Heterodera zeae Koshy, Swarup and Sethi, 1971 (Heteroderidae): Probability Of Introduction on Cereals in Bulgaria

Institute of Soil Science, Agrotechologies and Plant Protection „N. Poushkarov“, BG - 1080 Sofia, Bulgaria


KARADJOVA, O., Z. ILIEVA, E. PETROVA and V. KRUMOV. Heterodera zeae Koshy, Swarup and Sethi, 1971 (Heteroderidae): probability of introduction on cereals in Bulgaria. Bulg. J. Agric. Sci., 21: 969–981

The present paper assesses the probability of entry and establishment of the corn cyst nematode Heterodera zeae in Bulgaria. The species is currently distributed in ten countries in Asia, Africa, Europe and North America and is one of the most economically important pests on corn and other cereal crops in India and Pakistan. In 2009, H. zeae was established in close proximity to the Bulgarian border with Greece (Kavala).
Three main pathways of entry of H. zeae in the country have been considered. The highest risk is associated with the import of bulbs, rhizomes, tubers and other underground plant parts with attached soil, intended for direct consumption and processing from countries where the pest is distributed. For this pathway, the probability of entry has been assessed as moderate.
A climatic model has been developed to assess the probability of establishment of the pest. It shows that the species can establish on the whole territory of Bulgaria, excluding the mountains Rila, Rhodope and Pirin, the mountains to the west and the north of Struma valley and the Central Balkans where the conditions are unfavourable for its development. The number of generations per year varies from 1.03 in the area of Kyustendil to 1.81 in the southernmost parts of the country.
The overall risk of entry and establishment of H. zeae in Bulgaria is low under the current climatic conditions.
The potential spread of H. zeae after introduction has been considered briefly to show that the process would be slow due to the expected low reproduction rate of the populations in Bulgaria and the limited natural spread of the species. The risk of economically important losses is low. More significant losses could be expected from corn in warm, dry years, in areas with light, sandy soils.

Key words: Heterodera zeae, entry, establishment, corn, wheat, barley, Climex

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