UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

OFFICE OF 

PREVENTION, PESTICIDES

AND TOXIC SUBSTANCES

DATE: 8/21/2000

SUBJECT: Review of Request for Residue Data Developed for 

Almonds to be Translatable to Pistachios for 

Establishing Tolerances. DP Barcode D212794.

 .

FROM: Bernard A. Schneider, Ph.D., Plant Physiologist

Chemistry and Exposure Branch 1

Health Effects Division (7509C)

THRU: William Hazel, PhD, Chairperson CHEMSAC

Health Effects Division (7509C)

TO: Hoyt Jamerson, Product Manager

MUERIB

Registration Division (7505C)

Dr. Keith W. Dorschner, Coordinator, Interregional Research 

Project No. 4 (IR-4) submitted a proposal to CHEMSAC on April 

24, 2000 on behalf of the IR-4, the California Pistachio 

Commission, and the University of California to request that 

residue data developed for almond is translatable to pistachio 

and will be used to establish tolerances for pistachio. 
Background:

On March 4, 1997 (see attached report of B.A. Schneider, 

D212794, CBTS# 15228), HED recommended that pistachios be 

included as a member of the Tree Nuts Crop Group (40CFR§180.41). 

It was also determined that the representative commodities 

almond and pecan for the Tree Nuts Group adequately represent the 

Crop Group. This policy paper was sent to Registration Division 

for implementation by publishing an amendment to the Crop Group 

final rule in the Federal Register. However, due to FQPA 

priorities, the Agency has no plans to amend the Crop Group 

Regulations at this time, but the Agency is allowing petitioners 

to request tolerances for pistachio based on residue data 

submitted for the Tree Nut Crop Group. Until the Federal 

Register Notice is issued revising the Crop Group Regulation, 

tolerances for pistachios will be listed separately from the Crop 

Group, but the tolerance will be established at the same level as 

the Crop Group. 

CONCLUSIONS

1a. The pistachio nutmeat is enclosed in a fleshy hull 

composed of three distinct tissue layers which include: an 

epicarp or outer layer; a mesocarp or middle layer; and 

endocarp the hard inner layer or shell.

1b. The epicarp and the mesocarp combine to form the fleshy 

hull that protects the nut. The endocarp will become the 

hard nutshell that protects the edible embryo or nutmeat 

(RAC). 

1c. it is the hard nutshell enclosed in the protective 

fleshy hull that splits or dehisces near harvest, and even 

though up to 80 % of the nut shells may be split at harvest, 

over 97 % are still enclosed and well protected from surface 

pesticide residues by the outer intact pericarp layers at 

harvest. 

1d. Only 2.4 % of the pistachios had both the outer hull and 

shell split at harvest and these are called "early splits".

1e. Early splits are not desirable and 91 to 93 % of the 

early splits are currently sorted out by high speed 
bichromatic sorters after harvest and discarded during 

processing because of being poor quality and being 

vulnerable to or carriers of aflatoxins. 

1f. Several research projects are designed to reduce the 

number of early splits by improved cultivar development or 

by developing better processing and sorting equipment. A 

new machine vision bichromatic sorting system will improve 

the number of early splits removed to > 99 %. 

2. Residue trial data and established tolerances comparing 

pesticide residue levels in pistachios with other tree nuts 

have consistently been similar.

3. Imported pistachios account for less than 1.0 % of all 

pistachios consumed in the U.S., thus early splits appearing 

from the different cultivars from these countries would be 

an extremely insignificant amount. 

4. Pistachios share the same weed, nematode, insect and 

plant disease, and post harvest storage problems that 

affect the other members of the Tree Nuts Crop Group. 

5. Almonds are a better representative commodity than 

pistachios for the Tree Nuts Crop Group because almonds have 

significantly higher percent hull splitting; more of the 

developed almond nutmeat is present during pesticide 

applications; almonds have a livestock feed item (hulls); 

almonds are produced in much larger quantities; and almonds 

have a more porous and soft shell. 

6. Based on similarities of pesticide residue levels, 

cultural practices, pomological similarities, production 

regions, and pest problems pistachios should be included as 

a member of the Tree Nuts Crop Group.

7. There are no animal feed items associated with 

pistachios.

