Slug damage is evident in many crops this autumn with wet weather being the primary factor in this regard, according to Teagasc.
However, crops following oilseed rape and fields with a history of slug damage, have fared worse.
The fact that field conditions were not suitable for rolling only increased the pressure on crops. Slug grazing in oilseed rape is common but the main concern from now on will be winter wheat.
Slug damage
Slugs often do most damage to winter wheat at the early stage by eating the endosperm, resulting in the characteristic seed hollowing.
Barley and oats are less susceptible at this stage due to their extra seed coat.
Chopped straw may also be an additional factor, as this will provide slugs with a source of food and land can take longer to dry out in a season like this year’s.
Where growers suspect slugs may be a problem, they should lay down traps using a plastic bag or slate with muesli underneath to attract them.
Growers should monitor the traps daily to quantify the populations. If you see five or more slugs per trap, on average, treatment is warranted on emerging or struggling crops.
Slugs are most active at night so the best time to check slug traps is early in the morning. If the threshold of five or more slugs per trap, on average, across the field is reached then consider control options.
Control of slugs
The only cultural control option is rolling if crop and ground conditions are suitable. Chemical control will be based on products containing metaldehyde or ferric phosphate.
It is important to use the recommended rate on the label.
Applying reduced rates reduces the number of baiting points, resulting in poorer control. Better to apply one full label rate rather than a reduced rate twice.
There are three types of slug-related damage to look out for.
These are: Shredding of the crop leaves; poor emergence caused by hollowed-out seed; and the appearance of yellow leaves, caused by slugs grazing below the soil surface.
This last issue is a recently identified phenomenon, where slugs are concerned. The damage created is similar to that caused by yellow jackets.
The challenge for growers right now is to get crops established as effectively as possible and get them away from any pest-related problems.
The longer this takes, the greater opportunity for pests to cause damage.