Insects | Credits

SCAFFOLDS Fruit Journal, Geneva, NY                Volume 4
Update on Pest Management and Crop Development    July 3,1995 


                                                      43F       50F
Current DD accumulations (Geneva 1/1-7/3):          1462      1012
                       (Highland 3/1-7/1):          1548       987

Coming Events:                              Ranges:
American plum borer 2nd flight begins           906-1876    973-1265
Obliquebanded leafroller summer larvae hatch   1076-1513    630-980
Lesser peachtree borer flight peak             1099-2330    667-1526
Codling moth 1st flight subsides               1112-2118    673-1395
Redbanded leafroller 2nd flight begins         1198-2029    804-1381
Spotted tentiform leafminer 2nd flight peak    1295-1979    854-1355
San Jose scale 2nd flight begins               1449-1975    893-1407
Comstock mealybug 1st flight peak              1528-1782    981-1185
Apple maggot 1st oviposition                   1566-1724   1001-1232
Oriental fruit moth 2nd fligh peak             1612-2908   1062-2066

TRAP CATCHES (Number/trap/day)
                                  6/19   6/22   6/26   6/29    7/3
Spotted Tentiform Leafminer       12.2   15.3   49.3   67.5    104
Oriental Fruit Moth (apple)          0    0.7    8.1   20.8   14.9
Lesser Appleworm                     0    0.7    6.3   17.7   11.5
Codling Moth                       5.3    2.2    1.1    4.5    1.9
San Jose Scale                       0    0.2      0      -      0
American Plum Borer (cherry)        .2    0.2    0.1      0      0
Lesser Peachtree Borer (peach)       -    5.1    1.6    0.8    3.4
Lesser Peachtree Borer (cherry)    4.2    3.3    3.1    3.3    2.1
Peachtree Borer                      -    5.1    2.5    0.7    1.1
Obliquebanded Leafroller           3.3    3.0    1.1    0.7      0
Pandemis Leafroller                0.8    1.0      0    0.2    0.1
Apple Maggot                         0      0    0.3*   0.2    0.2

Highland (Dick Straub, Peter Jentsch)
                                   6/5   6/12   6/19   6/26    7/3
Spotted Tentiform Leafminer        0.9    2.9    9.1    9.2    2.6
Oriental Fruit Moth                1.1    1.4      0    0.4    0.6
Fruittree Leafroller                 0    0.3      0    0.2    0.3
Codling Moth                       4.9    3.5    1.1    8.6    0.8
Lesser Appleworm                     0      0      0      0      0
Sparganothis Fruitworm             0.1*   1.1    3.0    2.4    3.8
Tufted Apple Budmoth               1.4    1.0    1.6    1.3    2.8
Variegated Leafroller                0    0.5*   0.6    4.9      -
Obliquebanded Leafroller             0    0.8*   1.6    5.9    7.2
Apple Maggot                         -      -      -      -      0
                                                       * = 1st catch

   Obliquebanded Leafroller DD (base 43) since 1st catch (on 6/12) = 
     = 552.  We will reach 600 DD in the next 2-3 days.
   Spotted Tentiform Leafminer DD (base 43) since 1st catch (on 6/19)
     = 444.
   Obliquebanded Leafroller catch at peak.  DD (base 43) since 1st 
     catch = 547.
   Spotted Tentiform Leafminer 2nd flight began, 6/12.  DD (base 43) 
     since 1st catch = 547.


By:(Art Agnello & Harvey Reissig, Entomology, Geneva)


We have reached the prime part of the season for the buildup of mite populations, so regardless of how attentively you have watched the numbers in your specific orchards up to this point, a careful examination of at least the traditional trouble spots is recommended at this time, for a number of reasons. First, we are past the period of effectiveness of most early season applications of oil, etc., and even the small percentage of survivors from the most successful pre-bloom control programs can be expected to increase to problematic levels by early July. Also, this is normally the time when we see a big jump in numbers of motile forms because the first crop of European red mite summer eggs has completed their hatch. Numbers in some of our field plots went from less than 2 to 7-8 in just a few days last week. Finally, the hot and dry weather of late has been ideal for mite growth, so even though the ERM threshold goes up to 5 per leaf in July, the mites' rate of increase tends to turn exponential under these conditions.

This type of weather is also much favored by twospotted spider mites. I have seen at least one case of significant damage to pears in Wayne Co. caused by this species, and it's unlikely to be an isolated example. Recall that the TSSM overwinters as an inactive adult female beneath bark scales or under debris on the orchard floor. Occasionally, when winter temperatures are warm enough, the mites remain active and maintain a low population on weed hosts or cover plants in the orchard. As summer approaches and temperatures rise, mite populations increase and they begin to move up the tree trunks to the foliage. Characteristically, lower portions and canopy centers are attacked first, then the mites spread to the outside of the trees as their population increases. Feeding on pear leaves causes a unique browning or blackening of the foliage. It is not uncommon to have a colony of only 2-3 mites near the midrib of a leaf, and as a result of their feeding there is a blackening of large sections of leaf from the midrib to the margin. A low number of TSSM is more damaging than a similar count of ERM, and foliar blackening may appear after the mites have been controlled, brought about by a period of hot weather shortly after an effective spray has been applied.

If you miss the chance to control either of these species now, there may be no recovering before some significant damage is done to this very susceptible stage of the trees and fruit. Most growers should be going through their orchards now anyway, to assess the obliquebanded leafroller situation, so it shouldn't be much more trouble to pull off a few intermediate-age leaves and examine them for mites at the same time.


