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Seasonal population fluctuations of the diamondback moth, Plutella xylostella (L. ) (Lep. : Plutellidae) on different cauliflower cultivars
Gholamhosein Hasanshahi a , Habib Abbasipour a , Alireza Askarianzadeh a , Jaber Karimi a & Fat emeh Jahan a
a Facult y of Agricult ural Sciences, Depart ment of Plant Prot ect ion , Shahed Universit y , Tehran , Iran
Published online: 05 Feb 2013.
To cite this article: Gholamhosein Hasanshahi , Habib Abbasipour , Alireza Askarianzadeh , Jaber Karimi & Fat emeh Jahan (2013): Seasonal populat ion f luct uat ions of t he diamondback mot h, Plut ella xylost ella (L. ) (Lep. : Plut ellidae) on dif f erent caulif lower cult ivars, Archives Of Phyt opat hology And Plant Prot ect ion, 46: 10, 1136-1149
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Seasonal population fl uctuations of the diamondback moth, Plutella xylostella (L.) (Lep.: Plutellidae) on different cauli fl ower cultivars
Gholamhosein Hasanshahi, Habib Abbasipour*, Alireza Askarianzadeh, Jaber Karimi and Fatemeh Jahan
Faculty of Agricultural Sciences, Department of Plant Protection, Shahed University, Tehran, Iran
(Received 10 December 2012;final version received 18 December 2012)
The diamondback moth,Plutella xylostella(L.) (Lep.: Plutellidae) is one of the most important pests of cruciferous plants throughout the world. In recent years, it has been identified as a serious pest of the cauliflower fields in Tehran province.
Resistance of P. xylostellato all main groups of insecticides has been recorded and it is ranked in the 20 most resistant pest species reported until now. According to many researchers, to solve the problem of pest resistance to chemical pesticides, an integrated pest management programme should be used. Despite this condition, it seems that the use of resistant cauliflower cultivars is an appropriate policy for inte- grated control of the pest in thefield. In order to identify the most resistant cultivar in thefield, eight cauliflower cultivars in a completely randomised design withfive replicates were planted at the Shahed University research field (south of Tehran).
Density of eggs, larvae and pupae ofP. xylostellawere measured every 10 days in these cultivars. The results showed that there is no significant difference between numbers of eggs per plant on different cultivars. But number of larvae and pupae per plant were significantly different among different cultivars. Smilla and Snow mystique cultivars had the highest number of larvae and pupae. On the other hand, Buris and Snow crown cultivars had the lowest number of pupae and Snow crown and SG cultivars had the lowest number of larvae per plant. According to the results, the Buris and Snow crown cultivars had the lowest infestation and had a kind of resistance to pest.
Keywords:Plutella xylostella; populationfluctuation; cauliflower; resistance
Introduction
Cauliflower is one of the plants of Brassicaceae family and can be grown in moderate and tropical climates (Tindall 1983). In recent years, the diamondback moth has been identified as the most destructive pest of cruciferous plants throughout the world and annual management cost is estimated to be about a billion dollars (Talekar 1992;
Talekar and Shelton 1993; Verkerk and Wright 1996). Larvae of different ages feed on the underlying tissues of leaves and parts of leaves are irregularly chewed. But remains of veins and epidermis are often found with indentation-like structures being formed in the affected area (Capinera 2001). Nowadays, this pest is found wherever crucifer plants are grown and it is said that most of these pests have been distributed between all of Lepidoptera globally (Talekar and Shelton 1993). This pest can be controlled if the
*Corresponding author. Email: [email protected]
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density exceeds 0.3 larvae in each kohlrabi plant. Efforts to fight this pest are taken if the density of larvae before flowering is more than 0.2 larvae in each plant and after start of flowering, 0.5 larvae in each kohlrabi plant (Kirby and Slosser 1984; Alonso 2005). The last outbreak of this pest was seen in 2000 in Tehran (Marzban and Baniameri 2005). Research conducted in Karaj and Tehran (Iran) on its population density has shown that the highest population density of larvae on the plants occurred in the late season and during the harvest (Golizadeh 2008; Hasanshahi et al. 2012a).
Due to the fact that diamondback moth control has been exclusively dependent on the use of chemical pesticides in the previous years, resistance of this insect to the available pesticides is seen nowadays (Tabashnik et al. 1990; Mota-Sanchez et al. 2002; Khaliq et al. 2007; Mahmoudvand et al. 2011a, 2011 b; Hasanshahi et al. 2012b) and this raises the need to research other methods of control such as resistant plants. Resistant cultivars reduce pest damage with the least cost for the farmer (Reagan et al. 1997).
