From ONvegetables
By: Janice LeBoeuf, Vegetable Crops Specialist, OMAFRA
Field peppers are susceptible to a number of pests and disorders that can lead to fruit rots. This can make managing rots quite difficult. This article outlines some key points to understand about the variety of pests, disorders, and contributing factors that lead to fruit rots.
Bacterial soft rot
- Caused by Pectobacterium (formerly known as Erwinia) and other bacteria
- Can cause pre- and post-harvest rots
- Pathogen cannot penetrate intact outer fruit surfaces, but can attack the fruit stem, the calyx, injured fruit tissue, or internal fruit tissue
- Favoured by warm, moist conditions
- High nitrogen fertilization may increase susceptibility
- These pathogens are ubiquitous in the field, but can be spread very effectively on worker hands, tools, harvest containers, packing line equipment, dump tanks, and through insect movement and feeding
- Try to minimize tissue injury which can allow easy entry to the soft-rot bacteria; this includes injury by insects, sunscald, blossom-end rot, growth cracks, other diseases, hail, soil abrasion, field operations, or other causes
- Post-harvest decay much more likely if fruit is wet when picked
- Dry the harvested fruit by a combination of air drying and cooling
- Cool before shipping or storage; maintain cold chain to avoid condensation
Anthracnose
- Caused by several Colletotrichum species of fungi
- Develops over a wide temperature range
- Fruit are more susceptible as they ripen
- Produces microsclerotia; rotating out of solanaceous crops for at least three years reduces risk
- Fungicides available (Table 1); must be used preventatively (fruit of any size can be infected)
| TABLE 1: ANTHRACNOSE FUNGICIDES FOR FIELD PEPPER | |||
|---|---|---|---|
| Group Name (Group #)
|
Trade Name (Common Name) |
Rate | Notes |
| DMI (group 3) |
Inspire (difenoconazole) |
512 mL/ha (207 mL/ac)
|
PHI: 0 days. Do not make more than 2 sequential applications of any group 3 fungicides. 12-hr REI. 📅 🌱 |
| SDHI (group 7) |
Aprovia (benzovindiflupyr) |
500–750 mL/ha (202–304 mL/ac)
|
PHI: 1 day. Do not make sequential applications of any group 7 fungicides. 12-hr REI. 📅 🌱 |
| AP/PP (group 9/12) |
Switch 62.5 WG (cyprodinil/ fludioxonil) |
775–975 g/ha (314–395 g/ac)
|
PHI: 0 days. Do not make more than 2 sequential applications of any group 9 or group 12 fungicides. 12-hr REI. 📅 🌱 |
| QoI (group 11) |
Cabrio EG (pyraclostrobin) |
560–840 g/ha (227-340 g/ac)
|
PHI: 0 days. Do not make sequential applications of any group 11 fungicides. 12-hr REI. 🌱 |
| QoI/DMI (group 11/3) |
Quadris Top (azoxystrobin/ difenoconazole) |
625 mL/ha (253 mL/ac)
|
PHI: 1 day. Do not apply until 21 days after transplanting. Do not make sequential applications of any group 11 or group 3 fungicides. 12-hr REI. 📅 🌱 |
| inorganic (group M1) |
Copper 53W (copper sulphate) |
4 kg/ha (1.6 kg/ac)
|
PHI: 2 days. 48-hr REI. |
| 📅 = Do not use on areas treated with product the previous season | |||
| 🌱 = See label for recropping or rotational crop restrictions | |||
| PHI = pre-harvest interval; REI = restricted entry interval | |||
Phytophthora
- Caused by Phytophthora capsici (oomycete)
- Causes Phytophthora root and crown rot; also fruit rots
- Inoculum survives in soil for many years
- High rainfall/irrigation, high humidity promote development; often shows up first in low/wetter areas of field and spreads from there
Fruit may be infected through the stem or through the fruit skin (often at the ends of the fruit where water and spores may accumulate or where fruit touches the soil)- Persists in the soil; rotating out of host crops for at least three years may reduce risk (longer is better)
- Difficult to manage with fungicides (Tables 2a and 2b); some only affect foliar phase, not root/crown infections
- Some varieties show limited tolerance
- Can spread in water and through soil movement (eg. field traffic); can contaminate surface water irrigation sources
| TABLE 2A: PHYTOPHTHORA FUNGICIDES FOR FIELD PEPPER | |||
|---|---|---|---|
| Group Name (Group #) |
Trade Name (Common Name)
|
Rate | Notes |
| phosphonate (group 33) |
Confine Extra (mono- and di-potassium salts of phosphorous acid)