RECOMMENDATIONS
Chemistry Branch recommends including the pistachio 

(Pistacia vera L.) as a member of the Tree Nuts Crop Group 

(40CFR§180.41). All deficiencies regarding including pistachio 

nuts in the tree nut crop group have been resolved. We expect 

pesticide residues in the pistachio nutmeat to be similar to the 

other nut crops that are members of the Tree Nut Crop Group, 

because the outer hull remains’s intact completely covering and 

protecting the nutmeat even after the shell has split. These 

early splits are further removed during processing by automated 

high speed bichromatic machines and by hand sorting such that > 

99 % of the culls are removed at the packinghouse. 

Common names for pistachios to be added to the Crop Group 

Index are `green almond' and `pistacia nut'. There will be no 

change to the representative commodities for the Tree Nut Crop 

Group. The representative commodities are almonds and pecans.

NOTE: Chemistry Branch would like to thank both IR-4 and Dr. 

Louise Ferguson, Extension Pomologist, University of California 

at Davis and Mr. Eric Harmon for arranging and collecting weekly

samples of in-hull pistachio during the growing season for us to 

investigate. The resultant observations and data were essential 

in determining that pistachios should be a member of the Tree 

Nuts Crop Group.

Table 2. Updated Comparison of Established Tolerances for 

Pistachio and Tree Nut Crops. 

Pesticide (CFR 

Citation)

Pistachio 

Tolerance 

(ppm)

Tree Nut Crop 

Tolerance (ppm)

Benomyl 

[§180.294]

 0.2 0.2 (nuts) 

Glyphosate 

[§180.364(a)] 

 0.2 0.2 (nuts)

Azoxystrobin 

[180.507]

 0.01 0.01

Halosulfuron 

 0.05

0.05
Pesticide (CFR 

Citation)

Pistachio 

Tolerance 

(ppm)

Tree Nut Crop 

Tolerance (ppm)

[180.479] 

 

Urea [180.1117]

exempt

almond, pistachio

Magnesium 

phosphide 

[§180.375]

 0.1

0.1 (almonds, filbert, 

pecans, 

walnut)

Permethrin 

[§180.378]

 0.1

0.05 (almond, filbert, 

walnut)

Azinphos-methyl 

[§180.154]

 0.3

0.3 (almond, filbert, 

pecan, walnut)

Carbaryl 

[§180.169]

 1.0

1.0 (almond, filbert, 

pecan, walnut)

2,4-D 

[§180.142(b)]

 0.2

0.2 (nuts)

Napropamide 

[§180.328(a)]

 0.1 0.1 (nuts)

Oryzalin 

[§180.304]

 0.05 0.05 (nuts)

Oxyfluorfen 

[§180.381]

 0.05 0.05 (tree nuts group 

(except almond 

hulls) 

Paraquat 

dichloride 

[§180.205]

 0.05 0.05 (nuts)

Phosmet 

[§180.261]

 0.1 0.1 (nuts)

Aluminum 

phosphide 

[§180.225]

 0.1 0.1 (almonds, Brazil 

nuts, walnut)
Pesticide (CFR 

Citation)

Pistachio 

Tolerance 

(ppm)

Tree Nut Crop 

Tolerance (ppm)

Methyl bromide 

(§180.123]

 200 200 (almonds, Brazil 

nuts, bush nuts, 

butternuts, cashews, 

filberts, hickory nuts, 

pecans, walnuts) 

DETAILED CONSIDERATIONS

BACKGROUND:

Chemistry Branch has considered the inclusion of pistachio 

nuts to the tree nut crop group four times (memos of F. Griffith, 

Jr., RCB No. 1057, 9/25/85; R.W. Cook, 2/25/85; E. Leovey, 

4/16/80, and R.B. Perfetti, 10/9/79), and all of these previous 

requests were rejected by CB (previously RCB). All of the 

outstanding deficiencies regarding including pistachio nuts in 

the tree nut crop group have been resolved, except for CB 

concerns "that the unsealed husks or shells (splits) found in 

pistachio nuts would expose the edible portion to significantly 

higher residues than would occur in other tree nuts" (memo F. 

Griffith, Jr., RCB No. 1057, 9/25/85).