Resistant cultivars according to the type of resistance mechanism could influence the pest population in a short period or long term and/or despite the pest, yield reduction is not seen. (Nouri-Ghanblani 1995). Crucifer plants have a different sensitivity to the diamondback moth and one of the reasons for this is the presence of wax on the leaf surface. Kohlrabi and turnip are among the most resistant crucifers against this pest (Eigenbrode and Trumble 1994; Eigenbrode et al. 1995; Capinera 2001).
Materials and methods Sampling procedure
This research was conducted in the cauliflowerfields south of Tehran. Eight common cul- tivars of cauliflower including Smilla, Snow mystique, White cloud, Buris, Galiblanka, Snow crown, SG and Tokita were selected. Seeds of each cultivar were planted in small containers (flat wooden boxes) and after aboutfive weeks (stage of 6–8 leaves), the plants were individually transferred to a farm. Different cultivars were planted in a completely randomised design with five replications. Twenty-five plants per each plot were culti- vated. Plot size was 9 m2(33 m). Sampling was done according to age requirements of insects once every 10 days. In all samplings, four plants per each plot were investigated randomly and all available larvae and pupae on plants were counted. Due to the presence of dust on the leaf surface, egg count was not possible. So, only the number of eggs on the underside of the leaves was counted.
Content of chlorophyll and phenol on different cauliflower cultivars Measuring of phenol amount
The concentration of phenolics in plant extracts was determined using Folin-Ciocalteu reagent (Singleton and Rossi 1965). The absorbance was determined using a spectro- photometer at λmax= 725 nm. In this experiment, the amount of total phenol was measured by a standard calibration curve with gallic acid (Mousavinejad et al. 2009).
Measuring of chlorophyll amount
Measuring of chlorophyll content of total chlorophyll was done by the method of Arnon (1975). Leaf samples (1 g) were homogenised with acetone (80% v/v), filtered and made up to a final volume of 20 ml. Pigment concentrations were calculated from the
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absorbance of extract at 663 and 645 nm using the formula (Hendry and Grime 1993) given below:
Total Chlorophyllðmg=gFWÞ ¼20:2ðA645Þ þ8:02ðA663Þ
FW1000 V
Statistical analyses
Analyses of variance (ANOVA) (PROC GLM) for a completely randomised design were performed to test the differences between treatments, and means were compared at the 5% level of significance using Duncan studentized range test (Littell et al. 2002; SAS Institute 2004). For analysis and mean comparison, mean of different developmental stages in each sampling date was considered as a replicate.
Results
Populationfluctuations of eggs
Populationfluctuation ofP. xylostellaeggs on different cultivars is shown in Figure 1. The lowest density of eggs on each leaf was on Buris and Snow crown cultivars and the high- est density of eggs was on Smilla and Snow mystique cultivars in the beginning of the sea- son. Also, the highest density of egg in leaf occurred on the Snow mystique cultivar (0.37
± 0.02) and the lowest density of egg was recorded on Buris cultivar (0.59 ± 0.02) during the season. The highest density of eggs on different cultivars was seen on 11 October. In this time, the highest and the lowest density of eggs per leaf were observed on Snow mys- tique and Buris, respectively. Egg densityfluctuations ofP. xylostellaon Smilla and Snow mystique cultivars were more than those on the other cultivars during the season. So, the density of eggs on these two cultivars was higher than those of the other cultivars. Egg fluctuations on Buris and Snow crown cultivars were lower than the other cultivars during
Figure 1. Populationfluctuations of eggs ofP. xylostellaon different cauliflower cultivars.
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the season. So, population densities of egg on these two cultivars were lower than those on the other cultivars. It means that these two cultivars attract fewer adult females for ovi- position (may be due to antixenosis resistance).
Populationfluctuations of larvae
Populationfluctuations of different larval instars ofP. xylostellaon different cultivars are shown in Figures 2–6. It can be seen that Buris and SG cultivars had the lowest number of larvae in comparison with other cultivars in the beginning of the season. Smilla and Snow mystique cultivars had the highest number of larvae among cultivars in the beginning of season. The lowest number of larvae was observed on Snow crown cultivar (0.009
± 0.001) and the highest number of larvae was seen on Snow mystique cultivar (0.03
± 0.002) during the season. The highest number of first larval instars in all the cultivars was observed on 10 September (Figure 2). Also, the lowest number of larvae was observed in all the cultivars in the beginning of the season. The highest number of larvae was observed on Buris and Snow crown cultivars at the peak time density offirst instars’
larvae (10 September). Number of larvae on Tokita cultivar was low in the beginning of the season but it was more than the other cultivars on 11 and 20 September. It seems that, this cultivar exhibits antixenosis and does not have enough antibiosis resistance.
