Diseases | Credits

SCAFFOLDS Fruit Journal, Geneva, NY                               Volume 4 
Update on Pest Management and Crop Development                 May 1, 1995 


                                                     43F       50F
Current DD accumulations (Geneva 1/1-5/1):          230        97
                       (Highland 1/1-4/30):         259        96

Coming Events:                              Ranges:
Tarnished plant bug adults active                 71-536     34-299
Rosy apple aphid nymphs present                   91-291     45-148
Pear psylla 1st egg hatch                        111-402     55-208
Green apple aphids present                       127-297     54-156
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
Green fruitworm flight subsides                  170-448     75-251
Redbanded leafroller 1st peak                    180-455     65-221
Spotted tentiform leafminer 1st flight peak      180-420     65-217
Peach at pink                                    152-269     68-119
Sweet cherry at bloom                            187-326     83-150
Pear at white bud                                217-423     99-217
Tart cherry at white bud                         257-326    109-149
McIntosh at pink                                 258-356    113-182

Geneva, 5/1
   Apple (McIntosh): Early Tight Cluster
   Pear: Early Green Cluster
   Sweet Cherry (Windsor): Early White Bud
   Tart Cherry (Montmorency): Bud Burst
   Peach: Half-inch Green
   Plum: Bud Break
Hudson Valley Lab, Highland, 5/1
   Apple (McIntosh): Pink 
   Pear (Bartlett): White Bud 

TRAP CATCHES (Number/trap/day)
                                  4/17   4/20   4/24    5/1
Green Fruitworm                    0.3    0.2    0.3    2.7
Redbanded Leafroller                 0      0    1.0*   0.6
Spotted Tentiform Leafminer          0   1.2*    157    371
Oriental Fruit Moth (apple)          0      0      0      0
Oriental Fruit Moth (peach)          0      0      0      0
Lesser Appleworm                     0      0      0   0.07*

Highland (Dick Straub, Peter Jentsch)
                                  4/11   4/17   4/24    5/1
Green Fruitworm                    1.0    0.3    0.7      0
Pear Psylla eggs (/terminal bud)   0.5    2.5   12.6      -
Redbanded Leafroller               0.5    2.6   10.4    8.7
Spotted Tentiform Leafminer          0   <0.1*  13.0   45.6
Oriental Fruit Moth                  0   <0.1*     0    9.3
Fruittree Leafroller                 -      -      0      0
                                                       * = 1st catch

Geneva: Lesser appleworm 1st catch.  Green fruitworm at peak flight.
Orleans Co.: Rosy apple aphid and Pear psylla 1st hatch.
Highland: Rose leafhopper nymphs increasing.


By: D. Rosenberger

Highland, NY:       Immature     Mature   Discharged   Tower shoot
Peru, NY, 4/24        92%           8%         0%      169 spores
Highland, NY, 4/25    58%          36%         6%     1063 spores


By: Dave Rosenberger, Plant Pathology, Highland

In the Champlain Valley (Peru), ascospore maturity early last week was still below the 15-17% mature spores level I usually consider the threshold for beginning fungicide applications in commercial orchards. However, some pseudothecia contained mature spores and were beginning to discharge ascospores. The high leaf-to-leaf variability caused by dry weather resulted in significant discharges in our tower shoot (169 spores) while the % mature spores remained relatively low. Ascospore maturity was expected to advance very rapidly, especially after the area finally received some rain last week.

In the lower Hudson Valley, the rain and moderate Mills' period April 21-22 resulted in only a slight increase in the proportion of empty asci detected, changing from 4% on April 20 to 6% on April 25. However, large numbers of spores are available for discharge. No infection periods occurred the week of April 24-29, but we had a light infection period beginning Sunday afternoon, April 30.


By: Dave Rosenberger, Plant Pathology, Hudson Valley Lab

Choosing a brown rot fungicide can be complicated, especially for growers with more than one kind of stone fruit and with concerns about controlling other diseases at the same time that they are applying brown rot fungicides. Many products that are labeled for controlling brown rot are not labeled for all stone fruit crops. The following chart has been compiled as an aid for selecting the most appropriate brown rot fungicide for the crop and disease complexes involved. Only the most commonly used brown rot fungicides are included.

Note that restrictions in addition to those noted on the table may apply. Always read the product label. Indar is a new fungicide that is not yet labeled in New York, but the New York label may be available in time for preharvest applications later this summer.