|
5-10 L/ha (2-4 L/ac) |
Foliar blight. Suppression. PHI: 1 day. May be applied as foliar sprays or through sprinkler chemigation. See label for tank-mix and crop tolerance information. |
| CAA (group 40) |
Forum (dimethomorph) |
450 g/ha (182 g/ac) |
Suppression. PHI: 0 days. Do not make sequential applications of any group 40 fungicides. 12-hr REI. 🌱
|
| CAA + piperidinyl-thiazole-isoxazolines (group 40 + U15) | Orondis Ultra A + Orondis Ultra B (mandipropamid + oxathiapiprolin) |
600 mL/ha (243 mL/ha) + 175-350 mL/ha (71-142 mL/ac)
|
Foliar blight. Suppression. PHI: 1 day. Do not make sequential applications of any group 40 or group U15 fungicide. Do not apply foliar applications in the same season as a soil application. 12-hr REI. 📅 🌱 |
| benzamide (group 43) |
Presidio (fluopicolide) |
220-292 mL/ha (89-118 mL/ac)
|
Suppression. PHI: 2 days. Tank mix with Revus when targetting phytophthora blight. Do not make more than 2 sequential applications of any group 43 fungicides.12-hr REI. 📅 🌱 |
| microbial (group 44) |
Serenade SOIL (Bacillus subtilis) |
2.7-14 L/ha (1.1-5.7 L/ac)
|
Suppression. PHI: 0 days. Soil application. See label for application details. |
| QxI/CAA (group 45/40) |
Zampro (ametoctradin/ dimethomorph) |
1 L/ha (0.4 L/ac)
|
Suppression. PHI: 4 days.Use of a spreading/ penetrating adjuvant may improve performance. Do not make sequential applications of any group 40 or group 45 fungicides. 12-hr REI. 🌱 |
| 📅 = Do not use on areas treated with product the previous season | |||
| 🌱 = See label for recropping or rotational crop restrictions | |||
| PHI = pre-harvest interval; REI = restricted entry interval | |||
Several preventative treatments are registered for pepper seedling production in the greenhouse, as well.
| TABLE 2B: PHYTOPHTHORA FUNGICIDES FOR PEPPER SEEDLINGS (GREENHOUSE) | |||
|---|---|---|---|
| Group Name (Group #) | Trade Name (Common Name) |
Rate | Notes |
| CAA (group 40) |
Revus (mandi-propamid) |
600 mL/ha (243 mL/ac) |
Suppression. Make one application as a drench, immediately before transplanting. Do not make sequential applications of any group 40 fungicides. 12-hr REI.
|
| microbial (group 44) |
Double Nickel 55 (Bacillus amylolique-faciens) |
25–250 g in 100 L of water. See label for application details. | Phytopthora (soil). Partial suppression. Make preventative applications to transplants in the greenhouse before transplanting. Follow up applications of 100–500 g/ha (40–202 g/acre) can be made by drip irrigation or directed spray at 2–4 week intervals after transplanting. Re-entry permitted once spray deposit has dried.
|
| not classified (group NC) |
Mycostop (Streptomyces) |
Refer to label for rates and applica- tion details. | Suppression. Drench or soil spray application. Apply first spray after emergence using lower rate.
|
| REI = restricted entry interval | |||
Bacterial spot
- Caused by a number of Xanthomonas species
- Seedborne; limited survival on plant debris in soil
- Can produce lesions on foliage and fruit
- Fruit lesions can be invaded by secondary rot pathogens
- Foliar lesions can defoliate the plant; exposed fruit are more susceptible to sunscald and then secondary rots
- Potential for transmission during transplanting operations: clean and disinfect transplant plug trailers, transplanting equipment regularly; workers should sanitize hands or change gloves often
- Moisture, high humidity, and warm temperatures favour the disease; windy rainstorms can wound plant and move bacteria around, resulting in more severe outbreak
- Rotate away from susceptible crops (tomato, pepper); control solanaceous weeds
- Some varieties have tolerance to certain races of the pathogen
- Bactericides are available (Table 3), but may not result in an economical benefit
| TABLE 3: BACTERIAL SPOT BACTERICIDES FOR FIELD PEPPER | |||
|---|---|---|---|
| Group Name (Group #) |
Trade Name (Common Name) |
Rate | Notes |
| hexopyranosyl antibiotic (group 24) |
Kasumin 2L (kasugamycin) |
0.5 L in 100 L of water applied in sufficient volume to ensure thorough coverage. See label for max. rates. | Suppression. PHI: 1 day. May be tank-mixed with Kocide 2000. Do not make more than 2 sequential applications. 12-hr REI.
