Erioischia Brassicae Research Articles

Carabidae as potential biological agents for controlling infestations of the cabbage root fly

Laboratory tests with carabid ground beetles found in Wellesbourne fields indicated that intermediate-sized beetles such asBembidion tetracolum, Amara familiar is andAgonwn dorsale were more effective predators of cabbage root fly (Erioischia brassicae) eggs than small beetles, e.g.Bembidion lampros andTrechus quadristriatus, or large beetles, e.g.Harpalus rufipes andPterostichus melanarius. Further tests indicated thatA. dorsale would be an ideal predator, as it can survive up to one month without food, is not killed byP. melanarius, aggregates naturally, and eats large numbers of cabbage root fly eggs/larva.A. dorsale is also relatively easy to retain near the stems of plants by simple barriers and is not cannibalistic. Unfortunately, sufficientA. dorsale were not available for greenhouse trials. Greenhouse trials withB. tetracolum indicated that two beetles per plant were sufficient to control the high levels of cabbage root fly infestation normally encountered in the field at Wellesbourne.

The effect of plant density on populations of the cabbage root fly on four cruciferous crops

SUMMARYTo study the effects of plant density on populations of the cabbage root fly (Erioischia brassicae), cabbage, cauliflower, Brussels sprout and swede were each planted in plots with twenty‐four concentric circles of plants at spacings ranging from 10 to 90 cm between the individual plants. Plants treated with a root drench of chlorfenvinphos and untreated plants were each sampled at ten plant densities which ranged from 1–5 to 68‐3 plants/m2.In the absence of insecticide, the numbers of overwintering cabbage root fly pupae produced ranged from c. four per m2 at the lowest plant density to 200 per m2 at the highest. The number of pupae per m2 was proportional to plant density to the powers 0–98,0‐77,0–69 and o‐6i for the swede, cauliflower, cabbage and Brussels sprout crops, respectively. The magnitude of each cabbage root fly population was determined mainly by plant density but also by the cultivar used as host plant.The results suggested that, in a given locality, when changing from low to high plant density crops during a growing season it should be unnecessary to apply insecticide to control cabbage root fly; conversely, a change from high to low plant densities would necessitate an extremely efficient application of insecticide.

The Distribution of Cabbage Root Fly Eggs in Large Fields of Swedes

SUMMARYObservations made in 1968, 1969 and 1972 on the distribution of eggs of cabbage root fly (Erioischia brassicae (Bouché)) in large fields of swedes in north Northumberland showed that oviposition was at random, as many eggs being laid in the middle of the field as near the hedges.

Effect of temperature and photoperiod on diapause induction inErioischia brassicae(Bch.) (Diptera, anthomyiidae) under controlled conditions

AbstractExperiments were carried out to determine the optimum temperatures and photoperiods for inducing diapause in the cabbage root fly,Erioischia brassicae(Bch.). The induction of diapause occurred at certain receptive stages between the first and third instars of larval development. When developing larvae were subjected to 20±1°C and a 16-h photoperiod for 7–14 days followed by 13±0·5°C and a 10-h photoperiod for 28–35 days, diapause was induced in 84–97% of the pupae; 88–99% of pupae entered diapause when developing larvae were subjected to 13±0·5°C and a 10-h photoperiod for 28–42 days followed by 20±1°C and a 16-h photoperiod for 11–18 days. Similar results were obtained when developing larvae were subjected to 13±0·5°C (day)/7±0·5°C (night) and a 6-h photoperiod. The fecundity of flies from the diapausing pupae was not adversely affected. Application of these results should enable cabbage root fly to be cultured economically for intermittent use.

