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• availability (some have been withdrawn)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