Integrated Pest Management in Watermelon

Camilla B. Yandoc

Watermelon Pests

•Insects & Mites

•Weeds•Diseases•Nematodes

Common Insect Pests

Aphids Rindworms Sweetpotato whitefly

Cutworms

Aphids & Whiteflies

• Downward curling & crumpling of leaves (aphids)

• Honeydew excreted by both insects attracts sooty molds

• Both are efficient vectors of plant viruses

Cutworms & Rindworms• Cutworms: reduce young watermelon stands

• May feed on leaves of young seedlings

• Rindworms: general term for worms that feed on rind (fall armyworms, corn earworm, cutwroms and loopers

• Foliage & stem damage• Eat away irregular patterns of the rind

Occasional Insect Pests

•Cucumber beetle•Mites•Mole crickets•Wireworms•White-fringed beetle•Leafminers•Thrips

Occasional Insect Pests•Root maggots•Flea beetles & fleahoppers

•Leafhoppers•Plant bugs•Grasshoppers•Melonworms & pickleworms

Insect Damage

• Foliar damage (holes)• Stem damage• Root damage (wilting, stunting & death of plant)

• Fruit damage• Drying up of leaves (sucking insects)

• Leaf spots, mottling or discoloration

Insect & Mite Management

•Sampling•Establish ETL•Recognize & identify beneficials

Important Practices:

Aphid Control

Biocontrol lady beetles, syphrid fly larvae,lacewings & tiny wasps

cultural control reflective plastic mulchStylet oil sprays (interferes with virus transmission)

Sweetpotato Whitefly Control

Monitoring use of trapsCultural control planting location & sanitationWeed control control alternate hosts Chemical control alternate different classes ofinsecticides

Cutworm & Rindworm Control

Mechanical control (cutworm): thorough soil prep

Chemical control(cutworm): broadcast application of approved insecticides before planting

Chemical control(rindworm): spray before worms > 1/2 in length, spray all of exposed fruit

Control of Other Insect Pests

Chemical controlinsecticide sprays for fleabeetles, leafminers, mites,mole crickets,wireworms,fleahoppers,leafhoppers, plant bugs,grasshoppers, melonworms and pickleworms

Control of Other Insect Pests

Cultural control avoidance (white-fringed beetles), plowing & deepturning of crop litter before planting (root maggots), overhead irrigation (mites)

Insect & Mite Management

• Reflective mulch• Planting location/timing• Sanitation• Weed control• Overhead irrigation• Plowing & turning in crop debris

Cultural Practices

Diseases• Reduce crop yield & quality• Poor disease control due to delayed accurate diagnosis & delayed implementation of control measures

• Disease control consists of a sequence of properly timed control measures (cultural, mechanical & chemical)

Root & Stem Diseases

• Anthracnose• Damping-off • Fusarium wilt

•Gummy stem blight•Fusarium rot

Root & Stem Disease Management

Gummy stem blight postharvest plow-down of debris, crop rotation, fungicidal sprays, use fungicide treated seeds

Anthracnose resistant varieties, fungicidal sprays, clean seeds,sanitation

Fusarium wilt resistant var.,healthy transplants,crop rotation, soil fumigation, delayed thinning

Foliar Diseases

Anthracnose

Downy mildewCercospora leaf spot

Other Foliar Diseases

•Alternaria leaf spot•Bacterial leaf spot•Watermelon mosaic

Foliar Disease ManagementCercospora leaf spot sanitation (removal of crop debris, diseased vines & weed hosts), crop rotation, fungicide sprays

Downy mildew fungicide application, resistant var., avoid irrigation, reduce canopy density

Foliar Disease Management

Alternaria leaf spot protectant fungicides Bacterial leaf spot avoid overhead irrigation, sanitation, protective sprays (copper sprays)

Foliar Disease Management

Watermelon mosaic stylet oil application to interfere with virustransmission & insecticides tocontrol aphid (vector)population

Fruit Diseases

Bacterial fruit blotch

Anthracnose

Bacterial rind necrosis

Other Fruit Diseases

•Bacterial leaf spot•Blossom-end rot•Speckle•Watermelon mosaic

Fruit Disease Management

Bacterial fruit blotch plowing infested soil, elimination of inoculumsources, field rotated out for3 years or more, copper sprays (Kocide DF Kocide 2000),use of high quality transplants

Fruit Disease Management

Anthracnose resistant varieties, fungicides, use clean seeds

Bacterial rind necrosis use less susceptible cultivars

Fruit Disease Management

Blossom end-rotsoil testing & liming,irrigation during fruit development (preventive),foliar Calcium application (curative)

Disease Management

• Sanitation• Healthy transplants• Resistant varieties• Crop rotation• Weed/Insect vector control• Liming & irrigation

Cultural Practices

Disease Management

•Fungicide sprays•Soil fumigation•Fungicide seed treatment

Chemical Control

Weeds

• Compete with the crop for nutrients, sunlight, water and space

• Serve as alternate hosts of nematodes, viruses and insect pests

Weed Management

• Polyethylene mulch• Cultivation• Soil fumigant• Hoeing & disking• Herbicides

Cultural, Mechanical & Chemical Control

Economically Important Nematodes

•Root-knot nematodes (Meloidogyne spp.)

•Sting nematode (Belonolaimus longicaudatus)

•Reniform nematode (Rotylenchus sp.)

Nematode Damage

• Root galls interfere with normal water & nutrient uptake

• Reduced size of root system limits availability of water & nutrients

• Aboveground damage: stunting, wilting & chlorosis

• Roots attacked by nematodes are predisposed to secondary invasion by root rotting plant pathogens

Nematode Management

•Planting location•Resistant varieties•Crop rotation•Land preparation•Use of clean & healthy transplants

Cultural Practices

Nematode Management

•Fumigants•Non-fumigants•Chemigation

Chemical Control

A Grower’s Pest Management Tactics:

• Insect control: chemical insecticides

• Weed control: mechanical control (cultivation)

• Disease control: resistant varieties & chemical fungicides, removal & destruction of diseased seedlings

What Growers Do in the Field…

• Scout for presence of insects and diseases (major pest problem)

• Watch the weather and spray accordingly (follow recommendations)

• Some spray protective fungicides even when weather is dry (for insurance)

What Growers Do in the Field..

• May spray 1 or 2x a season for aphid control, some never spray because insect problem is minor

• Follow recommendations for tillage & crop rotation

• Plant in soils without RKN problems

What Growers do in the Field

• Fusarium Wilt control: crop rotation, use of resistant varieties, scouting for diseased transplants and removal of infected transplants

• Gummy stem blight & Downy mildew control: fungicide sprays based on weather(likelihood of disease occurrence) or presence of spots

References• Zitter, A.T., D.L. Hopkins, and C.E. Thomas (eds.). 1996. Compendium of Cucurbits Diseases. APS Press.

• Maynard, D. N. (ed.). 1992. Watermelon Production Guide for Florida. Florida Cooperative Extension Service & IFAS

• Mr. Melvin Poole (Gainesville watermelon grower)

• Mr. Gerry Brinen (County Extension Office)