Table 1.
Plant-parasitic nematodes found in commercial pecan orchards in Georgia in 2017, 2018, and 2019.
| County | Nematode genera and ecoregions |
|---|---|
| Piedmont region | |
| Clarke | Meloidogyne, Paratrichodorus, Mesocriconema, Helichotylenchus, Xiphinema, Paratylenchus, Hemicycliophora, Heterodera |
| Rockdale | Meloidogyne, Paratrichodorus, Mesocriconema, Helichotylenchus, Xiphinema |
| Spalding | Meloidogyne, Mesocriconema, Tylenchorhynchus, Helichotylenchus, Xiphinema |
| Walton | Meloidogyne, Hoplolaimus, Pratylenchus, Paratrichodorus, Mesocriconema, Tylenchorhynchus, Helichotylenchus, Hemicycliophora, Xiphenema |
| Coastal Plain region | |
| Appling | Meloidogyne, Hoplolaimus, Paratrichodorus, Mesocriconema, Helichotylenchus |
| Berrien | Meloidogyne, Paratrichodorus, Mesocriconema, Helichotylenchus |
| Bibb | Meloidogyne, Pratylenchus, Paratrichodorus, Mesocriconema, Helichotylenchus, Xiphinema |
| Colquitt | Meloidogyne, Paratrichodorus, Mesocriconema, Tylenchorynchus, Helichotylenchus, Xiphinema |
| Cook | Paratrichodorus, Mesocriconema, Xiphenema |
| Crisp | Meloidogyne, Paratrichodorus, Mesocriconema, Helichotylenchus, Xiphinema and Heterodera |
| Decatur | Meloidogyne, Paratrichodorus, Mesocriconema, Helichotylenchus, Xiphinema |
| Dougherty | Meloidogyne, Hoplolaimus, Paratrichodorus, Mesocriconema, Helichotylenchus, Xiphinema, Paratylenchus |
| Grady | Paratrichodorus, Mesocriconema, Helichotylenchus, Xiphinema |
| Houston | Meloidogyne, Hoplolaimus, Pratylenchus, Paratrichodorus, Mesocriconema, Helichotylenchus, Xiphinema |
| Irwin | Meloidogyne, Paratrichodorus and Mesocriconema |
| Jefferson | Meloidogyne, Paratrichodorus, Mesocriconema, Tylenchorhynchus, Helichotylenchus, Xiphinema |
| Lee | Meloidogyne, Mesocriconema |
| Mitchell | Meloidogyne, Hoplolaimus, Pratylenchus, Paratrichodorus, Mesocriconema, Helichotylenchus,Xiphinema, Paratylenchus |
| Peach | Meloidogyne, Hoplolaimus, Pratylenchus, Paratrichodorus, Mesocriconema, Tylenchorhynchus, Helichotylenchus, Xiphinema |
| Taylor | Meloidogyne, Paratrichodorus, Mesocriconema, Xiphinema |
| Tift | Meloidogyne, Paratrichodorus, Mesocriconema, Tylenchorhynchus, Paratylenchus |
| Turner | Meloidogyne, Paratrichodorus, Mesocriconema, Helichotylenchus, Xiphinema, Paratylenchus, Hemicycliophora |
| Ware | Meloidogyne, Hoplolaimus, Paratrichodorus, Mesocriconema, Helichotylenchus and Xiphinema |
| Wilcox | Meloidogyne, Paratrichodorus, Mesocriconema, Helichotylenchus,Xiphinema |
| Worth | Meloidogyne, Paratrichodorus, Mesocriconema, Xiphinema |
Table 2.
Survey of frequency and abundance of five major nematode genera on pecans in Georgia during 2017–2019 by county in two pecan growing ecoregions, Piedmont (P) and Coastal Plain (CP).