                                                            noted on the
             Crops labeled                                label or other
             for brown rot   Spray timings  PHI(4)        concerns about
Fungicide    control(1)      on label(2)     days  Rate/A  this compound
Captan       Ch,Pe,Ne,Pl,Ap  BB(3) & Prhvst   0    4-8 lb   4-day worker
                                                   varies     re-entry 
                                                  by crop  interval des-
                                                            pite 0-d PHI

Bravo 500    Ch,Pe,Ne,Pl,Ap  BB only          -   4.5-8 pt  Do not apply
                                                            shuck split

Botran 75W   Ch,Pe,Ne,Pl,-   BB                    4 lb    Tart cherries
             Ch,Pe,Ne,-,Ap   Prhvst: 10-1(3)  1             not labeled
                                                         for any applics

Benlate(6)   Ch,Pe,Ne,Pl,Ap  BB                    1-2 lb  Max 4 lb/A/yr
  50W                        Prhvst: 21-1(3)  3             (Ch, 6 lb)
                                                        Resistance probs
                                                          -- must use in

Topsin-M(6)  Ch,Pe,Ne,Pl,Ap  BB                    1.5 lb     Resistance
  (70W)                      Prhvst: 21-1(3)  1  (Pe, 2.25 lb)     probs

Rovral(7)    Ch,Pe,Ne,Pl,Ap  BB & Prhvst      0    1-2 lb  Max 5 appl/yr

Ronilan(7)   Ch,Pe,Ne,-,Ap   BB & Prhvst     14    1-2 lb     Max 3 BB &
  50W                                                     1 Prhvst spray

Funginex(8)  Ch,Pe,Ne,Pl,Ap  BB                    36-48    Max 3 BB & 3
  1.6EC      -,Pe,Ne,- -     Prhvst: 21-0(3)  0    fl oz   Prhvst sprays

Nova(8) 40W  Ch,Pe,Ne,- -    BB               7   2.5-6 oz      Max 3.25
                                                       marginal activity 
                                                            on brown rot
Orbit(8)     -,Pe,Ne,Pl,Ap   BB & Prhvst:
  3.6E                         21-0(3)        0    4 fl oz    Max 3 BB &
                                                                2 Prhvst 

Indar(8)     Ch,Pe,Ne,-,Ap   BB & Prhvst:                NOT YET LABELED
  75WSP                        21-1(3)        1     2 oz       IN NY (5)
                                                           Max 1 lb/A/yr
                                                              Apply with
                                                           wetting agent
(1) Ch = cherry; Pe = peach; Ne = Nectarine; Pl = plum; Ap = apricot 
(2) General spray timings listed for brown rot; other spray timings may 
  be needed for controlling other diseases listed in chart below. 
(3) BB = blossom blight; Prhvst = preharvest sprays, with numbers that 
  follow indicating preharvest spray timing in days as specified on the 
  labels; e.g., 10-1 means applications can be made beginning 10 days 
  before harvest with additional applications up to 1 day before harvest  
(4) PHI = preharvest interval in days.
(5) This product just received its federal label; the label for New York 
  State is expected later this year. 
(6-8) Fungicide classes: (6) Benzimidazoles; (7) Dicarboximides;  
  (8) Sterol-inhibitors.  Pathogens may develop cross-resistance to 
  fungicides within the same class.  

             cherry     peach  powdery  coryneum  black  peach
Fungicide    leaf spot  scab   mildew   blight    knot   leaf curl
Captan          X         X      -        X        -        -

Bravo 500       -         X      -        X        X        X

Botran 75W      -         -      -        -        -        -
Benlate(6)      X         X      X        -        X        -

Topsin-M(6)     X         X      X        -        X        -

Rovral(7)       X         -      -        -        -        -

Ronilan(7)      -         -      -        X        -        -

Funginex(8)     -         -      -        -        -        -

Nova(8) 40W     X         -      X        X        -        -

Orbit(8)        -         -      -        -        -        -

Indar(8)        X         X      -        -        -        -


By: Art Agnello, Entomology, Geneva


This occasionally serious pest of fresh market pears gives a number of growers problems each year. Pear rust mite outbreaks may be worse in areas receiving extensive sprays of materials destructive to predators, and the development of miticide-resistant strains are suspected in some cases. Scouts and growers have difficulty detecting these pests until after they have already damaged the crop because of their minute size. The overwintering stage is a light brown, wedge-shaped adult, which is nearly invisible without a 15X hand lens; these mites settle in any protected area on the trees, such as behind leaf buds, especially on wood 1 or 2 years old.

The mites become active as tree growth starts in the spring, and feed upon the first green tissue at the bud base, later moving to the foliage or fruit. The summer forms are nearly white in color, and even smaller than the overwintered adults. The more tender foliage is preferred, so populations on leaves decrease as the leaves mature and toughen. Damaging populations sometimes develop on the fruit soon after petal fall, sheltered in the hairs around the calyx and remaining active for a few weeks, until sometime in mid-July when they appear to leave the fruit.

