| Phenacoccus solenopsis Tinsley and P.solani Ferris are new recorded of invasive pests in China in recent years,causing serious damage to vegetables,flowers and crops,etc.At present,the researches on P.solenopsis are deeper,while there are few reports on P.solani over the world,which mainly focused on its distribution,host plants,quarantine and population dynamics,lack of scientific and comprehensive study.Aenasius bambawalei Hayat is an obligatory accompanying parasitoid of P.solenopsis,and plays an important role in the population control of P.solenopsis.It is generally believed that A.bambawalei parasitizes P.solenopsis only,but we found that A.bambawalei after a short-term adaptation,can successfully parasitize another mealybug species,P.solani,which has not been reported about its natural enemies in China.Thereby,what is the parasitic wasp's choice preference between two mealybugs,and how do different hosts have effects on the offspring characteristics of the parasitic wasp? Herewih,the present paper studied the biological characteristics of P.solani and P.solenopsis,and the host preference of A.bambawalei for two mealybugs.The results will provide a scientific basis for the effective control of two mealybugs and full development and utilization of A.bambawalei.The results are as follows:1.The studies on the biological characteristics of P.solani had shown that: P.solani was a parthenogenetic,thelyotokous species.Eggs were laid in a scattering mode,hatched outside the mother within only 24.3 min.Female adults could produce two forms of eggs in the same batch,namely with-eyespot and without-eyespot egg.There were no significant difference in body length and width between two kinds of egg,but with-eyespot egg could hatch,while the without-eyespot couldn't.Moreover,the outline of the appendage,bristles,tube glands and cone receptors of with-eyespot egg could be seen,and the intact blood cells,nucleus,mitochondrion and muscle fibres exited inside.The surface of without-eyespot egg was smooth,the inside only lipid droplets,endoplasmic reticulum and free ribosomes could be seen.The life cycle of P.solani includes eggs,1~3 instar nymphs and female adults.At 27 ± 1 ?,the nymphal stage lasts 14-22 d and the total life span is 33-64 d.Adult female has high fecundity,with the number of eggs laid per female ranging from 135 to 337(244 on average).The main morphological characteristics of each developmental stage: egg,oblong,yellow and transparent in appearance,with one pair of reddish brown compound eyes;the 1st instar nymph,also yellow in color,and moves fast;the 2nd instar nymph,protuberances appear on the marginal surface of body;the 3rd instar nymph,dark yellow in color,its protuberances become visible,and caudal valve protrudent;adult female,covered with a thick layer of white waxy powder,protuberances become more visible,body color becomes darker,and legs dark red in color.2.The studies on the biological characteristics of P.solenopsis had shown that: the reproduction mode of P.solenopsis was gamogenesis,the life cycle of female included eggs,1~3 instar nymphs and female adults;the life cycle of male included eggs,1~2 instar nymphs,pre-pupa,pupa and male adults.The female nymphal stage of on the potato leaves was 13-22 d,and the total lifespan is 25-53 d;the developmental period of the male nymph and pupa stage was 15-24 d,the total lifespan was 19-26 d,the total lifespan of the female adult is longer than that of male adult.The number of eggs laid per female ranging from 41 to 714.The body length and body width reached the maximum at oviposition stage.It was easy to distinguish between various developmental stages by the depth of black spots on the back of the body.3.The effect of two mealybugs on parasitic efficiency of A.bambawalei: A.bambawalei did not parasitize the 1st instar nymph of P.solani,and could parasitize the 2nd,3rd instar nymph and female adult,but only female adult was the host which could support the eclosion A.bambawalei.When the host was P.solenopsis or P.solani,the optimum ratio of A.bambawalei and mealybugs were15:2 and 20:2 respectively.The parasitic rates were 54.0% and 25.3% respectively.Moreover,the Longevity of the offspring female and male wasps emerged from the host P.solenopsis were distinctly larger than that from the host P.solani(female: 30.3 d vs 9.7 d;male: 26.0 d vs 6.9 d),The length of hind tibia of offspring female wasps was also significantly longer than that of the latter(female metaropod: 0.448 mm vs 0.375 mm),but the length of hind tibia of male wasps was not significantly different.4.Host choice preference of A.bambawalei to two mealybugs: the daily rhythm of A.bambawalei parasitism to P.solani was affected by the light.P.solani could be parasitized from 8:00 to 22:00,with the highest parasitic rates of 33.0% from 14:00 to 16:00.A.bambawalei with the host of P.solenopsis,patasitic P.solenopsis and P.solani at the same time,stay times(20.0 s vs 8.2 s),with in 30 min attack number(1.3 vs 0.4)and the number of contacts(4.1 vs 2.5)were significant difference,and the parasitic rates were 34.8% and 4.5% respectively.While A.bambawalei with the host of P.solani,patasitic P.solenopsis and P.solani at the same time,stay times(9.2 s vs 7.9 s)and with in 30 min attack number(0.8 vs 1.0)were no significant difference,but the number of contacts(4.7 vs 1.9)was significant difference,and the parasitic rates were 21.0% and 4.0% respectively.5.Effect of host conversion on Parasitic Efficiency of A.bambawalei.A.bambawalei collected from Guangxi,and with the host of P.solenopsis in field,was able to parasitize the P.solani after 6 h of adaptation,while A.bambawalei raised in the laboratory with the host of P.solenopsis,only needed to adapt for 3 h;A.bambawalei with the host of P.solani,only needed 1 h till parasitic. |
PDF Full Text Request