Management considerations are discussed for mitigating pome and stone fruit rots. Hail damaged fruit destined for juicing still need protection from rots.

We are in the middle of a delicious peach harvest and apples aren’t far away. Consequently, preventing fruit rots is now the priority. Significant rain is in the forecast for the region this weekend. Monitor your area for rainfall: If more than 2 inches of rain falls and you have already applied fungicides this week, another application will be needed to keep the rots at bay since there is a good chance the protection will have washed off. Some nuggets of wisdom to keep in mind:

Peaches and nectarines: A review of brown rot management strategies

Peaches and nectarines are ripening, which means ‘tis the season for brown rot. The fungus causing brown rot is quite opportunistic: it can kill blossoms and it can also ruin the fruit you’ve worked hard all season to grow. Brown rot disease is favored by warm, wet weather conditions. Under optimum temperature conditions, fruit infections can occur with only three hours of wetness when inoculum levels are high. Longer wet periods during infection result in shorter incubation times so symptoms develop more rapidly. It’s not uncommon to have brown rot appear “overnight” on fruit.

Hail damaged fruit need protection from fruit rots. Photo: T. Ford, Penn State

Spores produced on early maturing cultivars can fuel a continuing outbreak on late maturing cultivars – this is especially important for those who have battled rot infections already this season. To add another headache to the issue, insects can be important vectors of the fungal spores during fruit ripening: they can carry spores to injury sites produced by oriental fruit moth, Japanese beetle, green June beetle, and other insects that can injure fruit. Wounded fruit are much more susceptible to brown rot than unwounded fruit. It’s critical to be on top of insect management. Another concern to worry about is split pit. Unfortunately, these fruit are quite prone to rot problems. Keep in mind: under the right conditions, “healthy” fruit harvested can be contaminated and may decay later during storage.

Research at Rutgers has shown that timing brown rot sprays 18 days, 9 days, and 1 day before harvest provided greater than 95 percent control under heavy disease pressure. When following this regime, be sure to rotate chemistries by FRAC Group Code number for resistance management. For example, one could spray the following (provided the maximum number of sprays has not been exceeded for that chemistry):

  • 18 days: Fontelis (FRAC Group 7; 0 day PHI)
  • 9 days: Indar (FRAC Group 3; 0 day PHI)
  • 1 day: Merivon (FRAC Group 7 +11; 0 day PHI)

Other options to rotate:

  • Luna Sensation (FRAC Group 7 + 11; 1 day PHI)
  • Luna Experience (FRAC Group 7 + 3; 0 day PHI)
  • Topsin M (FRAC Group 1)
  • Inspire Super (FRAC Groups 3 + 9; 2 day PHI)
  • Orius (FRAC Group 3; 0 day PHI)
  • Tilt (FRAC Group 3; 0 day PHI)
  • Quash (FRAC Group Code 3; 14 day PHI)
  • Gem (FRAC Group 11; 0 day PHI)
  • Captan (FRAC Group M4; 0 day PHI)

Keeping in mind products that were used to control blossom blight, be sure to be in compliance by obtaining the current usage regulations and reading the product label. Depending on the number of sprays needed and what you may have used during bloom time, be sure to practice fungicide resistance management and rotate chemistries by FRAC group (“Spray by the Numbers”).

Alternative options for rot management

The key for growers who farm organically or prefer using alternative products is to spray as often as possible as disease conditions persist, manage insects, scout often, and prompt removal of infected fruit as soon as you see it. Spraying often ensures you have continuous protection; removing infected fruit from the trees ensures you are decreasing the amount of spores available to cause disease and hopefully minimizing an epidemic. Knocking infected fruit to the ground will be enough to limit spread. Vigilance is important and this may translate spraying every few days, especially if rain washes off products. According to studiesat Rutgers, sulfur is not effective for controlling brown rot. Some organic options labeled for brown rot control are Cueva, Double Nickel, Serenade Opti, and Regalia.

Apples: Hail damaged fruit still need protection from rots

We are nearing the home stretch of the apple season and folks will want to be considering sprays to keep their apples free of rot, especially while in storage. Not only a headache in the field, but the fungi causing fruit rots can be quite stealth since spores will land on the fruit and cause symptoms only after the fruit have been in storage. This is especially significant if your apples are headed for a packinghouse or even fresh market.

Prime apple growing areas in Pennsylvania received Mother Nature’s wrath over the last week with some pretty potent hail-producing storms. Consequently, a lot of fresh market fruit is now destined for juicing. Protection from rot fungi is critical for these damaged fruit since they are now more susceptible. Since these fruit are especially vulnerable, growers will want to consider using complete sprays.

I highly encourage growers to use Merivon (FRAC Groups 7 + 11; 0 day PHI) or Luna Sensation (FRAC Groups 7 + 11; 14 day PHI) as their last one or two sprays prior to harvest since these products do show efficacy keeping rots in check while in storage. This recommendation is both for fresh market and juicing apples: the pack houses and processors will thank you! There are a couple of sprays up to that point and the following are additional options for control (be mindful of the maximum limit for sprays for each product/FRAC Group):

  • Flint (FRAC Group 11; 14 day PHI)
  • Sovran (FRAC Group 11; 30 day PHI)
  • Indar (FRAC Grop 3; 14 day PHI)
  • Topsin M (FRAC Group 1; 1 day PHI)
  • Captan (FRAC Group M4; 0 day PHI – used alone or tank mixed with a single mode of action product)
  • Ziram (FRAC Group M3; 14 day PHI)
  • Serenade Opti (biofungicide – B. subtilus; 0 PHI)

We evaluated Serenade Opti the last few seasons for summer disease control at   16 oz/A as the last two cover sprays, with a conventional program up to these sprays. We observed minimal fruit rot diseases in the field and storage, at least on Golden Delicious. These results may vary with other cultivars, depending on their susceptibility to certain rot diseases, as well as severity of disease conditions.

– Kari A. Peter, Penn State University Extension

Source: Penn State University