7222

PUMPKIN PRODUCTION IN

CALIFORNIA

BRENNA AEGERTER, University of California Cooperative

Extension farm advisor, San Joaquin County; RICHARD SMITH,

UCCE farm advisor, Monterey County; ERIC NATWICK, UCCE farm

advisor, Imperial County; MARK GASKELL, UCCE farm advisor,

Santa Barbara County; and ELLIE RILLA, University of California

community development advisor, Marin County.

PRODUCTION AREAS AND SEASONS

Pumpkins (Curcurbita pepo L. var. pepo) are grown

in most counties of California. San Joaquin County

produces the most by far (70% of California produc-

tion in 2011), with Sacramento County as a distant

second. Although most pumpkins are grown for

jack-o-lanterns for the Halloween season, grow-

ers also raise other ornamental types. Even some

types that can be used for cooking (e.g., Sugar Pie

types and Fairytale pumpkins) are also grown and

marketed as ornamentals. Planting dates depend

on the variety’s growth rate: most are planted in

May or June for Halloween harvest, but some orna-

mental types may be planted in April. In Southern

California’s low desert, the buildup of whitefly pop-

ulations during spring and summer increases dam-

age and disease in pumpkins, melons, and other

cucurbits to such a degree that they simply cannot

be grown for fall harvest.

VARIETIES AND PLANTING

TECHNIQUES

The principal Halloween pumpkins are the jack-o-

lantern varieties and ornamental mini-pumpkins.

In the past, the leading jack-o-lantern variety was

Howden, a vining type. More recently, cultivars

have been developed with special attention given

to improvements in color, yield, consistency, and

size, including Aladdin, Gladiator, Magic Lantern,

Magic Wand, and Spartan. These modern varieties

have a more compact growth habit than the tradi-

tional vining types. Jack-o-lantern pumpkins tend to

range from 10 to 20 pounds (4.5 to 9 kg), although

size is to a great degree dependent on manage-

ment. Characteristics of a high-quality jack-o-lantern

include deep, rich orange color, upright shape, and a

strong handle (stem).

Other ornamental varieties include Jack-Be-Little,

Mini-Jack, Munchkin, Sugar Pie, and Sweetie Pie

(orange mini-pumpkins); Lumina (a white jack-o-lan-

tern pumpkin); and Baby Boo (a white mini-pump-

kin). There are also numerous smaller jack-o-lantern

or ornamental types that weigh from 1 to 10 pounds

(0.45 to 4.5 kg), such as Apprentice, Cannon Ball,

Field Trip, and Lil’ Ironsides. Other, “mammoth”

varieties have been bred specifically for exceptional

size. These mammoth varieties are not true pumpkins

(Curcurbita pepo L. var. pepo) but C. maxima, and are

more closely related to Hubbard squash.

Pumpkins typically require 90 to 120 days from

emergence to maturity. Timing for planting is critical.

Although varieties are rated according to their num-

ber of days to maturity, the actual growth time varies

with average temperatures and solar radiation. More

time is required to reach maturity in cooler, coastal

areas. Excessively high temperatures may result in

failure to set fruit. Halloween pumpkins should be

mature and have a good color 1 to 4 weeks prior

to Halloween. Because pumpkins store well under

ambient conditions, there may be advantages to har-

vesting the crop early and storing it for a few weeks.

Early crops may suffer less damage from insects and

diseases and may require fewer sprayings. Jack-o-

lantern or ornamental pumpkins that fail to mature

before Halloween have little commercial value.

University of California

Agriculture and Natural Resources

http://anrcatalog.ucanr.edu • Publication 7222

Vegetable Production Series

VRIC.UCDAVIS.EDU

UC Vegetable Research

& Information Center

PUMPKIN ACREAGE AND VALUE

Year Acreage

Average yield

(tons/acre)

Gross value/

acre

2011 5,900 14.5 $3,393

2010 6,200 16.0 $3,232

2009 5,100 14.5 $4,031

Source: California Agricultural Statistics: 2011 Crop Year

(Sacramento: USDA–National Agricultural Statistics Service)

http://anrcatalog.ucanr.edu

vric.ucdavis.edu

2 • Pumpkin Production in California • ANR 7222

CULTURE

Vining varieties such as Howden typically are plant-

ed in wide rows where the vines are allowed to run.

Newer varieties that have a more compact, bushy

growth habit are better suited to closer row spacings.

Vining types need more space for optimum produc-

tion, and as the planting density increases they pro-

duce fruit in greater numbers but of smaller size. The

grower can manipulate the crop’s variety, planting

density, irrigation, and fertilization in order to pro-

duce the size he or she believes the buyer will want.

