Abstract: Six different genotypes of sunflower (Helianthus annuus L.) were screened against Aphids (Aphis gossypii), whitefly (Bemisia tabaci), leaf miner (Phytomyza atricornis), green leaf hoppers (Empoasca spp.), painted bugs (Bagrada spp.), and sunflower seed weevil (Smicronyx spp.) at, early, growing and anthesis stages. The results concluded that SMH-9707 was found partially resistant against aphids, whereas SF-187 was found less-susceptible against leaf miner and resistant against whitefly. Suncross-24 was found highly susceptible against painted bug among all the six genotypes of sunflower. SF-187. Parsun-1 and suncross-24 were partially resistant against green leaf hoppers. SMH-9707 was found highly susceptible against sunflower seed weevil and SF-187 was found partially resistant.
Introduction
Sunflower (Helianthus annuus L.) ranks second to soybean in vegetable oil production. As an oil crop it was introduced in Pakistan during early 1960's and its commercial cultivation started in 1965. Sunflower appears to possess tremendous potential for eliminating the country's edible oil problem as it contains 40.50% oil and 17-20 % protein contents (Bakhsh et al., 1999). It is grown both in irrigated as well as arid zones in Pakistan. Most of the area under sunflower (Helianthus annuus L.) is grown in Punjab and Sindh. It is grown in more concentration in the areas of Sargodha, Faisalabad, Sialkot, Gujranwala. Sheikhupura, Kasur, Okara, Sahiwal, Multan, Rahim Yar Khan and Vehari. The insect pests attacking this crop include Aphids (Aphis gossypii Glov), Whitefly (Bemisia tabaci Genn.), leaf minor (Phytomyza atricornis M.), Green stink bug (Nezara viridula L.), Green leaf hopper (Empoasca spp.) and sunflower seed weevil (Smicronyx spp.) (Aslam et al., 2000).
Due to an increasing importance of sunflower (Helianthus annuus L.) it became necessary to study insect pests associated with this crop and to find resistant varieties for their control. Resistance of plants to insect attack may be defined as the relative amount of heritable qualities possessed by the plant which influence the ultimate degree of damage done by the insect. In practical agriculture it represents the ability of a certain variety to produce a larger crop of good quality than do ordinary varieties at the same level of insect population. Plant may be non-preferred for oviposition, shelter or food because of presence or lack of chemicals or physical factors (Maxwell et al., 1972). Rafiullah et al. (1998) screened sunflower genotypes against insect pests including loopers, whiteflies and lassids under field conditions and found that among the genotypes screened, Peshawar-28 and Parental line RHA-274 showed resistance to whitefly at both seedling as well as anthesis stage. Singh et al. (1994) studied comparative incidence of Bihar hairy caterpillar Spilosoma obliqua Walker on different cultivars of sunflower.
The objective of this study is to screen the sunflower genotypes against insect pests so as to find some genotypes which may show some resistance against different insect pests. By sowing such varieties the dependence on the heavy use of pesticides will be minimized and also our environment will be saved from the ill effects of pesticides.
Materials and Methods
Six different sunflower (Helianthus annuus L.) genotypes, grown in the field. of University of Arid Agriculture, Rawalpindi were screened to observe their susceptibility and resistance level against different insect pests which included Aphis gossypii (Aphids), Bemisia tabaci (whitefly), Phytomyza atricornis (Leaf Miner), Bagrada spp. (Punted bug), Empoasca spp. (Green leaf hopper) and Smicronyx spp. (sunflower seed-weevil).
The experiment was conducted in a Randomized Complete Block Design with four replications. Each genotype had 4 rows. The sunflower (Helianthus annuus L.) genotypes screened included Hysun-33, SF-187, PARSUN-1, Suncross-24, SMH 9706 and SMH 9707.
