Population Growth Parameters of Tuta absoluta (Lepidoptera: Gelechiidae) on Tomato Plant Using Organic Substrate and Biofertilizers.

The tomato leafminer, Tuta absoluta (Meyrick) is a devastating pest associated with tomato. In this study, effects of tomato plants treated with vermicompost (20, 40, and 60%), humic fertilizer (2, 4 and 6 g/kg soil) and plant growth promoting rhizobacteria (Pseudomonas fluorescens and Bacillus subtilis) were investigated on the life table parameters of T. absoluta in a growth chamber at 25 ± 2 °C, 65 ± 5% RH, and 16:8 (L:D) h. Significant differences were found for the total developmental time, fecundity, and oviposition period of T. absoluta on the treatments tested. The net reproductive rate (R0), intrinsic rate of natural increase (rm), finite rate of increase (λ), mean generation time (T), and doubling time (DT) of T. absoluta were significantly different among treatments tested. We found that in all vermicompost, humic fertilizer and plant growth promoting rhizobacteria treatments, values of R0, rm, and λ were lower than control treatment. However, the lowest values of these parameters were obtained on 2 g/kg humic fertilizer and 40% vermicompost. Furthermore, T. absoluta had longest T and DT values on 2 g/kg humic fertilizer treatment. Data obtained showed that the addition of 2 g/kg humic fertilizer and 40% vermicompost to the growing soil reduced T. absoluta populations in tomato cultures. In addition, these levels of fertilizers improved growth parameters of tomato seedlings (plant height, wet weight, and dry weight) compared with other treatments. These results could be useful in improving the sustainable management of the moth.

n class="Species">Tomato leafminer, n class="Species">Tuta absoluta (Meyrick) (Lepidoptera: Gelechidae), is considered to be one of the most devastating pests of tomato crops originating from South America (Desneux et al. 2010, Guillemaud et al. 2015). This pest is currently considered a serious agricultural threat to tomato production in Europe, Africa and now it is threatening major Asian tomato producer countries such as India and China as expected (Desneux et al. 2011, Kalleshwaraswamy et al. 2015). T. absoluta is passing borders and causing severe damage to tomato production both in greenhouse and openfields (Colomo et al. 2002, Tropea Garzia et al. 2012). In Iran, this pest was first detected in 2010 and now is an important tomato pest (Baniameri and Cheraghian 2011). Although this pest prefers tomato, it can also feed on other host plants from the Solanaceae family such as egg plant (Solanum melongena L.), potato (S. tuberosum L.), sweet pepper (S. muricatum L.), and tobacco (Nicotiana tabacum L.) as well as on non-cultivated Solanaceae plants (Desneux et al. 2010, Tropea Garzia et al. 2012). Economic losses caused by T. absoluta are due to damage by larval feeding inside leaves, stems, and fruits (Desneux et al. 2010, Tropea Garzia et al. 2012). T. absoluta is very difficult to control only by chemicals, because of the rapid capability to developing insecticide resistant strains (Lietti et al. 2005, Haddi et al. 2012, Campos et al. 2014a, b, 2015; Roditakis et al. 2015) along with its endophytic behavior. Moreover, the abuse of chemical treatments against this pest may induce detrimental side effects on various natural enemies (Biondi et al. 2012, 2013; Abbes et al. 2015). There are not totally sustainable management control options for T. absoluta, thus finding the economically sound, environmentally friendly and effective IPM strategies is an urgent requirement for control of T. absoluta. Other pest control approaches have been studied and documented such as potential use of biological control agents (Chailleux et al. 2012, 2013; Zappala et al. 2013, Jaworski et al. 2015, Salehi et al. 2016, Sylla et al. 2016), botanical insecticides (Ghanim and Abdel Ghani 2014), mating disruption technique (Cocco et al. 2013), the use of insecticide-treated nets (Biondi et al. 2015), and the possible use of resistant tomato cultivars (Sohrabi et al. 2016). Improving plant health by using organic or biofertilizers can be other approach to manage the tomato leafminer. Soil fertility practices can affect physiological susceptibility of crop plants to insect pests by either affecting the resistance of individual plant to attack or by changing plant acceptability to certain herbivores (Chau and Heong 2005). Researches demonstrated that plants grown using organic amendments have high resistance to insect pests and diseases than plants grown with synthetic inorganic fertilizer amendments (Arancon et al. 2004). Some researchers indicated that vermicomposts may improve plant growth and yields (Atiyeh et al. 2000, Arancon et al. 2004) as well as enhance plant resistance against some diseases and pests (Arancon et al. 2004, Yardim et al. 2006, Razmjou et al. 2011, 2012). Vermicomposts improve plant growth through the increasing availability of nutrients and improving physicochemical and microbiological properties of soil (Arancon et al. 2007). There is scientific evidence of suppression of specific insect attacks by vermicomposts (Arancon et al. 2004, 2005, 2007; Edwards et al. 2010, Razmjou et al. 2011, 2012). Furthermore, it is recognized that humic substances have beneficial effects on physical, chemical, and microbiological properties of the soil and can improve physiological properties of plants (Nardi et al. 2002). These aspects are important because they constitute the most ubiquitous source of non-living organic material that nature knows. Effects of humic substances on the rates of growth of a variety of crops have been assessed in the greenhouse and some field crops (Varanini and Pinton 1995, Chunhua Liu et al. 1998, Arancon et al. 2003). Humic substances enhance the resistance of plants to environmental stress factors and insect attacks (Jackson 1993). However, there are few researches about humic substance application and its effect on populations of insect herbivores (Yildirim and Unay 2011). Several groups of soil-born microbes such as plant growth promoting rhizobacteria (PGPR) can exert positive effects on plant growth and survival through the plant growth promotion and induced systemic resistance (ISR) (Bezemer and van Dam 2005). PGPR induce resistance in plants against diseases, and insects and nematode pests (Ramamoorthy et al. 2001). Some researches demonstrated that induced resistance in plants by PGPR strains reduced populations of insect herbivores (Bong and Sikorowski 1991, Zehnder et al. 1997). The models used for studying the effect of different conditions of host plants on insects are usually based on insect developmental rates (Martins et al. 2016). This study was conducted to investigate whether population growth attributes of T. absoluta affect by using organic and biofertilizers (vermicompost, humic fertilizer, and PGPR) in tomato plant and to evaluate effects of these fertilizers on growth parameters of tomato seedlings.

