26 April 1999
Slug threat to linseed — and other pests
I HAVE only recently ploughed ground which has been laid stubble all winter. I am growing a lot of spring linseed this year. Are slugs likely to pose a significant risk?
David Green, entomologist, ADAS, Wolverhampton
Slugs are a high risk feature this season, the mild and wet conditions are currently optimal for breeding. Surface trash in particular harbours slugs over colder periods and, even when turned under through ploughing, slugs will find their way to the surface; vigilance is an essential watchword.
Young linseed is very palatable to slugs, although all spring crops are particularly vulnerable at single shoot stage. Late-drilled crops should be checked for damage, especially those still emerging, and any crops that have had growth checked by colder weather.
Dusk is the best time to check for slug activity, as this is when they start to move actively. Slug evidence includes slime trails and leaf-shredding.
Trapping is very effective provided the chemicals used are fast-acting and do not allow the slugs to crawl away from the trap before dying . As plants mature, tiller growth rates will exceed the rate of slug damage.
Slug presence varies a lot from field to field and between areas of the country. Slug problems should be treated promptly with pellets.
The population is altering; mature slugs that have survived the mild winter from last summer and autumn are beginning to die. More young slugs are being caught in traps, indicating that eggs have the correct environmental conditions for hatching.
Flax flea-beetle activity so far has been minimal but, if the weather becomes drier, then attacks may occur. Crops should be monitored closely to check for slug nor beetle damage.