| Meloidogyne | Paratrichodorus | Mesocriconema | Helichotylenchus | Xiphinema | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| County | N | PFa | ABb | MDc | PFa | ABb | MDc | PFa | ABb | MDc | PFa | ABb | MDc | PFa | ABb | MDc |
| Clarke (P) | 10 | 80 | 27 | 160 | 10 | 3 | 3 | 30 | 16 | 37 | 30 | 1 | 1 | 20 | 4 | 5 |
| Rockdale (P) | 10 | 10 | 7 | 7 | 20 | 2 | 2 | 80 | 3 | 6 | 100 | 20 | 69 | 70 | 1 | 1 |
| Spalding (P) | 10 | 30 | 24 | 50 | –d | – | – | 40 | 2 | 2 | 100 | 23 | 111 | 30 | 1 | 1 |
| Walton (P) | 30 | 33 | 21 | 124 | 23 | 4 | 10 | 100 | 8 | 31 | 87 | 27 | 97 | 27 | 2 | 3 |
| Appling (CP) | 10 | 90 | 13 | 23 | 80 | 3 | 14 | 100 | 10 | 33 | 10 | 1 | 1 | – | – | – |
| Berrien (CP) | 09 | 44 | 188 | 658 | 22 | 2 | 3 | 56 | 16 | 41 | 11 | 1 | 1 | – | – | – |
| Bibb (CP) | 10 | 20 | 36 | 58 | 100 | 7 | 13 | 100 | 24 | 97 | 100 | 206 | 637 | 50 | 2 | 5 |
| Colquitt (CP) | 07 | 71 | 41 | 83 | 100 | 4 | 9 | 100 | 44 | 89 | 71 | 13 | 25 | 14 | 2 | 2 |
| Cook (CP) | 10 | – | – | – | 50 | 2 | 3 | 100 | 10 | 71 | – | – | – | 10 | 5 | 5 |
| Crisp (CP) | 12 | 58 | 11 | 43 | 58 | 3 | 5 | 83 | 14 | 49 | 58 | 28 | 100 | 42 | 2 | 5 |
| Decatur (CP) | 10 | 70 | 27 | 78 | 20 | 1 | 1 | 90 | 5 | 12 | 10 | 1 | 1 | 60 | 2 | 5 |
| Dougherty (CP) | 10 | 50 | 5 | 11 | 50 | 3 | 5 | 100 | 24 | 45 | 20 | 2 | 2 | 20 | 1 | 1 |
| Grady (CP) | 10 | – | – | – | 20 | 1 | 1 | 90 | 18 | 46 | 60 | 3 | 4 | 40 | 6 | 14 |
| Houston (CP) | 14 | 43 | 14 | 34 | 14 | 2 | 2 | 93 | 54 | 293 | 14 | 16 | 30 | 36 | 3 | 9 |
| Irwin (CP) | 10 | 40 | 38 | 67 | 40 | 2 | 3 | 100 | 49 | 309 | – | – | – | – | – | – |
| Jefferson (CP) | 10 | 70 | 10 | 60 | 70 | 3 | 8 | 90 | 40 | 121 | 10 | 1 | 1 | 40 | 1 | 1 |
| Lee (CP) | 10 | 30 | 2 | 2 | – | – | – | 100 | 11 | 26 | – | – | – | – | – | – |
| Mitchell (CP) | 10 | 40 | 5 | 12 | 70 | 4 | 14 | 90 | 37 | 121 | 50 | 3 | 5 | 10 | 2 | 2 |
| Peach (CP) | 20 | 15 | 35 | 84 | 95 | 10 | 29 | 85 | 18 | 72 | 95 | 27 | 187 | 50 | 2 | 4 |
| Taylor (CP) | 10 | 40 | 1 | 1 | 20 | 3 | 4 | 90 | 6 | 27 | – | – | – | 20 | 3 | 3 |
| Tift (CP) | 10 | 70 | 11 | 36 | 60 | 3 | 3 | 100 | 20 | 49 | – | – | – | – | – | – |
| Turner (CP) | 10 | 30 | 39 | 104 | 10 | 1 | 1 | 100 | 20 | 62 | 40 | 2 | 6 | 90 | 3 | 5 |
| Ware (CP) | 10 | 20 | 3 | 4 | 10 | 1 | 1 | 100 | 11 | 31 | 10 | 1 | 1 | 20 | 2 | 3 |
| Wilcox (CP) | 10 | 70 | 22 | 119 | 30 | 4 | 6 | 90 | 16 | 36 | 10 | 13 | 13 | 10 | 1 | 1 |
| Worth (CP) | 10 | 80 | 18 | 64 | 10 | 1 | 1 | 100 | 28 | 60 | – | – | – | 40 | 2 | 4 |
1 Notes: aPF = percent frequency‒Total number of samples in which nematode genera was detected divided by the total number of samples collected in that county (N), multiplied by 100 to convert to a percentage. bAB = Abundance‒Sum of nematode densities per 100 cm3 soil divided by the total number of samples in which the nematode genus was detected in the county on either survey date. cMD = Maximum density of each genera detected per 100 cm3 soil. dDashes indicate the absence of specific nematode genera.
Table 3.
Frequency of occurrence and abundance of plant-parasitic nematodes in commercial pecan orchards from two ecoregions of Georgia, 2017–2019.