Buris and Snow crown cultivars had the lowest number of second larval instars and Smilla and Snow mystique cultivars had the highest number of second instars’ larvae on leaf in the beginning of the season (Figure 3). Smilla and Snow mystique cultivars had the highest number of second larval instars and Buris and Snow crown cultivars had the lowest number of second instars’larvae during the season. The highest number of larvae was observed in all cultivars on 31 October. At this time, Tokita cultivar had the highest number of larvae (0.05 ± 0.01) and Snow crown had the lowest number of larvae per leaf (0.01 ± 0.001).
Figure 2. Populationfluctuations of first larval instars of P. xylostella on different cauliflower cultivars.
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Snow mystique and Tokita cultivars had the highest number of third larval instars in the beginning of the season. Third instars’ larvae were not observed in Buris, Galiblanka, Snow crown and SG cultivars in the beginning of the season. Snow mystique cultivar (0.4 ± 0.01) and Snow crown cultivar (0.01 ± 0.002) had the highest Figure 4. Population fluctuations of third larval instars of P. xylostella on different cauliflower cultivars.
Figure 3. Populationfluctuations of second larval instars ofP. xylostellaon different cauliflower cultivars.
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and lowest numbers of third instars’larvae during the season, respectively. Peak of third larval instars’density was observed in all the cultivars on September. Also, the highest and lowest numbers of third instars’ larvae were observed on Snow mystique cultivar (0.06 ± 0.01) and Snow crown cultivar (0.02 ± 0.01), respectively (Figure 4).
Figure 5. Populationfluctuations of fourth larval instars ofP. xylostellaon different cauliflower cultivars.
Figure 6. Population fluctuations of total larval instars of P. xylostella on different cauliflower cultivars.
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Infestation of plants with fourth larval instars was observed only on Snow mystique cultivar in the first sampling time. Fourth instars’ larvae were not observed on Buris, Galiblanka, Snow crown and SG cultivars until third sampling time. The highest num- ber of larvae was observed on Tokita cultivar (0.04 ± 0.02) and Snow mystique cultivar (0.04 ± 0.01). On the other hand, the lowest number of larvae was observed on Snow crown cultivar (0.01 ± 0.01) and Buris cultivar (0.01 ± 0.01) during the season. The highest number of fourth instars’larvae was observed in all the cultivars on 20 August.
At this time, the highest and lowest numbers of larvae were observed on Smilla cultivar and SG cultivar, respectively (Figure 5).
Population fluctuation of total larval instars of the diamondback moth, P. xylostella on different cultivars is shown in Figure 6. Smilla and Snow mystique cultivars were infected with by P. xylostella larvae more than other cultivars in the beginning of season. At the same time, no larva was observed on Buris and Snow crown cultivars.
On the other hand, the highest number of larvae was on Snow mystique, Tokita cultivars and the lowest number of larvae was on White cloud and Snow crown culti- vars at the end of the season. The highest number of larvae was on Snow mystique cultivar (0.17 ± 0.004), Smilla cultivar (0.15 ± 0.004) and the lowest number of larvae was on Buris cultivar (0.06 ± 0.03) and Snow crown cultivar (0.05 ± 0.002), respec- tively during the season. Peak of larval density in the different cultivars occurred on 10 September. At this time, the highest and lowest number of larvae were observed on Snow mystique cultivar (0.25 ± 0.01) and Snow crown cultivar (0.01 ± 0.01), respectively.
Populationfluctuations of pupae
Population fluctuation of P. xylostella pupa on different cultivars is shown in Figure 7.
