Sunburn on Coffee
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Sunburn, scorch, and sun-scald of coffee can occur when plants and branches are (suddenly) exposed to excessive sunlight and solar radiation. This type of damage is commonly observed following pruning and planting of young trees as the intense sunlight (and heat) causes the breakdown of chlorophyll in the leaf. Symptoms may be more severe when strong sun is combined with dry soil conditions.
Initial damage appears as pale, bleached or faded areas that then become brown and necrotic. Unless extremely severe, plants typically recover from sunburn damage. |
Manage sunburn with proper pruning techniques:
Manage sunburn for new plantings:
Additional reading:
https://extension.umd.edu/hgic/topics/sunburn-leaf-scorch-annuals-bulbs-groundcovers-perennials-and-vines
https://extension.unh.edu/resource/starting-plants-seed-fact-sheet
- Prune following the harvest season.
- Typically in late winter for farms with a seasonal harvest ending around Dec./Jan.
- Typically in spring/late spring for harvests ending around Mar./Apr.
- Descucker excess verticals and laterals to increase sunlight and airflow to remaining branches.
- Desuckering over verticals should be done at least once a year about 3-4 months after pruning.
- Each vertical on a stump competes with neighboring verticals for sunlight, water and nutrients.
- Excessive shading due to an excess number of verticals can cause etiolation where verticals "stretch" and grow rapidly to receive its essential light for photosynthesis. These lanky verticals often naturally fall over during production and must be propped up because their cells didn't strengthen as a result of rapid expansion.
- Remove excess secondary verticals that arise from primary verticals.
- Secondary verticals create additional shade for young verticals on the stump and can also encourage etiolation, disease and pests.
- Secondary verticals create additional shade for young verticals on the stump and can also encourage etiolation, disease and pests.
- A goal should be to have no more than 4 verticals per stump.
- The total number of verticals will dependent on tree age, health, shading, fertility and pruning style.
- Desuckering over verticals should be done at least once a year about 3-4 months after pruning.
Manage sunburn for new plantings:
- Acclimatize or harden-off young trees with increasingly greater sunlight and solar radiation over a 3-6 month period prior to planting in full sunlight.
- Decreasing shade over time, even by increasing spacing between potted plants, can help to increase stem strength.
- A lack of sun can cause etiolation, resulting in lanky, weak-stemmed trees that need to be propped to remain upright.
- Water plants prior to planting to increase tissue turgidity and reduce wilting.
- Irrigate the soil before and after planting for adequate soil moisture.
- Plant during the rainy season; although excess rain may be detrimental to plants and could result in pest and disease incidence. Treat as necessary for control.
- Sun protectants such as kaolin clay may help to protect leaves from sun exposure and act as an acclimatization tool.
- Avoid over-fertilizing young, newly planted trees as root-burn can occur and affect tree health. Slow release fertilizer may be helpful.
- Avoid planting during the heat of the day, if possible.
Additional reading:
https://extension.umd.edu/hgic/topics/sunburn-leaf-scorch-annuals-bulbs-groundcovers-perennials-and-vines
https://extension.unh.edu/resource/starting-plants-seed-fact-sheet
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