Causes of Defective Beans
After dry bean harvest, producers may wonder what caused beans to become injured or discoloured. It is typically easier to observe the plants throughout the season and identify disease or insect injury on pods to better understand the resulting injury on the beans within the pods. However, bean injury may have occurred closer to harvest and may be caused by environmental factors. It may not be possible to identify the cause of defective beans (pick) after harvest, but the images below may provide some guidance.
Anthracnose
This disease has been observed in numerous fields this season, after nearly a decade of little to no observed anthracnose. Most of the popular dry bean varieties this season are not resistant to anthracnose, and weather conditions have been ideal for disease development. Growing certified seed produced in arid regions significantly decreases the incidence of anthracnose but does not guarantee protection. Planting farm-saved seed has a high risk of anthracnose infection. Fungicides that provide protection against anthracnose are commonly used in Ontario, but disease may have developed later in the season. Samples can be tested for fungicide resistance. Pod lesions are sunken and are ringed in black. Beans within injured pods may have red-brown and black discolouration in a small area or covering much of the bean (Figure 1).
Figure 1. Anthracnose symptoms on white bean pods and seeds.
Bacterial Blight
Blight, whether it is Common Bacterial Blight or Bacterial Brown Spot, is relatively easy to notice on plant leaves and pods during the growing season. Leaf lesions are necrotic areas with yellow margins, and leaves become brittle and drop off the plant early. Lesions on pods can result in discoloration of the beans within the pods or may cause abortion of seed. Defective beans are usually an orange-brown colour and may be shriveled (Figure 2).
Figure 2. Orange-brown discolouration on cranberry beans caused by Bacterial Blight.
Frost
If plants experience a hard frost close to maturity, beans that are still green will shrivel and retain their green colouring, resulting in increased pick. Coloured bean seed coats that have not fully changed colour may remain white or off-white, and white beans that have not yet become bright or creamy white may maintain a yellow-ish colour. Early frost typically results in yellow beans in the harvest sample (Figure 3). With a later frost, white beans may look slightly grey. Pods that are already brown and dried down are often mature enough to escape frost damage. Delaying harvest until the beans dry down sufficiently will help prevent staining and improve separation during combining.
Figure 3. Early fall frost damage in white beans. Photo credit: D. Lange
Insect Feeding
Insects with chewing mouth parts, such as Western Bean Cutworm, chews holes in beans within the pods or may eat larger portions of the beans. The physical damage to beans results in increased pick. Cranberry beans also become discoloured when they are exposed to air through holes chewed in pods which further contributes to pick (Figure 4). Discoloured cranberry beans are orange or brown in colour.
Insects with piercing and sucking mouth parts may directly pierce beans within pods which can result in deformed beans (Figure 5). The site of insertion of the insect’s mouth parts may be visible as a small dot. Piercing of newly formed pods may result in pod abortion. Stink bugs and tarnished plant bugs are examples of insects that cause this type of injury.
Figure 4. Physical damage and discolouration of cranberry beans caused by Western Ban Cutworm feeding.
Figure 5. A white bean that was deformed by Tarnished Plant Bug feeding.
Wet Harvest Season
Mature dry beans that stand in the field during rain, or multiple rain events, are at risk of deteriorating quality. The longer the delay in harvest, the more likely the beans will be of low quality. Wet conditions promote the development of fungi on dead and dying tissue. The white beans (See Figure 6) had multiple rain events after a pre-harvest herbicide, which resulted in fungus growing within the pods.
Figure 6. Risk of adventitious fungal growth within pods increases with late harvest and reduces the quality of dry beans.