The Chemistry Branch had also previously thought that since 

the pistachio nut shell splits before harvest, it would be 

readily exposed to pesticide applications. However, literature 

references indicate (30, 31) that although the pistachio shell 

splits before harvest, the nutmeat remains inside an intact hull 

so it may not be exposed to a pesticide. The critical issue with 

pistachios will be to determine how intact the outer hull that 

surrounds the shell and nutmeat remains during the season from 

flowering to harvest. 

Since the critical remaining issue was to determine the 
exposure of the actual pistachio nutmeat to pesticide 

applications, Dr. Schneider arranged with IR-4 (G. Markle), to 

submit pistachio nuts at weekly intervals for up to a 6-week 

period ending at harvest. These samples helped CB determine the 

extent that the outer hull around the actual nutmeat stays intact 

and if it could prevent the possibility of direct pesticide 

residues to the nutmeat before harvest. IR-4 arranged for Dr. 

Louise Ferguson, Extension Pomologist, University of California 

at Davis and Mr. Eric Harmon, student at Fresno working for Dr. 

Ferguson to collect from a commercial pistachio orchard 

approximately one kg of in-hull pistachios from July until 

harvest on September 22, 1995. The samples were counted for 

number of hulls split, extent of hull cracking and dissected to 

determine if the nut shells were split or open. Chemistry Branch 

would like to thank these researchers for their cooperation in 

obtaining and shipping pistachios in various stages of 

development for the 6-week period before harvest. In addition, 

CB conducted a comprehensive literature search on pistachio hull 

splitting and current research projects in USDA on pistachios. 

All of the above combined data were used to determine the extent 

that the outer fleshy hull stays intact even after the inner 

shell splits. 

In order to understand the pistachio hull and shell 

splitting and their influence on potential pesticide residues in 

the nutmeat, an understanding of the botanical (pomological) 

terms that relate to the fruit or drupe of the pistachio is 

necessary and will be discussed below.

POMOLOGICAL FACTORS RELATING TO PISTACHIO HULL SPLITTING: 

Botanically, pistachios and almonds have fruits called 

drupes. In the case of tree nuts, the drupe consists of a single 

edible seed lying inside a thin but hard bivalve shell that is 

surrounded by a fleshy hull or pericarp. The pericarp consists 

of three layers or tissues. These three layers of the pericarp 

are as follows: [1] an epicarp or outer layer; [2] a mesocarp or 

middle layer; and [3] endocarp the hard inner layer (12). The 

epicarp and the mesocarp combine to form the fleshy hull that 

protects the nut. The endocarp will become the hard nutshell 

that protects the edible embryo or nutmeat (RAC). In both the 

pistachio and the almond the outer skin of the fleshy hull is the 

epicarp, while the bottom layer of the fleshy hull is the 
mesocarp, and these two layers help protect the nutmeat that is 

also encased in the hard shell (endocarp) from pest problems. It 

is the hard nutshell of the pistachio enclosed in the protective 

fleshy hull that splits or dehisces near harvest. 

After pollination and fertilization (April), the ovary walls 

or pericarp enlarges rapidly in length and diameter and within 

six to eight weeks (middle May) attains its full size (7). 

However, while the shell has become full-sized and hard it is 

still nearly empty. The embryo of the pistachio, which is in the 

shell, begins rapid expansion in late June and grows rapidly 

after this stage, maturing within 16 weeks or approximately 140 

days after pollination (3, 4, 5, and 15). As the fruit matures, 

the fleshy hull becomes soft and the endocarp layer partly 

separates from the shell. Inside the hull, the shell turns 

opaque white in color and splits (or dehisces) longitudinally as 

a normal part of abscission because of the seed (nutmeat) 

