Coming Pest Events | Pest Focus | Trap Catches | Insects | Diseases

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Coming Pest Events | Pest Focus | Trap Catches | Insects | Diseases

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Coming Pest Events | Pest Focus | Trap Catches | Insects | Diseases

Geneva: Obliquebanded Leafroller trap catch increasing. Degree days
(base 43°F) accumulated since 1st OBLR adult catch = 156.
(300-340 DD = 1st hatch).

Highland: Rose Leafhopper nymphs observed.
Potato Leafhopper damage observed.
1st catch of Sparganothis Fruitworm, Tufted Apple Bud Moth,
and Variegated Leafroller.
Degree days (base 43°F) accumulated since 1st OBLR adult catch
= 299. (300-340 DD = 1st hatch).

Coming Pest Events | Pest Focus | Trap Catches | Insects | Diseases

ORCHARD RADAR DIGEST

Geneva Predictions:
Roundheaded Appletree Borer
RAB peak emergence: June 12.
Peak egglaying period roughly: June 27 to July 12.

Codling Moth
Codling moth development as of June 14: 1st generation adult emergence at 70% and 1st generation egg hatch at 16%.
1st generation 20% CM egg hatch: June 15 (= single spray date where one spray needed to control 1st generation codling moth).

Obliquebanded Leafroller
1st generation OBLR flight, first trap catch: June 7.
If using BT insecticide, optimum date to begin 2 to 4 weekly low-rate applications for small OBLR larvae is roughly: June 26.

Oriental Fruit Moth
2nd generation OFM flight begins around: July 1.
Optimum 2nd generation - first treatment date, if needed: July 7.

Redbanded Leafroller
2nd RBLR flight begins around: July 3.

San Jose Scale
1st generation SJS crawlers appear: June 18.

Spotted Tentiform Leafminer
2nd STLM flight begins around: June 16.
Rough guess when 2nd generation sap-feeding mines begin showing: July 6.

Highland Predictions:
Roundheaded Appletree Borer
RAB peak egglaying period roughly: June 17 to July 3.

Codling Moth
Codling moth development as of June 14: 1st generation adult emergence at 91% and 1st generation egg hatch at 54%.

Lesser Appleworm
2nd LAW flight begins around: July 1.

Obliquebanded Leafroller
If using BT insecticide, optimum date to begin 2 to 4 weekly low-rate applications for small OBLR larvae is roughly: June 17.
Optimum first sample date for summer generation OBLR larvae: June 26.

Oriental Fruit Moth
2nd generation OFM flight begins around: June 23.
Optimum 2nd generation - first treatment date, if needed: June 26.

Redbanded Leafroller
2nd RBLR flight begins around: June 24.

San Jose Scale
1st generation SJS crawlers appear: June 10.

Spotted Tentiform Leafminer
2nd STLM flight begins around: June 8.
Rough guess when 2nd generation sap-feeding mines begin showing: June 26.

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MODEL BUILDING

Plum Curculio. Most sites should reach the 340 DD (base 50°F) spray cutoff for this pest this week, so if your trees are protected for the next 4-5 days, that should be sufficient. Our sample numbers:

Albion (May 17 PF estimate) - 279

Appleton/Niagara Co. (May 20 PF estimate) - 231

Clifton Park/Capital District (May 15 PF estimate) - 462

Geneva (May 17 PF estimate) - 313

Highland (May 10 PF estimate) - 453

Lyndonville (May 17 PF estimate) - 274

Sodus (May 17 PF estimate) - 290

Williamson (May 17 PF estimate) - 271

Oriental Fruit Moth. This pest's development is tracked using a 45°F DD model from biofix, defined as the first sustained moth catch. Peach growers should have applied their second (14 days after PF) application of a pyrethroid by now for this insect (plus plum curculio).

Codling Moth. With 250 DD (base 50°F) as a first spray date, we currently have:

Geneva (1st catch May 17) - 313

Albion (1st catch May 17) - 279

Williamson (1st catch May 18) - 255

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Coming Pest Events | Pest Focus | Trap Catches | Insects | Diseases

APPLE TREE DEATHS ATTRIBUTABLE TO HERBICIDES?
(Dave Rosenberger, Plant Pathology, Highland; and Mike Fargione, CCE, Hudson Valley Regional Fruit Program)

Over the past five years, we have noted with increasing frequency a kind of trunk injury on apples trees that does not fit the description of any known disease. The injury usually occurs at or near ground level and extends 2-8 inches up the trunk from the graft union. Frequently the injury is confined to one side of the trunk (Fig. 1), but in some orchards large numbers of trees are killed after trees become girdled. Bark on roots below the soil line and on the trunk above the cankered area remains healthy. The canker margin is usually rather distinct. In some orchards, cankers are most prevalent on the southwest side of trees, suggesting that winter injury may be involved. However, in other orchards, the injury may be more prevalent on the northern side of the trees. In eastern New York, tree losses from this trunk canker are becoming more common than tree losses from fire blight.

