By: Katie Goldenhar & Amanda Tracey
Anthracnose in Ontario field peppers has changed in some regions. Anthracnose has historically been caused by the fungal pathogens Colletotrichum coccodes and C. dematium. These are endemic to Ontario and mainly infect ripe fruit (Figure 1). The disease has typically been controllable through use of fungicides applied on a 14-day interval starting after fruit set. Since 2020, a new anthracnose species, Colletotrichum scovillei, has been reported in several Ontario pepper fields and is causing severe crop loss. This new species is more aggressive and causes more severe disease symptoms when not controlled through earlier and more frequent fungicide applications.
Figure 1. Anthracnose caused by Colletotrichum coccodes and/or C. dematium.
This new pathogen, Colletotrichum scovillei, has been reported in South Carolina, Ohio, Brazil, China, Indonesia, Japan, Malaysia, South Korea, Taiwan and Thailand. Colletotrichum scovillei is part of the C. acutatum species complex, which can cause symptoms on immature fruit. Colletotrichum scovillei hosts are primarily within the Capsicum (pepper) family.
Colletotrichum species are known to have latent infection periods, where they infect flowers or developing fruit and do not show symptoms until weeks after. Colletotrichum scovillei can cause lesions on small, immature fruit as well as mature fruit. Samples of asymptomatic fruit were collected and fruit without any visible lesions (between 1-5 cm) were found to be already infected. Infected fruit can have one or more soft, sunken lesions covered with salmon-colored spore masses (Figure 2).
Figure 2. Anthracnose caused by Colletotrichum scovillei on banana, bell, and jalapeño peppers.
Biology and Spread
Colletotrichum species may overwinter on infected pepper fruit left in the field or on infected plant material at the end of the production season. Additionally, if crop debris remains on equipment, this may serve as an overwintering source for the disease. Pepper anthracnose usually starts out as a ‘hot spot’ in the field and then fans out directionally with the prevailing wind and driving rain. The spores of Colletotrichum species are spread through splashing water, rain, irrigation, driving winds and equipment/people. Hot weather along with afternoon and evening showers are ideal conditions for anthracnose development.
Cultural controls for anthracnose should include starting with clean transplants. In the field, scout regularly and remove infected plants, including plants surrounding the diseased one as soon as symptoms are seen. Rotating away from peppers, ideally a 3-year rotation, can help reduce inoculum pressure. Avoiding the use of overhead irrigation can help reduce the leaf wetness period needed for infection. Remaining plant debris should be mulched/mowed and then incorporated into the soil as soon as harvest is finished to allow for the soil microorganisms to break down the residue. Clean and disinfect equipment including irrigation hoses, baskets, tractors, trucks, wagons, etc. before storage.
Other management strategies could include host resistance.Based on a report from South Carolina, there are some varieties including ‘Roulette,’ ‘Red Ember,’ ‘Aiji Rico’ that show tolerance to the disease. None of these cultivars are suitable to Ontario production, however it does demonstrate that there may be some genetic resistance in commercial cultivars that could be incorporated into northern cultivars.
Fungicides applications targeting this new anthracnose need to start at flowering and continue on a 7-to-10-day interval until harvest. Make sure the sprayer is well calibrated and the fruit is receiving adequate coverage. Table 1 outlines the fungicides registered in Canada for pepper anthracnose. Group 11 fungicides (Cabrio and Quadris Top) are heavily relied on for anthracnose control. When using group 11 (QoI) fungicides, the Fungicide Resistance Action Committee (FRAC) recommends that in programs in which applications of QoI are made with both solo products and mixtures, the number of QoI containing applications should be no more than 50% of the total number of fungicides applied per season. For example, if you are using 10 applications to control anthracnose, a maximum of 5 applications containing a QoI (group 11) should be applied. Ideally, only 1/3 of the spray program should include a group 11 fungicide.
Table 1. Fungicides registered on field peppers for the 2023 field season for anthracnose. Note that captan is an Emergency Use Label for the 2023 season.
|Active ingredient (s)||Product(s)||FRAC Group||Maximum # of applications per year||Pre-Harvest Interval (days)||Expected Efficacy (0=none, 3=excellent)|
|captan||Captan 80 WSP||M||3||3||3|
|azoxystrobin + difenoconazole||Quadris Top||11 & 3||31||1||2-3|
|difenoconazole + pydiflumetofen||Miravis Duo||3 & 7||21||0||1|
|difenoconazole + benzovindiflupyr||Aprovia Top||3 & 7||41,2||1||3|
|fludioxinil + cyprodinil||Switch Button||12 & 9||3||0||3|
1only 4 applications of any difenoconazole containing product per year
2only 4 applications of any benzovindiflupyr containing product per year
In 2022, Dr. Cheryl Trueman and Kevin Dufton conducted a fungicide efficacy trial on the Ridgetown campus with funding from the Fresh Vegetable Growers of Ontario and The Pickle Station. All treatments started at flowering and continued on a 7-day schedule except for one program which continued on a 14-day interval. Figure 3 shows the efficacy of individual fungicides and 3 programs. Key learnings include: (i) multiple registered fungicides with different FRAC groups were effective on this new Colletotrichum species including Cabrio (group 11), Aprovia (group 7) and Switch (group 9 and 12); Captan (group M) was effective and should be considered for ongoing management for disease control and to reduce the risk of fungicide resistance in group 11 and 7 products – noting that this is currently an emergency use label; (iii) a program with Canadian fungicides was as effective as the positive standard of the US program which relied heavily on chlorothalonil; (iv) it is important for fungicide applications to start at the flowering stage and continue on a 7-day schedule
Figure 3. Efficacy of various fungicides and 3 programs for control of Colletotrichum scovillei
Table 2. An example fungicide program for control of pepper anthracnose for the season. Less or more than 12 applications may be needed, depending on field history, variety, weather, etc. Always consult product labels before use.
|Week||Product (FRAC group)|
|1 (first flowering)||Quadris Top (11+3)|
|2||Switch/Button (12 + 9)|
|3||Captan (M) + Cabrio (11)|
|4||Aprovia (7) OR Aprovia Top (7+3)|
|5||Switch/Button (12 + 9)|
|7||Aprovia (7) OR Aprovia Top (7+3)|
|8||Switch/Button (12 + 9)|
|9||Quadris Top (11 + 3)|
|12||Cabrio (11) + Captan (M)|
Pepper growers should keep anthracnose at the top of their mind as planning continues for the 2023 field season. Reach out to Amanda Tracey (firstname.lastname@example.org) or Katie Goldenhar (email@example.com) for any questions or concerns regarding this disease.
A.P. Keinath, S.H. Zardus, and V.B. Dubose, and G. Rennberger. (2021) Evaluation of All-America Selections peppers, 2020. Plant Disease Management Reports. Vol 15: V040.
Goldenhar, K., Tracey, A., Trueman, C. & Dufton, K. (2023). Evaluation of fungicides for control of anthracnose on peppers in Ontario, 2022. Plant Disease Management Reports. Vol 17:V050.
Toporek, S. M., & Keinath, A. P. (2021). First Report of Colletotrichum scovillei Causing Anthracnose Fruit Rot on Pepper in South Carolina, United States. Plant Disease, 105(4), 1222-1222. https://apsjournals.apsnet.org/doi/full/10.1094/PDIS-08-20-1656-PDN