Cyromazine seed treatments to control onion maggot, Delia antiqua, on green onions

Cyromazine seed treatments were evaluated for onion maggot control in green onion crops. The more tolerant to organophosphates of two populations of onion maggots was chosen for further research, based on the results of adult assays in a Potter spray tower. In the laboratory, first-instar mortality was compared between film-coated seed treatment and soil drench treatment. The LC50 for the film-coated seed treatment was approximately one fourth that of the soil drench treatment. In choice assays, no significant difference was observed between the number of eggs deposited on seedlings grown from film-coated seeds with cyromazine and film-coated seeds without cyromazine. Field studies demonstrated that all rates of cyromazine seed treatment resulted in protection of onion plants from onion maggot damage. Green onions may not require as high a rate of cyromazine for control of onion maggots as the rate established for use in dry onions for two reasons: the seeding rate is much higher for green onions resulting in more AI/ha for a given amount of AI/kg of seed, and a given percentage of stand loss is more difficult to detect in green onions than in dry onions.     

Distant olfactory response of the onion fly, Delia antiqua, to host-plant odour in the field

ABSTRACT. Distant olfactory orientation of female adult Delia antiqua (Meigen) to the host-plant Allium volatile dipropyl-disulphide (DPDS) was examined in the field using mark-release-recapture experiments and observations of flight behaviour. Onion-reared, post-diapause, virgin females from a laboratory colony dispersed upwind when released in the centre of 25, 50 and 100 m radius circles of eight 50 μl UDPDS baits. Percentage recapture and dispersal directedness did not decrease as a function of increasing distance to baits. In all cases the mean flight direction of recaptured flies closely correlated with mean wind direction. However, modes of the circular distributions of recaptured flies were located further crosswind when odour-baits were more distant. When distance was held constant (25 m) and DPDS concentration serially reduced (500–0.05 μ/bait), flies dispersed randomly in the absence of DPDS, crosswind in response to 0.05 μl baits and upwind in response to all other baits. Percentage recaptures on DPDS-baited traps of all concentrations were significantly greater than unbaited traps. Results from markrecapture studies were corroborated by observations of flight behaviour downwind. Flies located 100 m downwind from 50 μl DPDS baits flew upwind on take off while take-off flights in the absence of DPDS were random. Our data indicate that Allium volatiles like DPDS are involved not only in the acceptance phase of host-selection, but also in the first and probably most important stage when onion flies are initiating search long distances downwind. We conclude that D. antiqua orients to host-plants using olfactory cues from distances that should be classified as long-range ( sensu Kennedy , 1977     

Modification of female onion fly,Delia antiqua (Meigen), reproductive behavior by male paragonial gland extracts (Diptera: Anthomyiidae)

Egg depositional rates of onion flies, Delia antiqua(Meigen), injected thoracically with extracts of male paragonial glands were identical (14.5 eggs/female/ day) to those of normally mated females. Moreover, when continuously exposed to males, extract-injected females refused to mate and produced unfertilized eggs for the duration of the > 15- day experiment. For this normally monocoitic dipteran, <1 male equiv of paragonial secretion completely reproduced the ovipositional responses characteristic of normal mating, and this effect required no involvement of the genitalia or genital chamber. We suggest that the receptor for the active chemical (s) (sex peptide?) would be an excellent target for biorational insect control by sterilization. Moreover, these primer sex pheromones might play an important role in insect reproductive isolation and evolution.     

Characteristics of summer diapause in the onion maggot,Delia antiqua (Diptera: Anthomyiidae)

Characteristics of summer diapause in the onion maggot, Delia antiqua, were clarified by laboratory experiments. Temperature was the primary factor for the induction of summer diapause in this species. The critical temperature for diapause induction was approximately 24 degrees C, regardless of the photoperiod. At 23 degrees C, the development of the diapausing pupae was arrested the day after pupariation, when about 7% of the total pupal development had occurred in terms of total effective temperature (degree-days). The most sensitive period for temperature with regard to diapause induction was estimated to be between pupariation and "pupation" (i.e., evagination of the head in cyclorrhaphous flies). Completion of diapause occurred at a wide range of temperatures (4-25 degrees C): The optimal temperature was approximately 16 degrees C, at which temperature only five days were required for diapause completion. The characteristics of summer diapause in D. antiqua are discussed in comparison with those of summer dormancy in a congener D. radicum and those of winter diapause in D. antiqua.     