The effect of plant density on populations of the cabbage root fly (Erioischia brassicae (Bch.)) and the cabbage stem weevil (Ceutorhynchus quadridens (Panz.)) on cauliflowers

AbstractTo study the effects of plant density on populations of the cabbage root fly (Erioischia brassicae (Bch.) ) and the cabbage stem weevil (Ceutorhynchus quadridens (Panz.)), cauliflowers were planted in 24 concentric circles to achieve spacings of 10–90 cm at 22 plant densities (1·5–83/m2). Some plants were treated with a root drench of chlorfenvinphos. Each week female cabbage root flies laid approximately three times as many eggs per individual plant at the lowest than at the highest plant densities tested. This was equivalent to approximately 350 and 5000 eggs/m2, respectively. The numbers of cabbage root fly pupae produced ranged from 11/m2 at the lowest to 210/m2 at the highest plant density. In the absence of an insecticide, increasing the plant density considerably increased the absolute population of the pest without affecting cauliflower yield. Approximately seven times as many flies were produced per unit area of untreated mini-cauliflowers as from an equivalent area of plants growing at a conventional density. When chlorfenvinphos was not applied, damage by the cabbage stem weevil occurred in 30% and 70% of the plants grown at the lowest and highest densities, respectively.

Dispersal of the cabbage root fly

SummaryThe dispersal rates of wild and culture cabbage root flies Erioischia brassicae were determined in release‐recapture experiments at Wellesbourne in 1971–3. The experiments were concerned mainly with the first 7 days of adult life. The flies, released from nine locations in the area, were recaptured in yellow water‐traps.Dispersal was affected by wind, rain and the terrain the flies were crossing. The flies least often recaptured were those released into the host crop when 6–12 days old. The results indicated the following pattern of behaviour.Flies moved little during the first 2 days of adult life but by the third day both sexes had dispersed to c. 100 m from the release point. Flies are known to mate about the fourth day and after this the males continued to disperse at c. 100 m per day for the three subsequent days. ‘Wild’ females from field‐collected pupae carried out a ‘migratory’ flight, however, and dispersed at c. 1000 m per day during the fifth and sixth days, the days preceding the start of oviposition. Similar rates of dispersal were recorded from flies released across host crop and non‐host crop areas.Some females did not stop at the first crop they encountered. The culture females from the laboratory‐reared pupae dispersed only c. one‐third of the distance of the wild females. There was considerable intermingling of local populations. The percentage recapture of young culture and wild flies released during the pre‐oviposition period of this species was 38 ± 4 and 19 ±4 for males, and 15 + 2 and 8+1 for females, respectively.The dispersal range of the cabbage root fly is probably within a 2000–3000 m radius of the site of infestation.

Soil Placement of Insecticide Granules for the Control of Cabbage Root Fly on Transplanted Canliflowers

SUMMARYSeven organophosphorus insecticides were evaluated as granular formulations for the control of cabbage root fly, Erioischia brassicae (Bouche), in west Yorkshire, on transplanted cauliflowers from 1966 to 1970 inclusive. The insecticides were chlorfenvinphos, diazinon, dimethoate, fonofos, mecarbam, pirimiphos‐ethyl and thionazin. Various methods of application were compared and the work evolved into a comparison of the effectiveness of continuous bands of granules applied below the surface immediately before plant insertion with that of surface bands applied immediately after plant insertion. The methods employed and the equipment involved are described.Chlorfenvinphos was the most effective chemical for protecting the roots from cabbage root fly attack. Diazinon, dimethoate, fonofos, mecarbam and thionazin all reduced damage in the early part of the season (except when applied by the bow‐wave method). The subsurface method of placement of all these chemicals except dimethoate was consistently more effective in reducing root damage and promoting higher yields than surface placement. Pirimiphos‐ethyl was not effective in protecting the roots by either method.

Sugars available from flowers visited by the adult cabbage root fly, Erioischia brassicae (Bch.) (Diptera, Anthomyiidae)

AbstractAnalysis by gas-liquid chromatography showed that flowers open at the time of the first generation of cabbage root flies, Erioischia brassicae (Bch.), contained nectars composed almost entirely of sucrose and fructose whereas those open during the second generation secreted fructose and glucose. There were qualitative as well as quantitative differences in the sugar composition of all the nectars analysed. In both generations, the most highly nutritive sources of nectars, 94% and 86% sugar solutions, were available from the umbellifers Anthriscus sylvestris and Heracleum sphondylium, respectively. Fructose and glucose were also the main sugars on pollen and anthers at the time of the second generation but, in addition, pollen samples contained large quantities of the sugar alcohol inositol. The surfaces of the pollen of the grasses Dactylis glomerata, Holcus lanatus and Arrhenatherum elatius all contained sufficient nutritive carbohydrates for maturation of the first batch of cabbage root fly eggs. One or more of the chemicals found only in water extracts of Arrhenatherum pollen was probably toxic to the flies. To obtain sufficient carbohydrates to mature the first batch of eggs, flies had to probe at least 1–2 mg of grass pollen each day, equivalent to the pollen produced daily by two flowering heads of Dactylis.