The highest number of pupae per leaf was observed on Snow mystique cultivar in the beginning of the season. At the same time, the lowest number of pupae per leaf was observed on Buris cultivar. Pupae were not observed in this cultivar until 31 July. The highest and lowest numbers of pupae were observed on Tokita and Buris cultivars at the end of the season, respectively. Also, Tokita and Snow crown cultivars had highest and lowest number of pupae during the season, respectively. The highest pupa density was observed in different cultivars on 11 October. At this time, the highest and lowest number of pupae were observed on Tokita cultivar (0.17 ± 0.05) and Snow crown cultivar (0.07 ± 0.04), respectively. Results showed that pupal density fluctuations on Smilla and Snow mystique cultivars are higher than those of other cultivars; it means that the number of pupa is the highest in these cultivars when compared with the other cultivars during the season. Population fluctuations of pupa on Buris and Snow crown cultivars are lower than the other cultivars and this shows that the numbers of pupae are the lowest in these cultivars when compared with those of the other cultivars during the season.
Population fluctuations of all the developmental stages of P. xylostella on the cauliflower cultivars are shown in Figure 8. Snow mystique cultivar had the highest density of insect and on the other hand, Snow crown cultivar had the lowest density among the cultivars in the beginning of the season. The highest and lowest densities were observed on Snow mystique and Buris cultivar at the end of season, respectively.
Peak insect density was observed in different cultivars on 31 October. At this time, the highest and the lowest densities were observed on Snow mystique cultivar (1.94 ± 0.50) and Snow crown cultivar (0.82 ± 0.19), respectively.
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Comparison of mean density of different developmental stage periods
Statistical analysis showed that there is significant difference in density of the different stages of the diamondback moth on different cultivars (Table 1). The highest egg densities were on Smilla and Snow mystique cultivars. The lowest egg densities were Figure 7. Populationfluctuations of pupae ofP. xylostellaon different cauliflower cultivars.
Figure 8. Populationfluctuations of total different stages ofP. xylostellaon different cauliflower cultivars.
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on Buris and Snow crown cultivars. The highest numbers of first instar larvae were on Snow mystique and Tokita cultivars. The lowest numbers of first instar larvae were on Buris and Snow crown cultivars. The highest numbers of second instar larvae were observed on Smilla, Snow mystique and Tokita cultivars. The lowest number of second instar larvae was observed on Snow crown cultivar. Snow mystique and Tokita cultivars have the highest numbers of third instar larvae. The highest numbers of fourth instar larvae were observed on Smilla, Snow mystique and Tokita cultivars. The highest numbers of total larval stages were on Smilla, Snow mystique and Tokita cultivars, while the lowest number of larvae was on Snow crown cultivar. Tokita cultivar had the highest number of pupae. Buris and Snow crown cultivars had the lowest numbers of pupae. The highest numbers of all the developmental stages of the diamondback moth were observed on Smilla and Snow mystique cultivars. Table 2. The lowest numbers of all the developmental stages of the diamondback moth were observed on Buris and Snow crown cultivars.
Content of chlorophyll and phenol on different cauliflower cultivars
Contents of chlorophyll and phenol of the eight cultivars are given in Table 3. Results of the experiments showed that there is no significant difference in contents of chloro- phyll and phenol among the different cultivars. Therefore, there is no relationship between diamondback moth (DBM) density and contents of chlorophyll and phenol in the different cultivars. Bayati et al. (2010) with evaluation of resistance of Asian pear cultivars to pear lace bug (Stephanitis pyri F.) based on the number of insects on leaves Table 1. Analysis of variance of density of different stages of the diamondback moth, P. xylostellaon eight cultivars of cauliflower.
Stage Resources changes df Mean Square F P-Value
Egg Different cultivars 7 1.05 24.52 0.00
Error 80 0.04
Total 87
InstarІ Different cultivars 7 0.001 12.39 0.00
Error 80 0.00
Total 87
InstarІІ Different cultivars 7 0.002 18.29 0.00
Error 80 0.00
Total 87
InstarІІІ Different cultivars 7 0.001 71.14 0.00
Error 80 0.00
Total 87
InstarІV Different cultivars 7 0.001 3.84 0.00
Error 80 0.00
Total 87
Total larvae Different cultivars 7 0.023 10.34 0.00
Error 80 0.002
Total 87
Pupae Different cultivars 7 0.008 4.61 0.00
Error 80 0.02
Total 87
Total Different cultivars 7 1.50 24.79 0.00
Error 80 0.05
Total 87
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Table 2. Comparison of mean (±SE) density of different stages of the diamondback moth,P. xylostellaon different cauliflower cultivars.