Sex determination of the onion fly,Hylemya antiqua (Meigen)

X and Y chromosomes of Hylemya antiqua occur in two forms each. X_L and X_S, and Y₁ and Y₂. The larger X_L has an intercalary proximal segment which is absent in the more common smaller X_S. The acrocentric Y chromosome (Y₁), does not differ morphologically from X_S. A smaller metacentric Y₂ is apparently not homologous with Y₁. Two types of males, XY₁ and XXY₂, coexist in at least one Dutch population. XY₂ has been observed in one individual only. In larval ganglion cells an association has been observed between chromosome Y₂ and a probably non-homologous, intercalary segment of autosome 4. A numerical somatic variation of Y₂ can lead to gynandromorphs and sex ratios significantly different from 1∶1. XX cells can differentiate into functional spermatozoa in XX/XXY₂ mosaic testes. This indicates the presence of a diffusable male determining substance, which can reverse the “genotypic” sex of a cell. The occurrence of some spermatozoa-containing “cysts” in ovaries of two gynanders suggests a more or less autonomous (independent of the gonadal environment) differentiation of XXY₂ germ cells. XXXY₂ males and XXX females do not show a serious reduction in fertility. Even XXXXY₂ males do not exhibit any sign of intersexuality and spermatogenesis seems unaffected. All 62 scored M II cells of X-tetrasomic males contained 2 Xs.     

Comparison of the circadian eclosion rhythm between non-diapause and diapause pupae in the onion fly,Delia antiqua

The influence of pupal diapause on adult eclosion rhythm of Delia antiqua was investigated. When non-diapause and diapause pupae were exposed to various photoperiods at 15, 20 and 25 °C, both of them emerged as adults close to the light-on time, but the phase of eclosion varied with photoperiod and temperature. Moreover, there was a significant difference in the eclosion time between non-diapause and diapause pupae; the eclosion peak of diapause pupae was earlier than that of non-diapause pupae. When non-diapause and diapause pupae were transferred to constant darkness (DD) after having experienced LD 12:12 at 15, 20 and 25 °C, both showed circadian rhythmicity in eclosion. Although the free-running period (τ) decreased slightly as temperature increased in both non-diapause and diapause pupae, the latter tended to show shorter τ than the former. This observation suggests that the observed difference in eclosion time in LD cycles between non-diapause and diapause pupae is due to differences in τ.     

Laboratory transmission and in vivo incubation of Entomophthora muscae (Entomophthorales: Entomophthoracae) in the onion fly,Delia antiqua (Diptera: Anthomyiidae)

A high-moisture infection chamber was used for the in vivo transmission of Entomophthora muscae within laboratory populations of the onion fly, Delia antiqua. This cadaver-to-fly transmission procedure provided an average experimental infection rate well above 95%. Laboratory infection and temperature-dependent incubation rates of E. muscae were further examined in adult populations of D. antiqua. The time from initial exposure until host death and pathogen sporulation was accurately predicted using a second-order function of the incubation temperature. A developmental base temperature of approximately 5°C was estimated, with 105 degree-days being the average number of heat units required between host infection and death. E. muscae transmission between D. antiqua and D. platura, two insect pests typically associated with Michigan onion production, was verified under laboratory conditions.     

Reduction of cabbage root fly (Delia radicum) damage by protective discs

Foam-rubber, carpet-underlay discs placed in position around the base of the stem directly after transplanting were as effective as certain recommended insecticides in protecting brassica plants from damage by cabbage root fly (Delia radicum). The three factors that contributed to the overall effectiveness of the discs were that only half as many eggs were laid around plants protected with discs as around unprotected plants, that predatory ground beetles preferred to aggregate in the humid microhabitat beneath the discs and consequently ate proportionally more fly eggs/larvae and that the discs acted as a mulch, conserving water around the roots of the plants, and thereby permitting them to tolerate greater amounts of damage. Application of the repellent benzyl benzoate to the discs improved effectiveness but 12 other insect repellents and two sticky compounds gave no improvement and most were phytotoxic. Root drenches of the insecticide chlorfenvinphos were repellent, reducing oviposition by approximately 25%. The costs of protecting brassica transplants with either discs or insecticide were similar and discs thus appear to be a reasonable method of cabbage root fly control for small-scale use.     

Comparison of the circadian eclosion rhythm between non-diapause and diapause pupae in the onion fly, Delia antiqua: the change of rhythmicity

When pupae of Delia antiqua were transferred to constant darkness (DD) from light-dark (LD) cycles or constant light (LL), the sensitivity to light of the circadian clock controlling eclosion increased with age. The daily rhythm of eclosion appeared in both non-diapause and diapause pupae only when this transfer was made during late pharate adult development. When transferred from LL to DD in the early pupal stage, the adult eclosion was weakly rhythmic in non-diapause pupae but arrhythmic in diapause pupae. However, the sensitivity of the circadian clock to temperature cycles or steps was higher in diapause pupae than in non-diapause pupae; in the transfer to a constant 20 degrees C from a thermoperiod of 25 degrees C (12 h)/20 degrees C (12 h) on day 10 after pupation or from chilling (7.5 degrees C) in DD, the adult eclosion from diapause pupae was rhythmic but that from non-diapause pupae arrhythmic. In a transfer to 20 degrees C from the thermoperiod after the initiation of eclosion, rhythmicity was observed in both types of pupae. The larval stage was insensitive to the effect of LD cycle initiating the eclosion rhythm. In D. antiqua pupae in the soil under natural conditions, therefore, the thermoperiod in the late pupal stage would be the most important 'Zeitgeber' for the determination of eclosion timing.     