Feeding and associated behaviour of the adult cabbage root fly Erioischia brassicae (Bch.) (Dipt, Anthomyiidae) under laboratory conditions

AbstractAdults of the cabbage root fly (Erioischia brassicae (Bch.)) reared in culture were inactive on the day of emergence but they fed on carbohydrate (sucrose) and protein (Yeastrel) on day 2. Without food, the egg follicles increased to approximately one-third of their maximum size and were then resorbed. When food was available, females ingested sucrose on days 2 and 3 to mature the first batch of eggs, without any stimulus from mating. Without either a mate or a suitable oviposition site, females retained most of their eggs. Females obtained sufficient food for egg maturation by day 4, when their egg follicles were 400 μm, approximately half the size of the mature eggs. Only females mating on day 4 laid eggs at the expected time 6±0·3 days after emergence. With a suitable oviposition site, these females laid 299±48 eggs, approximately twice as many as any other females, and ten times as many viable eggs. When males were not allowed to mate, peak ingestion was delayed from days 8–12 to days 14–18. Mated females provided with an oviposition site laid most eggs on days 5 and 6 and fed again on day 7. This second peak of feeding was delayed until day 9 when mated females were denied, or unmated females were given, an oviposition site. Similar volumes of sucrose were imbibed by females whether they laid or retained their eggs. Females denied both a mate and a suitable oviposition site laid less than 1% of the expected eggs.

Factors Affecting the Aggregation of the Adult Cabbage Root Fly (Erioischia brassicae (Bouche)) at Hedges

Members of various groups of insects, including weak fliers such as Cecidomyiidae and stronger flying Staphylinidae, accumulate on the leeward side of artificial and natural windbreaks (e.g. Lewis 1965, 1969, 1970; Lewis & Stephenson 1966). Many factors affect this accumulation, including the height and permeability of windbreaks and the wind speed, but it has been suggested (Lewis & Dibley 1970) that insects accumulate because they are carried on the wind and are caught in the turbulent circulating air mass to the leeward of the windbreaks. Hawkes (1 972a) showed that adult Erioischia brassicae accumulated at hedges and this behaviour was associated with feeding from hedgerow flowers. There was a diurnal population movement of flies between hedges and a brassica crop and this appeared to be incompatible with accumulation at windbreaks as a result of the insects being carried on the wind. This paper describes experiments to observe whether wind causes aggregation of E. brassicae at natural hedges and at a lath barrier representing an artificial windbreak.

Chemosterilization of the cabbage root fly under field conditions.

SUMMARYRemoving hedgerow feeding sites from within 40, 80 or 160 m of cauliflower plots, failed to reduce populations of the cabbage root fly (Erioischia brassicae (Bouché)). Oviposition on the plots was unchanged but the efficiency of yellow water‐traps was improved. Traps along‐side cleared hedgerows caught more gravid than non‐gravid females. In cages, 94% of the eggs laid were sterile when both sterilant baits containing tepa [tris‐(i‐aziridinyl) phosphine oxide] and hedgerow flowers were present.In the field, maximum egg‐sterility rarely exceeded 30% when sterilant was present when natural sterility averaged 8%. Chemosterilization was an inadequate control since sufficient eggs and larvae survived to produce root‐damage indices of 49 % in contrast to 2 % on insecticide‐treated plants.Most eggs were sterile when chemosterilant baits were placed 0.75 m apart and bait was most effective when placed around the crop during the pre‐oviposition period and through the crop at the time of maximum oviposition. Increasing the concentration of tepa failed to increase the effectiveness of the bait but a higher proportion of the eggs laid were sterile on large than on small plots. When chemosterilant treatments were stopped, egg‐fertility gradually reverted to the natural level.Protracted immigration, an innate tendency for females to disperse, reductions in the competitiveness of sterile males, and the failure of males to re‐disperse once sterilized, appeared to be the main factors limiting the levels of sterility in root‐fly populations exposed to tepa‐baited lures in the field.