enlarging and exposing the purple-red seed coat (last week of 

July thru August) but at this growth stage the outer hull still 

remains intact (8). This normal splitting of the nutshell is a 

highly desirable characteristic that plant breeders utilize in 

their selections, and is also favored by consumers because of the 

ease in hand-shelling the nut (8, 29, 30, 32). Nonsplit shells 

(21) may range up to 20% of the harvest and are sorted out during 

processing and sold as broken nutmeats. Currently, hulls are 

removed completely by abrasive peeling machines, followed by 

separation of split from unsplit shells by a water flotation 

method and/or by air jetting. Nuts that don't split are 

undersized, stained, and not desirable for the consumer. In 

addition, early splitting is a problem since it encourages 

aflatoxin and insect contamination/damage as well as staining to 

the shell that makes a low quality nut. Approximately 1.5 to 

2.5% of the nuts are unmarketable due to early splitting or empty 

shells (6, 14, 17, 21, and 22). Harvesting is gauged by the 

change in the color of the outer pericarp layer from translucent 

pinkish-green to opaque as well as a softening and loosening of 

the hull from the shell (8). The fruit or drupe will not abscise 

or drop from the tree at this time, but the hulls or pericarp 

(epicarp + mesocarp layers) will continue to dry and shrivel for 

several weeks. 

Early splitting of hulls exposing the nut is not a desirable 

characteristic, and currently there are several research projects 

on pistachios designed to either select for cultivars that 
produce less early splits by eliminating from breeding programs 

cultivars that exhibit this predisposing trait [7, 10, 11, 13, 

14, 18, 29, 30, 32] or to develop techniques to sort out these 

early split nuts while processing the harvested nuts [7, 14, 21, 

22, 29]. Current processing techniques used to sort out 

pistachios by automated high speed bichromatic sorters that will 

sort up to 144,000 pistachios/hour and combined with hand sorting 

for culls will remove 91 to 93 % of the early splits (33). A 

newly developed "machine vision" computerized system bichromatic 

sorter has been developed and can sort out > 99 % of the early 

splits (24, 25). 

ANALYSIS OF PISTACHIO HULL SPLITTING:

Chemistry Branch received eight separate shipments of 

approximately 1 kg in-hull pistachios from Dr. Louise Ferguson, 

Extension Pomologist and Mr. Eric Harmon at the University of 

California, Davis that were sampled from July until harvest on 

September 22, 1995. The samples were collected manually and at 

random on 9/21/95 from a commercial pistachio orchard using the 

cultivar `Kerman' in Kern County, Parlier, CA. Over ((% of the 

pistachios harvested in the U.S. are the `Kerman' cultivar. The 

samples were placed in plastic bags and kept refrigerated until 

shipment to Dr. B. Schneider's home in Columbia, Maryland where 

they were stored in the refrigerator and analyzed within 48 hours 

after receipt. The hulls at harvest were light greenish-yellow

in color and could be easily removed from the nut shell by 

rubbing between the thumb and forefinger. Over 2100 in-hulled 

pistachios were individually counted as part of this study. The 

samples were counted for number of hulls that split, extent of 

hull [pericarp and or mesocarp] cracking, color of hull, and were 

then dissected to determine if the nut shells were split or open, 

and the data is summarized in Table 1. For a discussion of the 

three tissue layers that comprise the hull see the previous 

section entitled: "Pomological Factors Comparing Pistachios and 

Other Members of the Tree Nuts Crop Group." 

The splitting of the hulls that occurred is different for 

the two tissue layers [pericarp and mesocarp] that surround the 

shell [endocarp]. The outer layer of the hull or pericarp 

splitting started at 30 days before harvest and was only 2.2% at 

that time but increased up to 50 % at harvest. In contrast, the 

inner or mesocarp layer of the hull that also feels leathery was 
completely intact until 14 days before harvest (1.1 %) splits 

with only 2.4 % splits at harvest. Therefore, only 2.4 % of the 

pistachio nuts that are split would be exposed to any surface 

pesticide residues. However, CB considers the 2.4 % of the 

pistachios that have the hulls and nut shells split at the same 

time an overestimation for several reasons. First, these early 

split nuts are usually sorted out after harvest during processing 

because poor quality nuts are removed and discarded before they 

reach commercial use [21, 22, and 23]. Newer machine vision 

sorting technology will sort out > 99 % of the early splits in 

the processing line. Also, these split nuts are mechanically 

separated from normal pistachios because they are vulnerable to 

or carriers of the carcinogenic aflatoxin mold [Aspergillus

flavus] (4, 28, 29). Another botanical related factor that 

protects the nutmeat in shells that have split from pesticide 

residues is the fact that the outer hull begins to split at the 

stem end, while the open nut shell faces downward in the opposite 

direction and is still fully protected by the leathery inner 

layer or mesocarp. So, when the shell is split open the hull is 

still intact, except in one to four % of the cases where the 

hulls adhere tightly to the shell and split along with the shell. 

