Search

Oviposition and fecundity of Cteniecra destructor (Brown) were studied in the laboratory and field. In a series of tests, total oviposition by individual field-collected females ranged from 495 to 1464 and averaged from 264.0 to 940.0 eggs per female. Temperatures from 50 to 86° F. had no effect on total fecundity but lower temperatures extended the oviposition period. Soil moisture from 8 to 20% in sifted clay loam soil (particle sine less than 0.177 mm.) had no effect on total oviposition. At 4% soil moisture females died rapidly and laid very few eggs. Food increased the total oviposition, the length of the oviposition period, and the longevity of females. Most eggs were laid during the first month after the onset of oviposition.Oviposition was shown to be cyclic in nature. Females usually laid eggs in large batches, followed by periods when practically no eggs were laid. This resulted in a series of irregular oviposition peaks which gradually declined in magnitude as the oviposition period progressed.

Marked beetles and pitfall traps were used in studying dispersal on the soil surface of adults of two species of wireworms, and their incidence of flight was determined by tanglefoot wind-traps. Approximately 7% of 1200 marked males and 4% of 855 marked females of Ctenicera destructor (Brown) were recovered. At 120 yards from the central release point, marked males were captured 24 hours after release, females in a minimum of 9 days. No evidence was obtained that adults of C. destructor fly. Of Hypolithus bicolor Esch., approximately 3% of 475 marked males and 2% of 1852 marked females were captured; both males and females were trapped at 60 yards in a minimum period of 6 days, and one female was taken at a maximum distance of 80 yards 10 days after release. Adults of H. bicolor flew during all three seasons of the study. There was a difference in the rate at which females of both species tended to disperse on the ground, suggesting a heterogeneity in the marked populations with respect to dispersal.

Bacteria pathogenic to crucifers were isolated from 92% of the eggs from flies of the cabbage maggot, Hylemyia brassicae (Bouche) of a population from rutabaga (Swede; Brassica napus napobrassicd) and from 90% of those from a population from Chinese cabbage (Brassica pekinensis). The larvae transmitted the decay-causing bacteria to healthy tissues and aided in the development and spread of the rot. Of bacterial isolates from the interior of surface-sterile puparia, decay was caused by 100% of those from the rutabaga population and 35% of those from Chinese cabbage. Pathogenic cultures were also obtained from 44% of the prepupal linings of the Chinese cabbage population. The light internal contamination of adults at eclosion showed that the flies became contaminated externally from the interior of the puparia. The two populations of H. brassicae studied were contaminated with distinctly different types of bacteria. Erwinia sp., the predominant isolate from the rutabaga population, grew best on rutabaga. It caused a slow necrotic collapse and a dark pigmentation of the tissues, but not a soft-rot. Many different types of bacterial contaminants were associated with the stages of the cabbage maggot from Chinese cabbage. Green pigmenting, non-pathogenic forms were very prevalent. All pathogenic cultures caused some type of soft-rot. Some of these cultures were identified as Pseudomonas sp. and Aerobacter sp. Zusammenfassung DIE BEZIEHUNG DER KOHLFLIEGE, HYLEMYTA BRASSICAE (BOUCHE), ZUR FAULNIS BEI EINIGEN KOHLGEWACHSEN Es wurde die Beziehung zweier Kohlfliegen-Populationen (Hylemyia brassicae Bouche) zu faulniserregenden Bakterien an Kreuzblutlern in Verbindung mit dem von den Larven verursachten Schaden untersucht. 92 bez. 90% der Eier und 100 bez. 35% der Puparien, die sich an Kohlruben und Chinakohl entwickelten, trugen pathogene Bakterien. Pathogene Kulturen wurden von 44% der Prapuppen-Haute aus Puparien der Chinakohl-Populationen erhalten. Die Larven vermochten faulniserregende Bakterien wirksam auf gesunde Gewebe zu ubertragen und forderten die Entwicklung und Ausbreitung der Faule. Beim Schlupfen waren die Imagines innerlich nicht stark kontaminiert, beschmierten sich aber offenbar auserlich durch Kontakt mit dem Inneren der Puppengehause und der Prapuppen-Haute. Ein als Erwinia spec, identifizierter Bakterientyp konnte durchgangig von allen Stadien der Kohlfliege isoliert werden, die sich an Kohlruben entwickelten. Er verursacht bei Kohlruben eine langsame nekrotische Faulnis und dunkle Verfarbung der befallenen Gewebe. Dieses Bakterium scheint antagonistisch zu anderen Bakterien zu sein, da nur sehr wenige andere Keime mit Stadien der Insekten dieser Population vergesellschaftet gefunden wurden. Umgekehrt fanden sich viele verschiedene Bakterientypen auf Stadien der auf dem Chinakohl lebenden Kohlfliegen. Die Virulenz der pathogenen Kulturen variierte betrachtlich, jedoch verursachten alle irgendeine Art der Weichfaule. Einige dieser aus dem Inneren oberflachlich sterilisierter Puparien isolierten Kulturen wurden als Pseudomonas spec, and Aerobacter spec. bestimmt. Die Art der bakteriellen Kontamination der Kohlfliege scheint hauptsachlich von der Empfanglichkeit ihrer kreuzblutigen Wirtspflanzen gegenuber verschiedenen Typen der Faulnis nach Verletzung durch die Kohlfliegenmaden abhangig zu sein. Die allgemeinen Zusammenhange zwischen dem Insekt und den faulniserregenden Bakterien werden beschrieben.

