Extension Responds: Flood-August 2007
Fruit growers concerns about the quick transition from extremely dry to very wet conditions
Contact: Teryl Roper, UW-Extension Fruit Crop Specialist
August 21, 2007
This very quick transition from extremely dry to very wet conditions poses some challenges for fruit growers. The following points are anticipatory of questions you may receive from both commercial growers and backyard gardeners.
1. As soils went from dry to saturated and as fruit remained wet for many hours it is not uncommon for fruit to absorb significant amounts of water from both the xylem and across the fruit cuticle (skin). This sometimes results in fruit cracking. Cracking is caused by water moving into cells faster than they can expand and adhere to neighboring cells. I know of no remedy for this malady once cracking begins. I know that some grape cracking has already occurred and if rains continue the cracking will get worse. Cracked fruit remaining on trees are likely to attract insects and they will release ethylene that hastens ripening of remaining fruit. Removing damaged fruit may be prudent, if possible.
2. Free standing trees on hillsides that have a full crop of fruit may tend to lean down the hillside unless supported. This is a result of the roots trying to hold on to saturated soils. If noticed early, steel t-posts could be driven uphill and the tree wired to the post to hold the tree in place. Removing some of the crop would also be helpful. Strong winds at this point could also be very detrimental. Strong winds would be a problem for trees in saturated soils regardless of the slope.
3. Trees planted on low lying areas with standing water will suffer from the soils remaining saturated for several days. Two situations can lead to tree injury. 1) Soils saturated with water become anoxic and root death can ensue. 2) Saturated or very wet soils are prime for development of Phytophthora (crown or collar rot) on apple trees. Some rootstocks are more resistant than others, but I don't think any are totally immune. As flood waters subside damaged trees will quickly become apparent.
4. Apple scab is a threat whenever we have prolonged leaf wetness. If growers did an excellent job of controlling primary scab early in the season the threat is less. For those with trees that have some scab lesions it may be possible that the recent rains would provide good conditions for the development of further scab on leaves and fruit. Protective fungicide sprays are warranted for the rain that is forecast for the remainder of the week.
Most of these observations would be true for plums as well as apples. Cherry and apricot harvest is finished so just preventing tree injury is the key there.