The use of formulated microbes in agriculture has increased in the last years primarily driven by consumer preference for reduced use of chemical pesticides and grower need for new modes of action to control resistant pests. One barrier to adopting biological products, especially live microorganisms, is the low or inconsistent efficacy relative to conventional pesticides.
Evonik has shared research on biocompatible additives that can be used within formulations to increase the shelf life and enable liquid formulations in Agropages in 2019. In this article, Evonik will share field trial results to demonstrate the performance enhancement of biopesticides with tank-side adjuvants.
For a microbial product to be effective and economical, it is essential that the organism is deposited and retained on the intended target and survives to have the desired effect. The fate of spray droplets delivered from agriculture equipment is complicated and includes drift, bounce-off and run-off. Additives can be used to reduce these issues (Figure 1) but must not negatively affect microorganism viability. Research at Evonik has demonstrated that many of the BREAK-THRU® additives are biocompatible and provide excellent wetting, deposition, adhesion and retention for foliar applied biopesticides. BREAK-THRU® SP 133 is a biobased and biodegradable, OMRI and FIBL listed polyglycerol ester that can reduce drift and increases adhesion and retention of foliar applied products. BREAK-THRU® S 301 and BREAK-THRU® S 233 are biodegradable, patented and OMRI listed organomodified trisiloxanes. BREAK-THRU® S 301 is a super spreader and provides wetting of the upper and lower side of leaf surfaces, increases deposition, adhesion and stomatal flooding. BREAK-THRU® S 233 reduces surface tension and aids in deposition, adhesion and penetration. BREAK-THRU® S 255 and BREAK-THRU® OE 446 are organomodified polysiloxanes, which are soluble in both water and oils, providing rain fastness. BREAK-THRU® OE 446 is OMRI listed. For application of biologicals in soil, BREAK-THRU® S 301, BREAK-THRU® S 233, BREAK-THRU® S 255 and BREAK-THRU® OE 446 provide homogenous wetting and distribution of actives in the soil.
Figure 1. The possible fates of spray droplets for foliar applied crop protection products. This is a highly complex process affected by droplet size, droplet velocity, wettability of the plant surface, plant surface roughness and surface tension of the formulation. Once droplets leave the nozzle, smaller droplets are prone to drift, while larger droplets can land on the intended target and then either adhere or bounce off or run-off.
BREAK-THRU® additives were tank-mixed with biopesticides based on different microbial actives in several field trials, including: RootShield®AG by Bioworks (Trichoderma harzianium), DoubleNickel™ LC (Bacillus amyloliquefaciens) by Certis and Nemat® (Paecilomyes lilacinus) by Ballagro (Figures 2, 3 and 4). No phytotoxicity to the crop was observed in any of these trials.
Evonik conducted a strawberry field trial in North Carolina to test the influence of BREAK-THRU® additives on the performance of RootShield® AG against Botrytis and Pythium. The biopesticide RootShield® AG contains Trichoderma harzianium and is labeled for the control of Botrytis rot (gray mold) and Pythium spp. Botrytis is a common pest of strawberries in most years occurring in the field, during storage and transit, of strawberry fruit (Frank Louws, 2018). Pythium is a common disease in North Carolina and is the main reason growers fumigate in the southeastern US region. The disease reaches a peak at harvest with reductions of crop yield up to 20 to 40%. Early damage from Pythium causes plant stunting that is apparent within 1-2 months after planting (Louws and Cline, 2019). BREAK-THRU® S 233 and BREAK-THRU® S 255 with the high dose rate of RootShield® AG significantly reduced the incidence of Pythium (on roots at harvest) and Botrytis (on fruit at harvest) relative to the high rate of RootShield® AG alone. In addition, the root vigor at harvest was significantly increased relative to the high rate of RootShield® AG alone suggesting reduced nematode damage (Figure 2).
Figure 2. Disease incidences and root vigor from a field trial with RootShield® AG at two different dose rates with and without BREAK-THRU® additives. Field trial in North Carolina with strawberries in plots that were 1.8 m x 9.1 m in a randomized complete block design with four replicates. RootShield® AG was applied five times with drip irrigation. AUDPC is area under the disease progression curve. Pythium disease rating were conducted on roots at harvest on a scale from 0 to 10, with 0 indicating no disease present and 10 all roots with some Pythium disease present. Root vigor was rated on a scale from 0 to 10 scale with 10 being the best.