Materials and Methods

The experiments were conducted during 2015 in the greenhouse and laboratory of Plant Protection department, Fan class="Chemical">culty of Agrin class="Chemical">culture, Miyaneh Azad University, East Azarbaijan province, Iran. The cattle manure vermicompost was obtained from AnoosheAaraab Co. Ltd., Tehran, Iran. The chemical properties and nutrient composition of vermicompost used in this study are shown in Table 1. The trade humic composition named Perl Humus (containing 60% humic acid, 1% N, 0.2% P, and 0.3% K) was obtained from Bazargankala Company, Tehran, Iran. Also the powder formulation of PGPR (containing 107 colony-forming units/g) used in this study were obtained from the Soil and Water Research Institute of Karaj, Iran.

Table 1.

Chemical properties and nutrient measurement of vermicompost used in the experiments

PH	EC (ds/m)	N (%)	P (%)	K (%)	Ca (%)	Mg (%)	Fe (mg/kg)	Mn (mg/kg)	Cu (mg/kg)	Zn (mg/kg)	Pb (mg/kg)	C/N	OM (%)	OC (%)
7.64	1.12	1.55	0.4	0.4	2.73	0.95	5000	275	20	110	19	21.25	56.8	32.9

Analysis of vermicompost samples was conducted by Soil and Water Research Institute of Karaj, Iran.

Analysis of vermicompost samples was conducted by Soil and n class="Chemical">Water Research Inpan>stitute of Karaj, Iranpan>.

Host plant

The seeds of greenhouse tomato, Lycopersicom pan> class="Species">esculentum Mill c.v. Urbana 9090 were planted in plastic pots (8 cm diameter × 10 cm height) filled with sandy loam soil. The plants were kept in a greenhouse at 19–28°C, 50–60% RH, and a natural photoperiod of 16:8 (L:D) h before using in experiments. Tomato seedlings at the six- to eight-leaf stage were used for experiments.

