- The phytosanitary condition of cereals did not raise any major concerns in the spring vegetation. With one exception. Many plantations were infected with viruses.
- Rodents became a local problem, and in areas with background frosts, after the stress subsided, the weakened plants were attacked by unusual plant pathogens.
IOR-PIB monitors crops throughout the growing season. I conduct increased control of winter crops after the start of growing season. What diseases were of economic importance this season? We can read about this in the list developed by the Institute.
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1. Viruses are the number 1 problem
According to IOR-PIB, in the 2023/2024 growing season, field observations began in early spring. Mainly to detect symptoms of viral diseases. Due to the lack of chemical virus control, the only form of crop protection are broadly understood preventive measures such as: selection of varieties with increased resistance, proper agrotechnics and finally chemical reduction of the number of insect virus vectors.
In drastic cases of severe infection of most plants on the plantation, it is even necessary to decide to eliminate and remove infected plants – sources of viruses for secondary infections.
In Poland, the greatest threats to winter cereal crops, mainly barley and wheat, are Barley yellow dwarf virus (BYDV) and Wheat dwarf virus (WDV).
Moreover, as a new threat to Polish cereal crops, the Barley virus G (BVG) was diagnosed and detected. A rather disturbing phenomenon was the increase in the number of mixed, more dangerous infections involving 2 or even 3 of the above pathogens.
The listed virus species are transmitted only and exclusively by vectors. In the case of BYDV, these are aphids, mainly the bird cherry-cereal aphid and the cereal aphid. The BVG virus is transmitted by the cereal aphid and the corn aphid, and WDV by the leafhopper – the striated leafhopper. The long, warm and fairly dry autumn in 2023 definitely favored the occurrence of these pests, which is why in the regions of southern and southwestern Poland, numerous plantations of winter barley and winter wheat with severe infection by viral diseases were recorded. In drastic cases, decisions were made to eliminate plantations.
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Winter barley heavily infected with viruses. Laboratory test results confirm this
2. Protect plantations during aphid raids
In connection with the above, IOR-PIB reminds that in the next growing season – in the autumn of 2024, in the early development stages of winter barley and winter wheat, special attention should be paid to the occurrence of vectors, and if necessary, intervention measures should be taken immediately. Appropriate procedures involving the destruction of vectors will ensure a reduction in the occurrence of viral diseases for which there are no plant protection products.
In the spring of 2025 (in the case of high intensity of virus vector feeding – even in the late autumn of 2024), when conducting field observations, special attention should be paid to changes in plant habit: stunting, excessive tillering. In addition, yellowish or orange-reddish discoloration of barley and wheat leaves is a very common phenomenon, which over time turns brown and dies prematurely. The above symptoms may indicate viral infections. However, unlike in the case of fungal diseases of cereals, disease symptoms are not sufficient, because different virus species can cause similar symptoms and therefore correct diagnosis is based on the results of laboratory diagnostic tests. These are serological DAS-ELISA tests, and in the case of ambiguous results, molecular tests – RT-PCR reactions.
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3. Rollers and the beetle – unusual cereal pests
In the later stages of development of host plants (cereals), local problems with feeding of leafrollers appeared. Changing cultivation conditions and restrictions related to the use of plant protection products cause local problems with these pests, especially in spring cereal crops. In Polish conditions, the most frequently observed are the eared leafroller (Cnephasia longana) and the grain leafroller (Cnephasia pumicana).
This is particularly visible in crops where insecticides are not used, e.g. in organic farming or in feed mixtures. So far, the range of leafrollers has been limited to the western part of the country, but in the coming years it is expected that its area of occurrence will expand. Mainly due to warm, dry and windy springs, which facilitate the spread of leafroller larvae. Climate warming also causes this species to spread in Poland towards the east.
The leafrollers are polyphagous and can develop on practically all types of cereals, grasses and many other crops. Initial feeding of the larvae on leaves does not cause major losses, later burrowing under leaf sheaths or into the stem can weaken the plants and facilitate the penetration of fungal infections. Direct losses are caused by the feeding of the caterpillars on ears and developing grains, of which one larva can eat even several. Leaves and ears are covered with delicate yarn, to which crumbling lumps of excrement are often attached.
