Melon Insects. Frank G. Zalom, Department of Entomology, UC Davis

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1 Melon Insects Frank G. Zalom, Department of Entomology, UC Davis

2 T. urticae Spider Mites Tetranychus spp. Adults about 0.75 mm long Eggs are spherical, laid on underside of leaves, sometimes in webbing Infestations may include a mixture of spider mite species Carmine Mite Many generations per year

3 Spider Mites Damage Leaves become pale, stippled, and in later stages of infestation dry up and die; resembles a virus Loss of color is pronounced on the under surface of leaves before it becomes apparent on the upper side Light infestations can be tolerated; heavier infestation can result in lowered yield and reduced quality of fruit Spider mite larvae have 6 legs

4 Spider Mites Control Good water management increases plant tolerance to mites If mite populations are building, either spot or completely treat the field before webbing occurs or before runners are 14 inches in length After runners are 14 inches long, mite feeding is less critical except to maintain the plant canopy; natural enemies often control pest mite populations at this time

5 Whiteflies Bemisia spp. Greenhouse whitefly Bemisia Greenhouse whiteflies hold their wings flat over body Bemisia hold their wings at an angle, rooflike over body 4th instar nymphs - Greenhouse whitefly nymphs have long waxy filaments around the edge of their bodies Bemisia nymphs do not Whiteflies colonize the underside of leaves Eggs Greenhouse whitefly

6 Whiteflies Damage Feeding by Bemisia causes leaves to turn whitish or silver Desiccation of plants occurs with moderate to heavy populations, and the production of honeydew gives rise to develop sooty mold Plant may become weak and nonproductive, and the fruit rendered unmarketable Bemisia transmits lettuce infectious yellows virus and squash leaf curl virus

7 Whiteflies Control When possible, plant melons at least 0.8 km upwind from key whitefly hosts such as tomatoes, cole crops, and cotton Inspect transplants for whitefly infestation Rotate with non-host crops Reflective mulch Use reflective polyethylene mulches on planting beds if virus transmission is a major concern

8 Whiteflies Bemisia pupae (yellow are parasitized) Control Several wasps parasitize nymphs; bigeyed bugs, lacewing larvae, and lady beetles are general predators If populations are higher at field margins than at field centers, treat only the field margins; this reduces treatment costs and preserves beneficials Preplant treatment with a soil applied neonicotinoid insecticide is Eretmocerus wasp effective

9 Armyworms Spodoptera spp. Damage Armyworms are primarily foliage feeders, but will also feed on fruit surface, creating circular or irregular holes Feeding is often superficial; however, damage canbe unsightly and decay organisms can enter wounds and rot the fruit Larvae occasionally develop inside the fruit

10 Armyworms Spodoptera spp. Control Infestations originate from moths or larvae that migrate from adjacent fields or weeds that are infested; cleaning up crop residue and weeds reduces density Monitor foliage for small larvae and treat before fruit damage occurs; treat only if armyworm feeding is observed on fruit Treat young larvae with Bt; larger larvae will require a different insecticide

11 Aphids Populations tend to start on lower leaves and move up the plant Cluster on the underside of growing leaves Aphids attacking melons have a wide host range Aphids move into melon fields from surrounding vegetation, carrying viruses as they move and feed from one plant to another

12 Aphid seasonal cycle Multivoltine; alternating generations Eggs Nymphs Sexual & Oviparous Stem mother Alate Parthenogenetic & Viviparous

13 Aphids Damage Vector of several viruses Feeding causes leaves to distort and curl Aphids produce honeydew, creating substrate for sooty mold Treatment may be needed when nearby fields are found to have a virus that affects melons watermelon mosaic virus Papaya ringspot virus

14 Aphids Management Prevent establishment of early colonies; spot treat with insecticide or remove and destroy the few heavily-infested plants as they appear in spring Control weeds in noncultivated areas from which aphids migrate Delay planting until warm temperatures (26 to 29 C) occur and the spring flight of early season aphids is over Avoid over-fertilizing with nitrogen

15 Aphids Management Beneficials can have a significant impact Use non-disruptive insecticides to conserve natural enemies Reflective mulches repel aphids Floating row covers exclude aphids Melon aphids and parasitized mummy Preserve habitat for beneficials; planting a habitat for beneficial insects, such as sweet alyssum, around the field may be helpful

16 Cucumber Beetle Diabrotica spp. Adults typically have black spots or black and yellow stripes Overwinter as adults; in spring, adults lay eggs at the base of plants Larvae feed on plant roots and complete their development in the soil; adults feed on vegetation About three generations a year

17 Cucumber Beetle Diabrotica spp. Adults migrate into melons from alfalfa, corn, and other crops and from uncultivated land Prefer smooth-skinned varieties such as honeydew, crenshaw, and casaba Adults are attracted to moisture and dislike heat; thus, melon fields are especially attractive in hot weather during and after an irrigation

18 Damage on zucchini Cucumber Beetle Damage The beetles chew holes in leaves and scar runners and young fruits, and can destroy flowers Feeding on stems of young plants followed by sustained winds result in severe stand reductions After the skin hardens, melons are much less subject to attack Larvae may injure plants by feeding on roots Beetles also spread squash mosaic virus

19 Cucumber Beetle Control Treat adults if there is an average of 1 beetle a plant during the seedling-to-10-cm-tall stage Infestations later in the season are usually not as damaging as earlier infestations because population densities tend to be lower Natural enemies usually do not reduce populations below economically acceptable levels