Eggs of Ctenicera destructor (Brown), Ctenicera aeripennis (Kirby) and bisexual and parthenogenetic strains of Hypolithus bicolor Eschscholtz must absorb water to complete embryonic development.In eggs of C. destructor incubated at 24.4 ± 0.5 °C. in sifted soil containing 15% water (wet weight basis), water absorption started during the second day of development and ended within 24 hours. The mean wet weight increased from 26.6 ± 0.2 (standard deviation) μg. to 39.2 ± 0.6 μg. by the third day. During this period the water content increased from 42% to 64%. After the third day, the mean wet weight remained constant but a significant increase (P < 0.01) in the mean water content and a significant decrease (P < 0.01) in the mean dry weight occurred.The progress of water absorption in eggs of C. aeripennis and the two strains of H. bicolor was similar to that in C. destructor. Differences from C. destructor were apparent, however, in the sizes of the eggs, in the initial and final amounts of dry matter and in the water contents.Water absorption by eggs of C. destructor started after one day of incubation at 25 ± 0.5 °C., after 1 to 2 days at 20°, and after 4 days at 15°. The rate of absorption appeared to be slightly more rapid at higher temperatures within the range of 15–25 °C.

Laboratory tests were carried out to determine if certain types of cover and surfaces were preferred by adults of Hypolithus bicolor Eschscholtz. Approximately 45% of the adults selected the rough stone when a rough stone, a smooth stone, a lump of dried manure and a square of paper were provided simultaneously as cover. Soil moisture did not seem to influence this selection, except that the cover in the soil at the highest moisture level was rejected. The selection of preferred cover appears to be in response to thigmo-kinesis coupled with a tendency of beetles to congregate in tight groups under the cover.

Experimental plantings of three cruciferous root crops, radish, turnip and rutabaga, indicated that heptachlor applied in various ways gave the most consistently good control of root maggots ( Hylemya spp.). A comparison of different methods of application for maggot control in radish and turnip showed that the best materials gave the highest degree of maggot control as seed or furrow treatments to radish, and as furrow treatments to turnip. The efficiency of a number of insecticides for control was compared by furrow treatment to turnip. Heptachlor or aldrin at 1 pound actual toxicant per acre gave more effective control than any of the other materials used. Similarly, as broadcast treatments to rutabagas made before planting and mixed with the top 3 inches of the soil, heptachlor and aldrin at 2 pounds actual toxicant per acre were the most effective control agents.