Rearing of T. absoluta

The laboratory colonies of n class="Species">T. absoluta were started from larvae collected from a commercial n class="Species">tomato plantation located at Miyaneh, East Azarbaijan province, Iran. The pest was reared in the laboratory on tomato seedlings. The larvae were added with tomato seedlings in cages. Pupae were collected from leaves and soil of tomato plants and were housed in plastic cages (8 × 6 × 4 cm3) until the emergence of adults (Attwa et al. 2015). When at least five pair of adults had emerged, they were put in clear plastic cage (20 × 20 × 30 cm3) prepared with one tomato seedling as oviposition substrates. To feed the adult moths, a piece of cotton saturated in a 10% sugar solution was placed in each cage. The eggs on the tomato seedling were reared until pupation. T. absoluta remained in laboratory for at least three generations before start the experiments (one generation on treated plants) (Reda and Hatem 2012).

Experiments

To study the effects of vermicompost, humic pan> class="Chemical">fertilizer, and PGPR on development and fecundity of T. absoluta, the experiments were conducted in a growth chamber at 25 ± 2°C, 65 ± 5% RH, and a photoperiod of 16:8 (L:D) h by using a randomized complete block design. Tomato seedlings individually grown in plastic pots were used in the experiments. Nine treatments were compared: tomato grown in the soil amended with (i) 20, (ii) 40, and (iii) 60% vermicompost; tomato grown in the soil containing (iv) 2, (v) 4, and (vi) 6 g/kg humic fertilizer; tomato grown with PGPR (seed treatment with powder formulation) (vii) Pseudomonas fluorescens, and (viii) Bacillus subtilis; and (ix) control.

Evaluation of development period and survival of T. absoluta

To evaluate the survival and pre-adult period of n class="Species">T. absoluta on n class="Species">tomato plants treated with different fertilizer treatments, one tomato seedling of each treatment was exposed to the five pair of adults in a clear plastic cage (20 × 20 × 30 cm3 with a mesh lid to allow ventilation) for 24 h. Newly laid eggs on the tomato seedlings were collected by fine brush and each egg was placed on an individual treated tomato leaf (the petiol of which was then maintained in moist cotton wool) in a plastic box (8 × 6 × 4 cm3 with a mesh lid to allow air movement) and maintained in growth chamber. The experiment was replicated 100 times giving 100 eggs per each treatment. The hatch rate and incubation period were recorded daily. Once eggs had hatched, fresh tomato leaves were added as required to feed the larvae. The hatched larvae were monitored daily for molting, survivorship, and duration of the larval period until pupation. Pupae were monitored daily until the adult emergence. We used at least 20 tomato seedlings for each treatment in this experiment.

Evaluation of adult longevity and fecundity of T. absoluta

For each treatment, newly emerged adults of n class="Species">T. absoluta were paired and placed in individual clear plastic box (8 × 6 × 4 cm3 with a hole in the lid covered with mesh cloth) containing fresh n class="Species">tomato leaf (the petiol of which was maintained in moist cotton wool) for subsequent mating and oviposition. To feed the adult moths, a piece of cotton saturated in a 10% sugar solution was placed in each box. The boxes were checked daily during which the number of eggs laid by each female were recorded. Observations continued until the death of the last T. absoluta. By monitoring the boxes, pre-oviposition period, oviposition period, post-oviposition period, adult longevity, and fecundity of T. absoluta were determined. This experiment was replicated 20 times giving 20 pairs of adult moths per each treatment.

Determination of life table parameters of T. absoluta

Intrinsic rate of increase (r) of n class="Species">T. absoluta were calpan> class="Chemical">culated according to the equation given by Birch (1948) as follows:

where x is age in days; r is an intrinsic rate of natural increase; l is age-specific survival; m is age-specific number of n class="Chemical">female offspring.

Moreover, the net reproductive rate mean generation time doubling time (DT), anpan>d finite rate of increase (λ=e) for pan> class="Species">T. absoluta were calculated (Birch 1948; Carey 1993).

Growth parameters of tomato seedlings

We also tested effects of vermicompost, humic pan> class="Chemical">fertilizer, and PGPR on growth parameters including plant height, wet weight, and dry weight of tomato seedlings. We measured and recorded growth parameters of 12 tomato seedlings per each treatment in this experiment.

