Parasit, hung. 19. 1986

The effect of cyromazine (IGR) on the third-instar larvae of osiris Wiedemann, 1830 (Diptera: )

Dr. Róbert FARKAS Department of General Zoology and Parasitology, University of Veterinary Science, Budapest, Hungary

"The effect of cyromazine (IGR) on the third-instar larvae of Musca osiris Wie- demann, 1830 (Diptera: Muscidae)" - Farkas, R. - Parasit. hung., 19: 77-80.,1986.

ABSTRACT. A trial was carried out to test the efficacy of cyromazine (Nepo­ rex**) against third-instar larvae of laboratory strain of Musca osiris Wiede­ mann, 1830. Its effect was studied at 0.1, 0.5, 1 and 2 ppm concentrations in rearing medium. It can be established that cyromazine is effective against pre­ viously not tested M usca osiris. Parallel to a decrease of drug concentration the effect became less pronounced. The larvae were able to develop and to pup­ ate at each concentration but a significant part of the resulting pupae were de­ formed. Most of them were rod-like, C-shaped, elongated or smaller than the normal ones. At higher concentrations (1 and 2 ppm) the development of adults from pupae was completely prevented. At lower concentrations (0. 5 and 0. 1 ppm) the extent of abnormality varied from no eclosion to complete eclosion. At a level of 0. 5 ppm pupal mortality was 64 per cent. There were two incomplete adult eclosions. At the lowest concentration pupal mortality was 48 per cent. In 16 cases the imagos died at different stages of hatching. R KEYWORDS: cyromazine, Neporex , Musca osiris (Diptera: Muscidae), mor- phogenetic effect.

Cyromazine (N-cyclopropyl- 1, 3, 5 triazine-2, 4, 6-triamine) is one of the hormonally active materials which cause physiological or/and morphological changes during the growth and de­ velopment of several species. This new group of the third generation pesticides is called growth regulators (IGRs). These chemicals especially offer a good potential for controlling manure-breeding (CHAMBERLAIN, 19 75). In recent years these drugs have been studied intensively in the view that most of them are not toxic for the environment and are very effective in rather low concentrations (HARRIS, FRAZER and YOUNGER, 1973; WRIGHT, 1974; MILLER and UEBEL, 1974; WRIGHT, CAMPBELL and OEHLER, 1974).

Cyromazine (CGA-72662) has been developed as the most effective compound of the triazines by CIBA-GEIGY Limited. Its mechanism of toxicity is not understood clearly. Studies on the effect of CGA-72 662 on in vitro chitin synthesis showed that cyromazine acts as a chitin syn­ thesis inhibitor, though this effect is less pronounced active than that of diflubenzuron (MIL­ LER et al. , 1981). On the other hand, it was demonstrated in histological studies on the ef­ fect of this chemical that there was no interference with normal cuticle deposition (TURN- BULL, PYLIOTIS and HOWELLS, 1980; AWAD andMULLA, 1984). We know that this new IGR interfered with the normal development of larvae. Ovicidal or chemosterilant effects could not be observed (HALL and FOEHSE, 1980).

R R Cyromazine and its products (Larvadex , Neporex ) have been evaluated against several fly species in laboratory and field trials. It was shown that this chemical is very effective against

7 7 Musca dornestica L. (HALL and FOEHSE, 1980; WILLIAMS and BERRY, 1980; MILLER et al., 1981; MULLA and AXELROD, 1983; KÜNAST and BOTHE, 1984), Musca auturnnalis De Geer (HALL and FOEHSE, 1980; MILLER et al., 1981), Stomoxys calcitrans L. (KÜNAST and BOTHE, 1984) and Fannia femoralis Stein (MULLA and AXELROD, 1983).

Musca osiris is a dipterous pest of cattle and sheep in Hungary (PAPP, 1976, 1985). The lab­ oratory stocks of this secretophagous fly species have been established (POLGÁR and PAPP, 1985) which offers anew possibility tötest the insecticides (FARKAS and SOUNTHONE, 1985).

In the laboratory experiment we studied the effect of various concentrations of cyromazine on third-instar larvae of this species.

MATERIALS AND METHODS

0.1, 0.5, 1 and 2 ppm concentrations of cyromazine were used. The formulation (Neporex WSG 2) was diluted in water to make the necessary solutions. When mixing the aqueous solu­ tion of the test chemical to freshly-collected bovine faeces, the active substance concentra­ tion was adjusted to 100 g.

