| The cotton aphid, Aphis Gossypii Glover (Homoptera: Aphididae), is acosmopolitan species widely distributed in tropical, subtropical and temperate regions. Itis polyphagous specie that can attack285plant species from74families. In China, A.gossypii, a main pest in fields and greenhouses, can attack113plant species andespecially for the cucurbit crops. Chemical pesticides, as a main control method, causedthe aphis resistance, declined the quality of fruits and deteriorated the environment. Inorder to explore efficient biological control agents, the tritrophic interactions amongplant-aphis-ladybird system were studied. The change of nutrient and the secondarycompounds of the plants before and after damaged by aphis were studied. The behavioralresponse of aphis and predator for five different plants were studied. It will provide thetheory basis of highly effective biocontrol agent against A.gossypii.1. The life table parameters of A.gossypii reared on five Host plants species havesignificant difference. The results showed that there were significant differences in theduration for various developmental stages, adult longevity, mean offspring number perday, net reproductive rate, intrinsic rate of increase, finite rate of increase, meangeneration time and population doubling time among the populations reared on the fiveHost plants. The time for the aphids to complete one generation was the longest onLagenaria siceraria var. turbinate, and had no significant differences among the rest fourplants. The population survival curves belonged to Deevey I on all tested plants, that was,the death occurred mainly during late period. Survival rate on C. sativus was higher thanthose on the rest four Host plants. Based on the intrinsic rates of increase, the sizes ofhost suitability were Cucumis melo var. saccharinus> Lagenaria siceraria var. turbinate> Cucurbita moschata var. melonaeformis> Cucumis sativus> Cucurbita pepo var.medullosa.2. The main nutrient and the secondary compounds of five aphis Host plantschanged after attacked by aphis. The soluble sugar, soluble protein, tannin and flavonewere detected. The results showed that contents of tannin and flavone increased after thehost plants were fed by the aphids, whereas the contents of the soluble sugar and solubleprotein were decreased significantly.3. The effects of five Host plants on the functional response of Hippodamia variegata (Goeze) to A.gossypii were studied. At the most prey densities, for the first tothird instar larvae of H.variegata, the amount of consumption to aphids reared on C.moschata and C.sativus was higher than that on L. siceraria and C. melo. For the fourthlarvae and adults, the amount of consumption on C. moschata and C. sativus was higherwhen the prey density was lower whereas higher on L.siceraria and C.pepo. Thefunctional responses of all instar larvae and adults were of Holling-II type. The handlingtimes decreased, and the instantaneous attack rates and maximum of predation increasedwith the increase of instar. The handling times of adults were longer than those of thefourth larvae whereas the instantaneous attack rates and maximum of predation werelower. All three above parameters were different when the predators predated the aphidsreared on different Host plants.4. Utilization was assessed with measures of consumption index (CI), relativegrowth rate (RGR), approximate digestibility (AD), efficiency of conversion of digestedfood (ECD) and efficiency of conversion of ingested food (ECI). The Host plants havesignificant effects on the consumption and utilization of fourth-instar and female H.variegate. Consumption by instars and females was highest for aphids reared on C.moschata and lowest on L. siceraria. For instars, RGR, ECI and ECD values werehighest and CI was higher when fed aphids from C. melo. For females, RGR, ECI andECD values were highest and CI was higher when fed aphids reared on C. sativus. Thus,aphids reared on C. melo were more suitable prey for fourth instar H. variegata, whereasaphids reared on C. sativus were more suitable prey for female adults.5. Behavioral responses of H.variegata were influenced significantly by volatilesfrom five different plants after feeding by aphis. Whether removing aphis from Hostplants or not, volatiles of the plants after feeding aphis attracted H.variegata apparently,whereas the health plants had no attractiveness.6. The five plants all belong to Cucurbitaceae. However, the components of themhave significant difference among them before and after fed by aphis. The variety ofcomponents of C. pepo, C. sativus and C. moschata increased after damaging by aphisexcept C. melo. Nine, nineteen and twelve components were identified from the extractsof the intact plants, aphid-infested and aphid-plant complex plants of C. sativus,respectively. The main components include1-octadecene,[E]-5-eicosene, hexadecaneand heptadecane. Aphid-induced components are p-xylene,1,2-dimethy-benzene,tridecane, α-farnesene, cedrol, octadecane, hexacosane and other seven unknowncomponents；Eleven, twenty and eighteen components were identified from the extracts of the intact plants, aphid-infested and aphid-plant complex plants of C. pepo,respectively. The main components include caryophyllene,1-octadecene, hexadecane andheptadecane. Aphid-induced components are ethylbenzene, p-xylene, m-xylene, α-pinene,tetradecane, longifolene, α-caryophyllene and other two unknown components；Five,seven and twelve components were identified from the extracts of the intact plants,aphid-infested and aphid-plant complex plants of C. moschata, respectively. The maincomponents include caryophyllene, hexadecane, heptadecane and one unknowncomponent. Aphid-induced components are α-pinene, Germacrene D, tetradecane,pentadecane, hexadecane, Homomenthyl salicylate,1-octadecene and other threeunknown components; Thirteen, six and twelve components were identified from theextracts of the intact plants, aphid-infested and aphid-plant complex plants of C.melo,respectively. The main components include3,7-dimethyl-1,3,7-octatriene, hexadecane,pentadecane, p-xylene and α-pinene. Aphid-induced components were not detected andcomponents of intact plants of ethyl benzene, p-xylene, m-xylene and3,7-dimethyl-1,3,7-symplectic three were not detected; Twelve, fourteen and eleven componentswere identified from the extracts of the intact plants, aphid-infested and aphid-plantcomplex plants of C.melo, respectively. The main components include1-octadecene,hexadecane, heptadecane, α-caryophyllene and [E]-5-eicosene. Aphid-inducedcomponents are p-xylene, longifolene and other one Unknown component. |
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