Weather Summary: Thursday, September 19 to Wednesday, September 25, 2024
| Location | Highest Temp (°C) | Lowest Temp (°C) | Rain for Week (mm) | Rain Since April 1st (mm) | GDD0C April 1st | GDD5C April 1st | CHU May 1st |
| HARROW | |||||||
| 2024 | 28.7 | 14.1 | 7.9 | 460.2 | 3299 | 2412 | 3630 |
| 2023 | 25.9 | 7.8 | 0.0 | 585.5 | 2998 | 2129 | 3300 |
| 2022 | 29.7 | 5.3 | 18.0 | 429.6 | 3168 | 2312 | 3585 |
| 10 YR Norm (11-20) | 23.7 | 10.2 | 15.5 | 535.4 | 3138 | 2250 | 3571 |
| RIDGETOWN | |||||||
| 2024 | 29.1 | 11.7 | 19.1 | 570.7 | 3130 | 2247 | 3415 |
| 2023 | 26.4 | 6.3 | 0.0 | 507.9 | 2862 | 2001 | 3095 |
| 2022 | 28.0 | 5.4 | 15.0 | 300.0 | 3012 | 2163 | 3339 |
| 10 YR Norm (11-20) | 23.5 | 8.2 | 16.9 | 480.9 | 2960 | 2075 | 3326 |
| SARNIA | |||||||
| 2024 | 28.7 | 11.5 | 15.9 | 482.0 | 3140 | 2259 | 3410 |
| 2023 | 26.7 | 8.3 | 1.4 | 483.5 | 2836 | 1977 | 3047 |
| 2022 | 26.5 | 8.1 | 15.6 | 339.9 | 3022 | 2178 | 3328 |
| 10 YR Norm (11-20) | 23.6 | 9.9 | 12.8 | 479.8 | 2943 | 2061 | 3329 |
| LONDON | |||||||
| 2024 | 28.7 | 12.5 | 36.4 | 591.3 | 3106 | 2220 | 3402 |
| 2023 | 24.8 | 6.3 | 1.2 | 551.6 | 2841 | 1982 | 3081 |
| 2022 | 25.2 | 4.4 | 15.5 | 346.0 | 2927 | 2086 | 3252 |
| 10 YR Norm (11-20) | 23.3 | 9.0 | 22.0 | 511.4 | 2932 | 2052 | 3301 |
| BRANTFORD | |||||||
| 2024 | 28.8 | 11.7 | 20.9 | 481.1 | 3044 | 2163 | 3320 |
| 2023 | 24.4 | 2.4 | 1.8 | 431.1 | 2815 | 1954 | 3038 |
| 2022 | 26.6 | 1.9 | 13.4 | 323.5 | 2937 | 2086 | 3191 |
| WELLAND | |||||||
| 2024 | 29.0 | 10.3 | 12.6 | 485.2 | 3124 | 2239 | 3444 |
| 2023 | 23.1 | 6.7 | 0.0 | 489.8 | 2874 | 2008 | 3129 |
| 2022 | 24.8 | 4.8 | 16.1 | 395.7 | 2992 | 2133 | 3342 |
| 10 YR Norm (11-20) | 23.9 | 8.8 | 17.0 | 451.5 | 2951 | 2069 | 3327 |
| GODERICH | |||||||
| 2024 | 26.3 | 12.5 | 7.8 | 377.6 | 2887 | 2010 | 3164 |
| 2023 | 25.2 | 6.0 | 0.0 | 370.8 | 2652 | 1809 | 2857 |
| 2022 | 23.9 | 5.4 | 9.6 | 300.6 | 2788 | 1950 | 3097 |
| 10 YR Norm (11-20) | 22.2 | 9.9 | 13.9 | 445.2 | 2713 | 1841 | 3070 |
| ELORA | |||||||
| 2024 | 27.2 | 10.9 | 28.0 | 453.3 | 2823 | 1950 | 3072 |
| 2023 | 22.7 | 2.3 | 3.3 | 470.2 | 2612 | 1766 | 2788 |
| 2022 | 26.3 | 0.2 | 13.8 | 269.9 | 2700 | 1862 | 2931 |
| 10 YR Norm (11-20) | 22.3 | 7.2 | 17.6 | 500.0 | 2650 | 1782 | 2943 |
| MOUNT FOREST | |||||||
| 2024 | 26.3 | 10.2 | 10.6 | 412.0 | 2823 | 1953 | 3090 |
