Over the last few months, I’ve received several calls from first time pumpkin growers
across the state. Most of these new growers are new to specialty crops in general,
with many knowing of the intensive spray schedules required for some crops and unsure
what is necessary for success. Many of these new farms are in northeast Arkansas,
with most being the result of a pressing need to diversify felt by many of our row
crop growers. As a product of Mississippi County, I have always felt we have great
sandy soil for vegetables and plenty of irrigation to keep things alive, but the hold
up has of course always been labor availability and the lack of infrastructure and
regional support. Pumpkins present an easier challenge than many other vegetable crops
because they are a late season crop that isn’t often impacted by nearby crop production,
require very little infrastructure and in-season labor and are only picked a few times.
Pumpkins are a great crop to grow in the Midsouth to diversify farms and support agritourism.
Pumpkins are typically thought of as low maintenance compared to many other specialty
crops like tomato or strawberry, however, pumpkins do require weekly scouting for
both diseases and insect pests, along with a preventative fungicide spray program.
Pumpkins can very easily be wiped out by insects and most farms deal with several
pests that must be controlled each year, which comes with the territory of a summer
planted crop. In the Midsouth region, a basic fungicide program is necessary for disease
prevention, and more targeted fungicides should be used if some major pumpkin diseases
are present.
Below I will outline tactics for building a pest management plan for pumpkins, including
what to scout for and what sustainable management tactics are likely to yield profit.
Please consult the Southeastern US Vegetable Crop Handbook for additional recommendations and visit our Hort IPM page for updates on the arrival of pests like melonworm.
Disease Management Cultural Control Tactics Much of the disease risk in pumpkins can be mitigated by integrating cultural control
tactics, such as sanitation and the use of resistant varieties into your production
program.
Plant pumpkins in well-drained areas. We’ve seen many cases of soil-borne pathogens
taking over fields that don’t drain well or are quickly inundated with water.
Plant earlier when possible. Planting windows are generally based on market sources
but being on the front part of that window can avoid increased risk of powdery and
downy mildew that comes in the late Summer/early Fall.
Remove all dying plants as they are found, especially before transplanting into the
field.
Avoid overhead irrigation. Many diseases are a function of leaf-wetness and sprinkler
irrigation can lead to increased risk. Drip irrigation is a great option for both
production efficiency and disease prevention.
Utilize crop rotation where possible. Integration of these tools is an important step
to mitigate risk from many of the diseases like Fusarium.
Fungicide Spray Program Pumpkins can be infected by a wide variety of pathogens and exhibit many diseases.
Many of these diseases are prevented by implementing a very basic spray schedule.
Pumpkins should receive an application of a fungicide that contains either chlorothalonil
or mancozeb every 10 to 14 days. This application interval should be tightened to 10
days based on rainfall events that create a more ideal environment for disease-causing
pathogens and are likely washing off protectant fungicides. This basic spray program
along with cultural control tactics will likely get many growers through the entire
growing season.
There are three diseases that all pumpkin growers need to scout for weekly to prevent
major losses. These diseases are downy mildew, powdery mildew, and plectosporium blight
(white blight). Each of these diseases occurs to varying degrees in Arkansas every
year, and often growers can tell you which they tend to deal with. The good thing
is that growers can respond to these diseases when they occur and don’t typically
need to use anything other than our basic spray schedule for prevention prior to these
diseases occurring in their pumpkins. Growers may integrate extra products for diseases
like powdery mildew preventatively if it is a yearly issue, as responding once the
canopy closes up is unlikely to suppress the disease.
Below is a decision tool that growers can use to choose their foliar fungicides throughout
the year (Figure 1) . It should be noted that the basic spray program will help to prevent these diseases
throughout the season. Each disease will be discussed at length below to provide a
guide on how to identify what’s damaging your pumpkins. As always, many of these diseases
can be difficult to identify based on leaf symptomology, and I recommend sending a
sample into the Plant Health Clinic for confirmation.
Figure 1. Decision tool for pumpkin fungicide spray schedule. Chlorothalonil or mancozeb should be utilized every 10-14 days even if no disease is found to be present.
