The Effects of Spirodiclofen on Reproduction of Two-spotted Spider Mite (Tetranychus urticae Koch)
Efekti spirodiklofena na reprodukciju običnog paučinara (Tetranychus urticae Koch)
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Author
Marcic, Dejan
Ogurlic, Irena
Keywords
Tetranychus urticaeSpirodiclofen
Reproduction
spirodiklofen
reprodukcija
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Show full item recordAbstract
Laboratory bioassay was conducted to evaluate the effects of spirodiclofen on the survival,
fecundity and fertility of two-spotted spider mite (Tetranychus urticae Koch) females
treated as 3-days old adults with a series of acaricide concentrations starting with the concentration
discriminative for eggs and immatures. After a 24 h exposure, the proportion of
females that survived treatment was 0.86 (6 mg/L), 0.71 (12 mg/L), 0.54 (24 mg/L), 0.50 (48
mg/L) and 0.44 (96 mg/L). Over the following five days, the survival rates of females treated
with 6 mg/L and 12 mg/L were considerably below the survival rate of untreated females,
but they still remained above the survival rates of females treated with other concentrations.
Total fecundity/fertility significantly decreased as concentrations of spirodiclofen increased.
The highest concentration, 96 mg/L, completely terminated egg-laying, while only two and
three females of those surviving the respective concentrations of 48 mg/L and 24 mg/L
laid viable eggs. On the other hand, 60% and 84% of female survivors of treatments with
the respective concentrations of 12 mg/L and 6 mg/L laid viable eggs; total fertility of these
females was reduced by 58.6 and 45.2%, respectively. On the first day after treatment, the
females treated with 24 mg/L, 12 mg/L and 6 mg/L laid eggs; viable eggs were laid only by
the latter group and the percentage of hatching was barely 3.1% (89% in control). On the
second day, the females treated with 48 mg/L also began to lay eggs, but viable eggs were
laid only by females treated with 12 mg/L and 6 mg/L (the respective percentages of hatching
were 28.5% and 65.3%; 93.9% in control). From the third day onward, viable eggs were
laid also by females treated with 48 mg/L, and the difference in hatchability was considerably
smaller or disappeared completely. Compared to control, gross fecundity was significantly
reduced by all concentrations on the first day only, and gross fertility on the first
two days of trial. No significant difference in gross fecundity/fertility was observed further
on until the end of the trial between untreated females and those treated with 6 mg/L and
12 mg/L. However, all concentrations significantly reduced net fecundity/fertility throughout
the trial, which indicates a considerable impact of the decreased female survival rate on
overall reduction in net fertility, especially from the third day onward. Sublethal effects of
spirodiclofen and its impact on T. urticae management are discussed. Efekti spirodiklofena na preživljavanje, fekunditet i fertilitet ženki običnog paučinara
(Tetranychus urticae Koch), preživelih tretiranje u uzrastu adulta starih tri dana serijom koncentracija
počevši od koncentracije diskriminativne za jaja i nezrele stadijume, ispitivani su
u laboratorijskom ogledu. Nakon ekspozicije od 24 časa, proporcija ženki koje su preživele
tretman bila je 0.86 (6 mg/L), 0.71 (12 mg/L), 0.54 (24 mg/L), 0.50 (48 mg/L) i 0.44 (96 mg/L).
U narednih pet dana, stope preživljavanja ženki tretiranih koncentracijom 6 mg/L, odnosno
12 mg/L, bile su znatno ispod stopa preživljavanja netretiranih ženki, ali su se zadržale
iznad stopa preživljavanja ženki tretiranih ostalim koncentracijama. Ukupni fekunditet/fertilitet
opadao je znaèajno, kako se koncentracija akaricida povećavala. Najviša koncentracija,
96 mg/L, potpuno je zaustavila polaganje jaja, dok su samo dve, odnosno tri ženke, među
onima koje su preživele tretiranje koncentracijom 48 mg/L, odnosno 24 mg/L, polagale
vitalna jaja. S druge strane, 60%, odnosno 84% ženki preživelih tretiranje koncentracijom
12 mg/L, odnosno 6 mg/L polagalo je vitalna jaja; ukupan fertilitet tih ženki bio je redukovan
za 58.6%, odnosno 45.2%. Prvog dana nakon tretmana, ženke tretirane koncentracijom
24 mg/L, 12 mg/L, odnosno 6 mg/L, polagale su jaja; vitalna jaja polagale su samo ove poslednje,
a procenat piljenja bio je svega 3.1% (89% u kontroli). Drugog dana, i ženke tretirane
koncentracijom 48 mg/L počele su da polažu jaja, ali su vitalna jaja polagale samo ženke
tretirane koncentracijom 12 mg/L, odnosno 6 mg/L (odgovarajući procenti piljenja iznosili
su 28.5%, odnosno 65.3%; 93.9% u kontroli). Od trećeg dana pa nadalje, i ženke tretirane
koncentracijom 48 mg/L polagale su vitalna jaja, a razlika u procentima piljenja između tretiranih
i netretiranih ženki bila je znatno manja ili je potpuno nestala. U poređenju sa kontrolom,
sve koncentracije su značajno redukovale bruto fekunditet samo prvog, a bruto fertilitet
samo u prva dva dana nakon tretmana. Do kraja ogleda nije registrovana statistički značajna
razlika u bruto fekunditetu/fertilitetu između netretiranih i ženki tretiranih koncentracijom
6 mg/L, odnosno 12 mg/L. Međutim, sve koncentracije su ostvarile značajnu redukciju
neto fekunditeta/fertiliteta u svih pet dana trajanja ogleda, što ukazuje na znatan doprinos
sniženih stopa preživljavanja ukupnoj redukciji neto fertiliteta, posebno počev od trećeg
dana pa do kraja ogleda. Subletalni efekti spirodiklofena razmatrani su u kontekstu suzbijanja
populacija T. urticae.