INCIDENCE OF ERGOT IN LITHUANIA AND ITS CONTROL
Z DABKEVICIUS and R SEMASKIENE
Lithuanian Institute of Agriculture, Dotnuva-Akademija, Kedainiai, Lithuania
Background and objectives
Ergot (Claviceps purpurea) is one of the most harmful diseases of the Poaceae family worldwide . A mild Lithuanian climate and a high precipitation rate are very favourable for the spread of this disease. In Lithuania, ergot incidence has increased markedly over the past few years as a result of the growth of many small farms and pastures, and because of a reduction in applications of chemical plant protection measures. Cultivation of new tetraploid and hybrid varieties of cereals and grasses, which are susceptible to ergot, is also a factor contributing to high ergot incidence.
Materials and methods
To establish which plant species are subject to Claviceps purpurea attacks, ergot incidence was observed in different regions of Lithuania, and in fields, trials, collections and nurseries of the Lithuanian Institute of Agriculture. With a view to determining the effect of high temperature on viability of ergot sclerotia, dry and wet seeds contaminated with sclerotia were heated at 40-80°C for periods of 10 min to 7 days. The effect of seed treatments on viability of ergot sclerotia was established in laboratory and field conditions. The seed of grasses and rye contaminated with ergot sclerotia were treated with various chemical and biological seed treatments, and afterwards were germinated on wet sand in the laboratory and outdoors in soil. Fungicide efficiency was established on fungal conidia in laboratory cultures and in a stand of meadow fescue in the field.
Results and conclusions
To date, 79 ergot-affected species and forms of cultivated and wild Poaceae have been identified in Lithuania. Ergot was found on six cereal species, 16 cultivated and 33 wild grass species, four grass weeds, 17 ornamental or newly-introduced plants grown only in collections, and on three interspecific hybrids. The following cultivated species were severely infected with ergot: Festuca arundinacea, F. rubra, F. pratensis, Festulolium sp., Poa palustris, P. pratensis, Secale cereale and Triticosecale. An especially high ergot incidence was found on tetraploid Lolium multiflorum and Secale cereal varieties as well as on the interspecific hybrids Triticosecale and Festulolium. Most plants within the Poaceae may be infected by one another; however, a certain specialization in Claviceps purpurea has been encountered.
After a series of tests, heating grass seed lots infected with ergot sclerotia was recommended. A large amount of ergot is killed when temperatures are raised to 45-50°C. Infected seed with a moisture content above 20% may be dried or heated at 45°C for not more than 24 h, without any effect on seed germination, or at 50°C for not longer than 6 h. Sclerotia and seed with a moisture content of up to 15% were less sensitive to increased temperatures, and a significant reduction in viability of ergot sclerotia was observed at 50°C, after exposure for 24 h.
All the seed treatments inhibited germination of ergot sclerotia. Benlate and Thiram were found to be most effective against ergot on fescue. In the laboratory experiments germination of ergot sclerotia was completely inhibited by six treatments out of 17 tested. However, in field conditions their efficiency was 42.1-91.9%, except Benlate which was 100%. All 10 treatments were very effective against ergot on rye; in laboratory conditions they inhibited formation of the stromas by 91.8-100%. However, in field conditions their efficiency was 47.7-97.7%. Benlate, Panoctine and Maxim-Star were found to be the best. Three biological seed treatments were less effective and inhibited the formation of stromas by up to 42%.
In tests on fungicide efficiency against Claviceps purpurea in vitro, Benlate had the highest toxicity for the conidial stage. However, this fungicide was less effective against ergot in field conditions. Benomyl (1.5 kg/ha mixed with the insecticide Fozolone at 0.8 kg/ha against pest-vectors of ergot conidia), when applied on meadow fescue twice, shortly before flowering and at full flowering, reduced the number of ergot-affected panicles by only 32.6-37.5%, and the total number of sclerotia by 28.9-46.0%. However, such a level of efficiency is too low for these chemicals to be recommended for application on seed stands.
1. Bove FJ, 1970. The Story of Ergot. Karger, Basel, Switzerland.