Add additional fungicides if powdery mildew, downy mildew, or white blight is observed.
Diseases Observed Response
No diseases
Chlorothalonil or mancozeb 10-14 days depending on rain events
Powdery mildew
Alternate TWO effective powdery mildew products, tank mix with chlorothalonil or mancozeb
Downy mildew
Alternate TWO effective downy mildew products, tank mix with chlorothalonil or mancozeb
White blight
Alternate TWO effective white blight products, don't need to tank mix if using Flint or Cabrio
Powdery Mildew Cucurbit powdery mildew is a common disease in Midsouth pumpkin production that can
range in severity from year-to-year. Cucurbit powdery mildew is caused by the fungal
pathogens Podosphaera xanthii and Erysiphe cichoracearum . This disease causes white powdery growths on leaves, stems, and petioles (Picture 1) , which then leads to necrosis as the disease progresses. Infection generally starts
in the shaded areas of plants on older leaves, but this diseases can quickly cover
entire plants. Powdery mildew leads to an overall decline in plant health and lower
plant yields and can quickly colonize large portions of fields and lead to great economic
loss. We often see more advanced powdery mildew infestations where growers are spraying
with Hi-boy sprayers with lower spray volumes. We recommend at least 30-40 GPA and
the use of blower sprayer where possible.
Powdery mildew should be scouted for each week and is generally more severe after
fruit set and in more dense plantings. Growers should scout the oldest leaves in the
densest areas of their fields first and should also keep an eye out for spots in the
field that are becoming chlorotic (turning yellow) (Picture 2) . Powdery mildew should not be confused with genetic silvering present on many pumpkin
cultivars (Picture 2) . When powdery mildew begins to be found in fields, growers should add an effective
fungicide to their spray program along with their base protectant fungicide on a 7-10
day spray interval. Fungicides effective against cucurbit powdery mildew include:
Gatten (flutianil, FRAC U13), Luna Experience (fluopyram + tebuconazole), FRAC 7+3), Quintec (quinoxyfen, FRAC 13), and Vivando (metrafenone, FRAC 50). Growers should rotate effective modes of action between each
spray to avoid potential issues with resistance, especially if utilizing quinoxyfen
containing fungicides.
Picture 1 . Cucurbit powdery mildew fungal spores present on the top of pumpkin leaves.
Picture 2 . Cucurbit powdery mildew spores, chlorotic symptomology, and genetic silvering on
pumpkin leaves. Genetic silvering (A) can be confused with powdery mildew due to its
color, but it will appear within leaf veins and have a blocky shape. Powdery mildew
spores (B) look more like powder and damage will be expressed as chlorosis (C) on
the opposite side of the leaf.
Downy Mildew Downy mildew is one of the most devastating diseases of cucurbits. In Arkansas, downy
mildew of cucurbits is only occasionally observed outside of the southeastern portions
of the state because the fungus that confers this disease, Pseudoperonospora cubensis , can only survive in living cucurbit plants. These plants do not survive the winter
in Arkansas and therefore this disease does not overwinter in the state. However,
this disease does overwinter in states further South, and it can work its way across
the Southeast in the summer and throughout the entirety of Arkansas as spores are
moved in the wind. This makes scouting very important for disease management, especially
considering the limited number of products that provide good suppression.
Cucurbit downy mildew presents as angular, yellow/light-green spots early, which turn
into necrotic yellow/brown lesions on the tops of leaves (Picture 3) . It can be further identified by gray/purplish spores on the underside of leaves
(Picture 4) . Growers should keep an eye out for these symptoms and consider tropical storm events
as likely accelerating events as the disease is blown up from Louisiana, Texas and
Mississippi.
Growers should scout at least once a week for downy mildew in pumpkins. These scouting
efforts should be intensified when forecasts indicate a risk for our area, or when
we have confirmed cases in the state. Fungicide products that provide good control
of downy mildew are Elumin (ethaboxam, FRAC 22), Orondis Ultra (oxathiapoprolin FRAC 49 + mandipropamid FRAC 40), Orondis Opti (oxathiapoprolin FRAC 49 + chlorothalonil FRAC M05), and Ranman (cyazofamid, FRAC 21). See the Southeastern US Vegetable Crop Handbook for further fungicide recommendations and products that provide fair control/prevention.
