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In this Issue
Eggplant, potato, and tomatillo: Flea beetles have been seen in northern Utah. Populations are small and damage is minimal this time of year, so no control is recommended.
Brassicas: Infestations of cabbage aphid are present throughout northern Utah. Inspect plants and control before dense populations form. Consider removing infested plants or spraying to manage this pest.
Cucurbits and solanaceous crops: Pythium fruit rot can occur when fruit is in contact with saturated soils, which may be more likely due to recent rainy weather.
Potatoes: Wireworms are an occasional pest in potatoes, but damage to tubers may be apparent at harvest.
Flea Beetles
Flea beetles have been seen in northern Utah. Populations are small and damage is minimal this time of year, so no control is recommended.
Crops affected: Many plant species can be affected by this pest, as many species of flea beetles are present in Utah. Brassicas and solanaceous crops are the primary hosts. They can also affect cucurbits and may injure root crops like carrots. In the last few weeks, the tobacco flea beetle has been seen most frequently feeding on eggplant, potato, and tomatillo.
Flea beetle feeding damage on potato leaves.
Tobacco flea beetle.
Western black flea beetle.
Tobacco flea beetle. Natasha Wright, Braman Termite & Pest Elimination, Bugwood.org
Symptoms and Life Cycle
Adult flea beetles are small, shiny insects with enlarged hind legs that hop when disturbed. They chew small, rounded holes or pits in leaves that have a characteristic ‘shot hole’ appearance. Feeding damage is more of a concern on seedlings, while mature plants are not typically negatively affected. Flea beetle larvae can feed on roots as well, which reduces plant health and vigor. Larvae of the tuber flea beetle can cause considerable damage to potato tubers.
Flea beetles overwinter as adults in protected sites like weedy field borders. Adults become active in spring and feed on weeds until they dry up or their preferred crop is available. Most flea beetles lay eggs in the soil at the base of the host plant, but several species lay eggs on leaves and twigs. Larvae emerge and feed on small roots or leaves for about a month until they pupate. When the second generation of adults emerges, they start the cycle over. Most flea beetles have two generations in Utah, but some species may have three.
Management
In the fall, when serious damage is less likely to occur, there is no need to actively monitor or control this pest. Treatment on mature plants is only necessary when populations are high.
Prepare for spring management of this pest in sensitive crops where flea beetles have been historically.
Adjust planting times to avoid peak flea beetle activity. Plant early into soil-warming mulches or protective covers to advance plant maturity before pests begin to feed, or plant crops later when the threat of damage is past.
Use row covers to reduce pest feeding on crops.
Plant trap crops (bok choy, daikon, radish, and pacific golden mustard) to lure flea beetles away from crops of interest or companion crops (bunching green onion, dill, and marigold) to block, confuse, or repel the pest.
Only spray when necessary. Click the following links in the Utah Vegetable Production Guide for flea beetle spray options in small-scale and commercial potato production.
Cabbage aphid
Infestations of cabbage aphid are present throughout northern Utah. Inspect plants and control before dense populations form. Consider removing infested plants or spraying to manage this pest.
Crops affected: Brassicas such as broccoli, Brussels sprouts, cabbage, cauliflower, and kale.
Cabbage aphid infestation on kale.
Cabbage aphid infestation on cabbage plant.
Winged cabbage aphid adult with nymphs.
Winged adult cabbage aphid. David Cappaert, Bugwood.org
Symptoms and Life Cycle
Cabbage aphids are easy to spot due to the white, waxy coating on their bodies. They feed on plant sap with piercing-sucking mouthparts and form dense colonies throughout the plant. They prefer to feed on leaves and can be found deep in the heads of cabbage and Brussels sprouts. As aphids feed, they excrete honeydew that covers the plant and provides food for sooty mold. Feeding leads to economic losses from reduced growth and yield, water stress, and contamination.
Cabbage aphids overwinter as eggs on crops and weedy relatives in the mustard family. In the spring, nymphs develop into winged females that birth live young on plants as they fly through a field. In the spring and summer, they reproduce rapidly, and in the fall, males and females mate and females lay eggs that overwinter.
Management
Inspect entire plants for aphids and watch for rapidly increasing populations.