These are called "early splits". Plant breeders are continuing 

to develop improved cultivars that will have even less early 

split nuts before harvest [32]. In addition, over 97.6 % of the 

pistachio nut shells that are split were still protected by an 

intact inner hull layer or mesocarp. Our research numbers are 

very close to those reported in the scientific literature and in 

USDA current research project reports which showed that 1.0 to 

4.0 % of pistachios are considered to be "early splits" in which 

the hull splits along with the shell [10, 21, and 29]. 

Table 1. Determination of Pistachio Hull Splitting From 53 

Days Before Until Harvest. (7/31 to 9/22/95). 

Days 

Before 

Harvest *

Sample 

Size 

(number 

of nuts 

Nut Shell 

Open 

(Splits) 

[%]**

Hull Splits (%) 

Pericarp (outer 

layer) 

Mesocarp 

(inner 
counted) layer)

53 272 0 0 0

43 232 0 0 0

36 235 0 0 0

30 229 50 2.2 0

22 251 50 8.0 0

14 270 52 13.0 1.1

7 450 58 42.0 2.0

0 250 80 50.0 2.4

* The dates of sample collection are as follows: 7/31; 

8/7; 8/14; 8/22; 8/30; 9/5; 9/12; and 9/22/95.

** The number of nut shells that are open was from the hull 

(split) samples. Nut shells counted in the unsplit hull 

samples averaged 40% shell split at the last sampling 

date. 

By this independent study, Chemistry Branch has confirmed 

that the shells of pistachio nuts split naturally in the orchard 

[< 80 %] prior to harvest, but the hull stays intact, covering 

and protecting the kernel from an invasion by molds, insects, and 

nonsystemic pesticides. Early split hulls were in the range of <

2.4 % by harvest, and none occurred before 14 days before 

harvest. As the pistachio drupe (fruit) matures the outer hull 

(epicarp + mesocarp) loosens from the shell (endocarp) that 

covers the seed (nutmeat) until the shell splits. The hull still 

remains’s intact completely covering and protecting the shell 

even after it has split. The early splits are usually sorted out 

prior to the pistachios entering commerce and in the future 

improved sorting techniques will remove > 99 % of the early 

splits.

Therefore, the deficiency regarding CB concerns "that the 

unsealed husks or shells (splits) found in pistachio nuts would 

expose the edible portion to significantly higher residue higher 

pesticide residues than would occur in other tree nuts’’ (memo F. 

Griffith, Jr., RCB No. 1057, 9/25/85) is resolved. We expect 

pesticide residues in the pistachio nutmeat should be similar to 
the other nut crops that are members of the Tree Nut Crop Group. 

For a discussion comparing pesticide residues in the tree nuts, 

see the next section of this report entitled: "Comparisons of 

Residue Levels in the Tree Nut Crops". 

COMPARISONS OF RESIDUE LEVELS IN THE TREE NUT CROPS

Over the years tolerances have been established for 

pesticides on almonds; pecans; pistachios; nuts; nutmeat; and the 

tree nut crop group (40CFR§180). There are 15 established 

tolerances for pesticides on pistachios that can be compared with 

those registered on similar pesticides for other tree nuts (Table 

2). In all cases except for permethrin, the established 

tolerances are identical. Even with permethrin [§180.378], the 

tolerance of 0.1 ppm established on a pistachio is well within 

the Crop Group limit of 5X for the other tree nuts that are 

established at 0.05 ppm. 

Table 2. Comparison of Established Tolerances for Pistachio and 

Tree Nut Crops. 