None of these products will provide good control as a salvage application, making
it necessary to scout often and respond quickly.
Picture 3 . Downy mildew symptomology observed in Clay County. Leaves toward the bottom of the
picture show signs of early symptomology with yellow angular lesions. Many leaves
of this picture show advanced symptomology with leaves rolling inward. Photo by Allison
Howell, Clay County UAEX.
Picture 4 . Angular lesions exhibiting grey/purple spore growth on the underside of the leaf.
This is a key characteristic of potential cucurbit downy mildew. Photo by Allison
Howell, Clay County UAEX.
Plectosporium Blight Plectosporium blight, which is also referred to as “white blight,” is a less common
disease in Arkansas that can quickly overrun pumpkin plants and lead to quality and
total fruit loss. Symptoms usually begin as white, diamond-shaped lesions that present
on leaf midribs, stems, fruit handles, and the rind of fruit (Pictures 5 and 6) . These lesions can eventually bleach sections of fruit or stems, and lead to decline
in the plant or the fruit quality. Plectosporium blight is not usually a major issue
in Arkansas, but it isn’t hard to find it sporadically in fields across the state.
Growers should scout for this disease and try to discern whether problems are beginning
to worsen. Downward cupping of leaves and tan midribs can be a sign of worsening plectosporium
blight, but abrasions should not be mistaken for lesions. A basic fungicide spray
program along with cultural controls should prevent this disease in most cases, especially
since it is more commonly observed in wet conditions. If symptoms begin to rapidly
progress and if excessive rainfall persists, use one of the following fungicides on
a 7-10 day schedule along with the basic spray schedule: Cabrio (pyraclostrobin, FRAC
11) or Flint (trifloxystrobin, FRAC 11).
Picture 5. Plectosporium blight lesions present on pumpkin stems. Lesions have progressed and
are beginning to bleach portions of this plant. Effected areas of the plant are more
brittle and prone to breaking. Photo: G Brust, University of Maryland.
Picture 6. Plectosporium blight lesions present on a ripe pumpkin fruit. Photo: William Nesmith,
University of Kentucky.
Insect Management Cucumber Beetles Spotted and striped cucumber beetles are known to be an issue in Arkansas and can
transmit bacteria that can cause bacterial wilt (Picture 7 and 8) . Adults feed on the foliage, flowers, and on the surface of the fruit, and plants
are susceptible to wilt transmission as soon as they emerge or are transplanted. Younger
plants (before the 4-leaf growth stage) are most susceptible to the disease, therefore
scouting twice a week is necessary early on. Thresholds depend on the type of cucurbit
you are trying to protect and the age of the planting. An insecticide application
should be made to pumpkins when one cucumber beetle is found per plant on average
until plants have 5 true leaves. After this growth stage an application should be
made when populations reach a few beetles per plant on average. Cucumber beetles are
known to migrate into fields quickly, which warrants frequent scouting. This is especially
important after an insecticide application is made, as re-infestation at densities
above threshold is possible in only a few days.
Many insecticides can be used to manage cucumber beetles, but considering that most
can flare aphids, scout your fields to make sure applications are necessary. Effective
insecticides include pyrethroids (IRAC 3A - bifenthrin, lambda cyhalothrin, etc.),
neonicotinoids (IRAC 4A - imidacloprid, acetamiprid, dinotefuran, thiamethoxam, and
clothianidin), carbamates (IRAC 1A - carbaryl), and organophosphates (IRAC 1B - malathion).
