Pest updates

Recent research on control of soil dwelling pests 2008

PRG 2008 Pest control

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• PCN Major pest slugs

Tandonia/ spp (keeled slugs) Arion spp (roundback slugs) Deroceras reticulatum (grey field )

Photograph courtesy of Bayer Keeled slugs Very important in potatoes: large <7cm, predominantly subterranean, feed on tubers.

Keel (characteristic mark)

Tandonia budapestensis (also T. sowerbyi, Milax gagates) Photographs courtesy of Bayer Efficacy of metaldehyde at different temperatures

Slug mortality

Species 6 °C 8 °C 10 °C 16 °C 20 °C 22 °C 25 °C % % % % % % % Deroceras reticulatum 0 15 15 40 80 100 100 Arion hortensis 0 10 20 50 50 - - Milax sowerbyi 0 10 20 20 20 - -

Dora Godan, Pest Slugs and Snails, Springer Verlag, Berlin, Heidelberg, New York Slug feeding behaviour

Track of D. reticulatum (red line) during the course of the test.

(Slug starved for 48 hours, observation period = 10 hours)

green dots = Ferramol blue dots = Metarex

A = Start position of the slug; E = End position of the slug X = resting position

The test slug was placed in an enclosure, half way between a group of “Ferramol” (ferrous phosphate) pellets and a group of “Metarex” (metaldehyde) pellets. The slug’s movements were tracked for the next 10 hours and it was observed feeding on the “Ferramol” but not on the “Metarex” pellets. “Sluggo” (Ferrous phosphate)

“Sluggo” The pellet size has now been reduced to give 50 baiting points per m2 at an application rate of 6 kg ha-1 Cost £2.00 – £2.50 per kg (depending upon order size) Fresh bait After 25 mm rain (Correct at January 2008) “Garland” is a garlic- “Garland”: slugs based product

Application of Garland for control of slugs Slugs (grey field slug) were 120 collected from soil and placed in perspex 100 containers (22cm length, 11cm width, 8cm deep). 80 Three slugs were placed in Mean +/- SE each of the containers and

60 covered in very coarse soil. There were three replicates Dead slugs (%) per treatment. 50mls of 40 each of the following four treatments was then applied 20 as a drench.

No dead slugs 1.Water (control) 0 2.S Box 15a (0.5%) Untreated S box 15a Adjuvant Garland 3.Garland (0.5%) Treatment 4.Adjuvant (0.25%) Assessments were made twenty-four hours after treatment application and no further change was Stockbridge Technology found 48 hours after application. Centre (STC), 2006 “Garland”: wireworms

Control of wireworms with "Garland" in pot experiments SAC, 2006 5 wireworms were 6 placed in each pot with a sugar beet seedling (3 5 P < 0.01 P < 0.02 leaves). Mean +/- SE Garland treatment (2.5 4 ml/litre (0.0025%)) was watered into one of each 3 pair of pots (100ml into approx 100g soil).

Root damage (0 - 5) 2 Plants were watered

Number of live wireworms or every 2 days to keep 1 soil moist..

Untreated Wireworms were 0 Garland Number Damage extracted from pots 4 weeks later and assessed for survival and damage to sugar beet (0-5). “Garland”: PCN (Experiment 1) 22 Experiment by SAC PCN cysts (G. rostochiensis) and 20 treatment products were

18 mixed in soil and placed in pots. “Vydate” was 16 applied at equivalent to the commercial rate. 14 Control Garland At one month intervals a Terpene 12 Plant Extract batch of pots from each Garland Granules Tyratech Granules treatment was harvested 10 GLD Vydate for assessment of live

Mean Mean No. of PCN eggs/g soil (± SE)

8 eggs. No potatoes were grown 6 in the soil, to represent treatment between 4 0 1 2 3 crops. Months exposed to treatments Differences between treatments were significant at 2 and 3 months. “Garland” liquid significantly reduced PCN populations compared with the control and “Vydate” treatments at 2 months and c.f. all treatments at 3 months. “Garland”: PCN (Experiment 2)

Experiment by SAC PCN cysts (G. rostochiensis) 25 were mixed in soil and placed in large pots. Granular treatments were mixed in the

20 soil and liquids applied a a soil drench 5 DAP “Vydate” was applied at equivalent to the commercial rate. 15 Garland Granules Garland Liquid Garland Liquid post planting Plant Extract One seed tuber of cv. “Cara” Plant Extract post planting

Mean Mean Plant Height (cm) Tyratech Granules was planted in each pot. GLD GLD post planting Vydate 10 Control with PCN Potatoes were grown for 120 Control with no PCN days to allow the PCN life cycle to be completed. Pots were then harvested and yield 5 and PCN population assessed.