Hysun-33 was kept as standard susceptible check because it was the commercial variety in Punjab. The data were collected from five plants of each genotype which were tagged randomly by adopting draws method. Data for different insects were recorded. The number of insects were counted per plant basis from the five tagged plants of each genotype. Data were taken on 4 days basis. The plants of sunflower cultivars were observed through naked eye for counting the number of insects. The lens was used for observing-aphids (Aphis gossypii) and whitefly (Bemisia tabaci). The leaf was turned upward for taking data for aphids, whitetly and leaf hoppers with forceps. Data were taken very carefully so that insects may not be disturbed. The number of insects found on leaves, stems and flowers were recorded- date wise in the form of tables.
The data were analyzed by using statistical software of MSTATC and LSD test was applied to compare the means. Means were compared with the susceptible (standard) check to find out cultivars susceptible, highly susceptible. partially resistant or resistant following Aslam et al. (1999).
Results and Discussion
Data were recorded on the number of Aphis gossypii (cotton aphid), Bemisia tabaci (whitefly), Phytomyza atricornis (leaf miner), Empoasca spp. (Green leaf hopper) Painted bug (Bagrada spp.) and sunflower seed weevil (Srnicronyx spp.). The results are explained and discussed below for each insect pest separately.
Cotton Aphid (Aphis gossypii): Table 1 reveals that SMH-9707 attracted the lowest number of aphids as compared to Hysun-33 and was found partially resistant against aphids. Other four genotypes SF-187, PARSUN-I, Suncross-24 and SMH-9706 were not significantly different from Hysun-33. So these four varieties are also susceptible to aphids.
Rogers and Thompson (1978) observed wild perennial species of Helianthus for resistance to aphids and found them significantly resistant to aphids.
| Table 1: | Mean number of aphids, leafminers and whiteflies observed during early and growing stage on six different sunflower genotypes |
Means followed by the same letters do not have significant difference at Alpha =0.05 | |
When day wise data were analyzed we found significant difference in means of aphid population with passage of time (Table 2). At first attack was less but as the temperature increased the aphid population was also increased but at higher temperature the population started declining (Table 2).
Ahuja (1990) found that the aphid population had a negative correlation with maximum and minimum temperature. Aphid's attack on sunflower crop during seedling stage was more rapid and then its population started declining (Table 2). Young seedlings of sunflower were more attacked by aphids (Hatam and Abbasi, 1994).
| Table 2: | Means number of aphid population observed during early and Growing stages on sunflower genotypes during different days at different temperatures |
Means followed by the same letters do not have significant difference at Alpha = 0.05 | |
Leaf Miner (Phytomyza atricornis): Table 1 reveals that SF-187 had minimum population mean value i.e. 0.5125 which was different from Hysun-33. By comparing SMH-9706 and SF-187, we conclude that SF-187 is partially resistant to leaf miner's attack and SMH-9706, SMH-9707 and Suncross-24 did not differ from Hysun-33. PARSUN-1 was intermediate in attracting the number of leaf miners. All the varieties had different zigzag/irregular mines. Phytomyza atricornis makes irregular mines into the leaves of sunflower plant (Sethi et al., 1978). The population of leaf miner also decreased with the passage of time on sunflower. Because leaf miner had more attack at seedling and growing stage and when the newly emerged foliage fell, their attack decreased (Table 2). According to Sethi et al. (1978) due to mines made by Phytomyza atricornis, leaves become yellow and fall down. As the sunflower crop became older, the attack of leaf miner was decreased (Table 2).
Whitefly (Bemisia tabaci): Data were recorded for evaluation of population and non preference of different sunflower cultivars against whitefly, the results found were significant (Table 1).
According to Table 1 there was significant difference between Hysun-33 and SMH-9707. Hysun-33 had mean population 0.4313 which is significantly different from SMH-9707 (0.6937). So SMH-9707 is highly susceptible whereas by comparing Hysun-33 and considering Hysun-33 as susceptible we concluded that PARSUN-1 is also more susceptible to whitefly. Whereas other two varieties Suncross-24 and SMH-9706 are susceptible and SF-187 is partially resistant. Rafiullah et al. (1998) conducted an experiment and observed resistance in Peshawar-21, Pesh-1, Pesh-3, Pesh-22, Pesh-28, HA-89, HA-300, HA-821 and HA-274 against whitefly. It was also observed that there was significant difference in population of whitefly as the days passed (Table 2). Whitefly attack was very high at young seedlings and it decreased with the passage of time. According to Hatam and Abbasi (1994), young seedlings were more attacked by whitefly. Mustafavi (1981) concluded that whitefly multiplied rapidly under high temperature. So at high temperature population was more, but it decreased with passage of time (Table 2).
