New Tree-fruit Specialist!
Mr. Jon Clements joined the UMass Fruit Team this week. Jon's telephone number is:413-478-7219. Also, he will attend the High-density Study Group Meeting on May 3 (at Tougas Family Farm in Northborough) and the twilight meetings on May 9 (Clarkdale Fruit Farms, West Deerfield), 10 (Sunnycrest Orchards, Sterling), and 11 (Sunset Orchards, Scituate, RI). Please come and meet him.
Jon has worked in fruit research and extension for just over ten years. From 1989 to 1998, while a Field Research Technician at the University of Vermont, Jon assisted Professor's Joseph Costante, Lorraine Berkett, and Elena Garcia with applied research at the University of Vermont Horticultural Research Center and in commercial orchards. Jon's experience included working with scab-resistant apple cultivars, new apple varieties, training and pruning systems, and plant growth regulators. While at the University of Vermont, Jon was instrumental in developing the 'Apple-Crop' e-mail discussion group and 'Virtual Orchard' world wide web site. In 1998 he received his M.S. degree under the tutelage of Professor Costante and a research project looking at the effect of pruning on 'McIntosh' fruit quality. Also in 1998, Jon accepted a position with Michigan State University Extension as Berrien County Horticulture & Marketing Agent in southwest Michigan. Jon's responsibilities included developing Extension programming for Berrien County's commercial tree fruit growers who produce apples, peaches, and cherries on over 13,000 acres. Jon also worked closely with Michigan State University's Fruit Area of Expertise (AOE) Team on statewide fruit research and Extension activities. Jon's desire to get back closer to home (he is a native Vermonter) and familiarity with the New England fruit industry brought him to UMASS Extension where he will assume the hefty role of statewide Tree Fruit Extension Specialist.
Scab Moving Into Position
Today's squash mounts from Amherst leaves tell a story quite unlike last week's: the scab spores are, on average, 45 % mature. We calculated the degree-day accumulation for Sterling, MA. This site is central among the many orchards that are participating in UMASS Apple IPM/ Horticulture research this year, and is predictably within a day or two of the UMASS orchard in Belchertown for phenological events. As of May 1, the Sterling site reached 272 degree-days. This is less than one would expect for 45 % spore maturity, but it does indicate that the primary scab season is definitely under way. If you look at Figure 1 on page 9 of the 1998-1999 New England Apple Pest Management Guide, you will see that, at least for orchards with similar rainfall and phenology, we are getting into the steep part of the curve right between the lag phase and the accelerated phase of primary scab season. During the last week, there was sufficient prolonged rainfall to have a significant wetting period during April 27-28. Again, this is specific to Sterling, but is likely to be very similar for all MA orchards except for those at high elevations in the western part of the state, which may still have mostly undeveloped spores.
Pending Bloom
Given the weather forecast for late this week, many orchards will approach bloom over the weekend. Growers concerned about a tight window for pollination may want to consider mowing this week; knocking down dandelions and other early-season bloomers will reduce within-orchard competition and maximize the efficiency of working bees.
Moving on Up
Even with the warm daytime temperatures over the weekend (4/29-4/30), very few tarnished plant bug adults have been captured on white rectangle monitoring traps. In fact, not a single scouted orchard has exceeded treatment thresholds; nearly all growers have opted to omit prebloom insecticides this season. The lack of TPB captures to date is good news, as TPB activity and injury generally peak near bloom. In years of heavier TPB activity, damage can accumulate through the blossom period, yielding fruit with rough, scabby patches similar to curculio-damaged fruit. Fortunately, this does not appear to be much of a concern this season.
This week (5/1-5/5) likely signals the end of TPB trap efficacy—late pink is the time of year when white traps lose their ability to visually outcompete developing blossom clusters. Growers who are approaching mid-pink and have not yet placed traps for monitoring European apple sawfly should consider moving white traps to head-height on the south side of the canopy to monitor abundance of EAS.
Pupa Scoopa
Captures of adult leafminers have also steadied in the past week, perhaps easing some of the concern of a long period of emergence from overwintering pupae (generally making treatment more difficult). Orchards approaching pink should have a pretty good idea of the first-generation potential; most monitored blocks have significantly exceeded trap-capture thresholds, suggesting that post-bloom treatment with Provado, Agri-Mek, or SpinTor may again be a popular tactic.
Thriple Threat
Despite early-season presence in a few orchards, the thrips population has not built to alarming numbers in any monitored sites. In fact, Bill Coli has reported that scouting of a few Berkshire orchards (notorious for thrips buildup) has shown little thrips presence in buds and very low captures on yellow monitoring traps. This suggests that thrips invasion likely poses little threat in most orchards, though growers are encouraged to be attentive to thrips activity as blossoms develop. We have no solid explanation for the relative lack of invading thrips, although last year's dry summer and the effects of soil-borne fungal pathogens may have reduced the overall thrips population.
To clarify a point made in last week's issue, slow early-season apple bud development does not necessarily spark buildup of thrips in orchards. In fact, the potential for thrips buildup and damage this season is closely linked to weather patterns, maple flowering, and population survival during the past year. A drawn-out spring simply offers thrips in the orchard a greater period of time to damage succulent tissue—potentially exaggerating damaging effects this season.
Sighted Mites
Egg hatch of European red mites has begun in a few monitored orchards—current estimates place hatch at roughly 15%. Hatch will certainly peak this week, and growers who have not already done so may still have a window (5/3-5/4) for an effective oil application. In general, the mite load this season seems light, and an oil application early in egg hatch can go a long way toward effective ERM management.
It's Time!
We all dread the thinning season, but the only time that we can avoid it is when there is no crop. I'll take thinning. As we approach bloom (which should begin in earnest this week, at least at some locations), you must begin to consider your thinning strategy for this year. Over the last ten years, we have revised our recommendations significantly. This revised strategy includes a critical petal-fall treatment to all cultivars potentially requiring thinning.
Petal-fall thinning has two advantages. First, it thins fruit early, resulting in the best chance for enhanced fruit size. Secondly, it initiates competition among developing fruitlets, ultimately enhancing the ease of later thinning (which will be required in most cases).
Timing is from petal fall up to when fruit diameter is about 3 mm. The basic treatment is an application of Sevin (1 quart of Sevin XLR per 100 gallons dilute) In previous years, some orchards have experienced leaf damage as a result of this treatment, but in general, the enhanced thinning compensates for this problem. If more aggressive thinning is desired, NAA (6 ppm) may be added.
