Leatherjackets are the larvae of Crane flies (Daddy Longlegs). They are soil living larvae with a thick grey-brown skin, no legs and can grow up to 5cm in length.
Adults lay eggs between July and September in grass and cereals
Eggs hatch 2-3 weeks later and the larvae feed in mild spells during autumn to late spring, pupating in the soil late May-June
90% of the time adults stay and lay eggs near to where they emerge, causing the population to continue to increase in the same field if they are not dealt with.
There are several signs that indicate the presence of leatherjackets:
Large numbers of adult Crane flies in July and August
Feeding by rooks, crows and starlings
Bare patches appearing in the grass
Leatherjackets feed on the roots and stems of grass plants at or below ground level.
New leys - Reseeded leys can be completely destroyed by leatherjackets
Established grassland - Leatherjacket feeding not only reduces yield, but can also lead to the destruction of large areas of fields. At the economic threshold of 1 million per hectare, the weight of leatherjackets feeding below ground can be greater than the weight of livestock above ground
Ploughing grassland in July and subsequent cultivations can destroy up to 50% of leatherjackets.
Dursban* 4 insecticide gives reliable, consistently high levels of control of leatherjackets. It is acknowledged as the standard treatment. The control achieved is such that dry matter yield can by increased by as much as 80%. Treatment with 1.5 L/ha of Dursban 4 before the first signs of damage could save the crop from months of feeding. This will increase the yield response considerably.
Crops identified at risk should be sprayed at the earliest signs of damage. Avoid periods of prolonged frost as pests are less active. Temperatures above 5°C give best results as that is when leatherjackets are near the soil surface. Spray 1.5 L/ha Dursban 4 in 200-1000 litres water.
LEATHERJACKET SPRAYS TAKEN OFF THE MARKET
Dow AgroSciences have received notification from the Irish regulatory authorities (PCD) concerning the current approval for chlorpyrifos-ethyl containing products (sold in the Republic of Ireland under the trade name Dursban 4). This notification outlines the timelines for the managed withdrawal of all chlorpyrifos-ethyl containing products and including dates for usage, storage and disposal of the product.
Below please find the timelines concerning the withdrawal of Dursban.
- Dursban 4 cannot be sold by distributors, wholesalers or retailers after the 31stMarch 2016.
- Growers cannot spray Dursban 4 after the 31st March 2016.
- Dursban 4 can be stored by wholesalers/retailers and growers up to and including the 30th September 2016 to facilitate product recovery by Whelehan Crop Protection.
- Dursban 4 that is one year old or less can be returned via the supply chain (retailers and wholesalers) if unopened and in good general condition. Dursban 4 that is older than one year and/or opened and/or considered in poor condition must be disposed of as hazardous waste at the expense of the person in possession of the product.
With the chemical option gone to control these pest we have to start looking at alternatives because these pests can devastate new leys if not controlled, but the risks can be avoided through effective cultivations and the use of brassica break crops.
The use of fast–establishing hybrid brassicas (such as Swift or Redstart) or Maris Kestrel kale have the added benefits of providing an additional source of high quality grazing, reducing the effect of any forage shortfalls between leys. This can be timed to provide late summer, autumn or even winter grazing for cattle or sheep.”
Ploughing and cultivating in summer, and sowing a break crop, will disrupt the life cycle of the crane fly and is known to reduce leatherjacket populations by 50%.
- Tags: Leatherjackets