It was previously thought that the only leafhopper species present in N.Y. apples were white apple leafhopoper, WALH (which exhibits two generations after petal fall and in mid- to late August), and potato leafhopper, PLH (which appears sporadically between these broods, depending on weather). Then, an apparent additional brood was noted in eastern N.Y. between July and early August. This brood tended to overlap the late August population, so that various stages of WALH were often found on leaves throughout the summer. Field observations showed that many of the leafhoppers seen in apples during midsummer are actually a closely related species, rose leafhopper (RLH). A study of the leafhopper species complex in the Hudson Valley showed that RLH completes its first generation on weed hosts such as multiflora rose; adults begin ovipositing on apple in mid-June and nymphs appear by early July. From this time until harvest, both species are likely to be present on apple trees; usually one greatly predominates over the other, but the factors influencing the species mixture have yet to be determined.

WALH (or leafhopper species complex) appears to have two fairly distinct generations in western N.Y. Eggs from the single summer generation usually begin to hatch from late July to early August, continuing until mid- to late August. Adults appear in late August and are active until fruit harvest. Nymphs and adults feed on leaves during the summer, removing chlorophyll and causing white stippling. Excrement from nymphs and adults on fruit leaves small black spots that resemble the summer disease, flyspeck. During harvest, adults fly throughout the tree canopy, annoying pickers.

WALH nymphs and adults are usually most common on older fruit cluster leaves inside the tree. The number of WALH on a single older fruit cluster leaf should be counted on each of 10 clusters from 5 to 10 trees. Economic threshold levels for WALH feeding damage on apples have not been developed in New York, but the thresholds suggested in other states vary from an average of 0.25 to 2 WALH nymphs and adults per leaf. Treatment for second- or third-generation WALH (or RLH mixture) is recommended in New York if an average of one or more nymphs and adults per leaf is detected. Several parasites, predators, and a fungus attack WALH, but because these natural enemies are normally destroyed by pesticides they cannot adequately control WALH in commercial orchards. Chemical control is usually most effective if treatments are applied primarily against nymphs after most eggs have hatched.

Potato leafhopper is generally a more serious problem in the Hudson Valley than in western N.Y. or the Champlain Valley. PLH does not overwinter in the Northeast but instead migrates on thermals (warm air masses) from the South. Adults usually reach the Hudson Valley by May or early June and are found from mid- to late June in western N.Y. Because PLH migrate constantly during the season, there are no distinct broods or generations and the pest may be present continuously in orchards from June through harvest. We are currently seeing PLH nymphs in a number of N.Y. orchards.

PLH feeds on tender young terminal leaves. Initially, injured leaves turn yellow around the edges, then become chlorotic and deformed (cupping upward) and later turn brown or scorched. Damage is caused by a toxin injected by PLH while feeding. PLH also occasionally causes symptoms similar to the effects of growth regulators, such as excessive branching preceding or beyond the point of extensive feeding. PLH damage is often mistaken for injury caused by herbicides, nutrient deficiency, or overfertilization. PLH injury may not be serious on mature trees but can severely stunt the growth of young trees.

Nymphs and adults should be counted on 50-100 randomly selected terminal leaves in an orchard. Older trees should be sampled approximately every three weeks during the summer. Young trees should be sampled weekly from early June through July. PLH nymphs are often characterized as moving sideways like crabs, whereas WALH generally move forward and back. No formal studies have been conducted in New York to determine the economic injury level for PLH on apples, so we suggest a tentative threshold of an average of one nymph or adult PLH per leaf. Little is known about the natural enemies of PLH, but it is assumed that they cannot control this pest in commercial New York orchards.

Populations of all leafhopper species in New York are resistant to the conventional organophosphate materials. Moreover, many of the pesticides in other chemical classes that are effective against PLH are toxic to beneficial mites. Effective materials include Provado, Sevin, Cygon, Thiodan, Carzol, Lannate, and Vydate.


This is a suitable time to assess the need for control of the various fruittree borers in your orchards; most of the problem species are flying now and of course, laying eggs, so some well-directed trunk sprays might be advisable. The peachtree borers (both species) are well into their season's appearance, and now is a good time to make an application of Lorsban 4EC, Asana, Pounce or Ambush to the trunks (do not spray fruit) of cherry trees for lesser peachtree borer control; no spray is needed if Thiodan was used within the previous 30 days. For peaches, add Penncap-M and Thiodan (either formulation) to this list. Plums can also suffer from these pests, and Thiodan, Asana, and Penncap-M are labelled for use. American plum borer is an increasingly common pest of tart and sweet cherry, and a Lorsban 4E can be helpful before harvest (6-day PHI) and afterward, but the most effective period for treatment was at petal fall.

Dogwood borers should be laying eggs in susceptible apple orchards now (those with succulent burrknot tissue or suckers). The larva of this clearwing moth feeds on apple trees, primarily on burrknot tisse on clonal rootstocks. Burrknots are aggregations of root initials that can develop on the above-ground portion of the rootstock; all commercial dwarfing and semi-dwarfing rootstocks have a tendency to develop burrknots. Some chemicals with hormone effects, such as NAA, can increase the expression of burrknots, as will failure to keep the area around the trunk weed-free and open to sunlight. White latex paint brushed on the exposed portion of the rootstock will prevent new infestations of the borers, and also protect against southwest injury to the bark. Dilute trunk applications of an insecticide with good residual activity can provide control of established infestations. At this point in the season, a spray of Lorsban 50WP or Thiodan 50WP would be the most effective materials if applied anytime until Aug. 15, bearing in mind the specific pre-harvest intervals.

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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