How Your Pest Management Practices Affect Your Watermelon Yield, Pollinators, and

Natural Enemies

Rick FosterExtension Entomologist

Integrated Pest Management = IPM

• “a system in which a combination of methods is used to maintain pest populations at low levels while allowing profitable vegetable production with minimal adverse effects on the environment.”

Foster and Flood, 2005

Key Points About IPM

• Combination of methods• Profitable• Limit adverse side effects• Key principle: Don’t apply insecticides unless the benefits

of that application outweighs the costs (money, time, environmental, etc.)

Striped Cucumber Beetles• Feed on leaves, stems, flowers, and fruit• Transmit bacterium that causes bacterial wilt of cucurbits

to muskmelons and cucumbers• Watermelons not susceptible to bacterial wilt

Economic Thresholds

• Muskmelons and cucumbers – 1 beetle/plant• Watermelons – 5 beetles/plant (exception for fruit

damage)

Common Strategy for ManagingStriped Cucumber Beetle in Watermelon

• Apply neonicotinoid insecticide at planting time• Little or no scouting for beetles• Add a pyrethroid insecticide (cheap) when applying a

fungicide (expensive)

Common Neonicotinoid Insecticides

• Admire Pro• Platinum• Actara• Assail

Characteristics of Neonicotinoid Insecticides

• Highly effective against a wide variety of insect pests• Safe for humans and other mammals• Highly systemic (move through the plant)• Highly toxic to pollinators – except Assail• Highly water soluble• Persistent

IPM in Dent Corn/Soybean Rotation Crops

• Almost all the corn and most of the soybean seeds planted in the Midwest are treated with a neonicotinoid insecticide

• Studies have concluded that treating soybean seeds in the Midwest has little or no value

• Most Midwest corn entomologists agree that treated corn seeds rarely provide any insect protection

Best Management Practices:Treatments

• Untreated control• Low rate of Platinum at planting• High rate of Platinum at planting• Warrior as needed for SCB• Low rate of Platinum; Warrior as needed

SCB Populations: Beetles/Plant VincennesTreatment June 2 June 9 June 14 June 21 June 29 July 7

Untreated 0.34 0.88 5.59 1.22 0.19 0.28

Low Platinum

0.06 1.78 4.81 1.25 0.25 0.25

High Platinum

0.12 1.00 4.63 0.84 0.16 0.22

Warrior 0.06 1.00 5.87 0.72 0.09 0.06

Low Platinum; Warrior

0.16 1.50 5.06 0.47 0.13 0.09

P>F 0.61 0.06 0.47 0.51 0.68 0.40

Planted May 18, 2017

SCB Populations: Beetles/Plant LafayetteTreatment June 

6June 12

June 15

June 20

June 22

June 27

July 3

July6

Untreated 0.50 1.88 3.41 2.25 0.07 b 1.09 0.97 b 0.31

Low Platinum

0.00 0.22 2.19 3.53 0.35 a 1.38 1.56 ab 0.38

High Platinum

0.00 0.72 1.38 2.72 0.36 a 2.25 1.69 ab 0.88

Warrior 0.16 1.38 1.88 2.13 0.14 b 0.81 0.97 b 0.56

Low Platinum; Warrior

0.00 0.25 1.53 2.97 0.22 ab 1.97 1.75 a 0.66

P>F 0.44 0.11 0.12 0.59 0.003 0.06 0.009 0.17

Planted May 26, 2017

SCB Populations: Beetles/Plant LafayetteTreatment June 

6June 12

June 15

June 20

June 22

June 27

July 3

July6

Untreated 0.50 1.88 3.41 2.25 0.07 b 1.09 0.97 b 0.31

Low Platinum

0.00 0.22 2.19 3.53 0.35 a 1.38 1.56 ab 0.38

High Platinum

0.00 0.72 1.38 2.72 0.36 a 2.25 1.69 ab 0.88

Untreated 0.16 1.38 1.88 2.13 0.14 b 0.81 0.97 b 0.56

Low Platinum

0.00 0.25 1.53 2.97 0.22 ab 1.97 1.75 a 0.66

P>F 0.44 0.11 0.12 0.59 0.003 0.06 0.009 0.17

Watermelon Threshold =5 beetles/plant

• In small plot studies, we reached the threshold once in Vincennes and never in Lafayette

• What about commercial farms?