Pesticide (CFR 

Citation)

Pistachio 

Tolerance 

(ppm)

Tree Nut Crop 

Tolerance (ppm)

Benomyl 

[§180.294]

 0.2 0.2 (nuts) 

Glyphosate 

[§180.364(a)] 

 0.2 0.2 (nuts)

Magnesium 

phosphide 

[§180.375]

 0.1 0.1 (almonds, filbert, 

pecans, 

walnut)

Permethrin 

[§180.378]

 0.1 0.05 (almond, filbert, 

walnut)

Azinphos-methyl 

[§180.154]

 0.3 0.3 (almond, filbert, 

pecan, walnut)
Pesticide (CFR 

Citation)

Pistachio 

Tolerance 

(ppm)

Tree Nut Crop 

Tolerance (ppm)

Carbaryl 

[§180.169]

 1.0 1.0 (almond, filbert, 

pecan, walnut)

2,4-D 

[§180.142(b)]

 0.2 0.2 (nuts)

Napropamide 

[§180.328(a)]

 0.1 0.1 (nuts)

Oryzalin 

[§180.304]

 0.05 0.05 (nuts)

Oxadiazon 

[§180.304]

 0.05 0.05 (Brazil nuts, bush 

nuts, 

butternuts, 

cashews, chestnuts, 

filbert, hickory 

nuts, macadamia 

nuts, pecans, 

walnuts

Oxyfluorfen 

[§180.381]

 0.05 0.05 (tree nuts group 

(except almond 

hulls) 

Paraquat 

[§180.205]

 0.05 0.05 (nuts)

Phosmet 

[§180.261]

 0.1 0.1 (nuts)

Aluminum 

phosphide 

[§180.225]

 0.1 0.1 (almonds, Brazil 

nuts, walnut)

Inorganic 

bromides 

(§180.123]

 200 200 (almonds, Brazil 

nuts, bush nuts, 

butternuts, cashews, 

filberts, hickory nuts, 

pecans, walnuts) 
IR-4 also submitted comparative field residue data for use 

of azinphos-methyl (IR-4 and Miles Agriculture Division) and 

carbaryl (Rhone-Poulenc) on various tree nuts and pistachios that 

were previously reviewed by CB to establish the tolerance levels 

for these pesticides. Tolerances for azinphos-methyl [§180.154] 

were established at 0.3 ppm for pistachio, almond, filbert, 

pecan, and walnut; while tolerances for carbaryl [§180.169] were 

established at 1.0 ppm for pistachio, almond, filbert, pecan, and 

walnut (Table 2). 

Therefore based on residue data used to establish tolerances 

for use of 15 pesticides in/on pistachios and other tree nuts, CB 

concludes that residues from pistachios are similar to those 

found on all other members of the Tree Nut Crop Group. 

EVALUATION OF REPRESENTATIVE COMMODITIES FOR THE TREE NUTS CROP 

GROUP:

The current representative commodities for the Tree Nuts 

Crop Group are almond and pecan. Botanically, both pistachios 

and almonds have fruits called drupes. In the case of tree nuts, 

the drupe consists of a single edible seed lying inside a thin 

but hard bivalve shell that is surrounded by a fleshy hull or 

pericarp. Since CB is recommending to include pistachios as a 

member of the Tree Nuts Crop Group, it also investigated whether 

pistachios should replace almonds as the representative 

commodity. Pistachios are not considered a replacement for 

pecans because of the relatively limited geographical production 

area for pistachios, whereas almonds and pistachios are grown in 

the same region. 

Almonds are still considered to be a better representative 

commodity than pistachios for several reasons: first, the nutmeat 

and shell develop simultaneously in almonds (Feb-mid-June) so 

that any pesticides that are systemic and applied to the foliage 

during this time may be translocated to the nutmeat. Pistachios 

on the other hand have the shell growing during this stage and 

increasing in diameter, but the embryo and nutmeat do not begin 

their growth until July 1. Therefore, the nutmeat in pistachios 
is not present from pollination (mid-April through June) in 

contrast to almonds (20). Secondly, differences in maturity of 

the hulls make almonds a worst case for estimating pesticide 

residues. In almonds, the outer hull readily splits, but the nut 

shell does not, whereas in pistachios the outer hull stays almost 

completely intact (for more details see analysis of pistachio 

hull splitting section) while the nutshell begins splitting 

(dehiscing) from late August until September 15. One of the ways 

to determine the physiological maturity of the pistachio is by 

the ease in which the hull (epicarp + mesocarp) separates from 

the nut shell. Pistachios must be harvested before the hull 

degenerates so that the nutshells will not be stained (7). 