10 20 30 40 50 60 70 Field trials are Days since planting planned for 2008 “Garland”: PCN (Experiment 2)

120 Experiment by SAC

100

Mean Yield (g) per plant Mean (g) Yield (± SE)

80 Garl. Gr. Garl. Liq. Garl. L. post Pl. Ext. Pl. Ext. post Tyra GLD GLD post Vydate Cont+PCNCont.noPCN Treatment

“Garland” treatments resulted in significantly higher yields than the Control + PCN (P < 0.05) but lower yields than the “Vydate” treatment (P < 0.05). “Garland”: PCN (Experiment 2)

Experiment by SAC 14

12

10

8

6

4

2

Mean Mean Multiplication of PCN (Pf/Pi) (±SE)

0 Garl. Gr. Garl. Liq. Garl. L. post Pl. Ext. Pl. Ext. post Tyra GLD GLD post Vydate Cont+PCN Treatment

Application of “Garland” liquid and granules resulted in similar multiplication rates to that in the “Vydate” treatment. “Garland”: spraing

• Scottish Agronomy included “Garland” in a field experiment on spraing and transmission of TRV in 2006. • There was no affect on the numbers of Trichodorus or Longidorus individuals recorded. • Although there appeared to be some reduction in spraing infection (0.8 % c.f. 2.3 % in untreated plots), TRV was found in only two of the four replicates and the treatment differences were not significant. “Garland”: FLN

• In a pot experiment by SAC, “Garland” reduced populations of Longidorus, Trichodorus and Pratylenchus (P < 0.001). • Root growth of sugar beet seedlings was reduced by nematodes, compared with a no nematode control. • “Garland” did not result in reduced root damage • Leaf growth increased with “Garland”, compared with a nematode/no application control but was still lower than in the no nematode control. “Garland”: summary

• Results from initial experiments are interesting. • Slug control appears effective but application costs are £20 - £30 ha-1 for application of 1.5 – 2 litres ha-1. • SAC researchers suggest affects on PCN could be due to a vapour action or fumigant effect of the ingredients or break down products. • “Garland” appears to affect PCN eggs in the cysts, rather than nematode juveniles, as the yield protectant effect is less than that of “Vydate”. • “Garland” could offer an alternative to “Telone” with greater ease of management than a crop of Solanum sisymbriifolium. “Telone”: revoked

• (a) Suspended approval from 20 March 2008 for the advertisement, sale and supply by any persons of the pesticide product listed in the schedule.

• (b) Suspended approval from 20 March 2009 for the storage and use by any persons of the pesticide product listed in the schedule.

• Date of issue: (a) 7 December 2007 • Date of suspension: (b) 20 March 2008 • Date of expiry (c) 20 March 2009 • PSD 7 December 2007 PCN: tolerance

• Tolerance of a potato cultivar to PCN is a measurement of its yield response to PCN infestation. • A series of experiments has been performed by GrowScience to examine tolerance of some popular or new cultivars, by comparing yield in untreated and “Vydate” treated plots. • Experiments were performed in two seasons – 2005: 14 cvs at two sites • Holbeach (Lincolnshire), fine sandy silt loam, G. pallida population of 20-22 eggs/g soil, unirrigated • Trunch (Norfolk), sandy loam, G. pallida population of 16-19 eggs/g soil, irrigated. – 2006: 12 cvs at two sites • Spalding (Lincs), fine sandy silt loam, G. rostochiensis population of 17-19 eggs/g soil, unirrigated • Cawston (Norfolk), sandy loam, G. pallida population of 11-14 eggs/g soil, irrigated. • Seven cultivars were grown in all trials. Tolerance of potato cultivars to PCN Keer, GrowScience, 2007 Marfona Maris Peer Sante Lady Rosetta Emerald Estima Vivaldi Pentland Dell King Edward Increasing Lady Claire tolerance Hermes Saturna a = unirrigated Desiree site Sovereign b = irrigated Melody site Maris Piper Cara 2005 a Everest 2005 b Markies 2006 a 2006 b 0 20 40 60 80 100 120 140 160 180 200 220 Mean Relative yield (% untreated) PCN: tolerance

• In these experiments, the greatest tolerance (i.e. least response to nematostat) was shown by: – Markies – Everest – Cara – Maris Piper • The least tolerance was shown by – Marfona – Maris Peer • Mean yield responses to nematostat were: – 2005, unirrigated site = 31 % – 2005, irrigated site = 32 % – 2006, unirrigated site = 18 % – 2006, irrigated site = 15 % Free living nematodes

Free living nematodes feeding on the roots of young potato plants can cause roots to proliferate at the expense of shoot growth. Infested plants may therefore be stunted.

Damage may be Root dry weight (g) incurred at relatively low FLN populations (e.g. 50 per 250 g soil)and can easily be 100 nematodes overlooked per 250 g soil

Evans, SAC, 2007 Nematode population in 250 g soil Free living nematodes

• FLN can cause feeding damage in addition to transmission of tobacco rattle virus (TRV) causing spraing. • Tests are available for FLN populations and for transmission of spraing by FLN – not all populations carry the virus. • Where nematostats for control of FLN are recommended for application in furrow, this provides a higher concentration near young roots than does the overall application for control of PCN.