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Avoiding the Introduction of Exotic Pests Through Proper Site Preparation

Avoiding the Introduction of Exotic Pests Through Proper Site Preparation John M. Halbrendt Fruit Research & Extension Center Biglerville, PA jmh23@psu.edu PPV Quarantine Area, Quarantine Removed/Replanting Allowed: 1/22/07

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Avoiding the Introduction of Exotic Pests Through Proper Site Preparation

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  1. Avoiding the Introduction of Exotic Pests Through Proper Site Preparation John M. Halbrendt Fruit Research & Extension Center Biglerville, PA jmh23@psu.edu

  2. PPV Quarantine Area, Quarantine Removed/Replanting Allowed: 1/22/07

  3. Could the introduction of Plum Pox Virus (PPV; Sharka) into Pennsylvania have been avoided? If PPV eradication is successful, can we prevent re-introduction? Are there other exotic diseases we need to be concerned about?

  4. Lessons Learned from Plum Pox Virus Peach ‘Encore’

  5. • Prior to 1999 PPV was not known in North America • Virus can be vectored by aphids, or move long distances in infected propagation material • Entry into US/PA - unknown

  6. PPV Symptoms - Apricot

  7. PPV Symptoms - Plum Plum

  8. PPV - Leaf Symptoms

  9. PPV - Blossom Break

  10. Do other exotic diseases pose a serious threat to Pennsylvania? • > 40 virus-like agents that infect Prunus • Some recorded in U.S. • Several new outbreaks, in peach and in sweet cherry • Several causing severe • economic damage

  11. Examples of other Endemic and “Exotic” Virus Diseases infecting Prunus of concern to Pennsylvania growers

  12. Prune Dwarf Virus- pollen / seed borne transmission PDV Infected Healthy • Common and widespread • Management:  Virus-free certification

  13. Prunus Necrotic Ringspot (PNRSV) Pollen borne virus Fruit yields may be decreased by 40 to 50 percent, depending on conditions

  14. Cherry Leaf Roll Virus (CLRV) • Infection by Cherry leaf roll virus alone is difficult to recognize; symptoms are vague, and difficult to distinguish from other stress • Infection by CLRV and another virus such as PDV or PNRSV can produce very dramatic symptoms • Vector unknown

  15. Diseased Healthy Cherry leaf roll virus & Prunus necrotic ringspot virus SYMPTOMS: Weak terminal growth; delayed fruit development; poor leaf color and size

  16. Cherry Rasp Leaf Virus (CRLV) • Distribution - Western States, e.g., Colorado • Transmitted by grafting and by dagger nematodes • Alternate Hosts - weeds such as dandelion • Fruit production is reduced and young trees may die

  17. Cherry – Rasp Leaf Symptoms • Prominent projections (enations) are found on undersides of leaves • Deformed leaves; many are extremely narrow, folded, and distorted • Not all parts of a tree will show symptoms at the same time

  18. Flat Apple Disease caused by CRLV

  19. Peach Rosette Mosaic Virus • Distribution - MI and NY • Vector - dagger nematodes (also found on grape) (Photo by Don Ramsdell)

  20. PeachMosaic Pale green areas vary from tiny flecks to large blotches These spots become necrotic and fall out causing "shot-holes”

  21. Cherry Mottle Leaf Virus • Mottle-leaf • pattern -principle symptom • Most severe on • Bing, • Royal Ann, • and Lambert • Mottling - irregular and chlorotic, causing a leaf distortion • early in the season; leaves pucker increasing as the • season advances

  22. Cherry Twisted Leaf Virus Symptoms • Abrupt kink in the midrib or the petiole, which causes the leaf to appear twisted • Leaves develop asymmetrically or stay small; spurs appear bunchy due to shortened internodes • Once the tree is infected, the disease spreads rapidly to all branches

