Study On Basic Of Biology And Applied Technology For Controlling Maruca Vitrata (Lepidoptera: Pyralidae) By Sex Pheromone

The legume pod borer, Maruca vitrata, is a serious pantropical insect pest of grainlegumes, such as cowpea, Vigna unguiculata, common bean, Phaseolus vulgaris, hyacinthbean, Dolichos lablab and pigeon-pea, Cajanus cajan. In cowpea, infestation was higheron flowers (52.3%) than on pods (37.8%) and leaves (9.9%). Without control measures,flower infestation rates up to 90% were reported. The losses in grain yield have beenestimated to range from 20 to 60%. The larvae of M.vitrata damage flowers, flower buds,terminal shoots and young pods by webbing or boring, which protects the larvae fromnatural enemies and insecticides. The major results are summarized as following:1. Study on adult behavior and circadian rhythm of sex pheromone production andrelease of M. vitrataThe results showed that the emergence activity of M. vitrata occurred throughout theday, and 86% of females and 73% of males emerged during the scotophase. Thedifferences of emergence behavior between both sexes were statistically significantduring the 4th, 5th and 8th hour of the scotophase (t＞4; P＜0.05). The mating behaviortook placed from 19:00 to 05:00. The mating duration varied from 20 to 90 minutes. Thehighest mating frequency occurred during the 5th hour of the scotophase for 3-day-oldmoths. Single mating peaks were observed for 1-, 6- and 7-day-old moths, while doublemating peaks were observed for 2- to 5-day-old moths. Adults of the same age spentlonger time in mating during the first half of the scotophase than during the second half ofthe scotophase. The mating behaviour of the moth was age-dependent. Young and oldpairs spent more time in mating than mature pairs of the middle age. Advanced onset oftime and peak for mating were observed directly by older moths. The EAG response ofmale moths was highest to the crude extract of pheromonal glands and air collection from3-day-old virgin female moths and during 5th and 9th hour of the scotophase. In the fieldtests, the highest percentage of the male moths was trapped during 23:00-01:00, and moremale moths were trapped by 3-day-old virgin female moths than by female moths of otherage. The emergence activity, mating activity and the female sex pheromone release weresynchronized at different ages and time of the scotophase. The sex pheromone release was almost constant throughout the scotophase, but mating behavior concentrated between thetwo mating peaks.2. Effect of delayed mating and multiple mating of M. vitrata on reproductionDelayed mating and multiple mating of M. vitrata affected the reproduction. Thelongevity of females and males, fecundity of females increased firstly, and then reduced,but fertility of eggs did not change much when males and females mating were delayed atsame time.; The longevity of females, fecundity of females and fertility of eggs reduced,but the longevity of males increased firstly, and then reduced when females mating weredelayed; The longevity of females and males and fecundity of females increased firstly,and then reduced, but fertility of eggs reduced when males mating were delayed; Themating success rate, the longevity of males and females, fecundity of females reduced,but mating duration was prolonged, fertility of eggs did not change much when maleswere multiple mating. Males can mate for 4 times in the whole life while females canmate only one time.3. The age of M. vitrata affected the mating.Effect of male and female age on the mating success and circadian rhythms of maleresponse to female sex pheromones of the legume pod borer were investigated. Theactivity of thc females remained at a high level until the 3rd days after adult emergence,whereas in males, the peak of activity occurred on the 3rd day and activity remained at ahigh level until the 6th days. The mating frequency of same-aged pair was low at1-day-old, reached a maximum at 3-day-old and thereafter decreased rapidly with age.The declines in female mating success were more pronounced under warm than coolthermocycles, while were not obvious for males. The time spend mating was longer inolder than in younger females. Very young and very old males generally spent more timein mating than mature individuals. The duration of mating was considerably prolonged atall ages under cool than warm thermocycles. Effect of male and female age on the matingsuccess and circadian rhythms of male response to female sex pheromones of the legumepod borer were synchronized, which showed male response play an important role incopulation of Maruca vitrata.4. Identification of female sex pheromone of M. vitrataSex pheromone gland extractions from Maruca vitrata virgin female mothsoriginating in Wuhan