The modern, compact pumpkin varieties are

grown on raised beds with rows 80 (or sometimes

90) inches apart. Small-fruited varieties are grown

on similar beds but with double rows of plants on

each bed. The larger, vining varieties usually are

grown with wider spacings of 3 to 5 feet (0.9 to 1.5 m)

between plants and 6 to 10 feet (1.8 to 3 m) between

rows. Some small-scale growers hand-plant their

pumpkins in hills with these same spacings and

leave two plants per hill. In some areas, growers use

40-inch (100-cm) beds and plant every other bed.

Approximately 2 to 3 pounds (0.9 to 1.4 kg) of seed

is required to achieve a final stand of 3,000 to 4,000

plants per acre. Growers commonly plant excess seed

and then thin the plants to the desired plant spacing

after emergence.

SOILS

Pumpkins are grown on a wide range of soils.

Growers with soil that has a high clay content may

have more problems with root and stem diseases

because of a wetter soil surface and higher humidity

in the lower canopy. For this reason, growers typically

use raised beds on such soils. Crop management on

heavier soils is often complicated further by exces-

sive moisture or poor irrigation management. Sandy

soils also require close attention to water manage-

ment (more frequent irrigation) to prevent moisture

stress and the resulting interruption of foliage or fruit

growth.

IRRIGATION

Water management is critical to the development

of vigorous vines to support fruit growth and

the maintenance of the foliage canopy to protect

developing fruit from sunburn. Most pumpkins

are grown with drip irrigation, although there are

growers who use furrow irrigation. Excessive irri-

gation aggravates root and stem rot problems and

increases humidity in the lower canopy, which con-

tributes to foliage and fruit diseases. If you use fur-

row irrigation, your irrigation management should

emphasize infrequent, deep watering to encourage

deep root development and allow time for the soil

surface to dry between irrigations.

With drip irrigation, two lines of tape are typically

used on beds with 80-inch centers. The tape usually

is placed 10 to 12 inches deep and, ideally, the soil

surface remains dry to prevent fruit rot and crown

rot. Drip irrigation has the advantage of being able

to provide smaller, more frequent irrigations, which

minimizes water stress on the vines while avoiding

the saturated soil conditions that promote disease.

FERTILIZATION

Phosphorus (P) and potassium (K) fertilizer applica-

tion decisions can be based on soil analysis values.

For soils with a pH value greater than 6.2, the soil

P is measured with the bicarbonate extraction test.

Soils with less than 15 ppm P definitely need to be

fertilized with P, and the crop yield from soils with

between 15 and 25 ppm P will also likely benefit

from P fertilization. Soils with more than 25 ppm P

have sufficient P for crop growth and crops will not

respond to additional P fertilization. In situations

where P fertilizer application is warranted, 40 to 80

pounds of P2O5 per acre (45 to 90 kg/ha) applied pre-

plant or at planting will satisfy crop needs.

Soil K is measured by extracting the soil with

ammonium acetate. Values of less than 80 ppm K

indicate a need for K fertilization, soils with a K value

between 80 and 120 ppm may have improved yields

with K fertilization, and soils with more than 120

ppm K have sufficient K to satisfy crop needs. Typical

K fertilization rates for deficient soils vary from 75 to

150 pounds of K2O per acre (84 to 168 kg/ha).

Nitrogen (N) needs of pumpkin are moderate in

comparison to those of other vegetable crops. Small

quantities of N can be applied preplant, but the bulk

of the crop’s nitrogen needs should be addressed 30

to 40 days later when rapid growth begins. Nitrogen

can be shanked into the soil with tractor-applied N

or it can be applied through a drip irrigation system.

Typical total N use by a pumpkin crop is 100 to 150

pounds per acre (112 to 168 kg/ha).

POLLINATION

Pumpkins require bee pollination for optimal yields.

Smaller ornamental pumpkins require a much higher

percentage of pollinated flowers for optimal yields

than do larger pumpkins. Each flower is receptive for

only one day, and multiple bee visits may be required

for optimal pollination. Although many growers rely

primarily on native bees for pollination, it is best to

introduce one to two beehives per acre of pumpkins

very early in the blooming period to ensure that ade-

quate numbers of bees are present and that the bees

can establish a pattern of visits to emerging flowers.

3 • Pumpkin Production in California • ANR 7222

FRUIT DEFECTS

There is a low consumer tolerance for fruit defects in

pumpkins. Even coloring and a symmetrical shape

are very important to consumers. Poor pollination

can result in misshapen fruit. High temperatures

can result in thinner-walled pumpkins that do not

hold up as well in shipping. Other fruit defects can

be caused by the fungi and viruses discussed below.