In the 2024 season, such pests as the Oxythyrea funesta were observed locally. The main reason for such threats is climate change – new species are appearing or pests that were previously marginal are gaining importance. In recent years, numerous appearances of this pest have been recorded mainly in the east and south of Poland. In 2019, it was reported from Wielkopolska, and in mid-May 2024, numerous beetles were observed in cereal crops on the premises of the Field Experimental Station of the Institute of Plant Protection – State Research Institute in Winna Góra.
Adult beetles attack young ears and completely eat their contents, leading to whitening and wilting of the plant tops. They can also cause damage to flowers of several species of ornamental and fruit plants. The symptoms of the feeding of the sedge resemble those caused by the sedge moth (Chaetopteroplia segetum). Due to the similarities in the bionomy of both species, it can be assumed that the damage caused by the sedge moths can also be significant, although this has not been the subject of research in Poland so far.
The spread and numbers of this species in Poland should be monitored, as it may soon gain economic importance and become a threat to other crops as well.
Control – due to the lack of registered insecticides, the only form of reducing the number of pests is agrotechnical treatments, such as avoiding sowing cereals near trees, forest walls, etc., especially if they are located on the side of the prevailing winds in a given region.
4. Stressed plants were attacked by fungal diseases
This season, the weather breakdown that was recorded in the second decade of April became a stress for plants. Plants weakened by spring frosts were more susceptible to infection, especially with frequent rainfall in spring. Therefore, ascochyta blight (caused by Ascochyta graminicola) was often observed on cereals (47 samples analyzed), a disease typical of plants in poor condition. In addition, there was septoria, brown rust and, less frequently, rhynchosporiosis, vascular leaf spot (caused by Cephalosporium graminearum) and black leaf spot of barley (caused by Bipolaris sorokiniana). Symptoms of both viral and fungal diseases were often observed on plants.
Assessment of the phytosanitary status in winter rapeseed and winter cereal plantations – bacterial and viral pathogens
Bacteria
In the 2024 season, samples of plant material (winter wheat, wheat, triticale, winter barley, rye) were tested for the presence of bacteria. The BIOLOG GENIII system was used to identify bacterial diseases, which operates based on the characteristics of the biochemical and physiological features of the examined. In exceptional cases, the identification is confirmed based on the 16S rDNA gene sequence.
In most of the samples examined, no plant pathogenic bacteria were found. The presence of bacteria constituting human microflora of the following genera was found several times: Klebsiella, Proteus, Pseudomonas fragie, Serratia liquefaciens, Acinetobacter nosomicalis or Enterobacter (this phenomenon is referred to as HPOPs – Human Pathogens On Plants).
From the plant samples of the sent material, it was possible to identify plant pathogenic bacteria, such as: Pseudomonas syringae, Pseudomonas viridilivida, Clavibacter michiganensis, Enterobacter cloaceae ss. dissolvens, Pectobacterium carotovorum, Pantoea ananatis, Kosakonia cowanii and Pantoea agglomerans, Pantoea sp. Pantoea agglomerans is not a typical plant pathogen, but has been isolated from hosts showing atypical disease symptoms. Currently, studies are underway on the pathogenicity and further characterization of these isolates.
General recommendations for the 2024/2025 growing season
IOR-PIB in Poznań reminds about the obligation to cultivate crops according to the principles of integrated plant protection. They indicate the priority of using all non-chemical methods before deciding to use a chemical plant protection agent. In this context, first of all, proper agricultural technology is a key element of the protection strategy. The following should be mentioned here:
– appropriate fertilization – adjusted to the needs of a specific field (in the case of production in the Integrated Production system this is a requirement),
– selection of resistant varieties,
– ploughing and sowing operations performed correctly and on time,
– systematic monitoring of the occurrence of diseases and pests,
– compliance with harmfulness thresholds,
– if it is necessary to use chemical agents, it is recommended to select agents with a different mode of action as well as the selection of agents with different active substances.
