2nd TSB project meetingBio-control of grain storage

insect pests Bryony Taylor, Dave Moore, Emma Thompson, Steve Edgington

Aims of work

• Create a formulation that:• is compatible with existing spray

equipment• produces a droplet range

appropriate for a contact biopesticide

• has an even coverage.• The undiluted formulation will:

• need to be stored without affecting the viability of the conidia

• have minimal separation or sedimentation

Aims of work

• If the formulation is to be used with a knapsack sprayer:

• it will need to suspend readily in a water based tank mix

• produce no clogging of the nozzle.

• If a ULV sprayer is considered the formulation will need to be:• oil based• compatible with ULV sprayer

technology.

Considerations-Current application technology used in grain stores• 61% of farms use fabric treatments only to treat their grain stores and a further 34% use both fabric and grain treatments

• 56% of fabric treatments were applied using spray technology which included knapsack and hand held sprayers

• Other methodologies include fogging, dusting (Pirimiphos methyl and silica), mist and smoke

Formulation issues

• Conidia are hydrophobic therefore need co-formulants to disperse in water• Bb conidia lose viability quickly when stored in a water based formulation• Emulsifiers need to be added to break the surface tension• Some have been shown to affect conidial viability• Careful screening needs to be carried out

Co-formulants

• Co-formulants to be tested were carefully considered and chosen on the basis of:

• suitability• previous research• listing in the adjuvant

section of the UK pesticide guide 2010

• availability (some have been withdrawn)

Q: Are these co-formulants toxic to Bb?

Dispersents:

Sample Contains Action Bentone SD 1 Organically modified clay mineral (<2%

Quartz) Dispersant/Anti compaction

Bentone SD 2 Organically modified clay mineral (<2% Quartz)

Dispersant/Anti compaction

Q: Are these co-formulants toxic to Bb?

Sample Description Purpose Label recommended amount

Codacide 95% Rapeseed oil, plus 5% emulsifiers

Emulsifiable oil, medium surfactant

Min 2.5L/ha

Addit Emulsifiable vegetable oil Mixture of vegetable oil, emulsifier and wetting agent

(250ml in 100L H2O)

NuFarm Cropoil

99% highly refined mineral oil

Mineral oil, low surfactant content

3.125% max, recommend 2L/200L/ha or amenity land

NuFarm Output

60% mineral/40% w/w surfactants

Mineral oil/ high surfactant content

Max 3.75L per 1000L of total spray liquid

Newman Cropspray 11E

An emulsifiable concentrate formulation containing 99% highly refined paraffinic oil

Emulsifiable oil, low surfactant content?

Max 2.5% spray

Q: Are these co-formulants toxic to Bb?

Sample Contains Purpose Amount in 100ml Libsorb Alkyl alcohol ethoxylate Wetter Not available Silwet L77 80% polyalkylene oxide modified

heptamethyltrisiloxane, max 20% alloxypolyethylene gylcol methyl esther.

Wetter

Not above 5%. Recommended 0.025-0.25%

Break-Thru S 240

Polyether-modified polysiloxane (Oxirane, methyl-, polymer with oxirane, mono[3-[1,3,3,3-tetramethyl-1-[(trimethylsilyl)oxy]disiloxanyl]propyl] ether

Non-ionic spreading and a penetration aid

Pesticides with contact action: 125 ml/ha to improve wetting and spreading

200-300ml/ha arable crops

Concentration

● For contact biopesticides it is recommended that 50-70 drops per cm2

● Normal amount of spray to apply to a grainstore is 5l/100m2 which is also the recommended amount on the Actellic 900 label

● The FAO recommend this may be increased on more porous surfaces to 10-20l/100m2 or reduced when applied to metalwork.

