General Information | Insects | Diseases | Credits
Volume 7, No. 6 April 27, 1998
COMING EVENTS 43F 50F Current DD accumulations (Geneva 1/1-4/27): 318 163 (Geneva 1997 1/1-4/27): 180 73 (Geneva "Normal" 1/1-4/27): 209 90 (Highland 1/1-4/27): 476 246 Coming Events: Ranges: Tarnished plant bug adults active 71-536 34-299 Pear psylla nymphs present 111-402 55-208 Lesser appleworm 1st catch 135-651 49-377 Spotted tentiform leafminer 1st oviposition 141-319 48-154 Obliquebanded leafroller larvae active 149-388 54-201 European red mite egg hatch 157-358 74-208 Redbanded leafroller 1st flight peak 180-455 65-221 Spotted tentiform leafminer flight peak 180-544 65-275 Comstock mealybug 1st gen crawlers in pear buds 220-425 82-242 Mirid bugs 1st hatch 328-432 156-231 McIntosh at bloom 310-544 130-275 Phenologies (Geneva): Apple (McIntosh) - Pink (Red Delicious) - Early Pink Pear (Bartlett) - Bloom Sweet Cherry (Darrow) - 50% Petal Fall Tart Cherry (Montmorency) - Bloom Peach - 10% Petal Fall Plum - Bloom (Highland): Apple (McIntosh) - Bloom Pear (Bartlett) - 80% Petal Fall Plum (Stanley) - Fruit Set Peach - Fruit Set Apricot - Shucks Off TRAP CATCHES (Number/trap/day) Geneva: 4/13 4/16 4/20 4/23 4/27 Green Fruitworm 0 0 0 0.2 0.1 Spotted Tentiform Leafminer 10.5 414 96 511 375 Redbanded Leafroller 1.5 8.7 9.6 11.5 4.8 Oriental fruit moth (apple) 0.1* 0.3 0.9 7.5 6.0 Oriental fruit moth (peach) 0 0 0 0 0 Highland (Dick Straub, Peter Jentsch): 4/6 4/13 4/20 4/24 4/27 Pear Psylla (eggs/leaf) 5.5 9.3 9.6 - 16.3 Pear Psylla (nymphs/leaf) - 0.5* 0.7 - 2.3 Green Fruitworm 0.1 1.0 0.4 0 0 Spotted Tentiform Leafminer 0.1 0.1 0.1 404 17.2 Redbanded Leafroller - - - 34* 8.3 Oriental Fruit Moth - - - 2.5* 2.3 Codling Moth - - - 0 0 Obliquebanded Leafroller - - - 0 0 * 1st catch PEST FOCUS Highland: 1st Redbanded Leafroller caught 4/23. Serpentine Leafminer mines, and Rosy Apple Aphid causing leaf curl on apple 4/24. European Red Mite eggs hatching. Pear Psylla hardshells observed.
McIntosh reached full bloom in the lower Hudson Valley on April 22. This is the earliest full-bloom date since 1977 when McIntosh reached full bloom April 22. Other years when full bloom on McIntosh occurred in April were 1976 (April 20), 1985 (April 29), 1986 (April 30), 1990 (April 28), and 1991 (April 27). In all other years since 1960, full bloom on McIntosh occurred between May 2 and May 19.
by Art Agnello & Dick Straub
Pear psylla nymphs were noted on the foliage in western N.Y. as early as April 15, and a couple of days before that in the Hudson Valley, so if things continue at this pace, it looks like we'll easily have the potential for some high nymphal numbers in the clusters by petal fall. This is a good time to formulate a management approach in those blocks with a history of high psylla pressure.
First of all, it should be remembered that Mitac is still effective in many orchards. This contact material has been around for some time and most growers are aware of how to use it and the results to expect. Results from our research trials have shown that two applications (3 oz/acre), as needed, often maintain populations below damaging levels. It is a decent rescue material in situations where previous treatments of something else have failed. Mitac is restricted to two applications per season.
Agri-Mek has also been available for several years, and although its effectiveness has sometimes been regarded as uneven, this is usually in direct relationship to how strictly the use guidelines have been followed. First of all, it's important to get the material into the leaf tissue, and in our trials this has meant applying it *soon* after petal fall, within 1-2 weeks, before the leaves harden off. This might even be more critical during a fast spring such as we seem to be experiencing this year. Apply it too late and it will just sit on the surface and be subject to rapid breakdown, and it's not a good contact material. Secondly, use it in combination with an adjuvant to get it into the leaves, preferably highly refined petroleum oil such as SunSpray Ultra Fine or Stylet-Oil. Finally, this is a product with a clear dose-response effect; there's no use trying to cheap out by using the low (10 oz/A) rate on a high pressure block. Use the 20-oz rate, and you'll have a better chance of staving off a summer resurgence.
