Effects of organic and conventional fertilization on the occurrence of Brevicoryne brassicae L. and its natural enemies in white cabbage

Figures & data

Table I. Meteorological conditions of the experimental years and long-term averages for the 1924–2000 period.

	Temperature (°C)			Precipitation (mm)
Month/ten-day periods	2004	2005	Long-term averages	2004	2005	Long-term averages
June
Average	13.7	14.8	16.6	77.4	66.6	50.4
July
I	14.9	17.9	-	29.0	0.8	-
II	15.3	19.6	-	21.0	2.8	-
III	19.0	20.7	-	0.4	0.2	-
Average	16.4	19.4	17.6	50.4	3.8	71.8
August
I	18.8	15.8	-	38.8	93.2	-
II	17.1	14.7	-	33.6	11.6	-
III	16.0	13.6	-	51.2	4.6	-
Average	17.3	14.7	16.3	123.6	109.4	75.8
I – first 10-day period, II – second 10-day period, III – third 10-day period.

Figure 1.  Dynamic of cabbage aphids and their parasitization by Diaeretiella rapae on non-fertilized (A, B), manure-fertilized (C, D) and synthetically fertilized (E, F) cabbage plants.

Table II. The occurrence of B. brassicae and D. rapae on differently fertilized white cabbage in 2004–2005.

	Mean number
Treatment	Aphids per plant	Parasitized aphids per plant	Parasitization (%)
	2004
Non-fertilized	2.75 a*	0.85 abc	28.50 c
Fertilized with manure	6.69 c	1.00 c	16.18 abc
Fertilized with synthetic fertilizers	3.22 abc	0.41 a	12.40 a
	2005
Non-fertilized	4.54 a	0.67 ab	16.50 b
Fertilized with manure	18.57 b	1.24 b	14.88 ab
Fertilized with synthetic fertilizers	5.85 a	0.79 ab	13.36 ab
*Means in the same column followed by the same letter are not significantly different (p = 0.05) according to Duncan's multiple range test.

Table III. The abundance of Coccinella septempunctata L. and Aphidoletes aphidimyza Rond. in the cabbage aphid (Brevicoryne brassicae L.) colonies in 2004–2005 (at the time of occurrence on plants).

	Mean number
Treatment	Coccinella septempunctata L. adults per plant	Aphidoletes aphidimyza Rond. larvae per plant
	2004 (VII 21–26)
Non-fertilized	0.03 ab*	0
Fertilized with manure	0.03 ab	0
Fertilized with synthetic fertilizers	0 a	0
	2005 (VII 13–22)	(VIII 05–24)
Non-fertilized	0.05 ab	0.075 ab
Fertilized with manure	0.06 b	0.17 b
Fertilized with synthetic fertilizers	0 ab	0.14 ab
(VII 21–26) (VII 13–22) – the time of Coccinella septempunctata L. occurrence on plants.
(VIII 05–24) – the time of Aphidoletes aphidimyza Rond. occurrence on plants.
*Means in the same column followed by the same letter are not significantly different (p=0.05) according to Duncan's multiple range test.

Table IV. The relationship between the number of B. brassicae and D. rapae on cabbage as affected by fertilization.

Treatment	Correlation coefficient	Equation of regression line y = a + bx	Regression coefficient b
	2004
Non-fertilized	0.4945**	y = 0.3927 + 0.1597x	0.1597
Fertilized with manure	0.5668**	y = 0.4934 + 0.0761x	0.0761
Fertilized with synthetic fertilizers	0.4652**	y = 0.2076 + 0.0643x	0.0643
	2005
Non-fertilized	0.4096**	y = 0.3488 + 0.0718x	0.0718
Fertilized with manure	0.3509*	y = 0.8920 + 0.0187x	0.0187
Fertilized with synthetic fertilizers	0.34042*	y = 0.4176 + 0.066x	0.066
The date were reported as means (n = 40). **Coefficient of correlation significant at the probability level p=0.01.
*Coefficient of correlation significant at the probability level p=0.05.