Abstract:
We have supervised, in dynamics, the rhizotrophic action exerted by
Diabrotica larvae (15 June, 3 July, 1 August) and philotrophic (15 June, 3
July, 1 August, 14 August) and stigmatrophic activity (1 – 14 August) exerted
by adults, stages connected to the patosystems Zea mays – Helminthosporium
turcicum, Zea mays – Fusarium roseum, Zea mays – Ustilago zeae, present
in 2006, in a comparative crop of Pioneer maize hybrid, from different
maturity groups (PR39D81 – extra-early, PR38R92 –early, PR38A24,
PR37D25, PR37M34, PR37W05 – half-early and PR35P12, PR36K67 – half
lattes).
Successive to the research of the relationship between the new pest
and the climatic factors from Arad region, where we have performed our
experiments in 2006, we may conclude: the climatic factors favoring the
insect Diabrotica virgifera virgifera Le Conte are: temperatures of 23-25ºC,
medium rainfall and air relative humidity of 70-75%. Thermal and hydric
requirements of this insect are similar to those of the pathogens from the
maize patosystems (Helminthosporium, Fusarium, Ustilago – with some
differences for the blight Ustilago). There is a positive correlation between
temperature, rainfall, atmospheric humidity and rhizospheric, philotrophic
and stigmatrophic aggression; the bigger the climatic values are, concordant
to the trophic optimal values, the bigger the attack aggression will be: 6.3
13.8%, 7.5-47.7%, respectively 46.4-51.0%.
The rhizotrophic larvae action has a reduced aggression compared to
the nutrition on a single leaf epidermis and on the stigmas of the future maize
cobs; the specified activity gets emphasized within the phenophasic interval
“7-8 leaves” – “milk ripeness”, when maize sensibility to pathogens is
increased.