Pear psylla nymph enclosed by its honeydew droplet
Because Agri-Mek has been the standard, usage of Provado (imidacloprid) has not been extensive in N.Y. Provado is also absorbed into the leaf and therefore acts primarily as a stomach poison. The label allows for two applications at 20 oz/acre, to be applied postbloom as needed. Provado has been included in our evaluations during the past six years. A summarization of the data suggests that an application at petal fall, followed by a second application within 14 to 28 days, works well against low to moderate populations. However, during two years with extremely high populations (1994 & 95), this two-application scheme did not work - but then, neither did anything else! Provado appears to be suitable for rescue situations. In 1997, a high pressure year in the Hudson Valley, Provado applied May 29 (9d post-petal fall) and July 9 had relatively high nymph numbers on the leaves, but low damage; it is possible that these treatments produced some sub-lethal effects that allowed nymphs to survive, but with reduced feeding and honeydew secretions. Results from Michigan in 1997 were similar.
Pear psylla "hard shell" (fifth instar) stage nymph
Pyramite, a new entry into the pear psylla arena this year, is likewise limited to 2 applications per season (with a 30-day interval, 7-day PHI). In 1997, its effectiveness was comparable to that of Provado in both the Hudson Valley and in Michigan. The high rate (13.2 oz/A) is likewise recommended here.
With a number of different options available, it is obviously possible now to attempt some combinations and rotations to manage your psylla susceptibility and prolong product field life. Maybe try Agri-Mek at petal fall, and one of the other materials for a midsummer rescue, etc. Regardless, don't be caught unaware this year; things could happen fast, and the successful pest managers will be anticipating instead of reacting.
by Dave Rosenberger
Plant Pathology, Highland
The first apple scab lesions appeared in unsprayed trees at the Hudson Valley Lab on April 21. Unfortunately, scab lesions also appeared in many commercial orchards at about the same time. In fact, apple growers in the Hudson Valley are facing the most severe scab year they have seen in at least a decade.
Why is scab appearing in so many orchards? Several contributing factors can be cited:
Why be concerned about a few scab lesions? This is a common sentiment when a little bit of leaf scab is found in orchards around Memorial Day. Unfortunately, we still have four weeks until Memorial Day. That means four extra weeks for scab to spread around before disease progression is slowed by June heat and by the increasing natural resistance in the growing fruit. Four weeks is enough time for at least two extra cycles of secondary scab. As a result, a near-perfect fungicide program will be needed to keep scab off of fruit in orchards where primary lesions are now evident.
What is the best fungicide program for controlling a running epidemic of apple scab? Captan used in combination with an SI fungicide is the safest bet. The rate for captan should be 4.5 to 6 lb/A for the 50W formulation or 2.8 to 3.75 lb/A for the 80W formulation. Dodine (Syllit), benomyl (Benlate), and thiophanate-methyl (Topsin M) should not be used for scab control because resistance to these fungicides is common throughout New York State.
Captan is more effective against scab than is mancozeb. In a 1997 field trial at the Hudson Valley Lab, we compared the activity of Dithane 75DF, Polyram 80DF, and Captan 50W in a block with severe disease pressure. Sprays were applied to small plots with a handgun, so spray coverage was excellent. As shown in the table below, captan provided the best control of both leaf scab and fruit scab. In fact, captan used alone was just as effective for controlling fruit scab as was the combination of Nova plus thiram.
Treatment and rate of % apple scab on McIntosh product per 100 gals cluster lvs terminal lvs fruit (June 17) ____________________________________________________________________ Control* 70 47 91 Captan 50W 1 lb 1 a 4 b 0 a Dithane 75DF 1 lb 4 b 8 c 9 b Polyram 80DF 1 lb 5 b 17 c 6 b Nova 40W 1.33 oz plus Thiram 75 WDGF 14 oz 0 a 1 a 0 a ____________________________________________________________________ *The control was not included in statistical analyses. Mean separations were determined using Fisher's Protected LSD, P = 0.05.
If captan alone was just as effective as a Nova plus contact fungicide combination, why bother with the SI fungicide? Adding the SI fungicide will improve control of secondary spread to new leaves. Note that the treatment involving Nova provided the best control of scab on terminal leaves. In the trial conducted last year, secondary spread of scab during summer was limited by dry weather. In a wet year, the extra control of foliar scab provided by SI fungicides could translate into less fruit scab at the end of the year.
The bottom line is that captan is our best protectant fungicide for apples. An SI fungicide applied with captan will provide additional protection against foliar scab and will reduce the numbers of spores and the viability of spores produced in the existing scab lesions. Captan alone works well against a running scab epidemic in years when rainfall stays at or below average. If the spring turns unusually wet, then the SI-plus-captan combination will probably prove superior.
Using captan at petal fall and first cover creates problems for those wishing to use Agrimek plus oil for mite control because captan and oil are not compatible. Where scab has not been well controlled, the best strategy may involve applying captan during bloom and at petal fall, then switching back to mancozeb for a single spray when oil is applied with Agrimek.
Scaffolds is published weekly from March to September by Cornell University - NYS Agricultural Experiment Station (Geneva), and Ithaca - with the assistance of Cornell Cooperative Extension. New York field reports welcomed. Send submissions by 3 p.m. Monday to:
Scaffolds Fruit Journal
Editors: A. Agnello, D. Kain
Department of Entomology, NYSAES
Geneva, NY 14456-0462
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Photographs courtesy of New York State Integrated Pest Management Program