Editorial
Luuk Meijering
Soil health theme editor
Winter wheat yellowing disease can be costly to your crop. Growers must take measures more often than before to prevent infections. There are already tolerant varieties of winter barley on the market, while tolerant varieties of winter wheat are not yet available.
Winter wheat yellowing disease is a growing problem, especially in the Southwest. The cause is higher temperatures in autumn and mild winters, combined with an ever-larger viral reservoir. This emerged during a webinar organized by Delphy together with Limagrain. Cereal yellowing disease is caused by barley yellowing virus, a persistent virus transmitted by aphids. Once infected, the louse continues to transmit the virus.
First infections in autumn
The first infections of a plot occur in autumn on early sown plots. Lice pick up the virus from infected host plants such as grasses, corn and grain stores. According to Delphy consultant Pierre Cammaert, the amount of host plants, and therefore the reservoir of the virus, is increasing because growers are sowing more green manures and have started cultivating the soil less intensively, which prevents greater grain storage .
Lice survive light frost down to -5 degrees
Last year, flying lice were found in November, which caused the yellowing virus to spread late in the season. In a mild winter, aphids survive by eating winter grains. According to Delphy project manager Arjan Hendriks, aphids can survive light frost down to -5 degrees. To get rid of live lice, you need to freeze at least 7 degrees for several days. A rainy winter with a lot of wind also reduces the aphids’ chances of survival.
Spot yellowing of the leaves
As soon as temperatures rise in spring, the surviving aphids become active again. A winged generation of aphids can already appear 170 days after the emergence of the crop. In 2023, this has already led to noticeable symptoms on the field in April. An infection can be recognized by patchy leaf yellowing starting at the tip of the leaf. When bolting occurs, growth is severely inhibited and infected plants have difficulty forming ears.
Prevent yellowing disease? Don’t sow winter wheat too early
The traditional way to prevent infection and spread of the virus is to not plant winter wheat too early. The old advice was not to sow before October, but due to climate change, sowing in October is also one of the risk factors for infection. Delphy also recommends checking plots for aphids when planting in November and December. And to carry out the check, if necessary.
Late planting presents a dilemma for growers. Sow on time and in good conditions or wait until the end of the year with an increasing risk of poor sowing conditions?
In case of high aphid pressure in autumn, chemical intervention can be used. To determine the right time to spray, Delphy tests a decision support system that alerts the grower when a new generation of aphids may be present in the field and control is worthwhile. The system works based on the emergence date of the crop and the sum of temperatures after emergence.
It is not yet a tolerant winter wheat
Breeding companies are working on virus-resistant yellowing cereal varieties. Martijn van Overveld, head of arable products at breeding company Limagrain, says it will take several years before a full-fledged winter wheat variety with a tolerance to barley yellowing virus is on the market. Tolerant varieties are still far behind in terms of yield.
In winter barley the development of tolerant varieties has advanced further. In 2015, the first tolerant fodder barley variety arrived on the market; however, this one had a low test weight and soft straw. Since then, development of the variety has continued and Limagrain is a tolerant winter barley variety suitable for brewing.
The product manager advises growers who want to sow early to choose hardy winter barley instead of winter wheat.
2024-01-06 13:04:00
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