Shallow feeding damage from soil insects can result

in warts that render the fruit unmarketable. The

exception to this would be specific ornamental vari-

eties that are prized for their warty appearance (e.g.,

Red Warty Thing).

INTEGRATED PEST MANAGEMENT

See the UC Integrated Pest Management Guidelines

(online at www.ipm.ucdavis.edu) or your local coun-

ty Farm Advisor for current pest management infor-

mation (see UC IPM Pest Management Guidelines, UC

Agriculture and Natural Resources Publication 3339).

Insect management. Seedcorn maggot (Delia pla-

tura) hollows out seeds or eats portions of seedlings.

Damage is common in early plantings in cool soils,

especially in fields with high organic matter content.

If conditions are favorable for a maggot infestation,

apply a registered insecticide as a broadcast spray

that is then incorporated into the soil, as an injection

into the seedline, or as a seed treatment at planting.

Wireworms (Limonius spp. and others) can kill young

plants and weaken older ones by feeding on the root

system. Flea beetles such as the palestriped flea beetle

(Systena blanda) and Epitrix spp. can attack seedlings,

causing severe damage or death of plants. Flea beetles

chew holes in cotyledons and young leaves. They

can be controlled with foliar applications of a reg-

istered insecticide. Epitrix spp. occasionally feed on

fruit late in the season if the plants are under foliar

stress. Squash bugs (Anasa tristis), which have suck-

ing mouthparts, kill pumpkin leaves and vines when

populations are high. They lay reddish brown, barrel-

shaped eggs in masses on the underside of leaves and

the juveniles actively feed on the fruit and foliage.

In milder southern and coastal areas, the sweet-

potato whitefly (Bemisia tabaci biotype B) and green-

house whitefly (Trialeurodes vaporariorum) are not

killed by winter temperatures and their populations

rise gradually throughout the spring. This pest may

build to serious levels and in that case may require

treatment with a registered insecticide. Aphids also

cause problems by weakening the plant through their

feeding, and both whiteflies and aphids are vectors of

viral diseases. Pumpkins in the low desert growing

areas of Southern California require soil injection of a

neonicotinoid insecticide at planting for whitefly con-

trol. Foliar sprays may be required after 30 to 45 days

for continued whitefly management. Insecticides

applied for whitefly control also prevent aphid prob-

lems. Pumpkins can only be grown in spring in the

low desert due to several whitefly-transmitted virus

diseases, including cucurbit yellow stunting disorder,

squash leaf curl, and cucurbit leaf crumple.

Leafminers (Liriomyza sp.) may damage cotyledon

leaves, but natural predators are usually able to con-

trol them as long as the predators are not eliminated

by repeat applications of broad-spectrum insecticides.

The western spotted cucumber beetle (Diabrotica

undecimpunctata) and western striped cucumber bee-

tle (Acalymma trivittatum) can attack in large numbers

and feed on younger and older plants. The larvae

feed on the roots and underground parts of the stem,

and the adults feed in flowers (causing blossom drop)

and on developing fruit. Cucumber beetles may be

present in large numbers on young seedlings and

they often require spraying with a registered insec-

ticide for sufficient control and to avoid serious eco-

nomic losses. The western striped cucumber beetle

should not be confused with palestriped flea beetle, a

much smaller insect.

The larvae of several species of armyworm

(Spodoptera spp.) and looper (Trichoplusia spp.) larvae

can also damage pumpkins. These larvae feed on

foliage and may damage fruit. Scout the field to deter-

mine worm populations during periods when the

fruit is most susceptible to damage, before the rind

begins to turn orange. These worm pests can be con-

trolled with registered insecticides (including Bacillus

thuringiensis products) and biological control.

Disease management. Powdery mildew

(Podosphaera fuliginea syn. Sphaerotheca fuliginea) is

common in pumpkin fields throughout the growing

season. This fungal disease can be a problem at any

time in coastal growing areas and, in late summer

and fall, in the inland valleys. Growers recognize it

as a white powdery growth on upper and lower leaf

surfaces. If not controlled, the disease will completely

destroy the foliage, and any fruit that survives will

be sunburned and discolored. The loss of productive

vines also severely restricts fruit yield and size. Since

1998, many commercially grown varieties have had

some level of resistance to powdery mildew. Powdery

mildew resistant (PMR) pumpkin varieties vary in

their susceptibility to powdery mildew, depending on

the number of resistance alleles they possess. Varieties

with two copies of the resistance allele (homozygous

varieties) generally develop less powdery mildew

than those with only a single copy (heterozygous

varieties); the common commercial varieties are

marketed as “intermediately resistant” to powdery

mildew. Fields should be frequently and carefully

4 • Pumpkin Production in California • ANR 7222

scouted for the disease and registered fungicides

should be applied at the first sign of the disease.