Different cultivars
Stage Smilla Snow mystique White cloud Buris Galiblanka Snow crown SG Tokita
Egg 1.35 ± 0.06a⁄ 1.46 ± 0.09a 1.06 ± 0.04b 0.59 ± 0.06c 0.95 ± 0.06b 0.60 ± 0.06c 0.95 ± 0.03b 0.98 ± 0.05a InstarІ 0.02 ± 0.001ab 0.03 ± 0.002a 0.02 ± 0.002c 0.01 ± 0.001d 0.02 ± 0.002bc 0.01 ± 0.001d 0.01 ± 0.002cd 0.03 ± 0.005a InstarІІ 0.04 ± 0.008a 0.04 ± 0.003a 0.02 ± 0.003b 0.01 ± 0.002cd 0.02 ± 0.003bc 0.01 ± 0.001d 0.01 ± 0.002bcd 0.01 ± 0.003ab InstarІІІ 0.03 ± 0.003ab 0.04 ± 0.004a 0.02 ± 0.003bc 0.01 ± 0.004c 0.02 ± 0.003c 0.01 ± 0.002c 0.01 ± 0.004c 0.03 ± 0.005a InstarІV 0.04 ± 0.005ab 0.04 ± 0.005a 0.02 ± 0.004bc 0.01 ± 0.005c 0.03 ± 0.006abc 0.01 ± 0.003c 0.02 ± 0.005c 0.04 ± 0.007ab Total larvae 0.15 ± 0.01a 0.16 ± 0.01a 0.09 ± 0.01bc 0.06 ± 0.01bc 0.09 ± 0.01b 0.05 ± 0.008c 0.07 ± 0.01bc 0.15 ± 0.02a Pupae 0.07 ± 0.009abc 0.09 ± 0.01ab 0.05 ± 0.008bc 0.03 ± 0.008c 0.05 ± 0.01bc 0.03 ± 0.008c 0.07 ± 0.01ab 0.11 ± 0.02a Total 0.15 ± 0.01a 1.73 ± 0.09a 1.22 ± 0.05b 0.69 ± 0.07c 1.11 ± 0.07b 0.69 ± 0.07c 1.11 ± 0.04b 1.25 ± 0.28a
⁄Same letters in each column show no significant difference.
ArchivesofPhytopathologyandPlantProtection1145
and content of chlorophyll concluded that in cultivars which had the highest number of pest and the highest injury rates, the amount of chlorophyll is high. Shuster et al.
(1980) showed tolerance of strawberry cultivars to two spotted spider mites and con- cluded that content of chlorophyll in tolerant cultivars is not significantly decreased despite the high density of the pest. Buntin et al. (1996) by studying the effect of pear lace bug damage on photosynthetic rate and leaf’s gas exchange concluded that the effects of pear lace bug feeding on parenchyma tissue and causing damage are increased stomatal resistance and limiting of gas exchange and decreased leaf chloro- phyll rate.
Discussion
Estimation of number of species of living organisms is considered as the most important activity in ecology research and integrated pest management. Sampling and estimation of number of the population is the central core of population ecology (Pedigo 1994). Sampling gives us comprehensive information about the presence or absence of pest, migration, feeding, reproduction, mortality, age structure, population growth shape, density, pest dispersion and analysing them helps to determine the amount of damages and time required for control. (Isaaks and Srivastava 1989; Pedigo and Buntin 1993). There was significant difference in the densities of different develop- mental stages of the diamondback moth, P. xylostella on the different cauliflower cultivars. Smilla, Snow mystique and Tokita cultivars are most susceptible cultivars among the different cauliflower cultivars. Also, Buris and Snow crown cultivars were the most resistant cultivars among the different cultivars studied. Therefore, there are resistance mechanisms in Buris and Snow crown cultivars so that they can restrain DBM density. Density of larvae and pupae of the diamondback moth on Brassica oleraceavar.acephalawere examined in South Carolina (Khan et al. 2004). Density of Table 3. Analysis of variance of content of chlorophyll and phenol in leaf of different cultivars.
Parameter Resources changes df Mean square F P-Value
Chlorophyll Different cultivars 7 0.014 1.29 0.29
Error 24 0.011
Total 31
Phenol Different cultivars 7 0.006 1.68 0.18
Error 24 0.003
Total 31
Table 4. Mean (±SE) content of chlorophyll and phenol in leaf of different cultivars.