  23. 4 healthy cherries among infected fruit Photo part of OSU Extension Plant Pathology slide collection, 1949 Apricot Ring Pox on Bing Healthy and Little Cherry-infected Fruit

  24. CherryRosette

  25. Prunus Stem Pitting Causal agent: Tomato ringspot virus (ToRSV) Vector: Dagger Nematode Distribution: Common and widespread Alternate Hosts: At least 23 species of broadleaf weeds Management: Virus-free trees; control nematode vector and broadleaf weeds (i.e., reservoirs of ToRSV)

  26. Peach Stem Pitting - Autumn

  27. Apple Union Necrosis and Decline(AUND) • Caused by ToRSV - vectored by dagger nematode • Common and widespread • Scion/stock interface reveals a poorly formed union • Susceptibility to this problem depends on the scion/rootstock combination

  28. AUND - Gingergold / M26

  29. Examples of other tree fruit virus diseases of concern to Pennsylvania growers

  30. Dapple Apple • Dappling more intense as fruit mature, surface somewhat flattened

  31. Apple Mosaic Virus • Leaves develop pale yellow to bright cream-colored areas as they expand during early spring

  32. Pear Stony Pit • The causal agent of pear stony pit has not yet been isolated • Transmitted by grafting

  33. Apple Decline - Cause Unknown; Appears to be Virus

  34. Elimination of Virus from Plants There is no practical way to eliminate a virus once it is in a field setting - the only solution is to destroy the host

  35. The Key to Virus Control: PREVENTION

  36. ONLY PLANT CLEAN TREES • Buy certified virus-free trees whenever possible • Buy from a reputable nursery • Ask questions! Are the trees virus-tested? Tested for which viruses? • All trees ~ pollinizers, replants, trial varieties ~ are important

  37. DON’T INTRODUCE PROBLEMS • Follow production guide recommendations for nematodes, weeds… • Don’t bring trees of unknown virus content near your trees • Don’t bring fruit of unknown virus content near your trees

  38. KEEP AN EYE OUT FOR ANYTHING UNUSUAL Bring in experts to consider possible causes….

  39. Symptoms of Virus Infection • Foliar discoloration or deformity • Change in growth habit • Change in maturity timeline • Stem pitting or union necrosis • Fruit deformation • Lack of vigor; decline • Inability to cope with other stressors

  40. START WITH A CLEAN SITE • Follow university site preparation guidelines • Test for nematodes • Consider previous crops • Check out the • neighborhood

  41. Cultural Practices - Minimize Alternate Hosts Weeds / Alternate Hosts for Dagger Nematode and Tomato Ringspot Virus

  42. Use GOOD TREE REMOVAL TECHNIQUES To Prevent Spread!

  43. Why is it important to remove old roots? • Root tissue may harbor pathogens • Roots may send up suckers • Roots interfere with soil • fumigation

  44. GOOD TREE REMOVAL TECHNIQUES ! • Kill / remove as much root as possible • Prevent sucker re-growth

  45. Sub-soil to remove old roots and loosen soil

  46. Evaluate the site for potential replant problems to determine if corrective measures are needed • Nematode assay • Soil fertility (include pH and organic matter) • Consideration of the cropping history (risk factors) and crop to be planted • Advice from consultant / specialist

  47. REPLANT PROBLEMS Biotic Abiotic Replant Disease Physical: Compaction Loss of OM Fungi Bacteria Actinomycetes Chemical: Herbicide Allelochemicals Fertility pH - toxicity Nematodes Complex Disease Nema + Virus Nema + Fungi

  48. Replant problems are caused by changes in soil conditions resulting from years of monoculture

  49. Remediation of replant sites is an attempt re-establish optimum soil conditions for healthy tree growth

  50. Soil Fumigation • Soil temperature40o-80o F • Soil moisture • Moist from 2” to 12” below surface • Determined by “feel” • Varies with texture • Soil tilth • Free of clods and plant residue • Seedbed-ready soil condition

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