and Guangzhou were analyzed by GC (DB-1, DB-WAX) andGC-MS (DB-17, DB-WAX). The result confirmed previously published finding that (E,E)-10, 12-hexadecadienal is the most abundant component of the legume pod borer. InWuhan, exactions were also found to contain (E, E)-10, 12-hexadecadienol and (E)-10-hexadecenal as components. The ratio of three chemicals is 51.4: 4.1:44.5 in thesex pheromone glands. In Guangzhou, (E, E)-10, 12-hexadecadienol can not be found insex pheromone gland extractions of Maruca vitrata. The ratio of two chemicals is 86.5:13.5 for (E, E)-10, 12-hexadecadienal and (E)-10-hexadecenal respectively.5. Male EAG response to female sex pheromoneDose-response curve of these chemicals demonstrated that (E, E)-10,12-hexadecadienal elicited the largest male EAG responses to either Wuhan orGuangzhou populaion, followed by (E, E)-10,12-hexadecadienol and (E)-10-hexadecenal.Study on binary synthetic lures showed greater EAG responses were to those including (E,E)-10,12-hexadecadienal, but two-component blends including (E,E)-10,12-hexadecadienol and (E)-10-hexadecenal elicited lowly males EAG responses. InWuhan, a two-components blend of (E, E)-10, 12-hexadecadienal and (E)-10-hexadecenalin a 5:5 ratio elicited significantly males EAG responses than any other binary syntheticlures; In Guangzhou, a two-components blend of (E, E)-10, 12-hexadecadienal and (E,E)-10, 12-hexadecadienol in a 5:5 ratio elicited significantly males EAG responses thanany other binary synthetic lures; Study on ternary synthetic lures showedthree-component blend of (E, E)-10, 12-hexadecadienal and two other components in a5:1:5 ratio elicited significantly males EAG responses in Wuhan. A three-componentblend of (E, E)-10, 12-hexadecadienal and two other components in a 5:5:1 ratio elicitedsignificantly males EAG responses in Guangzhou.6. Observation on ultrastructure of antennal sensilla in M. vitrataThe morphology of antennae of M. vitrata was observed under scanning electronmicroscope. Antennae is made up of scapus, pedicle and flagella, which cosists of 72-82segments and is 86-97 cm long. The inner side surface of antenna is covered withcataphyUa and most of the antennal sensilla lie on its outer, upper and lower surfaces.Compared with both sesxes, Sensillum coeloconicum and Ear-shaped sensillum offemales are longer than that of males, but Sensillun trichodeum is shorter than that ofmales; The number of all Sensillum of females are lesser on females antennae than malesantennae. Compared with different population, the sensillum of Guangzhou populationare more compact and short for both sexes. Sensilla cheatica are observed on Wuhanpophlation antennae and sensilla basiconica can be observed on Guangzhou populationantennae.7. Field-trapping experiment of synthetic sex pheromone luresField test with single synthetic sex pheromone lures demonstrated that (E, E)-10,12-hexadecadienal can catch more M. vitrata male in Wuhan, followed by (E, E)-10,12-hexadecadienol and (E)-10-hexadecenal. When adding (E)-10-hexadecenal to (E,E)-10, 12-hexadecadienal, the catches of males were increased significantly. Atwo-components lures of (E, E)-10, 12-hexadecadienal and (E)-10-hexadecenal in a 5:5ratio catched significantly male catches than any other binary synthetic lures; Athree-component lures of (E, E)-10, 12-hexadecadienal and two other components in a5:0.3:5 ratio catched significantly males than other ternary lures. In Guangzhou, (E, E)-10,12-hexadecadienal can catch more M. vitrata male, followed by (E,E)-10,12-hexadecadienol and (E)-10-hexadecenal. Adding (E, E)-10,12-hexadecadienolto (E, E)-10, 12-hexadecadienal, the catches of males were increased significantly. Atwo-components lures of (E, E)-10, 12-hexadecadienal and (E, E)-10, 12-hexadecadienolin a 5:5 ratio catched significantly males than any other binary synthetic lures; A ternarylures of (E, E)-10, 12-hexadecadienaI and two other components in a 5:5:0.7 ratio catchedsignificantly males.8. Optimation of sex pheromone lure and trap for M. vitrataThe experiments were conducted to compare different trap designs, and other aspectsof the lures. Lures showed no loss of effectiveness for up to 2 weeks. Attraction reducedgradually 2 weeks later. Result showed that shielding the lures from the sunsight withaluminium foil did not increase catches of M. vitrata, and the data are not significantdifference with no-sielding lures. 120 cm was the optimum height for captures than 90 cmand 150 cm, and 30 cm and 180 cm were not feasible for capture. A sticky-trap design and5 L water-bottle trap were found to be superior to water-pan trap and 1.5 L water-bottle.100μg is the optimum lure dose for capture, and more dose will not increase the catches,in reverse, the dose inhabited the attractant.