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SCAFFOLDS Fruit Journal, Geneva, NY             Volume 5 
Update on Pest Management and Crop Development   August 5,1996

Coming Events

                                                     43F       50F
Current DD accumulations (Geneva 1/1-8/5):          2192      1479
                       (Highland 1/1-8/5):          2642      1804

Coming Events:                             Ranges:
Oriental fruit moth 2nd flight subsides         1806-2783  1164-1963
Apple maggot peak flight                        2033-2688  1387-1778
Redbanded leafroller 2nd flight subsides        2037-3045  1342-2160
STLM 2nd flight subsides                        2037-3045  1342-2160
Comstock mealybug 2nd gen. crawlers emerging    2106-2768  1447-1924
Obliquebanded leafroller 2nd flight starts      2199-3040  1490-2076
San Jose scale 2nd flight peaks                 2136-2591  1567-1874


TRAP CATCHES (Number/trap/day)
Geneva:   
                                  7/18  7/22  7/25  7/29   8/1   8/5
Redbanded Leafroller                 0   0.4     0     0     0     0
Spotted Tentiform Leafminer        709   316   409   167    67    66
Oriental Fruit Moth                8.2   5.3  12.7  13.1  77.2   3.9
Lesser Appleworm                   1.3   2.5   1.8   1.8   3.3   0.8
Codling Moth                       1.0   3.1   6.3   1.8   6.2  13.9
San Jose Scale                     0.5   0.1   3.0   0.9   0.2   6.3
American Plum Borer                1.5   2.4   2.3   3.9   6.0   3.9
Lesser Peachtree Borer (cherry)      0     0   1.3     0     0     0
Lesser Peachtree Borer (peach)     1.3   1.0   0.3   0.1   0.3   0.4
Peachtree Borer                    5.2   1.4   3.7   1.1   1.3   4.8
Obliquebanded Leafroller             0   0.3     0   0.1     0     0
Apple Maggot                       0.1     0     0   0.4   0.3   0.3

Highland (Dick Straub, Peter Jentsch)
                                   7/1   7/8  7/15  7/22  7/29   8/5
Redbanded Leafroller               1.8   3.0   3.8   0.1   0.3   0.2
Spotted Tentiform Leafminer        1.7  33.9  38.3  27.9  19.1   109
Oriental Fruit Moth                0.4   0.9   0.5   0.9   0.2   0.1
Lesser Appleworm                     0   0.2   0.1   0.4   1.9   2.5
Codling Moth                       1.8   1.4   0.2   1.4   6.2   8.9
Fruittree Leafroller                 0     0     0     0     0     0
Tufted Apple Budmoth               1.0   1.1   0.9   0.4     0   0.1
Obliquebanded Leafroller           2.4   2.6   0.4   0.2     0   0.3
Sparganothis Fruitworm             1.8   0.9   0.3     0     0     0
Variegated Leafroller                -     0   0.1*  0.1   0.2     0
Apple Maggot                       0.2*  0.3   0.3   0.8   0.9   3.4
                                                       * = 1st catch




DISEASES

PEACH X-DISEASE

By: Dave Rosenberger, Plant Pathology, Highland

X-disease of peaches is caused by a mycloplasma-like organism (MLO), is transmitted by leafhopper vectors, and causes decline and death of affected peach trees. In infected trees, X-disease symptoms usually appear first on only one small branch or limb and then gradually spread throughout the entire tree over a period of 2-3 years. Leaves on infected branches develop irregularly-shaped, interveinal, red-brown lesions that are often surrounded by distinctly water-soaked areas of yellow or light green. Leaves curl upward, gradually turn completely yellow, and drop from the tree. Affected twigs usually retain a "horse tail" of green developing leaves near the end of the twig even as all of the older leaves abscise. The only other common disorder on peaches that produces similar symptoms is nitrogen deficiency. However, nitrogen deficiency generally causes more uniform yellowing throughout the tree, and the red spots on leaves are more uniformly round.

X-disease does not appear to spread from one infected peach tree to another. Instead, the inoculum for infecting peach trees usually comes from infected chokecherry bushes (Prunus virginianae) around the perimeter of orchards. Sweet cherry trees can also carry X-disease and provide inoculum for infecting nearby peach orchards.

Ever since it was discovered in Connecticut in the 1930's, X-disease has been a somewhat cyclical disease in areas where chokecherries are prevalent. The disease gradually builds to epidemic proportions in peach orchards, then gradually disappears again in cycles of 15-20 years. Reasons for this long-term cycling are not known but might be related to infection, death, and re-establishment cycles in chokecherries. In the Hudson Valley, X-disease has been in the low part of its cycle for the past 5-8 years. Peach growers should therefore begin preventive measures now to reduce potential losses of peach trees as the disease begins to build again in the region.