Green Leaf Hopper (Empoasca spp.): Data recorded showed highly significant results. It means that these six sunflower genotypes had significant difference in mean population of leaf hoppers (Table 3).
By comparing Hysun-33 with other five genotypes we found that SMH-9706 had significant difference having highest population mean i.e. 23.60 so it was highly susceptible. Whereas SMH-9707 having mean (22.86) did not differ from Hysun-33 and SMH-9706. Other three genotypes SF-187, PARSUN-1 and Suncross-24 had very less significant difference in population mean, so they were less susceptible, but by comparing with SMH 9706 which was found highly susceptible, SF-187, PARSUN-1 and Suncross-24, were found partially resistant against green leaf hoppers (Table 3).
| Table 3: | Mean number of green leaf hoppers, shield bugs and seed weevils observed during late growing and anthesis stages on six different sunflower genotypes |
Means followed by the same letters do not have significant difference at Alpha = 0.05 | |
Rogers (1981) evaluated twenty nine species of sunflower in laboratory for resistance to Empoasca spp. (Leaf hoppers). Development was significantly (at 5% level) prolonged and survival was sginficantly decreased on most of the species of Helianthus than on hybrid 896.
There was no attack of leaf hopper at seedling and early growing stages on any of the genotypes of sunflower. Rogers (1981) conducted research on various species of sunflower and found that several species of Helianthus had resistance against leaf hopper.
Painted Bug (Bagrada spp.): Hysun-33 had the lowest population so it was less preferred by shield bugs. By comparing SF-187, PARSUN-1 with Hysun-33, no significant difference was found, so these were also less attacked by shield bugs but these were susceptible ones, as we had considered Hysun-33 as susceptible although less preferred in this case. But Suncross-24 has highest population and significantly different from Hysun-33 so it was highly susceptible. SMH-9706 and SMH-9707 were found partially susceptible (Table 3).
Aslam et al. (2000) found that green stink bugs attack sunflower crop in different areas of Potohar region. Shield bugs were found sucking sap from flower bracts.
Tingid bug (Gleatus serophicus) suck cell sap from the leaves, stem and flower bracts of sunflower crop (Sandhu et al. 1973). Suncross-24 had highest population mean and Hysun-33 had lowest (Table 3). The attack of shield bug was observed only at anthesis stage. At seedling stage and early growing stage there was no attack of shield bug.
Sunflower Seed Weevil (Smicronyx spp.): Table 3 reveals that SMH-9707 had the highest number of sunflower seed weevils and SF-187 the lowest, so SMH -9707 was found highly susceptible and SF-187 was found partially resistant when compared with the standard one. Brewer and Charlet (1989) found resistance of sunflower germplasm against Smicronyx fulvus. It was also observed that sunflower seed weevil attacked sunflower only during the anthesis stage. The results reveal that SMH-9707 was found partially resistant against aphids, whereas SF-187 was found less susceptible against leaf miner and resistant against whitefly. Suncross-24 was found highly susceptible against painted bug. SF-187, Parsun-1 and suncross-24 were partially resistant against green leaf hoppers. SMH-9707 was found highly susceptible against sunflower seed weevil and SF-187 was found partially resistant.
The results show that there were great variations in the genotypes of sunflower as regards number of different insect pests attracted to them. These variations have proved very helpful in selecting sunflower plants resistant to insects. By planting resistant genotypes, the dependence on the use of pesticides will be reduced and pollution problems due to heavy use of insecticides will also be minimized.