The Estimation of the Dispersal Rate of the Adult Cabbage Root Fly (Erioischia brassicae (Bouche)) in the Presence of a Brassica Crop

Dispersal has been defined as any movement away from an aggregation or population (Southwood 1966) and it can result from migration or the 'trivial' movements associated with appetitive behaviour. Migration is usually considered to be a long distance, 'straightened-out' movement which, if successful, results in the arrival of the animal at a new habitat, and the term 'trivial' is applied to short meandering movements limited to one habitat. Greater dispersal is therefore likely to occur as a result of migration than from 'trivial' movements. A behavioural difference distinguishes migrants from non-migrants (Kennedy 1961); the temporary inhibition of the responsiveness of migrants to the 'vegetative' stimuli which finally arrest them separates migratory from 'trivial' movements which are readily interrupted by responses to such stimuli. Only some species of insects show migratory behaviour (see Southwood 1962) and thus there is variation in the innate tendencies of species to disperse. The dispersal of an insecticide-resistant strain of the cabbage root fly (Erioischia brassicae (Bouche)), was studied by Mowat & Coaker (1968). Their first observations indicated that considerable dispersal had occurred and this was attributed to an abnormally dense population and the destruction of the host-crop at the site of origin of resistance. In two subsequent years, the distribution of resistant flies changed only slightly and it was concluded that E. brassicae had little innate tendency to disperse. The assessment of the dispersal rate of a gene for resistance is an indirect method of measuring the dispersal of a wild population of flies and such estimates may be influenced by interfering factors such as the densities of populations in the area under study and the relative fitness of the strains. Experiments were, therefore, undertaken to measure the dispersal of E. brassicae more directly by the release and recapture of marked flies. The results of experiments to estimate its dispersal rate in the presence of a brassica crop are described in this paper.

The Separation of Eggs of Erioischia brassicae and E. floralis in Swede Crops

SUMMARYEggs collected from around the base of cultivated cruciferous crops in north‐east Scotland were hatched on suitable media contained in petri dishes, or on plants grown in pots in an outdoor insectary. Breeding in petri dishes was more successful.It was found that Erioischia brassicae(Bouche), the cabbage root fly, and E. floralis(Fall.), the turnip root fly, occur together in swede crops, but only E. brassicae in crops of cabbage and cauliflower. Despite the eggs of both species overlapping in size and the chorion patterns being indistingtiishable, plotting mean egg sizes over short consecutive periods showed that the main egg‐laying period of E. floralis was during August and September.The measurements of eggs collected before and after 1 August, when plotted on arithmetical probability paper, indicated an appreciable difference in the average size of eggs laid in the two periods, but only at those sites where both species were found.

The diurnal periodicity and cycle of behaviour of the adult cabbage root fly (Erioischia brassicae)

SUMMARYAdult cabbage root fly (Erioischia brassicae (Bouché)) exhibited a diurnal periodicity in behaviour. Trapping tests indicated that the flies fed from hedgerow flowers in the morning, visited the crop in the early afternoon and returned to the hedges in the late afternoon. In the laboratory the flies also showed a cyclical pattern in behaviour. Feeding preceded oviposition by 3 days and this was reflected in the field by a relative increase in the movement of females away from the hedges and to the crop when they became gravid. The diurnal periodicity and the cycle in behaviour of males was similar to that of the females, indicating that some of the flies' movement was non‐appetitive.The tendency of flies to stay for most of the day at hedges resulted in progressive declines in the numbers captured with increasing distances from hedges.

Egg-Laying by Some Dipterous Pests of Cultivated Cruciferae in North-East Scotland

The species of Diptera associated with the roots of cultivated Cruciferae in Britain, particularly Erioischia brassicae (Bouch6), the cabbage root fly, have been studied mainly in England (Smith 1927; Miles 1951, 1952a, b, 1953, 1954, 1955; Wright 1952, 1960, 1964-68). Little work has been done in Scotland, although Morison (1939, 1951) describes observations on E.floralis (Fallen), the turnip root fly. An analysis of the economic damage by E. brassicae and E. floralis in Britain (Shaw 1965) showed that E. brassicae becomes less important from south to north in the British Isles, whereas the reverse is true for E. floralis.