We’ve seen some complaints about the pyrethroids we normally rely on, although no
resistance has been reported in this pest. I recommend choosing bifenthrin over other
pyrethroids as it usually offers the best control. Neonicotinoids such as imidacloprid
and dinotefuran can also be applied as drip applications and may provide some aphid
and squash bug suppression. We have seen excellent control with dinotefuran as a foliar
spray for squash bugs. If you didn’t use a neonicotinoid drip application at planting
and are seeing high numbers of cucumber beetles, I recommend getting out an imidacloprid
application (soil only) ASAP to help rotate effective insecticide mode of action (MOA
– IRAC Code). If populations are excessive, use a knockdown foliar insecticide even
when you still expect protection from a systemic drip applied insecticide. You may
consider mixing in another insecticide from a different MOA in foliar sprays if you
feel like you aren’t getting acceptable control.
Picture 7 – Spotted and striped cucumber beetles. Photo courtesy of Ric Bessin, University
of Kentucky Entomology.
Picture 8 – Bacterial wilt disease symptomology.
Squash Bugs Like cucumber beetles, squash bugs are an issue as soon as plants are in the field
and can vector bacteria that cause cucurbit yellow vine disease, also known as yellow
vine decline (Picture 9, 10 and 11) . Smaller fields are most susceptible, and numbers generally are the highest on field
edges and during fruit-set and bloom. Fields should be monitored at least once a week
and monitoring should be focused on the underside of leaves, at the base of plant,
and under fallen leaves where squash bugs often congregate. Adults are difficult to
manage, and applications should target young nymphs or eggs. Apply an insecticide
when egg masses or nymphs are observed on every few plants. Effective insecticides
include pyrethroids (IRAC 3A - bifenthrin, lambda cyhalothrin, etc.), neonicotinoids
(IRAC 4A - imidacloprid, acetamiprid, dinotefuran, thiamethoxam, and clothianidin),
and carbamates (IRAC 1A - methomyl). Neonicotinoids such as dinotefuran and imidacloprid
(soil only) can also be applied as drip applications and may provide some aphid and
cucumber beetle suppression. Foliar applications of dinotefuran containing insecticides
have provided excellent control of squash bugs in our field trials.
Picture 9 – Squash bug adult pictured on a summer squash leaf.
Picture 10 – Squash bug eggs pictured on top of a pumpkin leaf.
Picture 11 – Yellow vine disease symptoms pictured on a pumpkin plant in Arkansas.
Melonworm Melonworm, Diaphania hyalinata , is a tropical moth species (Picture 12) that occurs throughout Central and South America, as well as sub-tropical regions
of the Southern United States. Melonworm is also referred to as rind worm or pickle
worm, although the pickle worm is related species of cucurbit feeding caterpillar,
Diaphania nitidalis , with a distinctly different biology and morphology that is not commonly found in
most of the Mid-South. Melonworm larvae feed on the foliage and fruit of plants in
the family Cucurbitaceae, including specialty crops such as squash, pumpkins, and
watermelon (Picture 13-16) . Melonworm immigrate to central and northern regions of the United States each year
during the summer months and commonly occur in the Southeast. Melonworm can disperse
as far north as the Great Lakes or northern regions of the Atlantic coast. In Arkansas,
melonworm typically have the largest impact on fall cucurbit crops such as pumpkins
and winter squash. This species does not overwinter in Arkansas and moves north from
sub-tropical regions of the US across the summer, typically arriving in early fall.
Melonworms don’t overwinter in Arkansas so their arrival each year depends on the
climatic conditions for the year. In 2021 moths showed up much earlier than previous
years (early August) and began multiplying rapidly before pumpkin harvest started.
Significant damage was easy to see at many commercial pumpkin operations across Arkansas
by late September. In 2022 only low numbers of melonworm were observed starting on
September 19, and infestations were not widespread. The occurrence of moths or larvae
in August or early September should be an early sign for growers that an insecticide
application may be necessary. If growers can easily find these white and brown moths
flying in plantings, or are seeing larvae on leaves, a pesticide application will
be necessary.
