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Mani SkariaProfessor

Weslaco, TexasTAMUK Citrus Center

DiaprepesRoot Weevil andFungus Phytophthora the

Texas Experience

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Decline of sweet orange trees

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Decline stages 1, 2, 3, and 41

2

3

4

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Phytophthora

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Structural roots

(both vertical andhorizontal)rotten, black

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The taco effect Trunk had no scaling or

gumming symptomsof Phytophthora

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Neighboring trees too

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10/29Helps initial diagnosis

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11/29Helps initial diagnosis

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12/29Look for adult or larvae

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Diaprepesadult

Leafnotching,grapefruit

Wingscollected

from the soil

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D= dying, dd = dead, R =replaced, M = missing trees. 1,2,3,4 indicate row numbers of sweet orange treeson sour orange planted in five section and severely affected by D. abbreviatus. Dooryard trees in all fourdirections are also affected. All as a result of importation of contaminated out of state plants.

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Orchard 1Orchard 2

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Citrus DiaprepesandPhytophthora

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Host Environment

& conditions

Pathogen Helper

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Weevil feeding damage

on the trunk &larger root

No symptoms on theabove ground trunk

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Adult

Larva atwork

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Little leaf notcher orgolden headed weevilCompsus auricephalu

Brown leaf notcher or

Mexican leaf notcherEpicaerus mexicanus

Sugarcane rootstockweevil Diaprepesabbreviatus

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Sampling forPhytophthora

- high water table

26 R 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1

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25 R R R R R D R R D D R R D R R 1

D 24 R R R R R D R R D R R R R R 2

R 23 R M D 3

R 22 D D R R D D R R R 4

R 21 R M R R R 5

R R 20 D D D R R R 6

R 19 R R R R R R D 7

R D D 18 R R R R D 8

R D R 17 R R D R R M 9R R R D 16 dd R R R R R D 10

D 15 R D M R R D D M R 11

D R M 14 D dd M R 12

D R 13 R

D D 12 D

M D 11 R R D

D R dd R 10 R dd R R R D 1

R D dd 9 R R R R R R D R 2

D D M R 8 dd R D R R D dd D R R R 3

R D 7 M dd D D M 4

R R 6 D R R D D D 5

R D 5 R R R

R 4

R 3

D D R 2 M

D D R 1 R M M M

7 6 5 4 3 2 1 1 2 3 4 5 6

1 2 3 4 5 6 7 8 9 10 1 1 12 1 3 1 4 15 16 1 7 1 8 19 2 0 21 2 2 2 3 24 25 2 6 2 7 28 29 3 0 3 1 32 3 3 34 3 5 3 6 37 38

1 D D R dd D D R R D R R R R

2 R R R D R D D D

3 D R R R D R R D D dd D D D D

4 R D R dd dd D M D D

5 D R D D D D D D R D D D D D D D D

6 M R R D D R R R R M D D D D D dd D

7 D D D dd D R D D R M D D D dd D R D D R D R D

8 M R R R D D D D D R R R D M D D dd D R

9 M M R M M M M M M M M M

Yellow =

treesremoved

Purple =

declining

Red = dead

trees

Blue =

missing

tree

Hobbs Drive

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Processing soil and root samples

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Orchard Survey

Orchards studied: 17Trees checked: 17,612Number of declining trees: 806 (4.6%)Number of dead trees: 125 (0.7%)

PhytophthoraAssay

Samples tested: 116Phytophthorain soil: 104 (89.7%)Phytophthorain feeder roots: 29 (25%)Phytophthorain large roots: 13

(11.2%)

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Mani SkariaProfessor

Weslaco, Texas

TAMUK Citrus Center

DiaprepesRoot Weevil andFungus Phytophthora the

Texas Experience

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