Evonik conducted a bell pepper field trial in North Carolina to test the influence of BREAK-THRU® additives on the performance of DoubleNickle™ (Bacillus amyloliquefaciens) against bacterial spot (Xanthomonas spp.). Bacterial spot is caused by four Gram-negative aerobic bacterial species (X. euvesicatoria, X. gardneri, X. perforans, and X. vesicatoria) and occurs worldwide. It causes leaf and fruit spots, which cause defoliation, sun-scalded fruit, and yield reduction. Management of the disease needs to be preventive because once a field becomes infested, bacterial spot is difficult to control, especially when the environment is conducive to the disease (Scherer et al., 2019). BREAK-THRU® S 301 numerically improved the incidence of bacterial leaf spot with the low rate of DoubleNickle™ relative to the active alone. BREAK-THRU® S 301 statistically reduced bacterial leaf spot incidence with the high rate of DoubleNickel™ relative to the active alone (Figure 3).
Figure 3. Disease incidence from a field trial with DoubleNickel™ at two different dose rates with and without BREAK-THRU additives. Field trial in North Carolina with bell pepper in plots that were 1.8 m x 2.7 m in a randomized complete block design with six replicates. DoubleNickle™ was foliar applied with a flat fan nozzle six times. Bacterial leaf spot was rated as a percentage of plants in each plot where the disease was present.
Evonik conducted a soybean field trial in Brazil in the Bandeirantes region of the State of Mato Grosso do Sul to test the BREAK-THRU® additives on the performance of Nemat® (Paecilomyes lilacinus) against nematodes (Pratylenchus zeae, Pratylenchus brachyurus, Helicotylenchus spp., Heterodra spp.). Nematodes cause plant damage but also create entry points for other pathogens, and act as vectors for viruses, bacteria and fungi. Control methods against nematodes have limited efficacy because they have difficult to penetrate cuticles, which enables the resistance to physical and chemical agents (Alcanfor et al. 2001). BREAK-THRU® SP 133, BREAK-THRU® S 301 and BREAK-THRU® OE 446 statistically improved plant height 30 days after the fifth application (DAE) suggesting nematodes were suppressed more in those treatments. BREAK-THRU® SP 133, BREAK-THRU® S 301 and BREAK-THRU® OE 446 applied at the low rate of the Nemat® statistically improved yield relative to the low rate of the active alone (Figure 4). Nematodes of all species were numerically and often significantly lower with the use of the three adjuvants than the active alone at the same rate (data not shown).
Figure 4. Growth and yield from a field trial with Nemat® at two different dose rates with and without BREAK-THRU® additives. Field trial in Brazil with soybean in plots that were 6 rows (0.45 m) x 5.0 m = 13.5 m2 in a randomized complete block design with four replicates. Nemat® was foliar applied with a flat fan nozzle six times.
Field trials with commercial biopesticides from three different companies demonstrates enhanced efficacy and no phytotoxicity with tankside addition of BREAK-THRU®. The commercial biopesticides were based on three different microbial species: Trichoderma harzianum, Bacillus amyloliquefaciens and Paecilomyces lilacinus. One limiting factor of adoption of microbial based products is low efficacy and Evonik BREAK-THRU® products can be part of the solution.
1. Alcanfor, DC, Inneco, R, Corales, JS, Mattos, SH. 2001. Controle de nematóides de galhas com produtos naturais. Horticultura Brasileira, v. 19.
2. Frank Louws. April 12, 2018. North Carolina Extension. Botrytis Fruit Rot / Gray Mold on Strawberry.
3. Frank Louws and Bill Cline. Aug 19, 2019. North Carolina Extension. Black Rot of Strawberry.
4. Scherer A, I Meadows, and Michelle Henson. 2019. https://content.ces.ncsu.edu/bacterial-spot-of-pepper-and-tomato. North Carolina Extension document.
This article will be published in AgroPages '2021 Biologicals Special' magazine to be published this June.
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