|
| microbial (group 44) |
Serenade Opti (Bacillus subtilis) |
0.6–1.7 kg/ha (0.24–0.69 kg/ac) |
Suppression. PHI: 0 days. Apply at 7-10 day intervals. Rotate with bactericides with a different mode of action.
|
| inorganic (group M1) |
Coppercide WP (copper hydroxide)
|
2.25–3.25 kg/ha (0.91–1.32 kg/ac) |
PHI: 1 day. Apply at 7–14 day intervals. |
| inorganic (group M1) |
Kocide 2000 (copper hydroxide)
|
2.52–3.2 kg/ha (1–1.3 kg/ac) |
PHI: 2 days. Apply at 7–10-day intervals. 48-hr REI. |
| inorganic (group M1) |
Parasol WG (copper hydroxide)
|
2.25–3.25 kg/ha (0.91–1.32 kg/ac) |
PHI: 2 days. Apply at 7–14-day intervals. 48-hr REI. |
| inorganic (group M1) |
Cueva (copper octanoate)
|
0.5%–2% (v/v) solution, applied in 470–940 L of solution/ha (190–380 L of solution/ac) | PHI: 1 day.Apply at 5-10 day intervals. 4-hr REI. |
| PHI = pre-harvest interval; REI = restricted entry interval | |||
Blossom-end rot
- A very familiar disorder of peppers – shows up on blossom-end or side-wall of the fruit
- Thought to be triggered when stressful (eg. dry, hot) growing conditions occur after a period of rapid growth
- Fluctuations in water supply or problems that interfere with water and nutrient uptake during periods of high demand can be triggers (root pruning by field equipment, other damage to root, compacted soil)
- Over-application of nitrogen has been associated with blossom-end rot
- Tissue damaged by blossom-end rot is susceptible to invasion by secondary rot organisms
- Applying calcium is not generally effective; need to address underlying issues with water and nutrient uptake
- Adequately schedule irrigation, if available
- Certain varieties may be more susceptible; learn from experience or from seed rep
Sunscald
- Occurs when pepper fruit are exposed to intense sunlight; especially if fruit was previously shaded by foliage
- Can resemble blossom-end rot, but sunscald will only be found on side of fruit facing the sun most directly
- Damaged tissue can be invaded by secondary rot organisms
- Some varieties may have better foliage cover and more consistent shading of fruit
- Ensure good growing conditions (adequate moisture, nutrients; address soil compaction issues)
- Prevent diseases that could cause defoliation, wilting, or stunting of plant
And more
The list of problems that can lead to pepper fruit rot is a long one. White mold and botrytis (gray mold) can add more fruit rot challenges in a wet season. Insects can open up wounds in the 
pepper fruit to allow rots to invade, but they can also spread the fungi and bacteria that cause rots as they feed, lay eggs, and move into and between fruit. When you picture a soft-rotted fruit, it’s easy to see that even insects that do not feed on pepper could move the soft rot bacteria around very easily as they wander through the field.
The pest insects will be discussed in a future article, but they include:
- European corn borer
- Stink bug (native and brown marmorated)
- Tarnished plant bug
- Pepper maggot
- Pepper weevil
- and others
Other causes of wounds in the pepper fruit include:
- Hail
- Growth cracks
- Natural openings under the cap
- Mechanical damage – picking, pruning
- Soil abrasion
Weed control is also important in reducing pepper rots (and other pepper pests) as weeds can be alternative hosts of pepper pathogens and insects.
Pepper rots love heat and moisture. You can’t change rainfall patterns, but ensure you grow peppers in well-drained fields — avoid those low spots that hold moisture too long. If irrigating, schedule carefully. Make sure you are monitoring soil moisture effectively — there’s soil variability in every irrigation zone. Monitor closely for leaks. A wet spot in the field can get problems started — and they spread from there.
It’s clear that there are no easy solutions when it comes to managing pepper rots. You really need to be on top of everything and hope your luck holds out.
For more articles visit: http://onvegetables.com
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