Charcoal rot (Macrophomina phaseoli) affects

pumpkins and other cucurbits. Leaves of the crown

area turn yellow and wither. If the disease spreads,

vines may wilt and die. The causal organism, a soil-

borne fungus with a wide host range, is common on

most soils in California’s Central Valley. The fungus

tolerates high temperatures and dry soil and the

disease is favored by water-stressed plants and high

temperatures.

Phytophthora crown and root rot (Phytophthora

capsici) is a serious fungal disease of pumpkins and

squash in places where soils are wet for extended

periods. Phytophthora may cause root rot, crown or

stem lesions, or foliar blight. Fruit may also be severe-

ly infested and may rot. Warm temperatures of 68° to

80°F (20° to 27°C) and poor drainage favor develop-

ment of this disease. Phytophthora can move rapidly,

and disease incidence may be higher in fields where

pumpkins are planted following other host crops such

as tomatoes or peppers.

Fusarium crown and foot rot, also called Fusarium

fruit rot (Fusarium solani f. sp. cucurbitae) may affect

the lower stem or crown area of the plant, caus-

ing plants to wilt and die. Fruit that are in contact

with the soil may also be affected by dry lesions that

have a concentric ring pattern and render the fruit

unmarketable. The fungus survives on soil and seed

and is most common on the central coast. Control

of Fusarium depends on the long-term (four-year or

longer) rotation of fields out of cucurbits and the use

of clean seed.

As is true for many other cucurbits, some of the

most serious diseases of pumpkins are caused by

viruses. Of the viruses affecting pumpkins in

California, the most important are transmitted by

aphids, whiteflies, and beetles. Transmission of each

virus is specific to particular insects. Viruses such

as Cucumber mosaic virus (CMV), Watermelon mosaic

virus (WMV), Zucchini yellow mosaic virus (ZYMV),

and Papaya ringspot virus (PRSV-W) are transmitted

by aphids in a nonpersistent manner—that is, the

aphids need only spend a few seconds or minutes

on the plant to probe the leaf surface and transmit

the virus. Conversely, Cucurbit aphid-borne yellows

virus (CABYV), which is common in the Southern

California low desert, is transmitted only when the

cotton melon aphid (Aphis gossypii) feeds on the plant

phloem. Squash mosaic virus is transmitted by the spot-

ted cucumber beetle and other related beetles, and

may also be seedborne.

Many of these viruses are present in native veg-

etation, weeds, rangeland plants, or other crop plants,

and many are readily transmitted to developing

pumpkins as the insect vectors move into pumpkin

fields. If possible, avoid growing other cucurbits in

the same area before you plant pumpkins so as to

avoid providing an opportunity for virus to move

from one crop to another. It is always desirable to

plant succeeding crops of pumpkins or other cucur-

bits upwind rather than downwind of previously

planted cucurbit crops. Other crops, such as peppers,

may also harbor a number of viruses that can affect

neighboring cucurbit crops.

Weed management. Weeds can reduce pumpkin

yields if they are allowed to compete with the crop

for nutrients and light. Pumpkins are grown during

the warm time of year, and key troublesome weeds

include summer grasses and broadleaf weeds such

as barnyardgrass and common purslane. Infestations

of perennial weeds such as field bindweed and nut-

sedge are difficult to control, so fields infested with

these weeds should be avoided. Weed control tech-

niques for pumpkins include cultural, mechanical,

and chemical control. A key preplant cultural control

is the use of pre-irrigation to stimulate a flush of weed

growth, followed by shallow cultivation. This tech-

nique can greatly reduce the quantity of early season

weeds. Mechanical cultivation can control a large

number of weeds early in the season before the vines

begin to cover the bed top. Only a few herbicides are

registered for use on pumpkins, but those include

pre-emergent and selective post-emergent materi-

als that can control a wide spectrum of weeds. Hand

weeding is generally necessary in pumpkin fields to

remove weeds that have escaped control by the meth-

ods just mentioned. However, good weed control

practices early on can help to make subsequent hand

weeding operations more efficient and less costly.

HARVESTING AND HANDLING

Pumpkin production across a broad range of envi-

ronments has shown that the jack-o-lantern types

typically yield 1,000 to 2,500 marketable fruit per acre,

weighing a total of 10 to 25 tons (11 to 27.5 t). Smaller

varieties will produce 2,000 to 6,000 marketable fruit

per acre, weighing a total of 5 to 10 tons (5.5 to 11 t).

Pumpkins can be harvested when the outer skin

is even-colored and hard. (The