● We aimed to test formulations at these concentrations

AIM: to deliver a dose of both 5 x 109 conidia per m2 and 2.5 x 1010 conidia per m2

Concentration

• If the target application rate is 10L per 100m2 for a porous surface, then we will need to apply:

1L for 10m2

100ml for 1m2. • AIM: 5 x 109 and 2.5 x 1010 per m2 • Need to suspend these amounts of conidia in co-formulant and then make up to 100ml using H2O

Concentration

• Spores per gram were calculated from a previously mass produced lot of IMI 389521 (received July 2008).

• The average spores per gram were calculated to be 6.7 x 1010

• Recent trials have shown that 75% entostat:25% conidia has been effective in trials using the dust formulation, thus we will test at these levels initially.

Experiment 1

• Codacide• Addit• Cropoil• Output• Cropspray 11E• Silwet L77

Amount of co-formulant to mix in the balance of 100ml water

Weight of conidia for 5 x 109 per m2

Entostat weight

1ml (1%) 0.075g 0.225g

Results

All adjuvants mixed well after 1 minute on the whirlimixer

Results

1 ml paste was mixed with 99ml water to see if a stable emulsion could be formed

Results

Codacide suspended easily forming a consistent emulsion

Addit was slightly more difficult to suspend and had ~10ml foam

Codacide Addit

Results

Cropoil suspended well, but residue left on glass

Output adhered to the original tube but with vigorous shaking suspended. It dispersed well, but had ~8ml of foam

OutputCropoil

Results

Cropspray 11E did not suspend in water

Silwet L77 suspended easily. Roughly 10ml foaming

Silwet L77Cropspray 11E

After 16h

Codacide:

Yellow scum on top, large particles settled at the bottom of the tube

After 16h

Addit:

Foam reduced however layer of white scum at top and settling powder at the bottom

After 16h

Cropoil:

Little sedimentation at bottom, however layer at top observed

After 16h

Output:

Settling observed, little floating matter

After 16h

Silwet L77:

Foam subsided, settling of powder at the bottom

Experiment 2: Viability study

• 0.1 g conidia and 0.3g entostat mixed with 8 co-formulants• Conidia only and conidia+entostat controls• Kept at 5˚C and 25 ˚C• Viability regularly checked

Viability Tests 5˚C

Viability Tests 25˚C

Conclusion

● Viability lower than previous batches (problem in transport?)

● Output co-formulant can be discounted● Variability may be due to large amount on

entostat/particles on plates● Continue and replicate studies

Observations• During viability study, at both 5˚C and 25˚C ; all liquid formulations re-suspended easily, even after 28 days of storage

• All formulations showed settling of a fine powder at the bottom of tube; apart from Silwet L77

• However, there was a gelatinous ‘blob’ in the middle of the 5˚C tube

Settling

Experiment 3● Codacide● Addit● Cropoil● Silwet L77● *Break-thru S 240* (new co-formulant)

● 0.373g conidia + 1.193g of entostat (1:3)

● 1ml of adjuvant added initially, then a further 1ml

● Water added to tube and inverted 10,20,30 times and 10sec, 20sec and 1min on the whirlimixer

● Those emulsifying were added to 98ml water

2.5 x 1010 formulations

Results

• 1 ml of liquid was not enough to form a paste• 2ml enough to form paste• All paste were very viscous

• Codacide:• Was not able to mix into water• Waxy floating particles present

• Addit:• Was difficult to form an emulsion after inversions/using whirlimixer• Eventual emulsion formed, however large particles present• In 98ml water, 10-20ml foam

• Cropoil• Was not able to mix into water• A waxy mat formed on top of the water

• Silwet L77:• Formed emulsion easily, although some paste stuck to side of tube• Dispersed well in water with 20-30ml foam

• Break thru S 240:• Mixed easily with water, with a little sticking to sides of tube• In 98ml water, after 10 inversions 30-40ml foam

Future experiments

● Reduce settling with addition of varying levels of clay

● Repeat viability experiments and include Breakthru

● Look at particle sizing of promising formulations

● Investigate how well formulations spray

● AOB:

● Project student started this week● Molecular characterisation of isolate

underway

Thank You