Cotton is very important industrial crop that providing the raw material of textile and food in Turkey. It is cultivated in 719, 294 hectares and yield 2,816 kg ha-1 (Anonymous, 2000). In our cotton production, it has increased by Southeast Anatolia Project (GAP) since 1995. Sanliurfa is located Southeast Anatolia Region of Turkey and covers 20% of Turkeys total cotton production area (Anonymous, 1998). Harran Plain is located within the borders of Sanliurfa Province in the South East Region of Turkey, which was the place where Mesopotamia civilization flourished, stretches southward from Sanliurfa to Syria border.
Lepidoptera is second among insect orders in number of Species (Carter, 1992). Spiny Bollworm, SBW (Earias insulana Boisd.) and Pink Bollworm, PBW (Pectinophora gossypiella Saund.) take part in this order and these pests are known to cause serious damage on cotton (Kiray, 1964; Karman, 1960). According to Falcon and Smith (1973) cotton phenology was separated three stages. These pests cause damage in boll stage and mature stage cotton. The means for the transition of the pests from one season to the next and the source of infestation are the blind bolls left in the fields after the harvest. SBW and PBW cause significant damage in cotton fields in GAP region. Various researchers (Uygun et al., 1995; Ünlü et al., 1995; Göven, 1995) reported that SBW has caused damage on cotton in GAP region for long years. Ozpinar et al. (1998) reported that PBW has caused harm on cotton in Harran Plain since 1997.
The consequences of infestation are of great importance since SBW and PBW cause a wide spread infestation in the entire Harran Plain. The infestation rates blind bolls for both bollworms were 13.7, 43.1 and 26.6% in 1998-2000, respectively (Ünlü, 2001).
The major aim of this study is to calculate field infestation ratio by using infestation rate of blind bolls cased by SBW and PBW in small scales of fields. In addition, in this study, field infestation ratio is predicted by short sampling time.
Materials and Methods
This study was conducted in Harran Plain during the years of 2002-2003 to determine infestation rate of SBW and PBW in blind bolls. After the harvest, 100 blind bolls from the each of 45 fields, which are in certain distance from each other, were collected each year. The bolls were splited in the laboratory and examined if they were infected with PBW and SBW larvae. The number of total and blossomed bolls were counted and recorded from each of the 20 cotton plants that were randomly selected. According to Ünlü (2004) field infestation ratio was calculated by using infestation rate of blind bolls of pests and number of total and blossomed bolls. This equation was given below.
| ILF : Infected Levels of Field (%)
|| NIB: Number of Infected Bolls (Piece)
|NCB : Number of Collected Bolls (Piece)
||TB : Total Bolls (Piece)
|OB: Open Bolls (Piece)
After the calculation of field infestation ratio, infestation ratio for each
location in both years (2002-2003) determined and infestation ratio of bolls
was determined by using equation 1. The scale of Snedecor
and Cochran (1980) was changed and a new scale between 0 and 45% was prepared.
This new scale is evaluated such as in below (Table 1).
|| The scale of infestation ratio
PBW has caused important damage on cotton in Harran Plain since 1997 and its population increased from year to year, spreaded all over the plain. Although SBW did not cause damage every year, its damage has continued especially in cotton fields that are located nearby Syrian border. Because of the fact that these pests are caused similar damage, infestation ratio of PBW and SBW was evaluated together in this study. According to this, infestation ratio and number of larvae in 2002-2003 years were given in Table 2.
Because the data are given as percentage, ArcSin transformation was applied to the data and then variance analyze table was prepared. At the end of the variance analysis, the difference between the locations was very significant (p<0.01). According to Duncan multiple comparison test by SPSS statistical programmed, the differences between the locations was determined (p<0.01).
Table 2 is examining, infestation ratio of these pest in blind bolls were collected from Harran Plain in 2002-2003 years were found 61.02 and 58.55%, respectively. The mean of each two years was calculated as 59.78%. Infestation ratio of these pests was a little low determined in 2003 than in 2002. We assume that this decrease is due to the normally planted cotton seeds were planted later in 2003.
The number of PBWs larvae was founded 6258 and 5935 pieces in all bolls in 2002-2003, respectively. The number of PBWs larvae was also decreased in 2003 such as infestation ratio (Table 2).
The number of SBWs larvae also provided similar results as did PBWs larvae. The number of SBWs larvae was determined 82 and 68 pieces in all bolls in 2002-2003, respectively.
