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Weather forecasting on the Internet is getting big. There are a number of ways to access weather. You can get Massachusetts weather via the UMass Fruit Advisor.
Using the Tree Fruit site, you can get Glen Koehler's Orchard Radar. This is a program that analyzes SkyBit weather data and predicts key pest management events. (SkyBit is a commercial weather service, available to growers, working out of Bolesburg, PA; for more information, contact Arthur Tuttle at 413-545-4378.) The Tree Fruit site has a great deal of useful weather data for you.
If you're interested in what's happening in New York, then an operation called the Northeast Weather Association (NEWA, a non-profit organization, is offering farmers, consultants, food processors, agricultural industry representatives, and others access to the information provided by a network of electronic weather instruments. NEWA obtains weather forecasts from both the National Weather Service and AccuWeather, Inc. Only NEWA members will have access to the information on the BBS/web site or faxes. NEWA provides specific localized pest and crop forecasts for apples and other crops. To find out more about NEWA, including services offered, membership fees, and other membership benefits call Curt Petzoldt at (315) 787-2206 or send a FAX to (315) 787-2360.
The scab situation for any one orchard will depend on one main thing: how long did trees stay wet in that orchard. As of the weekend, there were plenty of mature spores available in all orchards, whether there was a lot of scab in them last year or not.
As a result, the rains yesterday and today will be infection periods if they keep trees wet for the required time. With temperatures in the 50s and 60s, that means 10 to 16 hours will be sufficient. With spotty rains in the west, and more rain to the southeast, the infections will also be spotty.
Likely as a result of the warm stretch from 4/30-5/2, many orchards have experienced a flush of TPB activity. As one might expect, the greatest increases in trap captures have been seen in orchards that traditionally withstand heavy TPB pressure. Though a few orchards have exceeded thresholds for treatment based on trap captures, the vast majority of orchards remains below threshold levels. As orchards approach bloom, typical TPB fruit injury will likely peak. Damage inflicted during bloom looks less like the dimpling of fruit most often attributed to TPB and has more of a rough, scabbed over appearance, similar to plum curculio damage. Orchards which experience annual trouble with TPB and have seen a surge in trap captures should consider a pre-bloom treatment with either Guthion or Imidan.
Late pink is also the time of year when white rectangle traps begin to lose their effectiveness as a monitoring tool for TPB. Once white tissue begins to unfold in blossom clusters, the huge amount of white in the canopy overwhelms the visual stimulus of the traps. Because of this, we do not consider white sticky monitoring traps as a good indicator of TPB populations after mid-pink. Growers who have reached mid-pink and do not have traps in place for monitoring European apple sawfly activity should consider moving white traps to head-height on the south side of the canopy to monitor for EAS.
European apple sawfly pupae overwinter in the soil beneath apple trees, generally becoming active in the tree canopies at or near bloom. In orchards that experience heavy pressure from EAS, their timing of activity always makes for a tough management decision: whether to spray pre-bloom for an unknown threat, or wait until petal fall, running the risk of damage during bloom. This year, the timing of EAS emergence may be more conducive to an informed pre-bloom decision. The high soil temperature beneath the trees may be inspiring early emergence; dry topsoil (with the lack of evaporative cooling) will accelerate the development of soil-dwelling pupae.
At least one orchard (at tight cluster) has already exceeded the treatment threshold, and individual trap captures have been seen as high as twenty. Growers who traditionally see high levels of EAS damage should be cautious about this early activity, given that egglaying will begin as soon as blossoms open. If trap-capture thresholds are exceeded prior to bloom, an application of Guthion or Imidan at late pink should remedy the problem through petal fall, when plum curculio cover sprays will control EAS second-hand. For growers who do not see an abundance of EAS prior to bloom, the treatment thresholds through petal fall are 5 EAS per trap (in blocks not receiving a pre-bloom insecticide) or 9 EAS per trap (in blocks which did receive a pre-bloom insecticide).
Petal fall treatment with Guthion or Imidan will be highly effective against EAS in years when most cultivars drop their petals at roughly the same time. In years where petal fall is widely strung out, there is considerable risk of high EAS damage.
Rosy apple aphid activity has been observed in many monitored orchards. RAA are a deep bluish purple in color, and feed on young foliage. Foliar feeding by RAA causes sever curling of the leaves and, as their saliva is pumped through the plant tissue, stunting of fruit growth.
To monitor RAA abundance and activity, examine 10 interior clusters on 10 trees, and consider treatment if 1% or more of clusters are infested. Research from New York suggests choosing clusters for examination that show evidence of possible infestion. When monitoring, growers should focus on more susceptible common varieties, such as Cortland, Golden Delicious and IdaRed. If thresholds are exceeded, Lorsban at pink provides good control, as does Provado soon after petal fall.
What else can we say about the abundance of leafminers? Not much--aside from the fact that nearly all orchards from which we gather monitoring information have exceeded treatment thresholds. This season, few growers will go untouched by the LM population explosion. LM egglaying continues in earnest, and peak egg counts in one orchard at early pink have reached 100 eggs per cluster. These numbers are astounding (imagine 100 first-generation mines per cluster) given that the treatment threshold based on egg density is 2 eggs per leaf through pink.
As mentioned in previous issues of Healthy Fruit, we know of no LM management strategy that is more effective than use of Provado soon after petal fall. SpinTor may also be effective as an LM control agent, if used with a penetrating surfactant, such as LI 700.
The first European red mite eggs have begun to hatch, with young nymphs present in orchards at mid-pink. Growers who have not had the opportunity to apply a full oil program may consider use of Savey (through pink) or Apollo (now labeled for use up to 45 days before harvest). New England Fruit Consultants has been running trials comparing performance of Savey and Apollo for about a decade. From these trials, there is the suggestion that Savey is a slightly more effective material against ERM than Apollo, offering a greater likelihood of season-long control from a pre-bloom application. If considering a pre-bloom material, Savey may be the best option, as it is not labeled for post-bloom use.
If the plan is to use Apollo, growers may be able to maximize the duration of control by treating when the first summer eggs begin to hatch (late May to early June). This approach will (1) allow growers to get a better read on mite pressure; (2) extend the effectiveness of the material, offering a better chance at season long control; and (3) allow treatment before July, when this material is not maximally effective (as ERM growth stages are highly varied).
Psylla nymphs have hatched in most scouted orchards statewide. As stands to reason, orchards with the highest populations last fall are experiencing the highest infestation this season, up to 2-3 nymphs per cluster. In orchards where the population is light but building, fruit set is the best time to judge whether treatment will be necessary. Data from New York suggest that if 10% or more terminals are infested, Provado, Mitac, Agri-Mek, or Pyramite after petal fall will offer good psylla control.
Healthy Fruit is written by Dan Cooley, Ron Prokopy, Starker Wright, Wes Autio, and Duane Greene except where other contributors are noted. Edited by Dan Cooley. Publication is funded in part by the UMass Extension Agroecology Program, grower subscriptions, and the University of Massachusetts IPM Program. A text version can be e-mailed to you if you contact Doreen York. Please cite this source if reprinting information.
