Tree Fruit IPM Report for May 5, 2020

Tree Fruit Phenology: Tree Fruit Phenology remains advanced, but development is slowing. In southern counties peach orchards are at Shuck Split to Shuck Off. Pears are past Petal Fall. Red Delicious was about Full Bloom on 4/25 and is late bloom/Petal Fall on May 4. Other varieties still have considerable bloom. Cherries are just past full Bloom.

Peach:

Rusty Spot: Fungicides effective for rusty spot control on susceptible varieties should have been included in petal fall sprays. Include effective materials until about pit hardening (usually around June 15). See the production guide for effective materials.

Bacterial Spot: Copper formulations should be used starting at bloom or petal fall to suppress bacterial spot. Generally we recommend starting at 0.5 ozs metallic copper and gradually lowering the rate as the season progresses. The rate applied will depend on the formulation. Dr. Lalancette published a chart listing common copper formulations and rates for peach and nectarine applications. Avoid combining copper with captan especially if it has been overcast for several days. Also avoid acidic spray solutions when applying copper. Dr. Lalancette has published a handy guide for copper applications in early covers. Antibiotics such as mycoshield or fireline may also be used and offer slightly more residual activity during long wetting periods. No bacterial spot symptoms have been observed in southern counties to date.

Peach Scab: In addition to Rusty Spot and Bacterial Spot, Peach Scab requires protective applications starting at petal fall. Peach scab cankers (Fig. 1) begin to expand at bloom and by shuck split begin to shed spores during wetting periods. Topsin, Topsin/Captan combinations, Flint Extra, Inspire Super, and especially Quadris Top applied at petal fall are the best materials for blocks that had scab last year. Quadris Top, Flint Extra or Topsin should be used at the high rate to suppress overwintering lesions on the wood. Quadris Top contains azoxystrobin which is phytotoxic to many apple varieties. Phytotoxic residues can remain in the tank for long periods after an application is made, even if a tank cleaner is used. Do not use Quadris Top or Abound in the same sprayer used for apples. Bravo (chlorothalonil) is also a good protectant that may be applied no later than shuck split. Captan is also helpful in cover sprays after shuck split where scab was troublesome last year.

Fig. 1 Peach Scab lesions on peach twig.

Brown Rot: Maintain coverage with effective materials until pit hardening. Do not rely on sulfur alone unless a dry weather pattern develops. The Captan program, developed by Dr. Norm Lalancette would be a good program to follow, particularly as we get a little further into the growing season.

Green Peach Aphid: GPA colonies begin forming sometime during bloom. Examine trees for the presence of colonies from pink to shuck split. Count the number of colonies on ten trees and use a treatment threshold of 2 colonies/tree at petal fall for peach, and 1 colony/tree for nectarine. The best way to scout for aphids during bloom is with a beating tray. Blossoms may also be collected, opened, and examined for the presence of aphids using a hand lens. This is particularly important for nectarine blocks. Check 10 trees per block with the beating tray. Collect 50 blossoms per block and examine for the presence of aphids. If more than 1 colony of aphids are found in nectarines, or 2-3 colonies are found in peaches, an insecticide for aphids will be needed when all petals are off. The first aphid colonies in Peach were observed on 4/27 in Southern counties. See the NJ Commercial Tree Fruit Production Guide for recommended materials and rates.

Plum Curculio (PC): PC adults are active and will damage fruit if not controlled. PC is a key pest to control during the first few weeks after petal fall. Make sure to choose insecticides that are effective for PC control.

Tarnished Plant Bugs; and Other Catfacing Insects:  Catfacing insects are starting activity but cause little damage at this time of the year. Catfacing insects will become more of an issue as temperatures warm and mowing and other ground cover activities become more common. Any Insecticides applied at this time for OFM should control this complex. Orchards under OFM mating disruption will have more options since OFM is not a target. See the NJ Commercial Tree Fruit Production Guide for recommended materials and rates.

Spray Programs with little to no crop: If certain blocks have little to no fruit, disease control is more important that insect control. Without a minimal Scab program this year, you will have a difficult program next year. If you can afford Captan through second cover, perhaps with sulfur through mid-July, then 2021 will be a lot easier than if nothing is done this year. See Dr. Norm Lalancette’s article and recommendations from April 24. Maintaining copper applications through June will also suppress Bacterial Spot, preventing excessive defoliation and minimizing overwintering cankers for 2021. Oriental fruit moth has 4 generations per year. Most growers had 1 insecticide application on by the time any cold injury occurred. With no crop, this should be all that is needed. Peach tree borers, however, will have to be controlled in September. If you already had your mating disruption dispensers up, then nothing more is needed.

Oriental Fruit Moth: First generation timings are updated below:

Apples and Pears:

Spotted Tentiform Leafminer (STLM): Adults are flying, but are not considered a pest target at this time.

Plum Curculio (PC): This is THE insect to control at petal fall. Avaunt, Imidan, Actara, VoliamFlexi are the top options for control. Of these, Avaunt, Imidan and VoliamFlexi also do a good job controlling EAS (see below).

