Control Strategies to Cope with Late Wilt of Maize

Abstract

Control of maize late wilt disease (LWD) has been at the forefront of research efforts since the discovery of the disease in the 1960s. The disease has become a major economic restraint in highly affected areas such as Egypt and Israel, and is of constant concern in other counties. LWD causes dehydration and collapsing at a late stage of maize cultivation, starting from the male flowering phase. The disease causal agent, Magnaporthiopsis maydis, is a seed- and soil-borne phytoparasitic fungus, penetrating the roots at sprouting, colonizing the vascular system without external symptoms, and spreading upwards in the xylem, eventually blocking the water supply to the plant’s upperparts. Nowadays, the disease’s control relies mostly on identifying and developing resistant maize cultivars. Still, host resistance can be limited because M. maydis undergoes pathogenic variations, and virulent strains can eventually overcome the host immunity. This alarming status is driving researchers to continue to seek other control methods. The current review will summarize the various strategies tested over the years to minimize the disease damage. These options include agricultural (crop rotation, cover crop, no-till, flooding the land before sowing, and balanced soil fertility), physical (solar heating), allelochemical, biological, and chemical interventions. Some of these methods have shown promising success, while others have contributed to our understanding of the disease development and the environmental and host-related factors that have shaped its outcome. The most updated global knowledge about LWD control will be presented, and knowledge gaps and future aims will be discussed.

Cultivars Resistance Assay for Maize Late Wilt Disease

“…Many control methods have been tested against the LWD causal agent over the years (recently [ 9 , 33 , 34 , 35 , 36 ]). A focused research effort in recent years has yielded success, and now there is an effective and economical chemical (Azoxystrobin-based) fungicide method for dealing with the disease [ 23 , 37 ]. At the same time, application of this method requires changes in the growth method (double-row cultivation and dripline irrigation) [ 38 ], and there is a constant fear of the development of fungal resistance against the preparations [ 39 ].…”

“…One research direction designed to address these challenges is the utilization of biological pesticides. The potential for applying natural pesticides against M. maydis lines in Israel has been tested with different degrees of success in recent years [ 37 ]. Together with experiments carried out abroad [ 11 , 35 , 36 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 ], these efforts indicate a clear advantage for developing such an application [ 50 ].…”

“…The reason is that prolonged growth of a resistant maize cultivar (for several years) may eventually result in selection pressure that will lead to the outbreak of virulent strains of the pathogen capable of causing disease, as previously reported in Egypt and Spain [ 19 , 20 , 55 ]. This scenario occurred in Israel for the relatively resistant corn variety, Royalty, which became the leading corn variety during the LWD outbreak in the 1990s [ 26 , 37 ]. A program to develop new corn hybrids resistant to LWD has been operating in Egypt since 1980 [ 56 ] and in Israel for more than a decade (R&D North, Migal—Galilee Research Institute, Kiryat Shmona, Israel) [ 8 ], and has recently also been reported in India [ 16 ].…”

Crop Rotation and Minimal Tillage Selectively Affect Maize Growth Promotion under Late Wilt Disease Stress

“…Many such studies focused their attention on eco-friendly substitutions for traditional chemical methods. These include late wilt green control using soil conservation practices that promote antagonizing mycorrhizal fungi (reviewed in [ 5 , 36 ]). While this scientific course has been broadly explored against many plant pathogens [ 71 , 72 ] regarding M. maydis , considerable information gaps exist.…”

“…This fungal pathogen was known in the past under the synonyms Cephalosporium maydis [ 2 ] and Harpophora maydis [ 3 , 4 ]. Such efforts were part of a larger goal—improving existing methods and identifying new ones to eliminate or repress this destructive threat [ 5 ]. Indeed, Israel and Egypt are considered the world’s most LWD-affected areas, perhaps because the disease first evolved in this area [ 2 , 6 , 7 ], or due to favorable environmental conditions that enable the pathogen to thrive [ 8 ].…”