QUADRIS – BIOTIČNE LASTNOSTI IN NAČIN UPORABE

  Borut Florjančič

Novartis Agro d.o.o., SI-1000 Ljubljana, Slovenija

Azoksistrobin je drugi fungicid iz skupine strobilurinov, ki je prišel na tržišče, kjer je zaradi široke možnosti uporabe in ugodnih biotičnih lastnosti prevzel vodilno mesto na trgu strobilurinov.

Azoksistrobin deluje na bolezni rastlin iz vseh glavnih razredov (Ascomycetes, Basidiomycetes, Deuteromycetes, Oomycetes). Zaradi izredno dobrega delovanja na glive iz razreda Oomycetes, še posebej izstopa v skupini strobilurinov. Širino delovanja azoksistrobina potrjujejo številne registracije po svetu pri vseh glavnih gojenih rastlinah (vinska trta, vrtnine, poljščine, okrasne rastline).

Za razliko od ostalih strobilurinov se azoksistrobin premešča po rastlini sistemično preko ksilema. Po rastlinskem tkivu se v primerjavi z znanimi sistemiki počasneje translocira, kar mu omogoča zelo izenačeno razporeditev po listu v daljšem časovnem obdobju, obenem pa preprečuje kopičenje aktivne snovi na konicah listov. Močno in zanesljivo translaminarno delovanje je izjemno močno izraženo pri varstvu vinske trte pred peronosporo.

Azoksistrobin učinkovito zatira različne stadije gliv, delovanje je posebno dobro v času, ko ima gliva največje energetske potrebe. Azoksistrobin inhibira dihanje v mitohondrijih, tako da prepreči prenos elektronov med citokromoma B in C₁ v energetsko bogatih procesih tvorbe ATP.

V primeru peronospore vinske trte azoksistrobin odlično deluje na gibljive zoospore, preprečuje tvorbo micelija in sproščanje zoospor iz sporangijev.

Najboljše delovanje na peronosporo vinske trte dosežemo s preventivno rabo, čeprav ima azoksistrobin tudi kurativno delovanje, ki se kaže predvsem kot propad micelija.

Rastline tretirane z azoksistrobinom so intenzivno zeleno obarvane (t. im. “greening effect”), kar kaže na intezivno fotosintetsko aktivnost listnega zelenila, to pa naj bi bil glavni razlog za povečanje pridelka predvsem na enoletnih rastlinah. Povečanje pridelka pogojuje zbir dejavnikov, med katerimi imajo pomembno mesto učinkovito delovanje azoksistrobina na širok spekter bolezni in saprofitov, dobra selektivnost, vpliv na translokacijo asimilatov ter vpliv na izrabo vode.

Rastlinske bolezni lahko ob nepravilni rabi relativno hitro pridobijo odpornost na strobilurine, zato je FRAC izdal priporočila o številu in načinu aplikacij strobilurinov pri vseh pomembnejših gojenih rastlinah.

ABSTRACT

QUADRIS – BIOTICAL PROPERTIES AND APPLICATION MODE

Azoxystrobin was the second fungicide from the group of strobilurines to be put on the market. Due to its broad spectrum of application and favourable biotical properties it has gained the leading role on the strobilurine market.

Azoxystrobin gives good control against diseases of plants belonging to all the main classes (Ascomycetes, Basidiomycetes, Deuteromycetes, Oomycetes). Thanks to its excellent activity against fungi from Oomycetes class it has an outstanding position in the strobilurine group. Surely, the numerous registrations of azoxystrobin in all the major crops (grapevine, vegetables, agricultural crops, ornamentals) are a proof of its wide activity.

As distinguished from other strobilurines, azoxystrobin is transferred through the plant systemically via the xylem. It is translocated through the plant tissue at a lower rate as compared to other systemics. This enables very even distribution in the leaves during a longer period of time, whereas at the same time it prevents the accumulation of  the active substance at the leaf tips and margins. Strong and reliable translaminar activity is especially distinctive in the protection  against grapevine downy mildew.

Azoxystrobin provides excellent control at different stages of fungal development. Its shows particularly good activity when the fungus has highest energy demands. Azoxytrobine inhibits mitochondrial respiration by blocking electron transfer between cytochrome B and cytochrome C1 in energetically reach ATP formation processes.

In case of grapevine downy mildew, azoxystrobin has excellent activity on motile zoospores, it prevents the formation of  mycelium and the release of zoospores from sporangia.

The best effect on grapevine downy mildew can be achieved by preventive application, even though azoxystrobin also has curative activity which is demonstrated mainly as mycelial collapse.

The plants treated with azoxystrobine have intensive green colour (s. c. »greening effect«) which indicates photosynthetic activity of chlorophyll. This is supposed to be the main reason for yield increase, particularly in annual crops. The yield increase is conditional upon various factors, the most important of which are effective azoxystrobin activity on a broad spectrum of diseases and saprophytes, good selectivity, impact on translocation of assimilats and influence on water use.

In case of improper use of azoxystrobin, the plant diseases gain resistance to strobilurines in a relatively short time. For this reason FRAC has given recommendations on the number and mode of strobilurine application  in all major crops.