Showing papers on "Aphididae published in 1978"

Absence of Genetic Variability in the Green Peach Aphid, Myzus persicae (Hemiptera: Aphididae),

Abstract: An electrophoretic survey of genetic variability in 9 U.S. populations of the green peach aphid, Myzus persicae (Sulzer), revealed zero heterozygosity for 19 structural genes. This was contrasted with an avg heterozygosity of 0.07 for the potato aphid, Macrosiphum euphorbiae (Thomas), which has a similar life history. We propose that this finding reflects a recent, limited introduction of M. persicae, whereas M. euphorbiae is endemic. Several individuals, presumed to be morphologically similar species of Myzus, were detected both in natural and laboratory populations of M. persicae. Putative biotypes of M. persicae may be attributable to colonies derived from several species.

Electrophoretic study of genetic variation in British Myzus persicae (Sulz.) (Hemiptera, Aphididae).

Abstract: Thirty-five clones of the green peach aphid, Myzus persicae Sulz., representing a wide range of host plants and geographical origins, were examined electrophoretically. Only 11 of 26 enzymes were active enough for subsequent work. Since genetic crosses are very difficult to make in the parthenogenetic M. persicae, assigning bands to loci and alleles is necessarily arbitrary. Thirty-two isozyme bands were detected. Only two of these (Est-1 and Est-3) migrated to different distances in some clones. This is a very low level of interclone variation, considering the known properties and origins of the clones. The peculiar feeding habits of aphids may perhaps partly explain the inactivity of so many enzymes in M. persicae (which are active in other insects). The scarcity of interclone variation in isozyme migration distance in M. persicae clones may be the result of its fast parthenogenetic reproduction and high migration ability of alates, combined with the effects of natural and artificial selection (e.g., by insecticides). Surviving genotypes may be rather few, each represented by numerous individuals. The only type of widespread electrophoretic variation is in the intensity of two esterase bands (Est-1 and Est-2). Five hypotheses are presented to explain this variation and discussed in view of evidence from other organisms.

The influence of repellent materials and aphid extracts on settling behaviour and larviposition of Myzus persicae (Suizer) (Hemiptera: Aphididae)

Abstract: When incorporated into an artificial diet or painted on the surface of the membrane containing the diet, solutions of the insect repellent GD 880 (2-methyl-2-(octylamino)-1-propanol) killed aphids, whilst extracts of neem seeds (Azadirachta indica) or extracts of the bodies ofMyzus persicae (Sulz.) deterred settling and larviposition of apterous adults. The deterrent effect occurred even when the painted membrane was covered by a similar but untreated membrane. When applied in culture solutions to the roots of young kale plants, GD 880 and extracts of neem influenced aphids on the foliage only at concentrations that visibly affected plant growth, but neem extract (and to a lesser extent GD 880) decreased aphid colonisation when painted on kale leaves at non-damaging concentrations.

Effect of insecticides on the pea aphid, acyrthosiphon pisum (hemiptera: aphididae), and associated fauna on alfalfa

Abstract: Four insecticides effectively controlled the pea aphid, Acyrthosiphon pisum (Harris), but differed in their effects on other pest species and on predators. Two days after treatment, methidathion, dimethoate, and malathion reduced populations of all the pest species, but pirimicarb gave no control of the weevils Hypera postica (Gyllenhal) and Sitona scissifrons Say. Methidathion reduced populations of all predators, dimethoate reduced populations of all predators except Aeolothrips fasciatus (Linnaeus), and malathion reduced populations of all the predators except Nabis alternates Parshley. Pirimicarb reduced only the populations of syrphids. Of the insecticides tested, methidathion was the most disruptive to predators and pirimicarb the least.

The growth and voracity of larvae of Leis conformis (Boisd.) (Coleoptera: Coccinellidae) fed on the rose aphid Macrosiphum rosae (L.) (Homoptera: Aphididae) in the laboratory.

Abstract: The ladybird Leis conformis is one of the commonest predators of the rose aphid, and of other aphids in South Australia. When fed a surfeit of M. rosae the mean weights of larvae during development could be described by the equation: y = 0.45 exp[(O.0313t-0.2751)x] where t is temperature in degrees Celsius such that 15 < t < 29.2, and x is time in days, such that y < 40.6 mg. The mean weights could also be described by: y = exp (0.0347x-0.8551), with x in day-degrees above 10oC. The voracity of larvae could be described in third-instar aphid equivalents (TIES) by: y = exp(0.0347x+ 0.6219) where y is cumulative number of TIES eaten, and x is less than 131.4 day-degrees. The TIE units used to convert predator wet weight to aphid units eaten were based on the numbers of aphids of each instar that had to be eaten for a predator larva to gain one milligram of wet weight. It is suggested that the voracities of different ladybirds feeding on different aphids can be compared when voracity is expressed as the cumulative number of aphids eaten per stadium. The quantification of voracity in the field, and the possible use of L. conformis for pest control, are briefly discussed.

The scientific nomenclature of the spotted alfalfa aphid (homoptera: aphididae)

Abstract: On present evidence, the spotted alfalfa aphid is a recognisable segregate or biotype of Therioaphis trifolii (Monell) and should be known by this name or, more definitely as Therioaphis trifolii (Monell) f. maculata. The binomen Therioaphis maculata (Buckton) is not applicable.

Insecticide resistance in the green peach-potato aphid Myzus persicae (Sulz.) (Hemiptera: Aphididae)

Abstract: A population of the green peach-potato aphid (Myzus persicae) from a glasshouse in Christchurch was shown by laboratory methods to be highly resistant to maldison, demeton-S-methyl, and mevinphos. A degree of cross resistance to naled and acephate, which had not been used against these aphids, was demonstrated. Susceptible aphids from Levin were readily controlled by demeton-S-methyl, acephate, maldison, pirimicarb, mevinphos, and naled, but only pirimicarb adequately controlled the samples from Christchurch.

Factors influencing the determination of wing formation in the aphid, Rhopalosiphum padi (L.) (Homoptera: Aphidae)

Abstract: The determ ination o f wing form in the aphid RhopaTosiphum padi ( L . ) was examined w ith respect to photoperiods andp la n t hormones (GA= g ib b e re T l ic acid and ABA = ab sc is ic ac id ) and the underlying •physio log ica l mechanisms were considered. V irg inoparae o f R_. padi were reared under two photoperiodic r e g i ­ mens. One group was reared under increasing photoperiods, w h ile the other group was reared under decreasing photoperiods. When the number o f a la te and apterous o f fs p r in g produced were compared between regimens i t was found th a t aphids reared under increasing photoperiods produced more apterous progeny than those reared under decreasing photoperiods. Two p la n t hormones were tes ted fo r possible e f fe c ts upon wing dimorphism in R. padi and a s ig n i f ic a n t treatm ent e f f e c t (P = 0 .0 1 ) was received a t the F1generation in the 16-hour photoperiodic r e g i ­ men. Whether these p la n t hormones in f lu en ce wing dimorphism in the aphid v ia changes in the physiology o f the host p la n t or d i r e c t ly on the physiology o f the aphid is unknown. The volume o f the corpus a l latum in FL padi was measured as a parameter o f i t s a c t i v i t y . Aphid mothers th a t produced mostly apterous progeny had a la r g e r corpora a l l a t a (P = 0 .035) than those mothers th a t produced predominantly a la te o f fs p r in g . The data obtained confirm the studies o f White (1971 ). I t is proposed from these re s u lts th a t corpus a l latum a c t i v i t y and high t i t e r s o f JH are associated With the production o f apterous o f fs p r in g .