Grassland pests can negatively impact both new reseeds and older pastures. However, correct soil and sward maintenance can prevent pest invasions and negate their damage, helping to reduce the reliance on pesticides.

It is particularly important to consider pest infestations when preparing for a reseed; during sward establishment, there is little material for pests to feed from, and therefore seedlings are often targeted at their most vulnerable stage. Good seedbed preparation can mitigate the impacts of certain pests.

Leatherjackets

Leatherjackets are crane fly larvae which live in soil. They feed off roots and stems of plants, remaining in the soil after seedbed preparation. However, if a previous sward has been badly infected, it is likely they will remain and reinfest the new sward.

Infestations are often localised to specific areas of the field, the leatherjackets laying their eggs where they emerged. There are many signs of damage which is caused by leatherjackets, including large, bare patches of soil and bird activity.

There are different options for reducing the population of leatherheads, such as ploughing the field when they are most active. Infestation can also be prevented by leaving an interval of at least three weeks between grass leys. Break crops, such as brassicas, can be used between grass leys to disturb the pest cycle and reduce their interference. 

Arable crops are unaffected by leatherjackets and should be taken into consideration when planning a rotation. 

Frit Fly

Frit fly eggs can be laid around newly developed seedlings and can also emerge from the soil from a previously infested crop.

There is a much greater risk of infestation in seeds which were sown in the autumn rather than during the spring, the egg laying period being between July and October.  While perennial and Italian ryegrass are most susceptible, other plants such as clover, timothy and cocksfoot are mostly unaffected.

When left untreated, populations of larvae can exceed the number of grass seeds, causing a lot of damage which can become a serious problem. Signs of frit fly damage can include poorly established patches of plants, slow emergence, and weak seedlings.

Slugs

Slugs are nocturnal pests and feed from seedlings, such as grass and clover. The damage which slugs cause can often appear sporadic and uneven. 

However, seedbed preparation can help to deter slugs away from plants. When preparing a seedbed, it is important to consider implementing a fine and even seedbed, this exposing slugs to predators.