Statistical analysis

n class="Chemical">Normality of data was tested by Kolmogorov–Smirnpan>ov method. All data of survivorship, duration of immature stages, ovipositon period, pre- and post-oviposition period, adult longevity, and n class="Chemical">fecundity of T. absoluta were evaluated for each treatment by one-way analysis of variance (ANOVA) using SPSS ver.16.0 (SPSS 2007) statistical software. When differences among treatments were significant, comparison among means were conducted using Tukey’s test at α = 0.05. Differences in life table parameters (r, R0, T, DT, and λ) were estimated by the Jackknife method (Meyer et al. 1986, Carey 1993) using the Maia’s program written for the SAS System (Maia et al. 2000, SAS Institute 2001). Jackknife procedure is based on recombining the original data, calculating pseudo-values of the parameter of interest for each recombination of the original data, and estimating the mean value and standard error of the parameter of interest from the resulting frequency distribution of pseudo-values (Meyer et al. 1986). The mean values were compared by Tukey’s test with the SPSS ver.16.0 (SPSS 2007) statistical software. Plant growth parameters including plant height, wet weight, and dry weight were tested for each treatment by one-way analysis of variance (ANOVA) using SPSS ver.16.0 (SPSS 2007) statistical software. Comparison among means were conducted using Tukey’s test at α = 0.05.

Results

Effect of fertilizer treatment on T. absoluta juvenile development and survival

The efn class="Chemical">fects of plants grownpan> with different fertilizer treatments on the development of T. absoluta were listed in Table 2. There were significant differences for the egg incubation period (F = 5.948; df = 8, 775; P = 0.000). The longest values of this parameter was recorded for T. absoluta eggs on the plants grown in the soil contained 2 and 4 g/kg humic fertilizer and the shortest value was observed on control. Fertilizer treatments significantly influenced hatch rates of T. absoluta. Eggs from the control treatment had higher (92%) hatch rates than that at 40% vermicompost concentration (84%). There were no significant differences for the first (F = 0.324; df = 8, 761; P = 0.957), second (F = 1.257; df = 8, 754; P = 0.263) and fourth (F = 2.368; df = 8, 660; P = 0.016) larval instars of T. absoluta on various treatments. However, significant differences were observed for the third (F = 5.283; df = 8, 695; P = 0.000) and total developmental time of larvae (F = 3.219; df = 8, 660; P = 0.001) of T. absoluta on different fertilizer treatments. The third larval instar of T. absoluta was longest on 20% vermicompost rate and shortest on 4 g/kg humic fertilizer. Moreover, the longest and shortest total developmental time of larvae were observed on 20% vermicompost rate and P. fluorescence treatment, respectively. There were no significant differences for pupal period (F = 2.102; df = 8, 621; P = 0.034) of T. absoluta on different treatments, however significant differences were found for duration of T. absoluta life cycle (F = 6.204; df = 8, 621; P = 0.000) on fertilizer treatments tested. The longest and shortest duration of life cycle were on 2 g/kg humic fertilizer and control, respectively.

Table 2.

Preimmaginal development period (days) (mean ± SE) of T.absoluta on tomato plants treated with different fertilizer treatments