| 2023 | 23.2 | 3.1 | 0.0 | 407.8 | 2608 | 1767 | 2793 |
| 2022 | 24.6 | 3.8 | 8.2 | 386.5 | 2691 | 1859 | 2964 |
| 10 YR Norm (11-20) | 22.2 | 8.4 | 15.9 | 509.3 | 2644 | 1783 | 2971 |
| BARRIE | |||||||
| 2024 | 25.7 | 8.7 | 19.6 | 578.4 | 2775 | 1905 | 3038 |
| 2023 | 22.7 | 1.8 | 0.0 | 501.1 | 2612 | 1765 | 2806 |
| 2022 | 26.9 | 0.8 | 13.3 | 400.3 | 2651 | 1810 | 2906 |
| 10 YR Norm (11-20) | 21.8 | 7.4 | 12.3 | 451.4 | 2607 | 1749 | 2907 |
| PETERBOROUGH | |||||||
| 2024 | 28.0 | 6.6 | 41.8 | 487.6 | 2806 | 1932 | 3006 |
| 2023 | 24.2 | 0.6 | 0.0 | 431.0 | 2658 | 1802 | 2803 |
| 2022 | 25.1 | -0.6 | 8.7 | 350.2 | 2690 | 1838 | 2914 |
| 10 YR Norm (11-20) | 23.5 | 5.9 | 9.9 | 441.4 | 2676 | 1806 | 2925 |
| KEMPTVILLE | |||||||
| 2024 | 27.2 | 11.0 | 15.1 | 567.7 | 2974 | 2101 | 3276 |
| 2023 | 24.1 | 4.2 | 6.7 | 508.3 | 2828 | 1977 | 3023 |
| 2022 | 23.3 | 3.2 | 19.5 | 506.6 | 2847 | 1977 | 3117 |
| 10 YR Norm (11-20) | 23.2 | 7.4 | 15.9 | 499.0 | 2811 | 1943 | 3132 |
| SUDBURY | |||||||
| 2024 | 26.8 | 9.9 | 45.5 | 546.2 | 2637 | 1790 | 2898 |
| 2023 | 23.7 | 1.0 | 0.0 | 515.4 | 2465 | 1657 | 2649 |
| 2022 | 22.3 | -0.1 | 15.2 | 361.6 | 2475 | 1663 | 2766 |
| 10 YR Norm (11-20) | 20.8 | 7.1 | 25.5 | 485.9 | 2464 | 1656 | 2790 |
| EARLTON | |||||||
| 2024 | 27.4 | 4.7 | 55.5 | 539.8 | 2581 | 1741 | 2796 |
| 2023 | 25.0 | -0.2 | 0.0 | 403.5 | 2417 | 1608 | 2568 |
| 2022 | 20.8 | 1.6 | 38.3 | 449.6 | 2413 | 1610 | 2637 |
| 10 YR Norm (11-20) | 20.3 | 4.1 | 10.4 | 450.0 | 2295 | 1509 | 2567 |
| SAULT STE MARIE | |||||||
| 2024 | 24.8 | 7.6 | 25.9 | 547.7 | 2489 | 1628 | 2698 |
| 2023 | 25.6 | 3.3 | 0.0 | 378.6 | 2416 | 1605 | 2574 |
| 2022 | 25.3 | 2.6 | 21.5 | 470.2 | 2245 | 1436 | 2429 |
| 10 YR Norm (11-20) | 22.0 | 7.6 | 17.2 | 500.6 | 2288 | 1481 | 2524 |
| THUNDER BAY | |||||||
| 2024 | 26.6 | 0.7 | 2.1 | 345.1 | 2398 | 1559 | 2564 |
| 2023 | 27.0 | 2.0 | 5.0 | 310.0 | 2274 | 1487 | 2464 |
| 2022 | 23.1 | -1.0 | 7.1 | 563.3 | 2216 | 1440 | 2416 |
| 10 YR Norm (11-20) | 19.3 | 4.2 | 18.0 | 444.0 | 2211 | 1413 | 2423 |
| FORT FRANCES | |||||||
| 2024 | 25.3 | 1.3 | 9.4 | 490.3 | 2485 | 1636 | 2699 |
| 2023 | 28.0 | 7.2 | 30.8 | 343.2 | 2436 | 1642 | 2652 |
| 2022 | 23.1 | -0.9 | 2.5 | 624.7 | 2293 | 1519 | 2566 |
| 10 YR Norm (11-20) | 18.3 | 4.2 | 24.9 | 448.1 | 2337 | 1521 | 2575 |