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16 Agriculture 7(2001)
RESULTS AND DISCUSSION
Average intensity of attack of ECB was 51.67% on all
examined hybrids in the last ten years. The lowest attack
was 24.17% in 1990. Results in 1991 were missing, due
to war agression on our country. Since 1992 intensity of
attack of ECB has been considerable every year (Table 1).
Tablica 1. Intenzitet napada po godinama
Table 1. Intensity of attack per years
One of the reasons why intensity of attack increased
could be because 35% in 1991 of corn was not harvested.
Those conditions were favorable for ECB, and the attack
was increased to 78.15% (Ivezi} & Raspudi}, 1993). In
the same year, the hybrids BC 678, BC 66-61, BC 66-62,
BC 778 and Ivan 31-81 had the intensity of attack of ECB
100%, in 27 hybrids the attack was over 70%.
Tolerance of particular hybrids to attack of ECB was
also examined. Hybrid OSSK 552 was intolerant to ECB.
Yield loss of 15.48% because of ECB attack was determined
in several years’ trials in this hybrid. Hybrids OSSK
664 and OSSK 554 had yield loss from 4-5%.The greatest
loss in BC hybrids was determined in BC 66-61 (13.12%)
and the lowest yield loss had BC 462 (0,82%) (Raspudi}
et al., 1998).
Differences in attack intensity occurred between different
FAO groups. From 1992-1996, the lowest intensity
of attack was in the FAO group 100 (34.25%), in subsequents
FAO groups, the intensity was increased accordingly.
The greatest intensity was in FAO 600, with
71.76%. In all other groups, intensity varied from 45.83%
to 66.01% (Ivezi} et al., 1997).
Control of ECB has not been implemented in Croatia.
There were just couple of field trials with biological preparation
on the base of Bacillus thuringiensis, with only one
application, which decreased intensity of attack by 9%
(Valen~i} et al., 1988).
Control of ECB with biological preparation Biobit XL,
on the base of Bacillus thuringiensis, showed good results.
Comparing to untreated plots the intensity of attack
was 83 %, and on treated plots intensity decreased to 53%
(for one application applied on July 10). Intensity of attack
decreased to 35% in treatment with application implemented
on July 28 and in treatments with two applications
(July 10 and July 28) on 37%. Number of tunnels and larvae
per corn plant also decreased, so Biobit XL seems to
be efficient and ecologically acceptable preparation for
ECB controlling (Ivezi} et al., 1998).
In 1998 the first trials with GM corn plant were done
in Croatia (Raspudi} et al., 1999). Field trials showed tolerances
of GM corn to ECB attack (Table 2).
Hybrid Evelina Bt was tolerant to ECB, and hybrid
Landia Bt had 21% intensity of attack, while standard Landia
had 98%. Number of tunnels and larvae was also decreased.
Length of damages on corn plant on Landia Bt
was lower 98% comparing to check. Decreasing in attack
intensity in GM hybrids, caused better yield compared to
standard hybrids. Yield increased by 10.27% in Evelina Bt,
and for 26.67% in Landia Bt, comparing to their checks,
respectively.
Tablica 2. Razlika izme|u dva hibrida kukuruza i njihovih GM hibrida kukuruza
Table 2. Differences between two corn hybrids and their genetically modified counterparts