Therefore, in pistachios the outer hull stays intact through 

harvest preventing residue accumulation on the nutmeat, whereas 

the almonds split from their fleshy hulls at maturity which 

allows the nut to drop to the ground, and some cultivars such as 

`Nonpareil' can range from 18 to 82 % splits. The almond shell 

is also more porous or papery (genetically soft shelled) and 

softer than the pistachio shell (2, 16, 19). 

 

While the scientific literature (10, 30, 32) and our own 

analysis indicate that from < 1% to 4% of the pistachios have 

early split nuts and hulls, these are later removed as culls 

during processing to remove the stained nuts to prevent aflatoxin 

contamination. Pistachios are the only tree nut that has open 

split shells at harvest, but > 97 % of these are protected by an 

intact hull. Pistachios also have less opportunity for pesticide 

residue accumulation in the nutmeat because foliar translocation 

to the developing nutmeat does not occur when most pesticide 

applications 

to control insect and plant diseases are made, and the nutmeats 

at harvest are still protected by 

the outer hull. Imported pistachios during 1993-94 accounted for 

< 1.0 % of the total pistachios consumed in the U.S. (9). 

Approximately, 81.5 % are imported from Turkey. Therefore, any 

early split pistachios that may be imported would be an 

insignificant component of the diet. 

Pest problems in almonds and pistachios are similar [see 

section on comparison of pest problems in pistachio and other 

tree nut orchards]. Only almond hulls are a significant 

livestock feed item in the tree nut crops. Pecans, the other 

tree nut crop group representative commodity, have a much wider 

geographical distribution than either almonds or pistachios. 
Therefore, based on almonds having a livestock feed item; more 

percent hull splitting; more of the developed nutmeat present 

during pesticide applications; the same geographical region; and 

a more porous or papery shell, Chemistry Branch does not 

recommend to change the present representative commodities of the 

Tree Nut Crop Group. 

COMPARISON OF PEST PROBLEMS IN PISTACHIO AND OTHER TREE NUT 

ORCHARDS:

Pistachios share the same weed, nematode, insect and plant 

disease, and post harvest storage problems that affect the other 

members of the Tree Nuts Crop Group [1, 7, 8, 10, 14, 17, 18, 26, 

27]. Pests of almonds such as the naval orangeworm (Ameyelois

transitella) often invade pistachio orchards [1, 26].

LIVESTOCK FEED ITEMS:

There are no animal feed items associated with pistachios. 

The representative commodities for Crop Group 14: Tree Nuts are 

almonds and pecans, and only almond hulls are a livestock feed 

item in this Crop Group. 

HARMONIZATION WITH CODEX:

CODEX places pistachio in its Crop Group 22: Tree Nuts. 

Addition of the pistachio to U.S. Crop Group 14: Tree Nuts will 

harmonize the two Crop Group systems with regard to pistachios. 

REFERENCES:

1. Andrews, K.L. and M.M. Barnes. 1982. Invasion of 

Pistachio Orchards by Naval Orangeworm Moths from Almond 

Orchards. Environmental Entomology 11:278-279.

2. Campbell, B. 1995. Breeding for Resistance to Aflatoxin 

Contamination in Almond. Univ. CA. Project Report # 0500-

00029-026-00D. USDA Current Research Information Service.

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33. Weinberger, G. 1997. Personal Communication with Dr. 

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cc: Pistachio Commodity File, B.A. Schneider, R.F., Crop Group 

File.

B.A. Schneider:(3/3/97):804V:CM#2:(703)305-5555:7509C

RDI: R. Loranger (8/20/96); E.Haeberer (8/14/96); R. Perfetti 

(2/13/97). 

PART I - THIS LIST CONTAINS THE NINETEEN CROP GROUPS AND WHICH 

MEMBERS OF THE CROP GROUP ARE MOST SIMILAR TO THEIR 

REPRESENTATIVE COMMODITIES

Crop Group 14: Tree Nuts

Representative Commodities: Almond and pecan

CROP GROUP COMMODITY REPRESENTATIVE COMMODITY

 Almond Almond

 Beech nut Almond

 Brazil nut Pecan

 Butternut Pecan

 

 Cashew Pecan

 Chestnut Almond

 Chinquapin Almond

 Filbert Pecan

 Hickory nut Pecan

 Macadamia nut Pecan

 Pecan Pecan

 Pistachio Almond

 Walnut, black Pecan

 Walnut, English Pecan

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