Original scientific paper

THE USE OF YELLOW STICKY TRAPS FOR FORECASTING THE FIRST GENERATION OF THE CABBAGE MAGGOT (Delia radicum (L.), Diptera: Anthomyiidae)

Renata Bažok orcid.org/0000-0003-1655-8140 ; Department for Agricultural Zoology, Faculty of Agriculture, Zagreb, Croatia
Mirna Ceranić-Sertić ; Croatian Agricultural Extension Institute, Office Ogulin

Abstract

Due to the increased production of white cabbage in the region of Ogulin, Republic of Croatia, the numbers and the impact of the cabbage maggot (Delia radicum (L.)) are increasing as well. In this region, cabbage production fields are limited and cabbage maggot control is often not very successful due to the lack of pest forecasts. Investigations were conducted in 2008 and 2009 to determine if there were correlations between degree-day accumulation and cumulative capture of flies on yellow sticky traps (YST), BioPlantella, and if the correlation between degree-day accumulation or cumulative capture
of flies and infestation levels of eggs and larvae of first generation cabbage maggots exists. The presence of flies on YST was determined at the time of cabbage transplanting (mid April). Every seven days the traps were removed, the number of captured flies was recorded and new traps were set up. Cabbage infestation by eggs and larvae was determined once per week by visually inspecting four groups of 100 plants. The percentage of plants with eggs, average number of eggs/plant, egg infestation intensity and percentage of plants showing symptoms of larval infestation were determined. Weather conditions, in terms of average daily temperatures and amount of rainfall, were recorded by CDA. Degree-day accumulations, beginning 1 January each year, were calculated for each date of inspection by the using the lower developmental
base temperature of 4.3˚C. The strong positive correlation between degreeday accumulation and cumulative capture of flies on YST was noted for both years (R=0.9771 and 0.991; P=0.0001). These results show that fly emergence and the capture of flies on YST are dependent on temperature. Spring flight of the flies was observed in cabbage fields in both years 7-10 days after cabbage transplanting when degree-day accumulations reached 450-500. The ratio of
plants infested with eggs, average number of eggs/plant and intensity of egg deposition are correlated with the cumulative number of flies caught on YST. Correlation coefficients varied between medium (for % of plants infested by eggs, R=0.572) and strong (for average number of eggs/plant, R=0.736 and for infestation intensity, R=0.74). A medium correlation between the percent of plants showing symptoms of larval attack and cumulative capture of flies
on YST exists (R=0.432 in 2008 and R=0.499 in 2009). The regression line for both years can be described as a parabola. Lower fly populations in 2008 versus 2009 resulted in higher larval infestation in 2008 than in 2009. This led us to conclude that larval attack is influenced by fly population level, but also by other factors, of which the amount of rainfall during the egg hatching and larval infestation is the most important. The main difference between the
years was in the amount of rainfall in May when egg hatching occurs. It is impossible to determine fly capture levels, which will cause certain percent of larval infestation, if the amount of rainfall is not taken into account. The peak of larval numbers occurred at degree-day accumulations between 750-800.

Keywords

Delia radicum; infestation intensity; eggs; larvae; cumulative capture; correlations; degree-day accumulation

Hrčak ID:

67624

URI

https://hrcak.srce.hr/67624

Publication date:

11.10.2010.

Article data in other languages: croatian

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