Melonworm prefers to feed on pumpkins and winter squash, but can also be found on
fall squash and zucchini. Variation among cultivars may exist and is most pronounced
when several species of Cucurbita are used for one type of crop. For example, melonworm often prefer jack-o-lantern
pumpkin varieties over some ornamental types grown and sold together. Preference is
rooted in the Cucurbita species each pumpkin is derived from. Pumpkins planted to be picked in mid-September
are less likely to be impacted by melonworm in some years, suggesting that planting
date could be a useful way to help manage melonworm. However, planting date trials
in years of early infestations suggest no benefit from planting early, even when pumpkins
are picked in September. Row covers may be an option for home gardeners or small organic
growers to prevent melonworm from laying eggs at night, although permanent row covers
limit pollination, increase pests such as aphids, and are unlikely to remain free
of holes throughout the entire season. Melonworm trapping does not give a good indication
of presence, as moths are hard to catch with sticky traps and no commercial pheromone
lures exist for melonworm currently.
Melonworm need to be managed with effective insecticides once they are observed. Data
indicates that scouting for moths or larvae is the most sustainable way to time insecticide
applications. In fact, melonworm dispersal seems to be relatively uniform in latitude
and across geographically similar growing regions, which indicates that growers can
consider infestations in nearby areas to time insecticide applications. For example,
growers in Southeast Arkansas should consider insecticides when melonworm are found
anywhere in Arkansas, or even just in other areas of southern Arkansas. However, growers
in central Arkansas should only consider insecticide applications if melonworm is
found in northern or central Arkansas and should only increase scouting efforts when
melonworm is found in the southern area of the state. In most years we see melonworm
move quickly into southern portions of the Mid-South, especially Southeastern regions,
but this does not always translate into early infestations in central and northern
growing regions of the Mid-South.
Several insecticides have been found to be effective in controlling melonworm in pumpkins
and squash (Table 1) . Once melonworm is found it is likely that infestation pressure will continue until
harvest is completed, with some increases in infestation density noticeable as successive
generations emerge. Due to prolonged infestation pressure, insecticides should be
selected and scheduled based on the expected residual activity of the insecticide.
Data at the University of Arkansas indicate that short-lived broad-spectrum insecticides,
such as pyrethroids (bifenthrin, lambda-cyhalothrin, etc.) used to control cucumber
beetles and squash bugs, will also suppress melonworm. These insecticides may only
offer two to five days of residual, would need to be applied weekly, and should only
be relied on when also managing other pests that necessitate their use.
Broad-spectrum insecticides are not necessary for melonworm management and may do
more harm than good, as they can flare melon aphids and spider mites. Many cucurbit
operations open to the public are hesitant to apply insecticides to manage melonworm
due to public perception. In these instances, selective insecticides can be used to
assuage any fears of any potential impact. Data from Arkansas indicates that several
selective insecticides offer excellent suppression of melonworm when used appropriately.
Diamide insecticides (Mode of Action Group 28), those containing chlorantraniliprole,
cyantraniliprole, etc., are selective insecticides that primarily kill caterpillars
and offer 21 to 28 days of residual activity. Our data indicates that only 1 to 2
applications of chlorantraniliprole containing insecticides would be necessary per
year if applications were timed at first detection of melonworm and repeated on 21-28
day intervals. University of Arkansas data also indicate that very short-lived organic
insecticides, such as those containing Bt , Bacillus thuringiensis , are effective when timed early and used weekly. Although we have not tested other
organic options, we would expect those with proven efficacy on caterpillar pests,
such as insecticides containing spinosad, to be effective when sprayed weekly.
Table 1. Insecticides that can be used to manage melonworm including insecticide class and
mode of action (MOA) and estimated residual activity.
Trade Name
Active Ingredient
Insecticide (MOA)1
Residual (days)
Brigade
bifenthrin
Pyrethroid (3A)
<7
Warrior II
lambda-cyhalothrin
Pyrethroid (3A)
<7
Mustang Maxx
zeta-cypermethrin
Pyrethroid (3A)
<7
Sevin
carbaryl
Carbamate (1A)
<7
Coragen eVo
chlorantraniliprole
Diamide (28)
21+
Harvanta
cyclaniliprole
Diamide (28)
21+
Exirel
cyantraniliprole
Diamide (28)
21+
Intrepid
methoxyfenozide
Growth Regulator (18)
14-21
Radiant
spinetoram
Spinosyn (5)
<7
DiPel2
B.t. subsp. kurstaki Microbial (11)
<7
Entrust2
spinosad
Spinosyn (5)
<7
1 The Mode of Action (MOA) listed corresponds to the IRAC Group (Insecticide Resistance
Action Committee) number for each insecticide.