Cultivars
Parameter
Chlorophyll Phenol
Smilla 0.56 ± 0.04 1.12 ± 0.03
Snow mystique 0.53 ± 0.01 1.01 ± 0.02
White cloud 0.53 ± 0.09 1.08 ± 0.01
Buris 0.67 ± 0.04 1.12 ± 0.03
Galiblanka 0.65 ± 0.03 1.00 ± 0.01
Snow crown 0.50 ± 0.05 1.07 ± 0.04
SG 0.57 ± 0.01 1.04 ± 0.04
Tokita 0.55 ± 0.08 1.04 ± 0.03
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larvae and pupae in each plant was observed to be, at harvest time in Clayton Rawl farm, 0.15 and 2.25, respectively. Density of larvae and pupae in each plant was observed to be, at harvest time in Walter Rawl and Sons farm, 0.6 and 5.10, respectively. Density of larvae and pupae in each plant were observed at harvest time in Walter Clinton Sease farm and were found to be 0.15 and 1.45, respectively (Khan et al. 2004). Fathi et al. (2010) studied population densities of P. xylostella on the canola cultivars in Ardabil region of Iran. In this study, population density of the DBM was significantly different among the canola cultivars studied (P60.05). Among the 19 canola cultivars in this study, larval and pupal density was significantly higher on Zarfam, SLM043 and Licord and lower on Option500, Elite and Opera cultivars.
Population changes of the diamondback moth was evaluated in Karaj in 2007–2008 and the highest population density of the pest was calculated as 37.9 insects and the highest population density of larvae per plant was calculated to be 35.83 larvae (Golizadeh 2008). In this study, Snow mystique cultivar had the highest density of total develop- mental stages (1.94 ± 0.50) and Buris cultivar had the lowest amount of different stages in leaf (0.82 ± 0.19). The highest density of larvae and pupae per plant was on Smilla cultivar in the cauliflower fields of south of Tehran – (6.68 ± 3.36) and (4.92 ± 2.25), respectively. Population density of the diamondback moth was evaluated in south of Tehran in 2012 and the highest density of total developmental stages was observed in Palayin field during the season (42.50 ± 8.01) (Hasanshahi 2012). In our studies, the highest densities of larvae was on Smilla, Snow mystique and Tokita cultivars – (0.15
± 0.004), (0.17 ± 0.004) and (0.15 ± 0.004), respectively. The highest densities of pupae was on Tokita cultivar (0.11 ± 0.10) at the end of the season. Jahan’s (2012) studies on density of Brevicoryne brassicae on different cauliflower cultivars showed that Smilla cultivar had the highest density of cabbage aphid (2.13 ± 0.78) and Galiblanka cultivar had the lowest density of cabbage aphid (0.48 ± 0.18). The highest density of P. xylostella was reported as 25 larvae and 10 pupae in china (Shu-sheng et al. 2000).
Density of larvae and pupae in each plant was observed to be 2.46 and 0.05, respectively on canola in Tehran (Hasanshahi et al. 2012c). Using different cultivars – in addition to the effects they have on density and damage of pest –can be effective on the activity of parasitoids and their amount of parasitism (Nouri-Ghanblani 1995;
Sarfraz et al. 2008). Parasitism rate of D. semiclausumonB. oleraceavar.capitatawas more than B. campestris spp. in field sampling in Cameroon (Verkerk and Wright 1996). In field studies on plant species of the genus Brassica in New Zealand, rate of parasitism by Diadromus collaris and Diadegma semiclausum on B. oleracea var.
botrytis was more than the other cultivars (Beck and Cameron, 1990). Natural parasit- ism of DBM on different cauliflower cultivars was evaluated in South of Tehran in 2012 and the highest percentage of parasitism caused by D. anurum was recorded on Boris cultivar (19.92) and Abr-e-sefid cultivar (16.20) and the lowest percentage of parasitism was recorded on Takgol cultivar (3.42) and S-J cultivar (5.00). The highest percentage of parasitism caused by C. plutellaewas recorded on Dogol, while the low- est percentage of parasitism was recorded on Takgol. During the season, the highest and lowest percentages of parasitism withO. sokolowskiiwere recorded on Boris (7.93) and S-J cultivars (1.28), respectively. The total percentage of parasitism with all three parasitoids was significantly higher on Abr-e-sefid and Boris cultivars and was lower on Galibalanka and Takgol cultivars in comparison to other cauliflower cultivars (Hasanshahi et al. 2012d).
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In our studies, Buris and Snow crown cultivars had poor DBM and for these cultivars, integrated pest management programme and increasing crop surface in cauliflowerfields are recommended.
Acknowledgements
This work was supported by Faculty of Agricultural Sciences, Shahed University, Tehran, Iran.
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