Sterilisation of the cabbage root fly (Erioischia brassicae (Bch.)) (Dipt., Anthomyiidae) with tepa: laboratory and field cage tests

Adults of the cabbage root fly (Erioischia brassicae (Bch.)) fed on 0·1% tepa in 10% sucrose solution during the second and third days after emergence laid over 95% sterile eggs. Nearly complete sterility was also obtained from females fed on 0·l% tepa for two days between mating and oviposition. Tepa at 0·1% did not affect longevity of either sex or the competitiveness of treated males, although at higher concentrations longevity was reduced. When flies were enclosed in a large field cage and provided with food baits containing 0·1% tepa, sucrose and leucine along a hedgerow, 70% of the eggs laid were sterile.

An apparatus for dispensing mechanically the eggs of the cabbage root fly (Erioischia brassicae (Bch.) (Dipt., Muscidae))

An apparatus for dispensing the eggs of cabbage root fly (Erioischia brassicae (Bch.)) is described. It consists of an ‘Agla’ micrometer syringe, a 2-ml pipette and a 20-mlsyringe connected together by a three-way valve. The eggs are dispensed volumetrically, the standard errors being < ±10% for batches ranging from 30 to 300 eggs. This degree of variation had no measurable effects on the uniformity of pupae from cabbage root fly cultures.

A method for the continuous rearing of the cabbage root flyErioischia brassicae(Bch.) and some observations on its biology

A method for continuously rearing cabbage root fly,Erioischia brassicae(Bch.) is described.Adult flies fed on sucrose, brewers’ yeast and yeast hydrolysate laid an average of 220 eggs per female when caged together in large numbers and 376 eggs per female when caged singly. Egg viability was 86 per cent. Egg hatch was severely reduced by relative humidities of less than 90 per cent, and the embryo became more susceptible to desiccation as it matured. The larvae were reared on swede, and maximum survival was obtained when the swedes were inoculated with an optimum number of eggs calculated from the ratio of 1 egg: 1.6 g. of swede. Different ratios were obtained from turnip and winter radish indicating that survival was probably related to the nutritional value of the rearing medium as well as to its availability. An average of 68 per cent, of the eggs placed on swede produced pupae that were equivalent in size to wild pupae. The fecundity of the flies was directly related to pupal weight and to the availability of protein in their diet. Adult longevity was reduced more by mutual disturbance than by any other factor.

Dieldrin-resistant cabbage root fly in England.

SUMMARYThe existence of dieldrin resistance in Erioischia brassicae has been investigated in the main areas in England and Wales where brassicas are grown for human consumption. Dieldrin‐susceptible and dieldrin‐resistant flies were collected and bred as separate strains in the laboratory. In toxicity tests adult flies were treated with topically applied doses of insecticide in microdrops of cellosolve, and larvae were dipped in solutions of insecticide in 70% acetone and 30% water. Adults of the laboratory resistant strain showed a high level of resistance to dieldrin and aldrin and a lower level of resistance to γ‐BHC. There was no cross‐resistance with chlorfenvinphos or diazinon. Larvae of the resistant strain were shown to be resistant to dieldrin.Dieldrin resistance has been found in four areas in southern England, but not in a fifth major area, and resistant flies did not increase as rapidly in some areas as others. Sufficient migration of flies appeared to take place to produce similar percentages of resistant flies over areas of several square miles, but considerable differences were found in fly populations about 10 miles apart. It is suggested that the speed of development of insecticide resistance is affected by the proportion of brassica crops which are treated in an area, the amounts of insecticide applied to individual crops, and hence the insecticidal pressure applied to the E. brassicae population.

Root Drenches Against the Cabbage Root Fly

SUMMARYExperiments were done in Northern Ireland for two seasons using root drenches containing diazinon, mecarbam, chlorfenvinphos and bromophos against the cabbage root fly (Erioischia brassicae Bouche) on cauliflowers. All treatments were generally effective against this pest.