2 Organic products
Picture 12 - Melonworm moth on a mature pumpkin. These moths are easily observed on fruit or leaves
during daytime hours and are easily disturbed.
Picture 13 – Melonworm caterpillars present on the underside of a pumpkin leaf. These larvae
can be identified by their green color and the two white stripes on their back.
Picture 14 – Melonworm larvae pictured on a pumpkin leaf. Melonworm have 4 prolegs which will
distinguish them from other caterpillars such as cabbage looper which are common on
pumpkin.
Picture 15 – Feeding damage caused by melonworm which is usually characterized by “skeletonized’
leaves that only have veins remaining (pictured right) or by rolled leaves (pictured
left).
Picture 16 – Melonworm larvae feeding just under the handle/stems of pumpkins. Look for webbing
or excrement, as shown in this picture, as an indication that larvae are feeding underneath.
Aphids Melon aphid, Aphis gossypii , is considered a secondary pest in Arkansas pumpkin production (Picture 17) . Insecticides such as pyrethroids, pyrethrins, carbamates, or organophosphates that
are used to control cucumber beetles, squash bugs, and other pests, kill the natural
enemies that usually keep aphids suppressed (Picture 18) . If you have used broad-spectrum insecticides in your pumpkin patch this year, including
many organic options, then you need to be scouting for aphids. There are many product options for aphid control such as acetamiprid (IRAC 4A- Assail,
Tristar, and Anarchy), flupyradifurone (IRAC 4D - Sivanto Prime), sulfoxaflor (IRAC
4C - Transform), and Flonicamid (IRAC 9C - Beleaf). Acetamiprid, sulfoxaflor, or flupyradifurone
are likely going to be the easiest products to find locally. Aphid control is necessary
when populations are building on every few plants and the natural enemy complex was
collapsed by recent broad spectrum insecticide sprays.
Picture 17 – Melon Aphids on the underside of pumpkin leaves following a pyrethroid spray.
Picture 18 – Average melon aphids present on squash plants in Hope, AR in 2022. Plants were
either untreated, sprayed weekly with a pyrethroid (Warrior II), or received an insecticide
based on pests that were present (scouting pyrethroid and coragen). Scouting based
plots received only 1 insecticide application and minimal aphids were observed. Plots
receiving weekly pyrethroids had excessive aphid numbers and a large amount of plant
stunting.
Management Plan Many of the insecticides mentioned here will control both cucumber beetles and squash
bugs, and in most production areas of the state, these pests are likely to be present
at the same time. Due to the risk of flaring melon aphids, a good strategy is to start
early with a drip application of imidacloprid (Admire Pro) or dinotefuran (Venom or
Scorpion) to prevent flaring aphids. These products usually give at least 3 weeks
of suppression that should help protect from bacterial wilt or yellow-vine disease.
Foliar applications of pyrethroids are usually relied on for cucumber beetle and squash
bug suppression, but it is important to rotate in other Modes of Action like carbamates, neonicotinoids, or organophosphates where possible. Repeated use
of one chemistry is likely to lead to lowered success of control. This is especially
important when considering squash bug, as it is difficult to suppress this pest once
infestations are excessive. Many growers also count on broad spectrum insecticides
to suppress squash vine borer, which is not generally a serious pest of larger plantings.
See our fact sheet about squash vine borer for more information.
Melonworm is not likely to be a serious pest every year, but the losses we incurred
in 2021 and 2024 are a stark reminder that we need to be scouting every week beginning
in August. Even in 2022 when populations were very low, we still observed significant
damage in our plots and on grower operations. Rely on diamide products (IRAC 28) like
Coragen or Exirel or Shenzi once moths or larvae are observed in fields. A second
application may be necessary in 21 days if pumpkins still need to be protected. See
our melonworm fact sheet for more information.
If you have any questions, give me a call at 479-249-7352.
Aaron Cato