Most affected orchards have the following characteristics:

• The orchards are well-managed with a very clean herbicide strip.
• Trees affected are generally more than five years old with trunks at least three inches in diameter.
• Severity of damage is often variety-dependent, with especially severe injury noted on Cortland and Macoun trees.
• Affected orchards have received glyphosate (Roundup or generic equivalents) at least once per year.

At this point, we are just initiating research to determine the causes of this potentially lethal trunk canker. However, we are sharing our hypotheses at this time in hopes of minimizing further damage. We also encourage observers to contact us with other ideas, observations, and information.

Hypotheses for explaining herbicide-induced trunk cankers:

1. The trunk cankers result from hitting the lower part of the tree trunks with glyphosate sprays.
2. Stress within the glyphosate-sprayed bark may enable the white rot fungus, Botryosphaeria dothidea, to invade and kill the bark.
3. The glyphosate/B. dothidea interaction may be more lethal in trees that are under water stress when the glyphosate is applied as compared with non-stressed trees.
4. Cankers may not become apparent until several years after the injury that allowed canker initiation. Therefore, eastern NY growers noting cankers for the first time this summer may be seeing results of herbicide injury that occurred during the July-August drought of 2002.

Observational support for these hypotheses:
The patterns of injury on the trunks is often consistent with the exposure pattern that would be expected from an herbicide sprayer where the boom is adjusted to provide overlapping coverage in the line directly between trees within the row. The injury has been observed in orchards where only glyphosate and gramoxone are applied, so we can rule out residual herbicides as a potential cause. Gramoxone has a longer history of usage than glyphosate, and the trunk canker problem emerged relatively recently during the same time frame during which we suspect that orchard use of glyphosate was increasing. The extremely clean herbicide strips in many of the affected orchards suggest late summer applications of glyphosate are common in the affected blocks.

B. dothidea is endemic in most older apple orchards where it commonly occurs in superficial cankers that cause little damage to the tree (Fig. 2A). However, B. dothidea can become aggressively pathogenic in drought stressed trees. When that happens, necrosis can extend into the inner bark (Fig. 2B). Thus, B. dothidea is commonly present in older apple trees but can cause serious damage only when trees encounter stress conditions. Perhaps glyphosate alone can cause the injury that we are seeing, but we suspect that in many cases glyphosate and B. dothidea are acting together.

Management implications:
Drastic changes in ground cover management are not warranted at this time because we still have no experimental evidence that glyphosate injury is at the root of the problem. However, if our hypotheses are correct, then the following precautions are worth considering:
1. Glyphosate applications made after July 1st may be more likely to cause injury than those made during May and June, because trees are more likely to be under stress conditions during summer and fall. Gramoxone may be a safer alternative for summer and fall sprays.
2. If glyphosate is applied during late summer or fall, the lowest effective rate of glyphosate should be used, contact with the tree trunks should be minimized, and sprays should not be applied during periods when trees are likely to be water stressed (i.e., during drought periods or on very hot days).
3. Read glyphosate labels carefully! Many different formulations are currently available, so anyone using 10-yr-old notes when adding glyphosate to their spray tank may be drastically overdosing their trees.
4. Whether using glyphosate or gramoxone, always include a drift inhibitor in the spray tank to minimize the potential for unwanted drift of small spray droplets.
5. Glyphosate should never be applied in orchards using controlled droplet applicators (CDA sprayers) because these applicators by definition generate small droplets that are prone to drift.

In summary, caution is advised when applying contact herbicides during summer or fall. Everything possible should be done to avoid contacting trunks with the herbicide sprays. Finally, we emphasize that the relationships between trunk cankers and herbicide injury or infection by B. dothidea remain to be proven. We will appreciate input from anyone who can contribute further information on occurrences and causes of the trunk canker problem in apples.

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
P.O. Box 462
Geneva, NY 14456-0462
Phone: 315-787-2341 FAX: 315-787-2326
E-mail: ama4@cornell.edu

Online at <http://www.nysaes.cornell.edu/ent/scaffolds/>