Study On The Effect Of Fertilization On The Biological Characters Of Citrus Red Mite And Occurrence Of Other Important Citrus Pests

Fertilization of soil will affect the nutritional status of plants,and the composition of plant nutrition will change with the use of different types of fertilizers and application rates,thus affecting the growth and population density of phytophagous insects.Although the extensive use of chemical fertilizers in the past has increased crop yields,it has also caused a series of ecological problems.Bioorganic fertilizers and organic-inorganic compound fertilizers have been gradually promoted in recent years.In addition,many studies have shown that nitrogen is positively related to insect density and growth.Other nutrient elements such as phosphorus and potassium can also cause changes in insect population dynamics.Different pest species show different preferences of nitrogen,phosphorus and potassium.Understanding the relationship between different types of fertilizer and the occurrence of citrus pests is very important in cultural control.Citrus red mites?Panonychus citri Mcgregor?,citrus whitefly?Dialeurodes citri Ashmead?and citrus leafminer?Phyllocnistis citrella Stainton?are the major pests of citrus.In this thesis,the effects of bio-organic fertilizers,organic-inorganic compound fertilizers,and chemical fertilizers on the biological characteristics of citrus red mites were studied.At the same time,the occurrence of citrus whitefly and citrus leafminer on the citrus treated with the three kinds of fertilizer was observed and compared.Furthermore,the effect of foliage nutrition on the biological characteristics of citrus red mites was also investigated.The main research content and results are as follows:1.Effects of three fertilization treatments on the biological characteristics of citrus red mitesDifferent fertilizers applying in citrus had different influences on the biologicalcharacteristics of citrus red mite.The durations of egg,larva and nymph(1^stand 2^ndinstar),the survival rate of egg,larva and nymph(1^stand 2^ndinstar),whole generation,and the longevity of female adults,sex ratio were not significant different when feeding on the citrus applying with different fertilizers.But the durations of total egg to adult feed on compound fertilizers was significantly shorter than that on organic fertilizers.The pre-oviposition of females,generation survival rate,longevity of male adult and fecundity of female feeding on the compound fertilizers were shorter than that on chemical fertilizers.The order of net reproduction rate?R_o?,intrinsic rate of increase?r_m?and index of popupationtrend?I?ondifferentfertilizersapplyingcitruswascompound fertilizers>organic fertilizers>chemical fertilizers.The order of generation period?T?was compoundfertilizers<chemicalfertilizers<organicfertilizers.Andthe finite rate of increase???was not significantly different.Overall,the result indicated that the compound fertilizer treatment was the most favorable to the population growth of citrus red mites.The results of leaf nutrient test showed that the content of major elements ofcompound fertilizer,organic fertilizer and chemical fertilizer treatment was N:3.3%,3.2%and 2.7%,P:0.59%,0.56%and 0.48%,K:2.41%,2.49%,2.02%,respectively.And the N/K was 1.37%,1.29%and 1.34%respectively.The N content and the N/K of compound fertilizer treatment were the highest.N has a great effect on the reproduction and survival rate of citrus red mite,and the ratio of N and K has a great effect on its developmental period.The best population growth of citrus red mite rearing on the hostplants of compound fertilizer treatment might be related to these two indexes.2.Effect of three fertilization treatments on the occurrence of citrus whitefly,citrus leafminer and sooty moldThe numbers of adult,egg and nymph of citrus whitefly on the citrus young plants treated by the 3 kinds of fertilizer were monitored in a greenhouse.The results showed that although there was no significant difference of settling adults among the 3 treatments,the numbers of egg and nymph on the organic fertilizer-treated citrus were significantly fewer than the chemical fertilizer treatment.In addition,the index of sooty mold caused by the whitefly of organic fertilizer treatment was also lowest.These results demonstrate that applying of organic fertilizer can reduce the infection of citrus whitefly,and reduce the sooty mold which induces by this pest species.But the damage indexes caused by citrus leafminer were not significantly different among the 3 treatments,demonstrating that the fertilizers show different influence on different pest species.3.Effect of different foliar fertilizers on the biological characteristics of citrus red mitesDifferent foliar fertilizers also showed different effects on the biologicalcharacteristics of citrus red mite.The durations of egg,larva and nymph?1^stt and 2ⁿdd instar?,egg to adult;pre-oviposition of females;duration of egg laying;the survival rate of egg,larva,1^stt instar nymph and total nymph,total generation;and the sex ratio were not significantly different when feeding on citrus spraying with different foliar fertilizers.But the survival rate of 2ⁿdd instar nymph,longevity of male adult,and the fecundity of female adult on the 0.5%Urea treatment citrus were significantly higher than control.In addition,the longevity of female adult on the 0.17%Compound amino acid treated citrus was significantly higher than that on 0.5%Urea and control.The order of net increment rate?R₀?,intrinsic growth rate?R₀?,finite rate of increase???and index of population trend?I?of citrus red mite reared onthe 3 treatments was CK<0.17%Compound amino acid fertilizer<0.5%Urea.The order of generation duration?T?was 0.5%Urea<0.17%Compound amino acid fertilizer<CK.The results showed that 0.5%urea treatment was most beneficial to the population growth of citrus red mites,while 0.17%compound amino acid fertilizer did not show significant effect on the population of citrus red mites.So the compound amino acid is suitable for application.The results of leaf nutrient testshowed that the content ofmajor elements of0.5%Urea,0.17%compound amino acid and water was N:4.9%,4.9%and 3.6%,P:0.37%,0.37%,and<0.2%,K:2.58%,2.53%and 2.43%,respectively.And the N/K of the three treatments was 1.90,1.94,and 1.48 respectively.These data indicates that the content of N,P,K and N/K increased greatly after spraying with the two kinds of foliar fertilizer,thus promoted the growth of citrus red mite population.