Effects of different foliar fertilizers on the physiology and biochemistry of tomato and population ecology of Bemisia tabaci

Fertilization, an important resource of plant nutrient, has been found to affect the development and reproduction of herbivores and their ability to damage plants. The influences of amino acid foliar fertilizer, phytonutrient and branched-chain amino acids on the growth and nutritional status of tomato and then on the development, survival and reproduction of Bemisia tabaci were studied in the laboratory under condition of (25±1) ℃; L∶D = 14 h∶10 h; and 70%~80% RH. Nymph size and fecundity of B. tabaci were also observed and the potential of amino acid foliar fertilizer application in practice was discussed. Compared with the control, amino acid foliar fertilizer significantly promoted tomato growth which was evident in increased plant height, leaf stentering and leaf area. Phytonutrient also promoted plant growth but to a lesser degree than amino acid fertilizer. Except for nitrogen and sugar, minerals and nutrient contents in tomato leaves varied with fertilizers treatments. The concentrations of phosphorus, protein and free amino acid in tomato leaves were positively correlated with several tomato growth parameters, including plant height, leaf stentering, and leaf area. Negative correlation was observed between potassium and these parameters. Chlorophyll and water contents in tomato leaves showed minimal differences among treatments. The developmental duration of B. tabaci was longest on tomatoes treated with amino acid foliar fertilizer (22.95 d), followed by those treated with phytonutrient (22.83 d), and was shortest on control treatments (21.78 d). B. tabaci survival rate changed little under different foliar fertilizers applications. The body size of B. tabaci 1^st instar nymph was larger on tomatoes treated with branched-chain amino acids than on others, especially the control. As nymph developed, however, the 4^th instar B. tabaci grew largest on tomatoes treated with amino acid foliar fertilizer. The smallest nymph was also observed on the control group. The longevity of B. tabaci female adults was longest on tomatoes treated with branched-chain amino acids (26.64 d) and shortest on those treated with phytonutrient (16.92 d), and the difference between the two treatments was significant. Fecundity was highest on tomatoes treated with branched-chain amino acids (190.55 eggs), which was significantly higher than the lowest value (119.91 eggs) on the control. The highest intrinsic rate of increase (r_m) of B. tabaci was on tomatoes treated with phytonutrient (0.474 9). However, it did not significantly increase on tomatoes treated with amino acid foliar fertilizer (0.406 4) compared with the control (0.405 4). Fertilizer possibly improved crop growth and provided nutrition to herbivores. The balance between production increases brought about by fertilization and offset losses caused by insect infestation was a critical field yield factor. In this study, amino acid foliar fertilizer significantly promoted tomato growth, which caused increased B. tabaci feeding and oviposition. It, however, delayed B. tabaci developmental duration and did not necessarily increase the longevity and fecundity of B. tabaci female adults on tomatoes treated with the fertilizer. Amino acid foliar fertilizer did not enhance the intrinsic rate of increase of B. tabaci, namely did not facilitate B. tabaci population growth. This offset the effects of improved nutritional conditions in tomato and B. tabaci interaction.