Black Rot

Grape black rot turns Himrod berries into hard black mummies that stay on the cluster. It is not tomato leftover and not the gray fuzz of Botrytis bunch rot. A spray will not rewind a mummy.

Do this first: pull every mummy off the trellis, then water the soil, not the leaves.

Hard mummies on the cluster, or tomato leftover

Gardenia’s all-crops dump is leftover. Walk the Himrod cluster.

Tan leaf spots with black pimples in a ring

Young leaves take round tan spots with a darker rim. Black pimples sit in a ring inside the tan. Clusters can look fine until midsummer, then berries brown, blacken, and wrinkle into hard raisins. Walk the shaded, wet side of the vine after rain. Fail if you wait for a perfect photograph of a mummy before you stop overhead water. Two or three tan spots in June are the warning. Pull those leaves. Scout twice a week while nights stay humid. After a rain, flip the leaf and look for the ring of black pimples before you blame sun scald. Sun scald is bleached and dry; this spot holds moisture and specks. Two minutes with a hand lens beats a week of guessing. If Himrod is against a fence that never dries, thin one cane so morning sun hits the fruit. Fail if you wait until every berry is a raisin before you walk the leaves. A wet June on a shaded trellis will mummy a cluster that still looks green from the path.

Pull the mummies off the trellis

Mummies in the wires keep shooting spores all season. Floor mummies mostly finish by bloom. Tonight’s job is the raisins still clipped to last year’s stems. Bag them. Do not compost. Fail if you rake the ground and leave a necklace of raisins in the trellis. A winter walk under Himrod still shows last summer’s fruit — pull that before spring rain. In a small planting you can pick infected berries as they brown, before they harden. Bag those too. Fail if you drop mummies on the mulch and call it done — they still shoot. Two winters of raisins in the wires will keep bringing June spots even if you copper the leaves. A clean dormant prune that keeps fruiting wood without last year’s stems is the job. Walk the top wire; that is where home vines hide a necklace of raisins.

A spray will not rewind a mummy

A hard raisin does not unkink. Wait while the vine is still full and only a few clusters are gone. Act on the wire tonight. Fail if you copper a collapsing cluster or leave it as next year’s source. Protect bloom next year. Skip the brand aisle.

Bloom through four weeks — then the berry hardens

Fruit is open from bloom until about four to six weeks after. After that window the berry hardens to this fungus. Two to three wet weeks around bloom do more damage than an August bottle. Fail if you start a spray program in August when the raisins are already hard. Start next year at bloom, after the wire is clean. If last year was a mummy year, do not skip the bloom window even if May looks dry. One long wet spell at bloom is enough. Fail if you spray at veraison and leave June’s raisins. Two to three passes from first bloom through pea-size fruit beat a late panic. Keep the label honest: protectants need coverage before the rain, not after the berry is already brown.

Shade and wet leaves feed it

A vine under trees stays wet. Open the canopy. Water the soil in the morning. Fail if a sprinkler hits the clusters every afternoon. A dry leaf at bedtime is worth more than a bottle. Thin a crowded planting so morning sun hits the fruit. Two wet nights in a row on a shaded fence will do more than a dry August. Fail if you mulch up the trunk and splash soil onto the lowest clusters. Keep fruit off wet ground. A morning walk after dew tells you whether the vine ever dries.

Himrod in a humid year

Himrod is the live vine here. A humid June will mummy a cluster that looked perfect in May. Keep the fruit off wet ground. Fail if you wait for a Concord row that is not in this bed. Two to three years of mummies in the wires will keep bringing the job back. Train the vine so clusters sit in moving air, not in a wet pocket against the house. Fail if you let a second crop of late laterals tangle through the fruit. A humid year on Himrod is this job even when the vine still looks vigorous. Water at the roots. Keep the fruit dry at night.

Not a harvest-soft Phomopsis berry

Phomopsis cracks basal canes in a wet spring. If it rots fruit, it is near harvest and soft. Hard mummies before the berries color are this job. Fail if you treat a June mummy as a September soft rot. Walk both jobs on the same vine: tan leaf spots now, then the cluster. Two diseases can sit on one Himrod in a wet year. Pull the raisins anyway. Cut bleached basal wood in winter for the other job.

Pull the mummies — a bottle will not rewind a mummy

1. Confirm hard black raisins on the cluster, not gray fuzz.
2. Pull every mummy off the trellis. Bag them.
3. Water the soil in the morning. Stay off the canopy.
4. Open shade so clusters dry.
5. Protect bloom next year. Skip the brand aisle. Fail if the bottle replaces a clean wire.

Related reading

• Botrytis bunch rot — gray fuzz and slip-skin, not a hard mummy.
• Phomopsis cane and leaf spot — cracked basal canes in a wet spring.
• Blossom-end rot — leathery tomato leftover, not a grape mummy.
• Pierce’s disease — matchstick petioles, not a cluster raisin from this fungus.