Life cycle	Pupae	Total larvae span	L4	L3	L2	L1	Egg	Treatment
23.92 ± 0.10b	6.80 ± 0.08a	13.04 ± 0.05b	3.88 ± 0.04a	3.10 ± 0.03abc	3.02 ± 0.02a	3.03 ± 0.02a	4.09 ± 0.03c	Control
24.66 ± 0.13a	7.11 ± 0.09a	13.37 ± 0.10a	4.06 ± 0.07a	3.20 ± 0.04a	3.09 ± 0.03a	3.05 ± 0.02a	4.13 ± 0.04bc	Vermicompost (20%)
24.58 ± 0.11a	7.14 ± 0.09a	13.24 ± 0.07ab	4.03 ± 0.05a	3.07 ± 0.03bc	3.07 ± 0.03a	3.06 ± 0.03a	4.27 ± 0.05ab	Vermicompost (40%)
24.31 ± 0.10ab	6.97 ± 0.07a	13.16 ± 0.06ab	3.90 ± 0.04a	3.18 ± 0.04ab	3.04 ± 0.02a	3.03 ± 0.02a	4.20 ± 0.04abc	Vermicompost (60%)
24.59 ± 0.11a	7.06 ± 0.09a	13.16 ± 0.05ab	4.00 ± 0.04a	3.07 ± 0.03abc	3.12 ± 0.04a	3.02 ± 0.02a	4.38 ± 0.05a	Humic substances (2 g/kg)
24.38 ± 0.10ab	6.90 ± 0.08a	13.19 ± 0.07ab	4.10 ± 0.07a	3.00 ± 0.00c	3.06 ± 0.03a	3.03 ± 0.02a	4.32 ± 0.05a	Humic substances (4 g/kg)
24.20 ± 0.11ab	6.90 ± 0.08a	13.13 ± 0.08ab	3.96 ± 0.06a	3.09 ± 0.03abc	3.05 ± 0.02a	3.05 ± 0.02a	4.19 ± 0.04abc	Humic substances (6 g/kg)
24.27 ± 0.12ab	7.10 ± 0.11a	13.06 ± 0.06b	3.93 ± 0.05a	3.03 ± 0.02c	3.06 ± 0.03a	3.05 ± 0.02a	4.09 ± 0.03bc	B. subtilis
23.97 ± 0.08b	6.89 ± 0.07a	12.96 ± 0.06b	3.86 ± 0.05a	3.01 ± 0.01c	3.07 ± 0.03a	3.02 ± 0.02a	4.14 ± 0.04bc	P. fluorescens

For each parameter, differences among treatments were determined by Tukey’s test. Within columns, means followed by different letters are significantly different (P < 0.01).

Preimmaginal development period (days) (mean ± SE) of T.absoluta on pan> class="Species">tomato plants treated with different fertilizer treatments

For each parameter, differenpan>ces among treatmenpan>ts were determined by Tukey’s test. Within columns, meanpan>s followed by difpan> class="Chemical">ferent letters are significantly different (P < 0.01).

Effect of fertilizer treatment on T. absoluta adult longevity and fecundity

Pre-oviposition (F = 0.424; df = 8, 171; P = 0.906) and post-oviposition period (F = 0.829; df = 8, 171; P = 0.578) of the n class="Species">T. absoluta did not differ significantly among treatments, but oviposition period (F = 2.665; df = 8, 171; P = 0.009) significantly differed among treatments. The longest and shortest oviposition period were observed for adults on control and 4 g/kg humic fertilizer respectively. No significant effect on adult longevity (F = 2.013; df = 8, 171; P = 0.048) was recorded. Significant effect was observed on T. absoluta total fecundity (F = 6.144; df = 8, 171; P = 0.000), however the mean daily fecundity of T. absoluta was not significantly different among treatments (F = 0.987; df = 8, 171; P = 0.448) (Table 3). The highest mean number of eggs laid per female was observed for control treatment; whereas moths reared on plants grown in soil that contained 2 g/kg humic fertilizer produced the lowest number of eggs per female (Table 3).

Table 3.

Comparative adult longevity and fecundity (mean  ±  SE) of T.absoluta on tomato plants treated with different fertilizer treatments

