Wireworm biology & management

Transcription

1 Wireworm biology & management Dr Bill Parker Director of Crops Research AHDB

2 What you need to consider. Biology Species & recognition in the field Life cycle Risk Assessment Field history & characteristics Soil sampling Pheromone trapping Bait trapping In-crop checks Control Variety choice & lifting date Chemical control Biocontrols

3 Biology

4 What are wireworms? Larvae of click beetles Primarily a grassland insect Long-life cycles (4 years) Ubiquitous across the UK, but can be localised hot-spots

5 Typical Wireworm Life cycle Duration species dependent but normally 4 years in the UK

6 Click beetle species in the UK Dominated by three Agriotes species Beetles easy to ID Larvae difficult Often occur in mixed populations it he same field One species usually dominates (UK geography) Population age structure usually varied Non-Agriotes species Can safely ignore for practical purposes Agriotes lineatus Agriotes sputator Agriotes obscurus

7 Recognising wireworm larvae Agriotes species Athous (and other) species Pointed tails (& pits ) Fork tails NB: they have the same front end!

8 Risk assessment

9 Risk assessment timeline You need to be thinking months ahead of planting Risk assessment window Potato crop <<<<<<<<<<<<<<< 24 month period >>>>>>>>>>>>>

10 Field history & characteristics Field in grass for > 4 years or significant grass weed issue Not all long-term grass fields are infested (c %) Minimal or no cultivation in recent years Soil disturbance, particularly ploughing, reduces populations History of wireworms or wireworm damage in the locality Could indicate a local hot-spot Other things you could consider Soil type Organic matter content Field aspect

11 Long-term field experiment (Cambs ) 250,000 A - grass 200,000 Wireworm population (000/ha) 150, ,000 B - winter wheat (normal) C- winter wheat (minimum) R² = R² = ,000 R² = Oct-06 Jan-07 Apr-07 Aug-07 Nov-07 Feb-08 Jun-08 Sep-08 Dec-08 Populations tended to increase under grass & min till wheat plots Data source: SA LINK Project LK 0982

12 Other field characteristics (based on sites in Devon) Manure Quantity ph % Stones Organic Fertiliser Potassium A. lineatus 5cm Shear A. sputator Yrs since conversion OM% Recent years in grass Wireworms A. obscurus Grass Duration Soil Moisture Data source: Helen Hicks, PhD Thesis, University of Plymouth, 2009

13 Risk assessment timeline Risk assessment window Potato crop Site characteristics

14 Soil sampling the traditional approach Developed in 1940s OK for high populations Very unreliable for low populations Can do this at any time Best to do early autumn or early spring There is a lot of soil out there! Big sampling issue Ideally needs lab processing Just go out with a spade? A presence/absence test Poor correlation between what you find and subsequent damage levels

15 Relationship between soil population assessment & damage Data source: Parker & Howard, Agricultural and Forest Entomology (2001) 3, 85 98

16 Risk assessment timeline Risk assessment window Potato crop Site characteristics Soil sampling

17 Pheromone trapping Has some serious advantages Much more sensitive than soil sampling can detect low populations Much easier to do - very little labour Traps are commercially available But also needs care: Remember traps catch adults Need to trap for all 3 main species Trap location & duration of trapping critical Can only be used as an EARLY WARNING TOOL Should be backed up by other methods

18 Seasonal pheromone catch profile Llanafan (2000) Season long trapping is NOT the best way of doing it Data source: Parker & Howard, Agricultural and Forest Entomology (2001) 3, 85 98

19 Traps catch beetles quickly.. For various reasons short trapping periods (3 4 days) are best Data source: SA LINK Project LK 0982

20 Relationship between pheromone trap catch and residual wireworm population ( ) Residual wireworm population ('000/ha) y = x x R 2 = 53.5% Total summer beetle trap catch (all species)

21 Risk assessment timeline Risk assessment window Potato crop Site characteristics Pheromones Soil sampling

22 Bait trapping An alternative to soil sampling Wireworms are attracted to the CO 2 released by germinating grain Various ways of doing it Best done in early spring Easy to make home-made traps Points to watch Soil temperatures should ideally be above 10 o C Count wireworms in traps & surrounding soil Very localised result presence/absence test only

23 Complete risk assessment timeline Risk assessment window Potato crop Site characteristics In crop checks Pheromones Soil sampling Baits Use a range of methods to build up a risk picture

24 Control

25 Effect of harvest date on damage and variety choice? Data source: Parker & Howard, Agricultural and Forest Entomology (2001) 3, 85 98

26 Chemical control The only currently approved treatments are: Mocap (ethoprophos) & Nemathorin (fosthiazate) These reduce damage only NB: proper incorporation is critical X X X X Data source: Parker & Howard, Agricultural and Forest Entomology (2001) 3, 85 98

27 Biofumigation with mustards

28 Other biocontrols? Plant parasitic nematodes Generally not effective Biopesticides Metarhizium anisopliae, could emerge in the longer-term Trap/distraction cropping e.g. inter-cropping with wheat, some effect in specific circumstances

29 Sustainable Long-Term Management of Wireworm on Potato (Sustainable Arable LINK Project LK 0982) Babraham Farms

30 Thank you