Pollinator Sampling• Pollinator collection• 59 sampling dates during watermelon

flowering

Pest Sampling• Plants visually sampled for striped

cucumber beetles weekly• Beetle density used as a proxy for

intensity of management

• 30 commercial watermelon fields in IN and IL in 2017-18

• 2 organic production fields

Methods

• No field observed to have reached threshold for a sampling date (142 total sampling dates)

• 29 out of 2828 total plants sampled (1%) had five or more striped cucumber beetles

• 7 out of 15 fields never had a single plant with five or more striped cucumber beetles

Pest Sampling Data ‐2017

More Intensive

Intensity of Pest Management

Less Intensive

Organic Production

Sweat Bees40%

Honeybees28%

Two Spotted Longhorn Bee

(M. bimaculatus)7%

Bumblebees5%

Syrphid Flies11%

Other Non‐Bees8%

Other Bees1%

FLOWER VISITATION BY POLLINATOR GROUP

0

20

40

60

80

100

120

140

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

# of Pollin

ators O

bserved

Flower Visitation by Pollinator Group

Amellifera Bumblebees Melissodes Halictid OtherBees Syrphid OtherNonBeesHoneybeesSweat Bees

0

1

2

3

4

5

6

Organic

0

20

40

60

80

100

120

140

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

# of Pollin

ators O

bserved

Flower Visitation by Pollinator Group (Honeybees Excluded)

Bumblebees Melissodes Halictid OtherBees Syrphid OtherNonBeesSweat Bees

0

1

2

3

4

5

6

Honeybees

• Primary Managed Pollinators• Large eusocial colonies, queen and workers• Generalist foragers• Introduced to North America• Mid‐size bees

Bumblebees

• Native to North America• New managed pollinator (Bombus impatiens)• Primitively eusocial colonies, queen and a 

100+ workers• Generalist foragers• Large bees

Sweat Bees

• Native to North America• Solitary species, males and females• Generalist foragers• Small bees• Diverse appearances, bright green, blue, 

black, tan with various patterning

Syrphid Flies/Hoverflies

• Native to North America• Not bees• Small to mid‐size• Diverse appearances, often look like bees• Feed on aphids as immatures

Watermelon Cropping System Project

• 0.5 acre watermelon fields surrounded by 15 acres of corn

• Corn grown in 2017• Watermelon and corn grown in 2018• Will continue in 2019 and 2020

Watermelons: 0.5 acres

Conventional system

• Imidacloprid neonicotinoid soil 

drench at transplant

• 4 prophylactic Warrior II® pyrethroid sprays 

IPM system

• No soil drenching insecticides

• Warrior II® spray only in response to 

economic thresholds

Corn: 15 acres Conventional system IPM system

• Thiamethoxam neonicotinoid seed treatment

• No seed treatment

Paired systems located at 5 sites across Indiana

150 ft

150 ft

‐ 53%

‐ 46%

Pollinator Abundance

Floral Visits

Difference in watermelon pollinator communities

Conventional system

n = 258

IPM System

n = 851

Honeybee Hive Weight Summer 2018

Waxworm larvae

Eight replicates per field

**

*

**

*

Protected with a small metal cage and

left for 24 hr

Materials and Methods

*

*

Cucumber beetle eggs

*

*

*

**

*

*

*

Predation in watermelon

NS

NS

*

*

Predation in corn

+*

*

+

Summary

• Seed treatment for corn and soybean provide little or no benefit and may contribute to reductions in pollinators

• Planting time neonic treatments in watermelons provided no yield benefit

• Populations of striped cucumber beetles in watermelons rarely reach the economic threshold in commercial fields or in small or large plots

Summary (cont.)

• “Conventional” practices – Reduce the amount of predation– Reduce pollinator numbers, bee visits, and hive health for both

honey bees and bumble bees– Don’t improve yield (and may reduce it)

• Previous studies showed that spraying cantaloupes weekly significantly reduced yields rather than spraying according to IPM principles

Recommendations

• Ask your corn and soybean seed dealers to make untreated seeds available

• Don’t use planting time applications of neonics on watermelons

• Don’t add an insecticide to the tank just because you are already spraying a fungicide

• Scout for beetles and treat if necessary (7 plants/field)

Questions?