Fungal diseases of cucurbits

Abstract

Fungal diseases of cucurbits are caused by various fungi and fungus-like organisms which are frequent limiting factor in the production of cucurbit crops all over the world. Mycoses of cucurbits are usually categorized into three overlapping groups, disease of subterranean parts, diseases of aerial parts and fruit rots. Although each group comprises numerous, nonrelated fungal species with different taxonomic position, they share several epidemiological features demanding similar control strategies which can be successfully applied. Diseases of subterranean organs of cucurbits are caused by several soil-borne fungi and fungus-like organisms. The most frequent diseases of this group are seed rot and seedling root rot (caused by Pythium spp.), seedling damping-off and root and crown rot (Phytophthora spp., Rhizoctonia spp., Sclerotinia sclerotiorum), fusarium wilt (Fusarium spp.), verticilium wilt (Verticillium albo-atrum i V. dahliae) and other. The most common diseases of aerial parts, also known as diseases of cucurbits leaves are alternaria leaf spot and leaf blight (caused by Alternaria cucumerina, A. alternata), gummy stem blight (Didymella bryoniae), anthracnose (Colletotrichum orbiculare), downy mildew (Pseudoperonospora cubensis), powdery mildew (Podosphaera xanthii and Golovinomyces cichoracearum), cercospora leaf spot (Cercospora citrullina) and others. Diseases of cucurbit fruits are economically very important and are caused either as fi nal stage of several diseases of leaves or by fruit infection and colonization by soil-borne fungi. The most common causing agents worldwide are Phytophthora capsici, several Fusarium spp., Alternaria alternata, Rhizoctonia solani, Didymella bryoniae, Sclerotium rolfsii and others. Managing strategies for successful control of cucurbit diseases are based to target disease prevention, on one hand, and to slow down disease spreading. Starting the production with pathogenfree seed is crucial fi rst step in disease prevention coupled with growing disease resistant cultivars and using wide crop rotation schedule. The disease spread can be slowed by direct application of chemical or biological fungicide when necessary.

Mikoze vrežastih kultura mogu biti izazvane raznorodnim vrstama gljiva i pseudogljiva i čest su ograničavajući faktor u proizvodnji u mnogim delovima sveta. Uobičajeno je da se svrstavaju u tri osnovne grupe, bolesti podzemnih organa, bolesti nadzemnih organa i bolesti ploda pre i posle berbe. U svakoj od ovih grupa gljive i pseudogljive prouzrokovači su brojni i taksonomski veoma udaljeni, ali među njima postoje izvesne sličnosti u epidemiologiji zbog čega se za suzbijanje mogu primeniti neke relativno slične strategije. Više vrsta gljiva i pseudogljiva koje se održavaju u zemljištu (eng. soilborne fungi) obično su prouzrokovači bolesti podzemnih organa vrežastih kultura. Uobičajene bolesti podzemnih organa su: rano propadanje tokom klijanja i nicanja (prouzrokovači vrste roda Pythium spp.), propadanje ili topljenje sejanaca (Phytophthora spp., Rhizoctonia spp., Sclerotinia sclerotiorum), fuzariozno uvenuće i sušenje biljaka (Fusarium spp.), verticiliozna uvelost (Verticillium alboatrum i V. dahliae) i druge. Bolesti lista vrežastih kultura javljaju se ili isključivo na listovima ili tu započinju razvoj, a potom napadaju i vrežu i ostale biljne organe. Među značajnije bolesti lista vrežastih kultura ubrajaju se alternarijska pegavost lista (prouzrokovači Alternaria cucumerina, A. alternata), gumozno sušenje stabla (Didymella bryoniae), antraknoza (Colletotrichum orbiculare), plamenjača (Pseudoperonospora cubensis), pepelnica (Podosphaera xanthii i Golovinomyces cichoracearum), pegavost lista (Cercospora citrullina) i druge. Bolesti ploda vrežastih kultura su ekonomski veoma značajne i nastaju usled zaraze listova i stabla ili gljiva i pseudogljiva poreklom iz zemljišta sa kojima plod može biti u direktnom kontaktu. Najčešći prouzrokovači su Phytophthora capsici, vekoliko vrsta Fusarium spp., Alternaria alternata, Rhizoctonia solani, Didymella bryoniae, Sclerotium rolfsii i druge. Efi kasna kontrola bolesti vrežastih kultura zasniva se pre svega na preventivnim i agrotehničkim merama koje sprečavaju nastanak ili usporavaju širenje bolesti. Setva zdravog semena i gajenje otpornih genotipova i plodored, svakako su najznačajnije, kao i direktna primena hemijskih ili bioloških fungicida.