Nematode Management in Pecans

A. P. Nyczepir

Collaborators

• Bruce Wood, USDA-ARS

• Janete Brito, FL Dept. Agric. Cons. Serv.

• Don Dickson, Univ. Florida

HISTORY (Meloidogyne partityla on Pecan)

(Pecan Root-Knot Nematode)

• 1986 – 1st reported in South Africa.

• 1996 – 1st report in US (TX).

• 2001 – 2nd report in US (NM).

• 2002 – 3rd report in US (GA).

• 2005 – 4th report in US (FL)

• 2006 – 5th report in US (AZ & OK)

ABOVE-GROUND SYMPTOMS

(M. partityla on Pecan)

• Dead branches in

upper canopy.

• Some trees severely

stunted.

BELOW-GROUND SYMPTOMS

(M. partityla on Pecan)

Typical root galls Mature female

IDENTIFICATION

(M. partityla on Pecan)

• Protein Analysis (USDA – Byron) (see below)

• DNA Analysis (NM State Univ.)

GA GA GA GA GA

NM NM NM NM NM NM Mp-GA Mp-GA

Mi Ma Ma Ma

Distribution of M. partityla in Georgia

• In 2003-04, a survey was conducted in the major pecan growing regions of Georgia.

• Root samples infested with root-knot nematode were obtained from 13 different commercial pecan production sites.

• M. partityla was the predominant root-knot nematode found; occurring in 72% of the orchards sampled.

Nyczepir, Reilly, & Wood, 2004

Influence of M. partityla (Mp) on

severity of ME symptoms of pecan.

Uninoculated Mp-alone

Nyczepir et al., 2006

M. partityla is a contributing factor to promoting “Nickel” deficiency in pecan.

CONTROL

(M. partityla on Pecan)

• Chemical – no effective control (Temik).

• Cultural – unknown to date.

• Rootstock – unknown to date.

• Biological – unknown to date.

OBJECTIVE

(M. partityla on Pecan)

• Determine the susceptibility of 9 selected

pecan rootstocks to M. partityla.

• Determine the susceptibility of 5 selected

peach rootstocks to M. partityla.

METHODS

(M. partityla on Pecan)

• Open pollinated seedling stocks evaluated:

– Apache - Pawnee - Moneymaker

– Caddo - Schley

– Curtis - Stuart

– Elliott - Wichita

METHODS

(M. partityla on Pecan)

• Root-Knot Nematodes evaluated:

– M. partityla (Pecan root-knot).

– M. incognita (Southern root-knot).

– M. arenaria (Peanut root-knot).

• 1,400 eggs per pot

METHODS

(M. partityla on Pecan)

• Data recorded after ~160 days:

– No. egg masses per root system.

– No. root galls per root system.

– No. eggs per root system.

RESULTS

(M. partityla on Pecan)

• Regardless of rootstock, there were more (P < 0.05) egg masses & galls per root system assoc. with M. partityla vs. Mi & Ma.

• Pecan is a better host for Mp than either Mi or Ma.

RESULTS

(M. partityla on Pecan)

• All pecan rootstocks

tested supported

greater (P < 0.05)

numbers of M.

partityla than Mi or

Ma

• M. partityla

reproduces better on

pecan than either Mi

or Ma.

Egg/g root Eggs/mass

“Elliot”

METHODS (M. partityla on Peach)

• Peach seedling stocks evaluated:

Nemaguard

Lovell

Guardian

Halford

Flordaguard

METHODS

(M. partityla on Peach)

• 1,500 eggs per pot

• Elliott pecan (Control)

• Data recorded after ~127 days:

– No. egg masses per root system.

– No. root galls per root system.

– No. eggs per root system.

RESULTS (M. partityla on Peach)

• All peach rootstocks were rated as non-

hosts (highly resistant) to M. partityla

infection.

• Number M. partityla eggs per plant • All peach stocks (0 eggs/plant)

• Elliott (>17,000 eggs /plant)

Nyczepir and Wood, 2012

Field Microplot Study

OBJECTIVE: Conduct a long-term field

evaluation study to determine if ‘Curtis’ or

‘Elliott’ tree growth is impaired due to M.

partityla infection.

Influence of M. partityla on Tree Growth

Tru

nk D

iam

ete

r (m

m)

a b Tree growth of both ‘Elliott’ &

‘Curtis’ rootstocks was

suppressed in the presence

of M. partityla 2 years after

inoculation.

CONCLUSIONS

• All open pollinated pecan seedlings tested were

good hosts to M. partityla.

• All peach rootstocks tested were non-hosts to M.

partityla.

• Interplanting pecan & peach trees in a

commercial orchard does not appear to intensify

M. partityla populations between these 2 crops.

• Growth suppression was observed at the same

level in both ‘Curtis‘ & ‘Elliott’ stocks in the

presence of M. partityla.

Biological Control

Pasteuria penetrans

Is an endospore-forming bacterial parasite.

Has been shown to have great potential as

a biocontrol agent of root-knot nematodes.

Has never been evaluated against the

pecan root-knot nematode, M. partityla.

OBJECTIVE

Determine if Pasteuria penetrans

can effectively suppress populations

of M. partityla on pecan.

METHODS

• Evaluate three (3) different Pasteuria isolates for parasitism against of M. partityla (GA-pecan isolate) in the laboratory.

• Bacteria endospores of the most promising isolates will then be increased and re-evaluated under field microplot conditions at USDA-Byron.

RESULTS

• Laboratory results have identified specific

P. penetrans isolates that have exhibited

attachment & efficacy against the juveniles

of pecan root-knot nematode.

M. partityla juvenile

A B C

A B

METHODS

1) Nematode-alone (Mp) (4,000 eggs/pot)

2) Both organisms (Mp + Bacteria (720,000 spores/pot)

3) Control

Tree Growth T

runk D

iam

. (m

m)

a ab b a ab b

Tree Death (2013)

- Control = 0%

- Mp+Pp = 8%

- Mp-alone = 42%

SUMMARY

The findings of this research indicate that the Pecan Root-Knot Nematode is:

1. A potentially economically important pathogen to the pecan industry in the SE United States.

2. The search for an IPM management strategy (i.e., rootstock, biological, chemical, etc.) for control of this nematode pest on pecan is warranted.