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Abstract
Eman Mohamed MohamedAbd El-maksoud: Ecological and biological aspects of the tomato leaf miner Tuta absoluta (Lepidoptera: Gelechiidae) on tomato plants. Unpublished M. Sc. Thesis, Department of Plant Protection, Faculty of Agriculture, Ain Shams University, 2016. The tomato leaf miner, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) became a serious pest to tomato cultivations in Egypt since 2009. It causes great damage in the crop. The present study was carried out to estimate some biological and ecological studies on this pest. T. absoluta reared on artificial diet on at four constant temperatures 20, 24, 28 and 32ᵒC and 60-70 % RH. Data obtained indicated that incubation period were 6.8, 5.0, 4.0 & 3.5 days at 20, 24, 28 & 32°C, respectively. Percentages of hatchability were 72, 97, 89 & 95% on the same degree of temperature, respectively. Zero of development for egg stage was 7.0°C, thermal units for the egg were 88.4, 85.0, 84.0 & 87.5 DD’s at 20, 24, 28 and 32ᵒC, respectively. Durations of larval stage were 30.9, 21.9 & 15.7days at 20, 24 & 28°C, respectively. Zero of development was 10.0°C, while thermal of constant were 309.0, 306.6 & 316.8 DD’s at 20, 24 & 28°C, respectively. Percentages of mortality of larval stage were 52, 74, 74 & 100% at 20, 24, 28 and 32ᵒC, respectively. For pupal stage, durations were 15.8, 9.5, 8.1days at 20, 24 & 28°C, respectively. Zero of development was 11.2°C, thermal constant were 138.6, 121.5 & 136.6 DD’s at 20, 24 & 28ᵒC, respectively. Percentages of mortality were 10.0, 5.0 & 1.0% at 20, 24 & 28ᵒC, respectively. For adult, male longevity was 12.8, 12.0 &7.0 days at 20, 24 & 28°C, respectively. Zero of development was 9.8°C, thermal constant were 130.6, 144.8 & 134.7 DD’s at 20, 24 & 28ᵒC, respectively. Female longevity was 15.6, 11.8, 7.0 at 20, 24 & 28°C, respectively. Zero of development was 11.2°C, thermal constant were 137.3, 151.0 & 137.8 DD’s at 20, 24 & 28ᵒC, respectively. The mean numbers of eggs laid by female were 57.8, 79.3 & 145.3eggs at 20, 24 & 28ᵒC, respectively. Fertility of female was 72.0, 97.0 & 89.0% at 20, 24 & 28ᵒC, respectively. Durations of generation were 56.1, 38.6 & 30.7 days at 20, 24 & 28ᵒC, respectively.
The life table parameters, net reproduction rate (R◦), mean generation time (Gt), intrinsic rate of increase (rm), finite rate of increase (λ) and population double time (Dt) were: 2.85, 59.58, 0.02, 1.02 and 43.43 at 20 ºC; 6.29, 41.37, 0.07, 1.07 and 12.41 at 24 ºC; 10.03, 33.92, 0.13, 1.14 and 6.68 at 28 ºC; 3.15, 33.97, 0.04, 1.04 and 21.71 under laboratory conditions, respectively.
According to susceptibility of eight tomato cultivars to the infestation degree by T. absoluta, the eight cultivars could be arranged as follows; Red sun, Hybrid Super strain B and Castle rock were the more susceptible cultivars followed by Riogrande, Baladi and Nemaguard with a moderate infestation. Finally the Super set and Hybrid Bito86 cultivars were considered the most resistible ones.
The highest of Tuta absoluta mines occurred on the leaflets of Red sun was corresponding to the high level of N.P.K. On the other hand Hybrid Bito86 cultivar contained on the lowest infestation with corresponding to least values N.P.K. The same trend obtained for amino acid, total protein, total carbohydrate, α and β-esterases and peroxidase enzyme. The highest T. absoluta mines occurred on Red sun cultivars with corresponding to low level of total phenol while the highest content of phenol was found in Hybrid Bito86 cultivar. There are positive significant between the infestation by T. absoluta and density of non-glandular tricome/cm2 in the upper surface.
When tomatoes plant treated by plant growth regulators induced it’s resistance to infestation by T. absoluta. This treatments could be divided to into three groups; 1st group: Benzyle adenin and Kinetin, 2nd group: Salcylic acid, 3rd group: Control.
The normal distribution curve was used to determine the number of generation of T. absoluta, data obtained indicated that T. absoluta had 10.0 generations in the field per the year (from May 2015 to May 2016). When using linear method to determine the number of generations for T. absoluta, it could be found that this pest had 10.0 generations per the year. When using thermal units to determine the number of generations for T. absoluta, results revealed that this pest had 14.0 generations. There are a difference between 3rd method (thermal units) and the other previous methods. This pest certainly enters aestivation from end of July to half of October (about72.0 days) and emphasize that 32°C is considered as a fetal degree temperature for the first instars larvae of T. absoluta. During this period, there are four predicted peaks. Therefore, the chemical control was not obligatory and natural enemies are enough.
To find parasitoids and predators for biological control of this pest, samples of tomato leaves infested with T. absoluta were collected from Qualiobya and Giza Governorates. Three genera of hymenopterous parasitoids, Diglyphus sp. (Eulophidae), Elasmus spp. (Elasmidae) and Telenomus sp. (Scelionidae) are the first record in Egypt. The predatory bug, Nesidiocoris tenuis Reuter (Heteroptera: Miridae) was also recorded. T. absoluta showed two peaks of 30.3 and 25.0 leaf mines/10 leaflets on 7th and 28th of May, 2013, respectively. N. tenuis also recorded two peaks of 58.8 and 73.3 nymphs & adults/plant on the same previous dates, respectively. N. tenuis was mass reared to evaluate the predatory efficiency of nymph and adult stages on T. absoluta eggs. The nymph, adult male and female consumed 113.3, 81.5 and 125.3 eggs of Tuta absoluta, respectively. The 4thnymphal instars devoured the highest number (30.6 eggs), while the 1stnymphal instars ate the lowest (7eggs). Therefore, N. tenuis was highly effective in controlling T. absoluta eggs under laboratory conditions.
Key words: Tomato, Lycopersicon esculentum, Tuta absoluta, Developmental threshold, Thermal units, Life table, Susceptibility of Tomato, Cultivars, N, P , K, Total Protein, Total Carbohydrate, Total phenol, Total amino acid, Peroxidase enzyme, α, β Esterase enzymes, Tricomes, Seasonal abundance, Plant growth regulator, Generations, Parasitoids, Digluphus, Elasmus, Telenomus, Nesidiocoris tenuis, predatory efficiency.