Aphid Mummies Research Articles

Sowing Date and Cereal Aphid Infestations and Damage to Barley in Southwestern Québec12

In Southwestern Quebec, the sowing date of barley, Hordeum vulgare L., influenced infestation levels and crop damage by several species of cereal aphids. Seeding within the 1st 2 wk of May was preferable to sowing later in May and June. There were no significant differences in yield, number of earheads per meter, number of grains per earhead, or the 1000-grain weight between sprayed and unsprayed subplots of the early sown barley. The early sown barley, even when unsprayed, showed no significant reduction in any of the aforementioned variables when compared with sprayed and unsprayed subplots of later sowing dates. There were no significant differences in numbers of coccinellids or parasitized aphid mummies between sowing dates. Early sowing could be useful as a cultural control method for the several species of cereal aphids in Southwestern Quebec.

Parasites of the Greenbug and Other Graminaceous Aphids: Identity Based on Larval Meconia and Features of the Empty Aphid Mummy1

Statistical evaluation of morphological characters of empty aphid mummies was used to identify 4 species of aphids that occur on wheat and sorghum and 7 species of their parasites. No distinguishable differences were found between mummies of Aphelinus asychis Walker and A. nigritus Howard. Keys are presented for: the aphid species parasitized; the parasite species, based on adult forms; and the parasite species based on characters of the empty mummy. Marietta graminicola Timberlake is reported as a new parasite record for Schizaphis graminum (Rondani), probably being secondarily parasitic on that aphid.

STUDIES ON THE ARTHROPOD FAUNA OF ALFALFA: VI. PLANT BUGS (MIRIDAE)

AbstractThe food habits and biologies of the Miridae, or plant bugs, were studied during research on the arthropod fauna associated with alfalfa, Medicago sativa L., at Ithaca, N.Y., from 1966 to 1969. Seasonal history, population trends, and natural enemies are summarized for the following species found breeding on alfalfa: Adelphocoris lineolatus (Goeze), A. rapidus (Say), Lopidea marginalis (Reuter), Lygus lineolaris (Palisot de Beauvois), Plagiognathus chrysanthemi (Wolff), and P. politus Uhler. Field observations of predation and scavenging by mirids are reported, including feeding on the pea aphid, Acyrthosiphon pisum (Harris); potato leafhopper, Empoasca fabae (Harris); and alfalfa weevil, Hypera postica (Gyllenhal). The most common sources of animal food on the plants were Hylemya flies killed by fungus, and pea aphid mummies containing pupae of aphidiine wasps. It is concluded that utilization of some animal food on their host plants is a common phenomenon among the Miridae.

An Ecological Study of Aphids 1 on Strawberry in Southern California

Population growth trends of aphids and their natural enemies were studied on a summer planting of ‘Torrey’ variety and a winter planting of ‘Sequoia’ variety strawberries in southern California. Leaflets were sampled at weekly intervals from Sept. 21, 1967, through June 25, 1968, from a summer planting and from Dec. 3, 1968, through June 24, 1969, from a winter planting. The melon aphid, Aphis gossypii Glover; potato aphid, Macrosiphum euphorbiae (Thomas); and the strawberry aphid, Chaetosiphon frogaefolii (Cockerell) were the most common species present, with the strawberry aphid the most abundant, especially during the spring months. The braconid Lysiphlebus testaceipes (Cresson) was the most common primary parasite reared from aphid mummies, and Alloxysta bakeri (Kieffer) and Asaphes sp. were the two most numerous hyperparasites. Altogether, 4 primary and 8 secondary parasites were reared from the 3 species of aphids. The pathogenic fungus Entomophthora planchoniana Cornu was a primary mortality factor affecting the aphid populations, especially the strawberry aphid.

Comparative Behavior and Competition Between Two Aphid Hyperparasites: Alloxysta victrix and Asaphes californicus (Hymenoptera: Cynipidae; Pteromalidae) 1

A series of laboratory experiments was conducted to study one of the possible explanations why the endoparasitic hyperparasite, Alloxysta victrix (Westwood), was numerically more abundant by a 2:1 ratio in previous field studies over the ectoparasitic hyperparasite, Asaphes californicus Girault. It was hypothesized that perhaps a time factor or the day of attack in reference to the developmental stage of the Alloxysta larva/pupa within the aphid mummy could influence the competitive success or failure of the female Asaphes in her attempt at hyperparasitization as a tertiary. The host aphid was the pea aphid, Acyrthosiphon pisum (Harris), and the primary parasite was Aphidius smithi Sharma & Subba Rao. The developmental time of the 1st hyperparasite, Alloxysta, inside the aphid mummy was long enough to permit 11 test-days for attack by the 2nd hyperparasite, Asaphes . Results of these laboratory experiments on hyperparasite competition indicated that 89.3% of the hyperparasites which emerged from mummies containing Alloxysta and attacked by Asaphes during the 1st half of the test-period (Days 1–6) were Asaphes, and only 10.7% were Alloxysta. However, during the 2nd half of the test-period (Days 7–11), successful hyperparasitization by Asaphes decreased to 33.4%, and conversely 66.6% of the Alloxysta survived this attack and emerged as adults. Thus, the ectoparasitic Asaphes does not invariably dominate the endoparasitic Alloxysta when the 2 hyperparasites come into direct association, as had been supposed. The numerical abundance and apparent competitive superiority of Alloxysta over Asaphes in previous field studies is due not merely to its greater specificity and higher searching efficiency, but to its ability to compete successfully with Asaphes by increasingly surviving attack the later this occurs during its development inside the mummy.

INSECT PREDATORS OF MUMMIFIED PEA APHIDS

Aphid parasite larvae in early stages of development are frequently destroyed when insect predators feed on active aphid prey. Stary (1966) discussed insect predators that may feed on living aphids, and thus destroy parasite eggs or larvae. He noted, however, only one case of direct attack on an aphid mummy: that of chrysopid larvae on Aphis fabae Scopoli parasitized by the braconid Lysiphlebus fabarum (Marshall). No observations were reported of direct attacks on mummified aphids by coccinellids, syrphids, or other aphidophagous insects.

Differential Toxicity of Insecticides to the Cabbage Aphid and Two Associated Entomophagous Insect Species1

Ten insecticides were applied as sprays to cole crops, and the effects upon population levels of the cabbage aphid, Brevicoryne brassicae (L.), its principal parasite, Diaeretiella rapae (McIntosh), and coccinellids, Hippodamia spp., were measured. Demeton and endosulfan appeared to have a considerable selective advantage, being more toxic to the aphids than to the beneficial species. Phosdrin®(a mixture of the alpha isomer of 2-carbomethoxy-l-methylvinyl dimethyl phosphate (not less than 60%) and related compounds (not more than 40%)) and Zectran® (4-dimethylamino-3,5-xylyl methylcarbamate) were highly destructive to the mobile stages of the parasites and coccinellids, but were of low toxicity to the late larval and pupal stages of the parasite within aphid mummies. DDT, dimethoate, ethion, and phosphamidon showed evidence of low toxicity to D. rapae stages within mummified aphids and to D. rapae adults.