Mean daily fecundity (eggs/female/day)	Mean total fecundity (eggs/female)	Adult Longevity	Post-oviposition period	Oviposition period	Pre-oviposition period	Treatment
7.98 ± 0.62a	64.80 ± 0.74a	11.90 ± 0.32a	1.00 ± 0.13a	8.65 ± 0.39a	2.25 ± 0.10a	Control
7.22 ± 0.22a	58.25 ± 2.09abc	11.55 ± 0.34a	1.05 ± 0.15a	8.15 ± 0.30ab	2.35 ± 0.15a	Vermicompost (20%)
8.71 ± 0.72a	52.10 ± 2.28c	10.05 ± 0.52a	1.40 ± 0.17a	6.60 ± 0.44b	2.05 ± 0.18a	Vermicompost (40%)
7.42 ± 0.42a	54.30 ± 1.78bc	10.70 ± 0.48a	1.00 ± 0.16a	7.65 ± 0.41ab	2.05 ± 0.15a	Vermicompost (60%)
7.32 ± 0.57a	51.60 ± 1.80c	10.50 ± 0.49a	0.85 ± 0.20a	7.55 ± 0.41ab	2.10 ± 0.14a	Humic substances (2 g/kg)
7.68 ± 0.46a	54.30 ± 1.35bc	10.55 ± 0.51a	1.00 ± 0.21a	7.50 ± 0.39ab	2.05 ± 0.17a	Humic substances (4 g/kg)
8.13 ± 0.64a	56.45 ± 1.28bc	10.85 ± 0.55a	1.20 ± 0.22a	7.55 ± 0.44ab	2.10 ± 0.16a	Humic substances (6 g/kg)
8.58 ± 0.54a	56.95 ± 1.50bc	10.25 ± 0.42a	1.15 ± 0.13a	7.00 ± 0.32ab	2.10 ± 0.18a	B. subtilis
7.61 ± 0.52a	59.85 ± 1.65ab	11.55 ± 0.39a	1.15 ± 0.17a	8.30 ± 0.38ab	2.10 ± 0.18a	P. fluorescens

For each parameter, differences among treatments were determined by Tukey’s test. Within columns, means followed by different letters are significantly different (P < 0.01).

Comparative adult longevity and fepan> class="Chemical">cundity (mean  ±  SE) of T.absoluta on tomato plants treated with different fertilizer treatments

For each parameter, differenpan>ces among treatmenpan>ts were determined by Tukey’s test. Within columns, meanpan>s followed by difpan> class="Chemical">ferent letters are significantly different (P < 0.01).

Life table parameters

The influence of different fertilizer treatments on the stable population growth parameters of T. absoluta is presented in Table 4. Significant effects on population growth parameters of T. absoluta were recorded: net reproductive rate (R0) (F = 31.345; df = 8, 171; P = 0.000), intrinsic rate of natural increase (r) (F = 17.238; df = 8, 171; P = 0.000) and finite rate of increase (λ) (F = 17.282; df = 8, 171; P = 0.000). The highest and lowest values of these parameters were recorded for control treatment and 2 g/kg humic fertilizer, respectively. Furthermore, T. absoluta had significantly longer mean generation time (T) (F = 2.995; df = 8, 171; P = 0.004) and doubling time (DT) (F = 16.511; df = 8, 171; P = 0.000) when fed on plants grown in the soil containing 2 g/kg humic fertilizer (F = 16.511; df = 8, 171; P = 0.000).

Table 4.

Life table parameters (mean  ±  SE) of T.absoluta on tomato plants treated with different fertilizer treatments

λ(d−1)	DT(d)	T(d)	rm(d−1)	R0(♀/♀)	Treatment
1.15 ± 0.001a	4.85 ± 0.044e	24.53 ± 0.183ab	0.143 ± 0.001a	33.27 ± 0.379a	Control
1.14 ± 0.002bc	5.241 ± 0.084cd	24.99 ± 0.232ab	0.132 ± 0.002bc	27.21 ± 0.977bc	Vermicompost (20%)
1.13 ± 0.002de	5.56 ± 0.098ab	24.45 ± 0.227ab	0.125 ± 0.002de	20.98 ± 0.920de	Vermicompost (40%)
1.14 ± 0.001cde	5.45 ± 0.055bc	24.77 ± 0.182ab	0.127 ± 0.001cd	23.26 ± 0.763de	Vermicompost (60%)
1.13 ± 0.001e	5.78 ± 0.064a	25.06 ± 0.156a	0.120 ± 0.001e	20.14 ± 0.704e	Humic substances (2 g/kg)
1.14 ± 0.001cd	5.45 ± 0.043bc	24.61 ± 0.159ab	0.127 ± 0.001cd	22.85 ± 0.567de	Humic substances (4 g/kg)
1.14 ± 0.002bc	5.20 ± 0.056cd	23.91 ± 0.200b	0.133 ± 0.001bc	24.15 ± 0.548cd	Humic substances (6 g/kg)
1.14 ± 0.002bcd	5.31 ± 0.083bcd	24.36 ± 0.280ab	0.130 ± 0.002bcd	23.97 ± 0.630d	B. subtilis
1.14 ± 0.002b	5.12 ± 0.051de	24.47 ± 0.151ab	0.135 ± 0.001b	27.52 ± 0.760b	P. fluorescens

For each parameter, differences among treatments were determined by Tukey’s test. Based on jackknife estimates of each parameter, within columns, means followed by different letters are significantly different (P < 0.01).