In 2002, the highest infestation ratio was in Yardimci, Akkus and Koruklu as 96%. The lowest infestation ratio was in Haciekber and Fatmakuyu as 7 and 10, respectively. Infestation ratio of high level in 2003 was found in Kiliçli (97%), Abdurrahmandede (96%) and Asagi Yarimca (95%). Infestation ratio of low level in 2003 was determined in Sultantepe (10%) and Geçittepe (11%). In addition, according to 2002 infestation ratio of these pests was decreased in 25 localities and increased in 20 localities (Table 2).
|| Infestation ratio and number of larvae in blind bolls of
pink bollworm and spiny bollworm in Harran plain in 2002-2003
|* Mean value followed by the different letters are significant
at the 0.01 level
The field infestation ratios belonging to localities in 2002 (Table
3) and 2003 (Table 4) years were given in below, respectively.
In Harran Plain in 2002, the calculation by using blind bolls the lowest infestation
ratio of fields was determined in Haciekber as 1.75%, the highest infestation
ratio of fields was determined in Akkeci as 40.50%. The mean of infestation
ratio of fields of all locations was calculated as 13.79%. Infestation ratio
of these pests showed differences among the locations: out of the 45 locations,
four locations had infestation 0.1 to 5% (A), ten of them 5.1-10% (B), fifteen
of them 10.1-15% (C), seven of them 15.1-20% (D), eighth of them 20.1-25% (E)
and one of them 40.1-45% (I). According to these results, infestation percentage
of forty locations was ranged from 5-25% (Table 2). Nowhere
was found clean in 2002.
|| According to localities, calculation of the field infestation
ratios in 2002 in Harran
|| According to localities, calculation of the field infestation
ratios in 2003 in Harran
In Harran Plain in 2003, the calculation by using blind bolls the lowest infestation ratio of fields was determined in Sultantepe as 2.50%, the highest infestation ratio of fields was determined in Koruklu as 45.00%. The mean of infestation ratio of fields of all the location was calculated as 15.40%. Infestation percent of these pests showed differences among the locations: out of the 45 locations, four locations had infestation 0.1 to 5% (A), twelve of them 5.1-10% (B), eleven of them 10.1-15% (C), eight of them 15.1-20% (D), six of them 20.1-25% (E) one of them 25.1- 30 (F) one of them 30.1-35 (G) and two of them 40.1-45% (I). According to these results, thirty seven locations were ranged from 5 to 25% (Table 4). Nowhere was also found clean in 2003.
At the end of the study, PBW and SBW were found and spread almost everywhere
in Harran Plain and were determined to cause economical damage. In addition,
the pests were shown higher infestation ratios in collected bolls in 2002 (61.02%),
than 2003 (58.55%). The infestation ratio in 2003 was a little lower than the
previous year. The mean of boll infestation ratio of two years was materialized
such as 59.78%. The fields infestation ratios were calculated by using
boll infestation ratio and plant phenology in 2002 and 2003 years such as 13.79
and 15.40%, respectively.
The fields infestation ratios were determined to especially increasing in 2003 year. Singh and Sandy (1993), Purohit and Deshpande (1994) reported that, if infestation ratio of PBW and SBW is higher than 5%, damage of pests will have economic level and local producers have to apply insecticides. The results shown that, the fields infestation ratio is also higher than economic threshold and pests have economic importance in this study. It is important to notice that, a 1% increase in infestation ratio of bolls would reduce about 2.5-6% of cotton yield (Unlu and Bilgic, 2004). So, farmers should give an attention to these pests.
The number of PBWs larvae was determined as 6,258 and 5,935 pieces in 2002-2003 years, respectively. Similarly, the number of SBWs larvae was found as 82 and 68 pieces in same years, respectively. A parallelism was determined between infestation ratio of these pests and the number of larvae.
The number of larvae indicated that, maximum infestation in collected bolls was caused by PBWs larvae. While the maximum of PBW larvae occurred from a blind boll in 2002-2003 was 4.01±0.25 and 4.86±0.22, the minimum of PBW larvae was 1.00±0.57 and 1.10±0.33, respectively.
Results show that, infestation ratio caused by late planting cotton seeds (delayed planting time) in 2003 was decreased. Despite the decrease in the number of larvae, larvae density in a boll was high.
The higher infestation ratio of collected bolls was determined in the study. The means for the transition of the pests from one season to the next and the source of infestation are the blind bolls left in the fields after the harvest. So, the importance of these bolls will have existed in.
Ultimately in study, PBW was spreaded to the large areas of Harran Plain and continues to cause damage every cotton season. Although SBWs population in general area of Harran Plain was relatively low, but still damaging with higher populations in some areas (such as Fatmakuyu, Nusretiye and Yeserti) where cotton intensively produced near the Syrian border.
In addition, estimate of field infestation ratio by using the infestation ratio of blind bolls of these pests in estimation of field infestation ratio of these pests, because of the fact that used method in research that is more effective, easier and existing in short time than the other sampling techniques have more sampling time and manpower was determined.