Maintain healthy plants and avoid excessive fertilization, especially nitrogen, which can encourage aphid infestation.
Promote natural enemies such as lady beetles, lacewings, syrphid flies, and parasitic wasps.
Remove or destroy infested plant debris throughout the season to control aphids and in the fall to reduce overwintering populations.
Rotate modes of action when spraying as aphids are prone to developing resistance. Avoid broad spectrum chemicals that can affect natural enemies and lead to an increase in aphid populations. Organic sprays like horticultural oils and insecticidal soaps must come in contact with the pest, so ensure good coverage when applying to achieve control.
Click the following links in the Utah Vegetable Production Guide for aphid spray options in small-scale and commercial brassica production.
Pythium Fruit Rot
Pythium fruit rot can occur when fruit is in contact with saturated soils, which may be more likely due to recent rainy weather.
Crops affected: Primarily cucurbits and solanaceous crops.
Pythium rot on watermelon. Rebecca A. Melanson, Bugwood.org
Pythium fruit rot on cucumber. Gerald Holmes, Strawberry Center, Cal Poly San Luis Obispo, Bugwood.org
Pythium fruit rot on eggplant. Gerald Holmes, Strawberry Center, Cal Poly San Luis Obispo, Bugwood.org
Pythium fruit rot on squash. Gerald Holmes, Strawberry Center, Cal Poly San Luis Obispo, Bugwood.org
Symptoms and Life Cycle
Fruit rots can be caused by many pathogens. Pythium fruit rot causes water-soaked brown spots, white fungal growth, and rotted fruit with collapsed walls.
Pythium spp. are soilborne fungal-like pathogens that survive as resting spores in the soil. Under saturated conditions, Pythium infects plant parts in contact with the soil. Pythium can penetrate fruit and cause infection regardless of the presence of a wound.
Management
Stake plants to keep fruit off the ground or use mulch to prevent fruit contact with the soil.
Avoid planting susceptible crops in low, poorly drained areas of the field.
Avoid excessive irrigation that keeps soil saturated throughout the growing season. Modify water applications to match the weather and allow soil to dry between waterings.
Infected fruit should be removed and discarded.
Wireworms
Wireworms are an occasional pest in potatoes, but damage to tubers may be apparent at harvest.
Crops affected: Can affect many crops like brassicas, corn, cucurbits, leafy greens, legumes, root crops, and potatoes.
Wireworm adult (click beetle).
Wireworm feeding on potato tuber.
Wireworm damage on potato tuber.
Wireworm damage on potato tubers.
Symptoms and Life Cycle
Wireworms are the soil dwelling larvae of click beetles that feed on bulbs, crowns, roots, seeds, stems, and tubers. Wireworms feed on seeds of many crops and can reduce germination or kill seedlings before they emerge. Feeding damage can reduce growth and yield and directly damage crops such as carrot, onion, potato, and sweet potato or allow for secondary infection. In potatoes, damage will appear as tunnels through tubers or along the surface.
Click beetles overwinter in the soil and emerge in late spring. Females lay 50 to 400 eggs in the soil about 6 inches deep. Larvae live in the soil for 1 to 6 years and can be found at varying depths depending on the season. Larvae feed close to the soil surface in the spring and fall and retreat to cooler conditions deeper in the soil during summer. When larvae are mature, they pupate in the soil, develop into adults, and remain in the soil until the following spring. Adults feed on nectar, pollen, and some soft bodied insects and are seldom plant pests.
Management
Monitor for wireworm damage especially during potato harvest. Inspect the soil surface for wireworms after plowing or tilling in the fall.
Another monitoring technique is the use of baits (carrots, untreated corn or wheat seeds) to attract larvae. Bury the bait 4 to 6 inches deep and cover with soil. After 7 to 10 days, collect the surrounding soil and sieve it to get a count of wireworms. Typically, one bait per acre is sufficient and an average of one wireworm per bait is the treatment threshold.
Wireworms are common in Utah, but do not often cause serious damage. Chemical controls are best applied in the spring before or at planting and should only be applied when damage was caused in the previous season.
Once present in a field, wireworms can be difficult to eradicate. Good sanitation practices can reduce the spread.
Refer to this fact sheet on wireworms for more information on control and for a list of insecticide options.