X-disease in peaches can be prevented by keeping peach plantings separated from inoculum sources. In the Hudson Valley, new peach plantings should never be sited near old sweet cherry orchards because most older sweet cherry blocks have some trees with X-disease. Chokecherry plants that are within 500 ft of orchard perimeters should be removed. Chokecherry plants infected with X-disease develop red and yellow foliage in mid-late July. These infected bushes can be easily located in late summer and should be pulled out or cut off. Healthy green chokecherry plants should also be removed to prevent future build-up of inoculum around peach orchards. If chokecherries are cut off, the cut stumps should be treated with herbicide to prevent resprouting (See the Cornell Pest Management Recommendations for Commercial Tree Fruits).

When removing chokecherries, it is important to recognize the difference between wild black cherries (Prunus serotina) and chokecherries (P. virginianae). Prunus serotina does not harbor X-disease. P. serotina has more narrow leaves than chokecherry. It grows into a 60-80 feet tall tree whereas chokecherry is more bush-like and rarely exceeds 15-20 feet. P. serotina is frequently more abundant in hedgerows than is chokecherry, so failure to differentiate between the two can lead to much unnecessary work when the objective is only removal of chokecherry.

Peach growers who carefully monitor surrounding hedgerows and remove chokecherry annually during August will reduce risks that X-disease will become epidemic in their orchards over the next several years.




INSECTS

TAKING STOCK

By: Art Agnello, Entomology, Geneva

A few of our usual arthropod pests have been slightly less troublesome than normal this season, probably because of various weather irregularities, but the show isn't over just yet, and this would be a good time to take some next-to-last looks at potential trouble-makers before they can take us by surprise.

Apple Maggot - Catches have been light all around the region, but this first week in August has historically been the time for peak flight, and the soil is certainly soft enough to allow a normal emergence by whatever size population happened to make it through last summer. Be very diligent in checking any traps you have out, because we're getting indications that there may be a flush of adults coming soon.

Codling Moth - The model for 2nd generation codling moth larvae predicts that a control spray should be applied in problem orchards 1260 DD (base 50F) after the start of the FIRST flight (5/28 in Geneva, 5/20 in the Hudson Valley). As of today, 8/5, 1206 DD have accumulated in Geneva and 1464 at Highland. It's probably a little late in the Hudson Valley, but an OP application in problem orchards in western N.Y. is still a worthwhile option if no maggot sprays have been put on.

Spotted Tentiform Leafminer- Although we're past the prime control window of 690-1150 DD (base 43F) since the start of the 2nd flight, trees with more than 2 sapfeeding mines per leaf might still benefit from an application of a material such as Vydate or Provado, particularly to forestall the possibility of severe 3rd brood attack.

European Red Mite- Regardless of the low initial populations, it looks like this year won't be a rerun of 1994 after all, as healthy ERM outbreaks have been showing up in various blocks where the early programs were lacking either in quality (i.e., was there one?) or timing, and bronzed trees are not unheard of. Particularly in view of the hot temperatures expected this week, a careful foliar inspection should be conducted, at least in your problem blocks, to be sure a rescue treatment of some sort isn't needed where populations surpass this month's 7.5/leaf threshold.

Pear Psylla - One or two reports have reached me of increasing nymphal populations (after about 8 weeks of control by Agri-Mek), so the aforementioned hot summer weather could likewise stimulate some late season psylla activity this month. I would remind you that, if a treatment is needed, Provado does have pear psylla on the label now, and although we haven't tested it ourselves, anecdotal reports give it good marks (7 day PHI).

Comstock Mealybug- So far, we haven't seen any crawlers in our limb tape traps, but this is the time we expect them to be on the move. If you don't have traps out, check green shoots and cut a few pears to see whether any are showing up in the calyx. Penncap-M is recommended for this pest, and it is also on the Provado pear label.

Peachtree Borers- Eggs of both species are still able to hatch and get into your stone fruit trees, and this week is timely for any orchard on a seasonal control program of trunk sprays: cherries - Asana, Lorsban, Ambush, or Pounce; peaches - add Penncap-M and Thiodan to the above list (do not spray fruit).




LAST NOTICE

Don't forget that on Tuesday, August 13, Cornell Cooperative Extension and the N.Y.S. Horticultural Society are sponsoring a Fruit Field Day at the New York State Agricultural Experiment Station in Geneva, NY, to update growers on the latest research and extension advances in fruit crops. The field day will begin at 8:30 a.m. and end at 4:30 p.m. and is open to all interested fruit growers, consultants and industry personnel. The program will cover tree fruits, grapes and small fruits. Morning presentations will be for all participants and will highlight fruit breeding and enology, production systems, integrated pest management, genetic engineering, physiology, water and nutrient management. The afternoon presentations will be commodity-oriented, with separate tours for grapes, stone fruits, small fruits and apples. Cost is $10 per person, payable at the door; pre-registration is requested, so we can make sure everyone gets fed. Call Art Agnello (315/787-2341). Registration starts at 8:00 a.m., at the pavilion behind Jordan Hall.


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
Phone: 315-787-2341 FAX:315-787-2326
E-mail: ama4@cornell.edu


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