In control groups only water was used.

Treated and untreated larval media were seeded with 25 early (aged 67-68 hrs) third-instar larvae of Musca osiris. They were collected from our laboratory breeding.

There were four replicates at each concentration.

Table 1 The effect of cyromazine on third-instar larvae of Musca osiris

Pupal mortality Imagos died Conen of AI Pupae in different Normal ppm gained No. stages imagos No.

2. 0 91 91 100 1. 0 90 90 100 - - 0. 5 89 76 64 2 11 0. 1 97 56 48 16 25

1) 100 larvae/concn of AI 2) Corrected for control mortality by Abbott's formula

The faecal samples with larvae were placed in plastic jars with sawdust. The jars were clos­ ed with gauze. The experiment was conducted in a room of 28+2°C temperature and 60+10 per cent relative humidity.

The samples were checked every day. The number of the emerged imagos was recorded. Af­ ter a period of two weeks abnormal pupae, incompletely eclosed adults and abnormal adults were observed, counted and examined under stereomicroscope.

Evaluation was performed by using ABBOTT's formula and calculating the mortality percent­ age of pupae, corrected for the control mortality percentage.

RESULTS AND DISCUSSION

The obtained results are shown in Table 1. The majority of larvae developed further and were able to pupate at each concentration but a significant part of the resulting pupae were aber- rant. They were rod-like, C-shaped, elongated or smaller than the normal ones. Similar pupae could be seen when the larvae of Musca dornestica were exposed to sublethal dosages of Larvadex. These m orphogenetic effects were not observed in larvae and pupae of Fanni a femoralis, because larvae of this species do not contract before normal pupation (HALL and FOEHSE, 1980; MULLA and AXELROD, 1983). The aberrant pupal forms, which are often called "larva-pupa intermediates", are associated with ICRs (HALL et al. , 1979).

At higher concentrations (1 and 2 ppm) the development of adults from pupae was completely prevented.

At lower concentrations (0.5 and 0.1 ppm) some eclosions could be observed. At the level of 0.5 ppm there were 13 eclosions, 2 of these were incomplete and the adults died during the eclosion.

At the lowest concentration 97 of the 100 treated larvae were able to pupate, but 56 of them did not produce adults. In 16 cases the imagos died at different stages of eclosion. In most cases only the head or the head and the thorax emerged from the pupal shell. Similar effects produced by ICRs have been reported in Musca dornestica (AWAD and MULLA, 1984) and Sto- moxys calcitrans (WRIGHT and SPATES, 1971). The imagos wholly eclosed from two pupae but they were still attached to the puparium by their legs or wings.

It can be established that cyromazine is effective against previously not tested Musca osiris. Parallel to an increase of drug concentration the effect became more pronounced. Similar results have been reported in Musca dornestica (AWAD and MULLA, 1984). These authors found that at higher concentrations (l and 1. 5 ppm) eclosion was incomplete and at the level of 0. 5 ppm only 54 per cent of treated Musca dornestica larvae developed into deformed pu- paria or adults.

Comparing our data to those in the literature it seems likely that Musca osiris is more sen­ sitive to cyromazine than Musca dornestica.

FARKAS, R.: A cyromazine (IGR) hatása a Musca osiris Wiedemann, 1830 (Diptera: Muscidae) harmadik stádiumú lárváira

Laboratóriumi vizsgálatai során a szerző arra kereste a választ, hogy a rovarnövekedés-sza­ bályozók csoportjába tartozó ciromazin 0.1, 0.5, 1 és 2 ppm koncentrációi befolyásolják-e a Musca osiris korai 3. stádiumú lárváinak továbbfejlődését.

A vizsgálatok eredményei azt mutatják, hogy mindegyik koncentráció esetén a lárvák képesek voltak továbbfejlődni és bebábozódni, de a kialakult bábok többsége deformált volt.

A két legmagasabb koncentráció esetén 100 %-os bábmortalitás mutatkozott. A ciromazin adagjának csökkenésével nőtt az életképes, illetve a kelés különböző stádiumában elpusztult imágók száma.

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Received: 18 November, 1986 Dr. FARKAS, R. Department of General Zoology and Parasitology, University of Veterinary Science Landler Jenő utca 2. H-1078 Budapest HUNGARY