Effects of temperature on egg-chamber development in the onion fly, Hylemya antiqua (Diptera: Anthomyidae)

Young onion flies were placed in cages at four temperatures, 15°, 18°, 21° and 24°. Every 2 days the development of the egg chambers in the ovarioles, mating, egg production and mortality were scored. Influence of the temperature on the speed of egg-chamber development was very distinct. There was a high positive correlation between the development of the first and the second egg chamber. At 24° a significant difference in speed of egg-chamber development was found at two low levels of light intensity.

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Résumé L'influence de la température sur la maturation des follicules de la mouche de l'oignon, Hylemya antiqua Meigen, a été analysée.Des jeunes adultes ont été mis en 4 cages et soumis au régime des températures suivantes: 15°, 18°, 21° et 24°. La maturation des follicules de huit femelles a été vérifiée pour chaque température et après 2 jours, par examen des ovaires sur le vivant. L'activité d'accouplement a été également contrôlée, ainsi que la ponte et la mortalité.L'effet de la température sur la vitesse dé développement des follicules est très net. À 15° le premier follicule n'a pas encore atteint la maturité après 26 jours. Par contre aux températures plus élevées la maturation se déroule plus vite. Le développement du deuxième follicule est en corrélation positive avec celui du premier (r=0.866).À 24°, deux niveaux relativement bas de l'intensité de la lumière causent des différences dans la vitesse de développement des premiers follicules.

     

Fitness of a translocation homozygote in cage experiments with the onion fly,Hylemya antiqua (meigen)

Summary In Hylemya antiqua, a stock homozygous for an autosomal reciprocal translocation was isolated using egg-hatch reduction and karyotype analysis. Sibling translocation homozygous (TT) and heterozygous (T+) females were compared in respect to egg production and longevity. In one full-sib (5 TT and 8 T+ females) significantly higher values for both parameters for T+ than for TT females were scored, in four others (a total of 35 TT and 28 T+ females) no significant differences were found. Cage experiments were started with populations composed of equal numbers of wild type flies (++) and translocation homozygotes. The frequencies of the different karyotypes in three successive, non-overlapping generations, did not suggest substantial differences in fitness between ++ and TT flies. Possible causes of a surplus of T+ individuals found in these experiments are discussed together with the usefulness of the translocation for genetic control of H. antiqua.     

A rapid non-destructive technique for screening carrot seedlings for resistance to carrot fly damage

A technique based on fluorescence of carrot root tissues has been devised to enable large numbers of accessions to be screened for resistance to carrot fly using an epi-fluorescence microscope. The technique is non-destructive, and has been partly automated to assess at least 400 seedlings/hour. A data-capture and handling package provides prompt summarising and print-out of the results.     

Meiotic disjunction and embryonic lethality in sex-linked double-translocation heterozygous males of the onion fly,Hylemya antiqua (Meigen)

Summary The frequencies of disjunction types in double-translocation heterozygous males (2⁶2^Y6²6XY²) in Hylemya antiqua have been established in MII cells and eggs of testcrosses.Several disjunction types occurred but four predominated. A correlation was found between the frequencies of the disjunction types and the relative position of the centromeres. The frequency of numerical non-disjunction (NND) was 4%. Differences in frequency of NND between sex-linked and autosomal translocations of H. antiqua are discussed. A good correspondence between the frequencies of unbalanced karyotypes, and embryonic and larval mortality was found. The total genetic load which can be induced by the T14/T61 males is estimated to be 60–65%. Some duplication/deficiency karyotypes appeared to be viable in pupal and even adult stages. In 2⁶2⁶2^Y6²6²X males a regular coorientation between 2^Y and X was observed, in spite of non-homologous centromeres and a complicated synapsis of 2^Y. Application possibilities of the present material for genetic control of H. antiqua are discussed.     

Variation due to maternal age in the onion root maggot,Hylemya antiqua (Meigen)

A variety of characteristics were studied in populations of the onion root maggot, Hylemya antiqua, to determine the extent to which the age of the female producing a batch of eggs might affect heterogeneity in her offspring. Early-born offspring were found to be reproductively most successful. They had the longest mean expectation of life, a relatively low mortality rate into mid-life, the highest average fecundity, the highest mean rate of egg production, and they produced the highest percentage of female offspring. On the other hand, mid-born offspring were hardiest. They also had a long mean expectation of life, comparable to that for early-born offspring but, in addition, they had the lowest sustained mortality rate and the greatest ability to survive food stress. Their robustness may have been acquired at the expense of certain reproductive capabilities however, in that their average fecundity was lower than their early-born siblings', and their rate of egg production was more variable. Late-born offspring were the most mortality-prone and the least fecund, but they had the shortest mean generation time. These differences must be evaluated in terms of their effects on the rate of natural increase and on population growth. Maternal age was found to influence pupal size, although the provenance groups differed significantly from each other and, in fact, showed opposite trends within their respective cohort groups. Size itself, and the ability of a species to alter the size at which it pupates, may be characteristics which have evolved to fit a specific set of environmental conditions.     