| Coastal Plain region | Piedmont region | |||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Mean percentages of 6 soil samples | Mean percentages of 4 soil samples | |||||||||||||||
| Nematode genus | PFa | ABNb | STD | MDc | Sand | Silt | Clay | pH | PFa | ABNb | STD | MDc | Sand | Silt | Clay | pH |
| Heterodera | 2 | 35 | 9.3 | 138 | 87.5 | 5.92 | 6.56 | 6.6 | 3 | 4 | 0.7 | 5 | 65.5 | 17.25 | 17.28 | 5.45 |
| Xiphinema | 28 | 3 | 1.6 | 14 | 87.5 | 5.92 | 6.56 | 6.6 | 33 | 2 | 1.0 | 5 | 65.5 | 17.25 | 17.28 | 5.45 |
| Hoplolaimus | 7 | 4 | 1.5 | 15 | 87.5 | 5.92 | 6.56 | 6.6 | 3 | 2 | 0.4 | 2 | 65.5 | 17.25 | 17.28 | 5.45 |
| Pratylenchus | 1 | 1 | 0.1 | 1 | 87.5 | 5.92 | 6.56 | 6.6 | 13 | 4 | 1.5 | 7 | 65.5 | 17.25 | 17.28 | 5.45 |
| Paratylenchus | 1 | 6 | 2.9 | 42 | 87.5 | 5.92 | 6.56 | 6.6 | 3 | 4 | 0.7 | 5 | 65.5 | 17.25 | 17.28 | 5.45 |
| Mesocriconema | 93 | 23 | 35.2 | 309 | 87.5 | 5.92 | 6.56 | 6.6 | 75 | 7 | 7.2 | 37 | 65.5 | 17.25 | 17.28 | 5.45 |
| Meloidogyne | 44 | 25 | 47.6 | 658 | 87.5 | 5.92 | 6.56 | 6.6 | 37 | 23 | 27.0 | 160 | 65.5 | 17.25 | 17.28 | 5.45 |
| Hemicycliophora | 1 | 1 | 0.1 | 1 | 87.5 | 5.92 | 6.56 | 6.6 | 15 | 3 | 1.3 | 6 | 65.5 | 17.25 | 17.28 | 5.45 |
| Helichotylenchus | 30 | 44 | 58.6 | 637 | 87.5 | 5.92 | 6.56 | 6.6 | 82 | 23 | 27.7 | 111 | 65.5 | 17.25 | 17.28 | 5.45 |
| Paratrichodorus | 46 | 5 | 4.2 | 29 | 87.5 | 5.92 | 6.56 | 6.6 | 17 | 3 | 1.6 | 10 | 65.5 | 17.25 | 17.28 | 5.45 |
| Tylenchorhynchus | 4 | 23 | 11.1 | 164 | 87.5 | 5.92 | 6.56 | 6.6 | 8 | 2 | 0.9 | 6 | 65.5 | 17.25 | 17.28 | 5.45 |
1 Notes: aPF (Percent frequency) = Percent of total samples with species present, N = 222 and 60 samples from Coastal Plain and Piedmont regions, respectively. bABN (Abundance) = Sum of nematode densities per 100 cm3 soil divided by the total number of samples in which the nematode genus was detected. cMD (Maximum density) = Maximum count observed in 100 cm3 soil samples. Minimum was zero for all species. STD = standard deviation.
Figure 1:
3-D NMS ordination of PPN soil samples from 282 Pecan trees in the Piedmont and Coastal Plain ecoregions of Georgia, USA (Final stress of the 3-D NMS solution = 13.36, proportion of variance explained by all three axes combined = 0.911). Dark gray pyramids (▲) represent pecan soil samples collected from the Piedmont ecoregion (n = 60) and light gray pyramids (▲) represent soil samples collected from the Coastal Plant ecoregion (n = 222).Blue asterisk with names in bold text represent the centroids of the 11 PPN genera (sheath, lesion, cyst, dagger, lance, ring, RKN (root-knot), spiral, stunt, stubby root, pin (Praty)) in the 3-D NMS solution. Piedmont ecoregion soil samples were distributed from the left side of the NMS ordination space to the middle (front to back). Coastal Plain ecoregion soil samples were distributed primarily from the middle to the right side of ordination space. This spatial division of soil samples taken from the Piedmont and Coastal Plains ecoregions strongly suggests that the pecan PPN communities differ between ecoregions.
Table 4.
Indicator Species Analysis (see Severns and Sykes, 2020 for an analysis description) results showing which PPN nematodes were statistically associated (*) with pecan soil samples from the Piedmont (60 soil samples) or Coastal Plain (222 soil samples) ecoregions of Georgia, USA.
| Nematode genus | Indicator value (0–100) | Ecoregion | p value (from 5,000 randomizations) |
|---|---|---|---|
| Ring, Mesocriconema spp.* | 73.8 | Coastal Plain | 0.0002 |
| Spiral, Helichotylenchus spp.* | 48.1 | Piedmont | 0.0002 |
| Stubby-root, Paratrichodorus spp.* | 36.1 | Coastal Plain | 0.0028 |
| Root-knot, Meloidogyne spp. | 24.4 | Coastal Plain | 0.69 |
| Dagger, Xiphinema spp. | 15.3 | Piedmont | 0.85 |
| Sheath, Hemicycliophora spp.* | 14.8 | Piedmont | 0.0002 |
| Lesion, Pratylenchus spp.* | 13.0 | Piedmont | 0.0002 |
| Lance, Hoplolaimus spp. | 5.8 | Coastal Plain | 0.28 |
| Pin, Paratylenchus spp. | 3.6 | Coastal Plain | 0.64 |
| Stunt, Tylenchorhynchus spp. | 3.3 | Coastal Plain | 0.83 |
| Cyst, Heterodera spp. | 2.0 | Coastal Plain | 0.71 |