Observations on predation of eggs of Hylemya brassicae (Bouché) were made from the Belleville laboratory from 1953 to 1955 as part of a general study of the biotic agents that act against the maggots that attack cruciferous crops. In biological control programs more attention has been given to parasites than to predators. Predation is more difficult to observe and to evaluate and, unlike parasitization, cannot be even roughly appraised by the collection and examination of hosts. As a group, predators are less specific in their food requirements and less regular in their habits than parasites and consequently do not lend themselves so readily to manipulation for biological control purposes. Predators used with success in biological control have had a high degree of specificity to their prey. Non-specific predators may, however, in the presence of large numbers of suitable hosts on which to feed, be important factors in reducing populations of noxious insects. Predation on eggs of H. brassicae is an example.

The cabbage maggot, Hylemyia brassicae (Bouche) was reared from egg to adult under aseptic conditions on rutabaga (Swede; Brassica napus napobrassica). No larvae survived either on contaminated or uncontaminated rutabaga plugs sterilized by heat. A comparison of larval development on rutabaga inoculated with several species of decay-producing bacteria showed that larvae developed best on healthy uncontaminated rutabaga tissue or on rutabaga tissue that decayed slowly. Survival was lowest and puparia were smallest when larvae fed on plugs that were decayed rapidly by virulent soft-rot bacteria. ZUSAMMENFASSUNG DIE ENTWICKLUNG DER KOHLFLIEGE, HYLEMYIA BRASSICAE (BOUCHE), AUF ASEPTISCHEM UND FAULENDEM KOHLRUBEN-GEWEBE Die Kohlfliege, Hylemyia brassicae (Bouche), wurde vom Ei bis zur Imago auf keimfreiem Kohlruben-Gewebe gezogen. Insgesamt verpuppten sich 17 aseptische Larven; und die 6 Mannchen und 7 Weibchen, die spater daraus schlupften, waren ebenfalls bakterienfrei. Die Larven entwickelten sich nicht auf hitzesterilisiertem Gewebe, oder wenn dieses Gewebe mit faulniserregenden Bakterien versetzt wurde. Ein Vergleich der Larvalentwicklung auf aseptischen Kohlruben-Stucken, die mit verschiedenen Arten faulniserregender Bakterien infiziert waren, zeigt, das sich die Larven am besten entwickelten, wenn keine Bakterien anwesend waren oder wenn das Kohlruben-Gewebe nur langsam faulte. Es kamen weniger Larven zur Verpuppung, und die Puparien waren am kleinsten, wenn die Larven mit Kohlruben-Gewebe ernahrt wurden, das infolge Befalls mit Erwinia atroseptica (van Hall) Jennison oder Erwinia carotovora (Jones) Holland rasch faulte. Die Verpuppungs-Prozentsatze der Larven nach Futterung mit Kohlruben-Stucken, die mit E. atroseptica, E. carotovora, einer unbekannten Erwinia-Art (die eine langsame Faulnis verursacht) oder einem Gemisch von E. atroseptica und der Erwinia-Art infiziert waren, sowie in der Kontrolle (ohne Bakterien), betrugen 28, 55, 70, 81, und 75%. Eine unbekannte Erwinia-Art, die durchgangig von verschiedenen Entwicklungsstadien der Kohlfliege von Kohlruben-Feldern isoliert werden konnte, hemmte die von E. atroseptica ausgelosten Faulnisprozesse, wenn ein Gemisch der beiden Bakterien in Kohlruben-Gewebestucke gebracht wurde. Dies vermag zum Teil das geringe Auftreten der Weichfaule auf Kohlruben-Feldern zu erklaren, die von Kohlfliegen befallen sind.

Using oviposition as a measure of the preference of the cabbage maggot, Hylemya brassicae (Bouche), for various hosts in the family Cruciferae, the following species were compared: turnip, rutabaga, radish, cauliflower and black mustard. Significantly higher numbers of eggs were taken throughout the season from rutabaga and turnip than from radish and mustard and the fewest eggs were taken from cauliflower plants. Radish appeared to he particularly susceptible to oviposition for a very short period. Mustard growing as a weed would appear to be a significant source of second-generation maggots attacking cruciferous root crops later in the season.