10 Common Pests Of Watermelon You Need To Know About And How To Control Them

Watermelon, scientifically known as Citrullus lanatus, belongs to the family Cucurbitaceae which includes other plants such as cucumber, squash and pumpkin. The watermelon plant is a vine-like plant that is typically grown in warm, tropical or subtropical climates. The fruit is dominant during summer season especially due to its high-water content and delicious taste. Major watermelon producing states in India includes Uttar Pradesh, Andhra Pradesh, Tamil Nadu, Karnataka and Orissa. Watermelon crops are susceptible to a variety of pests that can cause significant damage to the plants and reduce the overall yield of the crop.  

Common insect pests affecting watermelon crops are discussed here; 

1. Red Pumpkin Beetle

Scientific name: Aulacophora foveicollis 

Pest stage of attack: Larva and adult 

Stage of occurrence: Seedling/Vegetative stage 

Identification of Symptoms

• Complete destruction of seedling due to adult feeding 
• Leaves show riddled holes or notches due to beetle infestation leading to complete defoliation 
• Larvae feed on roots and stems causing rotting and withering  

• The beetles may also feed on the fruits, causing scars or holes, which can lead to rotting or sunburned spots on the fruit 
• The undersurface of the fruits touching the soil surface will have larval tunnels in the surface. 

Management of Red Pumpkin Beetle in Watermelon

2. Fruit fly

Scientific name: Bactrocera cucurbitae 

Pest stage of attack: Maggots 

Stage of occurrence: Fruiting stage 

Identification of Symptoms

• The female fruit fly lays eggs under the skin of the fruit, which causes small puncture marks on the surface of the watermelon 
• After the eggs hatch, the larvae burrow into the fruit and feed on the flesh, contaminating it with frass excreta, thus making it susceptible to secondary infections by fungi and bacteria 
• The damage caused by the fruit flies can cause rotting and premature dropping of fruits 
• Infected fruits become distorted and malformed. 

Management of Fruit fly in Watermelon

3. Thrips

Scientific name: Thrips tabaci 

Pest stage of attack: Larva and adult 

Stage of occurrence: Vegetative, flowering, fruiting stage  

Identification of Symptoms

• Thrips feed on the leaf surface and suck the plant juice causing small, silvery white or stippling spots on the leaves 
• Under severe infestation, the leaves turn yellow, wither and become deformed. This can lead to reduced plant growth and yield 
• They may feed on the flowers of the plant, causing them to drop prematurely, which can reduce the number of fruit that the plant produces 
• Thrips may also feed on the watermelon fruits causing scarred or distorted fruit. 

Management of Thrips in Watermelon

4. Aphids

Scientific name: Peach aphid – Myzus persicae; Melon aphid – Aphis gossypii 

Pest stage of attack: Nymph and adult 

Stage of occurrence: Seedling, Vegetative, flowering  

Vector: Watermelon Mosaic Virus 

Identification of Symptoms

• Small, pear-shaped, soft bodies insects can be found on leaves or stems of the plant 
• Aphids’ feeds on the tender shoots and under surface of the leaves by sucking the leaf sap causing curling and crinkling of the leaves 
• They secrete a sticky, sugary substance called honeydew, which causes black sooty mould development that accumulates on the leaves and attracts other insects, such as ants 
• This also reduces the photosynthetic activity leading to stunted growth. 

Management of Aphids in Watermelon

5. Whitefly

Scientific name: Bemisia tabaci 

Pest stage of attack: Nymph and adult 

Stage of occurrence: Vegetative, flowering stage 

Vector: Watermelon leaf curl virus 

Identification of Symptoms

• Feeding activity of nymph and adult may lead to yellowing, downward curling and drying of leaves 
• They also cause sooty mould development due to honeydew secretion causing restricted photosynthesis 
• It can cause the leaves to turn yellow (chlorotic spots) and fall off prematurely 
• Affected leaves may become deformed.  

Management of Whitefly in Watermelon

6. Leaf eating caterpillar

Scientific name: Diaphania indica 

Pest stage of attack: Larva 

Stage of occurrence: Vegetative stage 

Identification of Symptoms

• Caterpillars feed on the young and tender leaves of watermelon plants, which can result in holes and ragged edges on the leaves 
• They fold the leaves and scrape the epidermal layer of leaves causing skeletonization of the leaves, where only the veins of the leaf remain intact 
• Under severe infestation, it can cause defoliation of leaves, thus reducing plant growth and vigor, resulting in smaller plants and fruit. 

Management of Leaf eating caterpillar in Watermelon

7. Serpentine Leaf Miner

Scientific name: Liriomyza trifolli 

Pest stage of attack: Larva 

Stage of occurrence: Vegetative, flowering and fruiting stage 

Identification of Symptoms

• Serpentine leaf miners create winding, snake-like tunnels on the leaves as they feed on the leaf tissue 
• It can cause the infested leaves to turn yellow or brown 
• Under severe infestation, these leaves dry and drop off from the plant 
• It may lead to stunted growth of the plant and reduce the overall plant vigour 
• The larva sometimes tunnels through the rind of the fruit, causing scars and reducing the fruit’s quality and marketability.  

Management of Serpentine Leaf Miner in Watermelon

8. Red Spider Mite

Scientific name: Tetranychus urticae 

Pest stage of attack: Adult 

Stage of occurrence: Vegetative, flowering and fruiting stage 

Identification of Symptoms

• Red spider mites using their long, needle like mouthpart, suck the chlorophyll content in the leaves and causes chlorosis  
• They feed on the underside of leaves, which can result in stippling or small yellow or white dots on the upper surface of the leaves 
• They often produce fine webbing on the leaf surface 
• Affected leaves completely dry and drop off.  

Management of Red Spider Mite in Watermelon

9. Cutworms

Scientific name: Agrotis spp, Peridroma saucia, Nephelodes minians, Spodoptera litura  

Pest stage of attack: Larva 

Stage of occurrence: Seedling stage  

Identification of Symptoms

• Cutworms often feed on the stems of young watermelon plants, cutting them at or near the soil line. This can cause the plant to wilt or die 
• They feed on the leaves, causing irregular holes or notches in the foliage 
• They are nocturnal and may not be visible during the day, but emerge at night, by burrowing in the soil near the base of the plant. 

Management of Cutworms in Watermelon

10. Cucumber Beetle

Scientific name: Diabrotica spp 

Attacking stage of pest – Larva and adult 

Stage of occurrence – Vegetative, flowering and fruiting stage 

Vector – Bacterial wilt disease 

Identification of Symptoms

• Larvae feed on the roots of the plants, causing wilting and stunting 
• Adult cucumber beetles feed on the foliage of watermelon plants, causing defoliation and thus reduces photosynthesis. 

• They feed on the surface of the watermelon fruit, leaving shallow, irregularly shaped scars on the rind. This type of cosmetic damage may not affect the quality of the fruit, but it can reduce its marketability. 

Management of Cucumber Beetle in Watermelon

NOTE:  

• Refer to the product label to find the right time of application and more details of the product. 
• It is advised to spray Bio-fungicides during early morning or evening hours when the temperature is relatively cool to get best results. 

Conclusion

Insect pests can affect watermelon plants at any stage of growth, from seedlings to mature plants and can cause damage to the leaves, stems and fruit. This can result in reduced plant growth, decreased fruit quality and size and in severe cases, even plant death. Effective pest management strategies, such as regular monitoring, good agronomic practices and the use of chemical and biological control methods, can help in controlling the pest damage, protect the yield and quality of watermelon crops.