Mite feeding causes leaves to turn brown or bronze, which may stunt the growth of young trees; on older trees the damage to fruit is far more significant. Severe russetting of the fruit can leave the entire surface rough and brown, which alters or destroys the desirable varietal skin appearance. Early in the growing season, mite feeding at the calyx or stem ends gives a localized russetting to those areas. If mite growth is unchecked, this feeding and russetting may spread over the fruit entirely, depending on the population numbers and the length of their feeding period.

Monitoring guidelines tend to be pretty complicated, but one rule of thumb is a 2-3% fruit infestation rate for fresh market pears; also, a spray should be applied if any pears contain 30 or more rust mites. If levels on individual fruits do not exceed 10 mites, there is generally a grace period of about 2 weeks within which a spray could be applied. A miticide such as Kelthane or Carzol should be used at petal fall if any of these thresholds are reached, but frankly, a preventive petal fall spray is probably the most advisable course of action in blocks with a history of rust mite infestations. Those growers electing to use Agri-Mek for pear psylla within the recommended 7-14-day post-petal fall time period will probably realize some added rust mite control from that spray. The effectiveness of summer sprays to control rust mite in N.Y. is questionable.


This is an old member of the insect community that had not been noticed for a number of years until recently. Pear leaf midge (Dasyneura pyri) is a gnat-like insect that has been responsible for increasing amounts of damage in Eastern New York pear orchards the past few years.

This insect occurs in Europe, the United Kingdom, New Zealand, and New Brunswick; however, its first reported U.S. occurrence was actually in the Hudson Valley in 1932. It has 3-4 generations per year, which are overlapping and variable in their timing. The adult is a dark brown fly, 1.5-2.0 mm in length; this small size, plus the fact that it lives for only 1-3 days, makes it difficult to observe in the orchard. The first generation adults begin to fly in late April, but this date can vary from mid-April to early May; the flight lasts until late May to early June. Eggs, which are reddish in color, are laid within the rolled margins of only undeveloped leaves, as soon as the leaves emerge from the bud. Several eggs, up to as many as 35, may be laid per leaf. The maggots (which are white to yellow-red in color) hatch out in 4-6 days and feed on the leaf surface for 10-12 days; this damage prevents the normal unrolling of the leaf. After the feeding period, some of the maggots drop to the soil and pupate close to the surface, while others pupate inside the rolled leaves. The entire life cycle takes 25-30 days, except that maggots of the last one or two generations of the season remain in the soil over the winter and pupate the following spring. The number of generations per year is probably determined by the length of the period during which there is new shoot growth in the summer.

Damage caused by pear leaf midge infestations can take a number of forms. This insect attacks only the foliage, which causes the edges of leaves to roll tightly upwards and inwards towards the midrib. Heavy infestations may cause shortening of extension shoots, an effect that is probably more important in nursery stock than in mature trees. During the early stages of an infestation, there is a slight, irregular puffiness or "lumpiness" to the rolled portion of the leaf, which may become reddened and brittle. Eventually the leaf curves downward like a sickle, and the red areas turn black; leaf drop may follow. Early in the season, infested leaves occur only at the tips of shoots. As the shoot extends, however, the young leaves at the tip may in turn be attacked by later generations, so that affected leaves may be found at several levels along the shoot.

At the present time, we can give only generalized guidelines for the control of pear leaf midge. Presumably, conventional management practices using insecticides had been controlling this insect, but economically damaging infestations have begun to occur because of either missed or poorly timed sprays, or because of an emerging pesticide tolerance in local populations. Successful control has been reported in New Hampshire using standard organophosphate compounds (i.e., azinphos-methyl, phosmet) to kill maggots rolled inside the leaves. In European orchards, diazinon also has been reported to be successful. In general, the best strategy appears to be spraying a known infestation in the late spring, after the first generation adults have laid eggs, but before pupation begins. Insecticide persistence is important; in problem orchards, 2-3 post-bloom applications are markedly better than 1-2. It may be necessary to examine the leaves regularly to determine the proper timing. To be practical, it is probably best to spray as soon as symptoms of an infestation are found (mid-May to early June).

Very little supplementary information is available about this pest. In New Zealand apple orchards, the use of the synthetic pyrethroid fenvalerate has been correlated with outbreaks of a closely related species (apple leaf midge). Bosc pears are slightly less susceptible than are Bartletts and Clapps. The prospects for natural control are uncertain, although two species of parasitic wasps have been recorded from the apple leaf midge. If insecticide resistance is the root cause of these infestations, and if they start to become more noticeable in commercial orchards, we may ultimately need to re-evaluate our pesticide use patterns in pears and begin looking for different approaches to this problem.

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
Dept. of Entomology, NYSAES
Geneva, NY 14456-0462
Phone: 315-787-2341 FAX:315-787-2326

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