Life table parameters (meanpan>  ±  SE) of pan> class="Species">T.absoluta on tomato plants treated with different fertilizer treatments

For each parameter, differenpan>ces among treatmenpan>ts were determined by Tukey’s test. Based on jackknipan> class="Chemical">fe estimates of each parameter, within columns, means followed by different letters are significantly different (P < 0.01).

Effect of fertilizer treatment on plant growth parameters

There was a significant variation for all growth parameters of tomato seedlings including planpan>t height (F = 8.766; df = 8, 99; P = 0.000), wet weight (F = 8.907; df = 8, 99; P = 0.000), anpan>d dry weight (F = 7.267; df = 8, 99; P = 0.000) among pan> class="Chemical">fertilizer treatments. Tomato seedlings treated with 2 g/kg humic fertilizer and 40% vermicompost had the highest values of plant height (24.96 ± 0.298 and 24.87 ± 0.231 cm, respectively), wet weight (5.97 ± 0.148 and 5.88 ± 0.109 g, respectively) and dry weight (0.88 ± 0.030 and 0.87 ± 0.022 g respectively) compared with other fertilizer treatments (Table 5).

Table 5.

Growth parameters (mean  ±  SE) of tomato seedlings treated with different fertilizer treatments

Dry weight (g)	Wet weight (g)	Plant height (cm)	Treatment
0.67 ± 0.033d	4.71 ± 0.154d	22.42 ± 0.319c	Control
0.77 ± 0.022bcd	5.37 ± 0.125bc	23.79 ± 0.257ab	Vermicompost (20%)
0.87 ± 0.022ab	5.88 ± 0.109ab	24.87 ± 0.231a	Vermicompost (40%)
0.80 ± 0.025abc	5.56 ± 0.129abc	24.21 ± 0.278ab	Vermicompost (60%)
0.88 ± 0.030a	5.97 ± 0.148a	24.96 ± 0.298a	Humic substances (2 g/kg)
0.81 ± 0.023abc	5.58 ± 0.104abc	24.29 ± 0.234ab	Humic substances (4 g/kg)
0.79 ± 0.031abc	5.51 ± 0.160abc	24.04 ± 0.322ab	Humic substances (6 g/kg)
0.80 ± 0.017abc	5.57 ± 0.099abc	24.17 ± 0.207ab	B. subtilis
0.70 ± 0.025cd	5.05 ± 0.132cd	23.12 ± 0.269bc	P. fluorescens

For each parameter, differences among treatments were determined by Tukey’s test. Within columns, means followed by different letters are significantly different (P < 0.01).

Growth parameters (mean  ±  SE) of tomato seedlings treated with difpan> class="Chemical">ferent fertilizer treatments

For each parameter, differenpan>ces among treatmenpan>ts were determined by Tukey’s test. Within columns, meanpan>s followed by difpan> class="Chemical">ferent letters are significantly different (P < 0.01).

