Ivan Ciglar

Monitoring the appearance and possibility for prevention of the apple sawfly in Croatia

The apple sawfly Hoplocampa testudinea Klug has recently become a widespread pest in Croatian apple orchards. It causes severe damage in the blooming period due to the fact that infested fruit fall off.This article shows results collected over three years of field research on trap catches of sawflies, the period of laying eggs, the appearance of larvae and detection of damage. In the climate of northwestern Croatia, adult sawfly appear in April during the blooming period of the early apple variety of Idared.By monitoring temperatures from January 1, adults were detected when the thermal constant reached 210 day-degrees. Our observations showed that the larvae emerged when the sum of thermal constants reached ca. 110 day-degrees.The investigation of effective control strategies with insecticides showed high efficacy of thiametoxam (Actara), imidacloprid (Confidor), thiacloprid (Calypso) and betacyfluthrin + oxydemeton-methyl (Enduro) and lower efficacy of phosalone (Zolone), chlorpyrifos-methyl (Reldan), and lambda cyhalothrin (Karate).

Side effect of some fungicides on the mite population in an apple orchard in Croatia.

The research into the side effect of fungicides used in the control of the most serious disease in apples (Venturia inaequalis) i. e. the research into the influence of fungicides on the population of phytophagous mites, was carried out at Nedeliŝće (North-West Croatia) during 1997 and 1998. The study is related to the population of the mites most present in apple orchards, such as red spider mite (Pananychus ulmi) and other mites (Aculus schlechtendali andTetranychus urticae). Fungicides which are known to be effective against scab, i. e.Venturia inaequalis, and used in fruit production in Croatia, were tested in order to investigate their secondary properties which have not yet been studied. The following fungicides were used: cyprodinil, dodine, dichlofluanid + bitertanol (as tank mix), and kresoxim-methyl. The tests were repeated three times; the application time was determined by monitoring the conditions for infection. The treatments were done curatively, i. e. up to 96 h after the onset of infection conditions. The mite population was estimated by the pressing method, which yielded the average number of mites per leaf. All the results were statistically processed by variance analysis and by Duncan’s Multiple Range Test, and are presented graphically and in tables. The paper also presents graphically the climatic conditions, scab infections and application time. The research over two years have shown a pronounced suppressive effect of dichlofluanid + bitertanol on populations of phytophagous mites, while the other fungicides used in the research had a neutral effect on the mite papulation.