European Apple Sawfly (EAS): This insect is active through bloom and into petal fall and first cover. Adult females lay eggs just under the skin of freshly set fruit, and the young larvae mine just under the skin. Where present, it is a primary target at petal fall. In orchards of mixed variety plantings, the petal fall spray for the entire planting is prolonged. This enables EAS to start damaging the first varieties where petals fell earlier before a petal fall spray could be applied to the entire block. DO NOT SPRAY ANY INSECTICIDE DURING BLOOM FOR THIS PEST! Doing this will kill bees, hurt pollination and fruit set, and is highly illegal!

Diseases: Apple Scab – Infection periods are predicted for 5/6 through 5/8. Primary ascospores are now 95% mature in northern and southern counties. Using the NEWA model, the prediction is for all mature spores to be released with as little as .1” of rain and temperatures above 50⁰F.

Fire Blight: Infection periods are predicted for 5/7-5/9 in northern counties. The high risk period for blight infections is over in southern counties. However, if bloom is still present, then antibiotics can still be used. Continue antibiotic applications just prior to infection periods and up to 1^st cover for shoot blight. Agri-Mycin may be applied after petal fall, but it must be rotated with oxytetracycline (Mycoshield or FireLine 17WP). Kasumin 2L may not be applied after petal fall. DO NOT use consecutive Agri-Mycin (strep) applications if 2 applications were already used during bloom. This will increase the likelihood of antibiotic resistance developing.

Rosy Apple Aphid:  If a pre-bloom application was not made, monitor for colonies during bloom and use a treatment threshold of 1 colony/tree at petal fall.

Codling Moth (CM): The first codling moth flight has started. Biofix dates were set statewide for Monday May 4. While southern counties should normally be earlier than in northern counties, that was not the case this season, partially due to differences in insect pressure, and only slight differences in degree day accumulations early in the season. Specific insecticide timings are too far out to estimate at the present time, but 250DD in southern counties usually falls close to Memorial Day.

Pear Psylla:  Dormant oil applications should have already been started to deter psylla egg laying. At the green cluster stage a pyrethroid is generally included with oil to knock down adults migrating into the orchard.  In lieu of oil, Surround may also be applied starting at swollen bud and continued through bloom. If using Esteem for psylla control make one application delayed dormant through popcorn or two applications; one at delayed dormant through popcorn and one at petal fall. Centaur is also effective and one application may be made pre-bloom or at petal fall. Sivanto Prime is also labeled for early season applications and should be combined with oil. See this 2020 blogpost from Peter Jentsch at Cornell for a more detailed control discussion.

Pear Diseases:  Include effective materials such as Ziram or EBDC formulations for Pear Scab and Rust diseases beginning at the cluster bud stage. At white bud use products effective for pear scab, rusts, and fabrea leaf spot. For both apples and pears, consider using Kasumin at bloom. Kasumin is an antibiotic like Streptomycin and Oxytetratracycline. It contains Kasugamycin which is a different chemistry. Kasumin is only labeled for bloom and petal fall applications while strep and oxytet are labeled for post bloom use. Using 3 different chemistries in rotation allows for resistance management while extending the protection into the post bloom period when late blossoms typically appear. which ever material you use, the addition of Actigard or other plant defense elicitors may improve control.

Tree  Fruit Trap Counts – Southern Counties

Tree  Fruit Trap Counts – Northern Counties

Grapes:

Grapes are currently about 3″ or more shoot growth in southern counties. The key disease pest at this stage is phomopsis. Insect pests to monitor for at this stage are grape flea beetle and climbing cutworms. See the Commercial Grape Pest Control Recommendations for New Jersey for more Information.

Blueberry:

Leps and Other ‘Worm’ Larvae:  Levels of leps have been minimal this week.  We have seen just a few spanworm and green fruitworm larvae, no treatments are needed. Small (about ½” long) Gypsy moth larvae are also present in a few places, having been blown in by recent winds. These are also not an issue to be concerned about at this time. As you look around your farm and, on the roadside, you may see well-structured silken tents in the branch crotches of wild shrubs and small trees. These are from the eastern tent caterpillar. We have not seen these in blueberry fields yet, but as the days go one you should be aware of these possibly moving into fields as they consume the foliage on the trees where they hatched.

Plum Curculio (PC): PC activity starting to increase slightly, most likely due to slightly warmer temperatures.  As long as there is bloom and bees are present, PC cannot be treated.  As the berries are fertilized and begin to swell, fresh egg scars should start to become visible. Check your field edges first to get an idea where hot spots are likely to occur and prioritize your first insecticide sprays after the bees come out.

Botrytis, Phomopsis and Mummy Berry Strikes:  Very little disease has been seen. Botrytis is present, but the highest levels seen have only been a few clusters on .5% of plants examined. Nevertheless, this disease can spread fast if given cool wet conditions like we are supposed to have later this week. See suggested fungicides in the Blueberry Production Guide.

Figure 2. Botrytis infection on blossom. Photo – Carrie Denson.