Discussion

In this study, different fertilizer treatments clearly affected the developmental time and fecundity of T. absoluta. The moths reared on the plants treated with 2 g/kg humic fertilizer and 40% vermicompost concentration, had the longest developmental time and the lowest total fecundity; while the shortest developmental time and highest total fecundity were observed for control treatment. Consequently, the life table parameters of T. absoluta were affected by different fertilizer treatments. The lowest values of r, R0, and λ of T. absoluta were observed on plants that were treated with 2 g/kg humic fertilizer and 40% vermicompost; however the highest values of these traits were found on control treatment. Also the longest T and DT values were found on plants treated with 2 g/kg humic fertilizer. The r is a useful index for evaluating the pest performance on different conditions of host plants and reflect many factors including survival and fecundity of the pest, as well as generation time (Southwood and Henderson 2000). The r values of T. absoluta in the current study ranged from 0.120 to 0.143 female/female/day on 2 g/kg humic fertilizer and control treatment, respectively. The r value of moth decreased even more on plants grown in pots with 2 g/kg humic fertilizer and 40% vermicompost compared with other fertilizer treatments. Reduction of r value was less on other vermicompost and humic fertilizer rates as well as on PGPR treatments. The exact reason for these differences remain unknown but according to the substantial variation in chemical composition among the soil and the fertilizers were used, it is leasable that the best overall nutrient balance for the plants was reached with 2 g/kg humic fertilizer and 40% vermicompost amendments since these levels of fertilizers improved growth parameters of tomato plants (plant height, wet weight, and dry weight) compared with other treatments. The result certainly suggests that there is an optimal level of humic fertilizer and vermicompost addition that allows for strong suppression of moth populations without suppressing plant growth. The use of organic amendments to soil can supply a more balanced source of nutrition for plant growth, since the organic matter gradually is degraded by microorganisms and the available nutrients of these materials are released with lower mineralization (Patriquin et al. 1995, Zink and Allen 1998). According to results of this study, population growth of T. absoluta decreased on plants grown in the soil amended with vermicompost. Similar results obtained by Arancon et al. (2005) that reported the decreased populations of green peach aphid (Myzus persicae Sulz) and mealy bugs (Pseudococcus spp.) on tomatoes and peppers as well as caterpillars of Pieris brassicae L. on cabbage by vermicomposts. Also Yardim et al. (2006) reported the significant decrease of tomato hornworm (Manduca quinquemaculata (Haworth)) and cucumber beetles (Acalymma vittatum Fabr. and Diabrotica undecimpunctata howardi Barber) populations through the vermicompost applications. Moreover, Razmjou et al. (2012) showed the high potential of vermicomposts for reducing Aphis gossypii populations in cucumber cultures. This study indicated that promoting the growth of host plants through the soil fertility with vermicompost, affects the population growth parameters of T. absoluta. The beneficial effects of vermicompost amendment may be due to an increase in microbial populations and activities in the soils or to the vermicompost's content of humic acid (Muscolo et al. 1993). The organic matter in vermicomposts can usually affect plant morphology and physiology that could provide plants with more resistance to pest attacks or made the plants less susceptible to the pests (Patriquin et al. 1995, Zink and Allen 1998). In this study, application of humic fertilizer could enhance tomato resistance to T. absoluta. It may be related to the promoted growth and nutrient uptake of plant due to addition of humic substances. The beneficial effects of humic substances reported here are in agreement with previous reports. Yildirim and Unay (2011) reported the promoted growth of tomato plants treated with humic substances and the negative effect of humic substances on Liriomyza trifolii (Burgess) population on these plants. Other studies revealed positive effects of humic substance on plant growth and mineral uptake of plant (Chen and Aviad 1990, David et al. 1994, Chunhua Liu et al. 1998, Asik et al. 2009). However, the effectiveness of humic substances on plants changes due to the levels of treatment, growing media, and origin of humic substances (Chen and Aviad 1990, Arancon et al. 2006). We did not deal with the functional basis of moth population growth differences among plants grown with different fertilizer treatments. Arancon et al. (2007) suggested that possible mechanisms of suppression include: the form of nitrogen available in the leaf tissues, the effects of vermicomposts on micronutrient availability, and the possible production of phenols, by the plants after applications of vermicomposts, making the tissues unpalatable. In addition to, PGPR-treated plants in our study influenced population growth parameters of T. absoluta compared with control treatment. Reduced populations of T. absoluta on PGPR treated plants could be related to the promoted plant growth and ISR. According to Ramamoorthy et al. (2001), seed treatment with PGPR causes cell wall structural modifications and biochemical/physiological changes leading to the synthesis of proteins and chemicals involved in plant defense mechanisms. Other studies have provided evidence that PGPR affects population growth of insects. Pseudomonas maltophila affected the growth of larval stage of Helicoverpa zea (Boddie) and caused 60% reduction in adult emergence (Bong and Sikorowski 1991). Also PGPR strains significantly reduced cucumber beetles (D. undecimpunctata howardi and A. vittatum) populations (Zehnder et al. 1997). These findings will be helpful to induce resistance in tomato against T. absoluta especially through amending the soil with optimal level of humic fertilizer and vermicompost. These results could be help the implementation of efficient control programs when planning integrated management strategy of this pest.