan. During 2007 seeds of five genotypes viz., CV-7, Nepal-S, NARC-4, CV-4 and Nepal-L were obtained from Institute of Horticulture, National Agricultural Research Centre (NARC), Islamabad. Plastic pots (45x45x15 cm size) were filled with fine soil and seeds were sown in these pots. Seed of each variety was sown into a separate pot on February 4, 2007. Pots were placed in a room furnished with electric heater. After two weeks pots
were put outside to acclimatize the plants to the open environment. These nursery plants were transplanted into the field on March 15, 2007. Experiment was laid out in a randomized complete block (RCB) design with three replications. Plants were transplanted on a ridge of 4 m length. Distance between ridges was 45 cm and the distance between plants was 30 cm. Each treatment consisted of three ridges. Treatments and replications were 0.5m and 0.9 m apart, respectively. Crop was irrigated when needed. Weeds were manually removed from the crop by hoeing.
The 2008 experiment was also a randomized complete block (RCB) design. Nursery plants of a local variety, Tattapuri, were purchased from the market for each transplanting date and were transplanted at three different sowing dates i.e., 3rd, 11th and 18th of March, 2008.
Beds were prepared and chili nursery plants were transplanted on both sides of beds. Each bed was 12 m long and 30 cm wide. Distance between beds was 45 cm and plant to plant distance was 30 cm. There were three replications in each sowing date. Each replication consisted of four beds. Replicates were 0.9 m apart. Uniform practices were followed in both the trials in each year.
In both years the chili crops were observed and B. tabaci numbers recorded from transplanting until the end of the growing season. Whitefly numbers were recorded early in the morning from five plants selected randomly from each plot in 2007. For this purpose plants were gently turned on opposite side of sun to count whitefly adults, as these are usually present on lower side of the leaves. Whiteflies were counted from the whole plants.
During 2008 numbers of whiteflies were recorded from 15 plants from each sowing date. Five plants for this purpose were randomly selected from each replicate of a sowing date. Similar method was employed for recording whitefly adults as described for 2007. Numbers of B. tabaci were recorded three times in each year, starting from 15th May and 7th May in 2007 and 2008, respectively.
Numbers of whitefly were converted to mean density per plant. Data on mean population were analyzed using Analysis of Variance (ANOVA) and differences among means were separated by calculating Least Significant Difference (LSD) test (at P= 0.05) (Steel and Torrie, 1980) by computer software MSTATC (MSU, 1982).
Results and discussion
Numbers of B. tabaci per plant were non-significantly different on all the genotypes during 2007. Numbers were less than two per plant on all genotypes on three sampling dates (Table I). Population density of B. tabaci was statistically similar and higher on chilies planted on 3rd and 11th of March, as compared to that of on 18th of March during 2008 across all the sampling dates. Higher numbers of B. tabaci were observed on 16th May 2008 on chilies transplanted on 3rd and 11th of March during 2008. Numbers of whiteflies adults were less than two per plant (Table II). Negligible numbers of B. tabaci after 23rd of the May were noted, therefore population was not recorded after this date. This might be due to rise in temperature as June is hotter than May in Multan.
Table I.- Population of whitefly, Bemisia tabaci (Genn.),adults per plant recorded on different sampling dates during 2007 at Multan.
Genotypes###Number of whiteflies###
###15th May###22nd May###29th May
CV-7###1.78 NS###1.61 NS###1.79 NS
Table II.- Whitefly, Bemisia tabaci (Genn.), adults population on Tattapuri variety of chilies planted on different dates and sampled during, 2008 at Multan.###
Date of###Number of whiteflies###
*In each column means not sharing similar letters are significantly different at P = 0.05
Whiteflies have been reported as minor insect pests of chilies from cotton growing areas of the Punjab, Pakistan (Attique et al., 2003) . This study recorded low numbers of whiteflies on chilies. Very low populations of whiteflies have been observed on chilies in Sri Lanka (Burleigha et al., 1998), but B. tabaci has been reported as major insect pest in India (Sanyal et al., 2008).
From this study it is concluded that whitefly attacks chilies in low numbers. Such low numbers of B. tabaci may not cause economic damage as we observed that apparently plants did not show any symptoms of damage due to feeding by this insect. However, further research should be conducted by comparing yield and growth of chili plants kept free from whiteflies by insecticides or by caging the plants with that of infested plants. In developing countries farmers usually apply pesticides without knowing status of pests and diseases. However, no literature reports pesticide use patterns from this area. Therefore, caution is needed for application of insecticides. This study might have limitations as experiments were conducted at only one location, and cropping schemes of the farmers may affect population of insect pests particularly whitefly as it is polyphagous pest feeding upon wide variety of plants. Moreover, there is need to investigate insecticide use pattern to determine whether pesticides are applied or not
Funds for research were provided by Bahauddin Zakariya University, Multan, Pakistan.
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(Received 21 June 2010, revised 13 July 2010)
Department of Clinical Medicine and Surgery, University of Veterinary and Animal Sciences, Lahore
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|Publication:||Pakistan Journal of Zoology|
|Date:||Apr 30, 2011|
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