Onion fly,Delia antiqua,oviposition and mating as influenced by insect age and dosage of male reproductive tract extract (Diptera: Anthomyiidae)

One hundred percent of virgin female onion flies,Delia antiqua, receiving 1/20 of a male equivalent of an aqueous extract of mature male reproductive tract remained unmated in the presence of males and began laying unfertilized eggs at a normally mated rate of about 20 eggs/female/day. The 50% behavioral response (BR₅₀) fell between 1/40 and 1/20 of a male equivalent. Sex peptide responses are not always all-or-none. Some females receiving extract at 1/40 male equivalent oviposited at an intermediate rate. Moreover, at low sex peptide dosages, some females were fully activated ovipositionally but were receiptive to mating. A low level of sex peptide was present in 1-day-old males. Sex peptide titer rose with age until plateauing by 6 days posteclosion. Males began mating at 3 days, when they first had ample mature sperm; 50% of 6-day-old males mated. The mean number of females inseminated per male exposed to an excess of virgin females over 24 h was 4.3±0.6 (±SE). Presence of mature eggs was not always a prerequisite for mating, although probability of insemination was correlated with egg maturation. One-day-old preovipositional females receiving 1/20 of a male equivalent of extract began ovipositing when they had mature eggs at 5–6 days old. Therefore, sex peptide may act early and permanently or have a long half-life and affect behaviors once females reach sexual maturity. Male flies provide females with an excess of sex peptide in many cases.D. antiqua males transferred ca. 5–10 times more sex peptide than necessary to activate females fully. We suggest this excess is related to the speed of female response. It is yet unclear whether sex peptide potency or titer in Diptera has become exaggerated by intra- or intersexual selection.     

The relationship of age and ovarian development to mating of Delia antiqua (Diptera: Anthomyiidae)

Abstract. The relationship between age and sexual receptivity for male and female onion flies, Delia antiqua (Meigen) (Diptera: Anthomyiidae), and factors affecting ovarian development were examined under various conditions. Confinement in small arenas had a significant negative effect on the rate of oogenesis over the first 10 days of adult life and, in some cases, on the percentage of females inseminated. The rate of oogenesis was not affected by male population density, but high density of females in large arenas appeared to have a priming effect. Few males in single-pair mating bioassays conducted over 24 h were sexually mature at 3–4 days post-eclosion, but > 50% mated when aged 6–7 days. Although females first mated at 3–4 days post-eclosion when confined for 24 h with sexually mature males, most females mated at 6–7 days of age when oocytes in the terminal ovariole position comprised 50% of total egg volume (stage 7 or greater on a 10-stage scale). No females aged 3 days were mated in no-choice and two-choice bioassays with sexually mature males over 24 h. Previtellogenic females (stage 3) were not inseminated, and ovarian development was only correlated weakly ( r = 0.48) with mating. Frequency of mating in mixed-sex groups of twenty flies was comparable with that in single pairs. However, more females were inseminated at 3–4 days, probably as a result of multiple matings by a few precocious males. These results do not support the hypothesis that females mate only when ovarioles are mature.     

Field and glasshouse studies on components of resistance to root fly attack in swedes

Field trials in two years indicated that egg-laying antixenosis was the major component of resistance in swede cvs Angus and Melfort against root flies (Delia floralis and D. radicum). Between four and eight times as many D. floralis eggs were laid on the susceptible cv. Doon Major as on the resistant cv. Angus. The degree of antixenosis effective against D. radicum was more variable in 1985, due to low numbers of adult flies, but in 1986, when adult fly numbers were higher, D. radicum laid 34 times as many eggs on susceptible cv. Sator Øtofte as on Angus. Root antibiosis against larval feeding is a second but less important component of resistance against D. floralis. In egg inoculation tests, 1.3-2.0 times more D. floralis pupae developed on Doon Major than on Angus or Melfort. Larval feeding on resistant cultivars was restricted to surface root tissue only, compared with deeper tunnelling on susceptible cultivars. Tolerance to root damage may also occur under certain conditions. Although increased dry matter content was significantly correlated with root antibiosis, its effect on larval feeding was apparently not due to increased tissue hardness. It seems likely that chemical differences in the outer root tissues influence larval feeding and development.