Pests and pest management practices

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Common Pests and their natural enemies

Spider plants have fewer pests and diseases than most leafy vegetables.  The most common and persistent pests are aphids and flea beetles which can be a problem on seedlings and during the growth stage. Bagrada bugs can also reach outbreak levels on seedlings. Flea beetles and to some extend caterpillars reach high densities during vegetative stage of growth which commonly lasts few weeks of the seedling stage.

Caterpillars and wild birds tend to cause extensive damage by feeding on seed pods. Continuous cropping of spider plants can lead to damaging infestations of root knot nematodes.

Natural enemies include insect predators and parasitoids, fungal and nematode pathogens. Others are birds and toads.

Aphids

Spider plant are attacked by both black and green aphids commonly found on many leafy vegetables. There are also other aphids that are less common. Adults and nymphs pierce plant tissues to feed on plant sap causing stunted growth and wrinkling of leaves and growing tips that can lead to total crop failure. Aphids produce honey dew which attracts black ants that defend them against their natural enemies. Aphids attract predators such as ladybird beetles, predatory bugs, lacewings and hoverflies.

Flea beetles

They are small shiny black beetles, sometimes with brown markings. They feed on the under surface of leaves leaving symmetrical shot holes in the foliage which can cause serious damage when beetle densities are high. Natural enemies of flea beetles include ground beetle predators and tachinid fly parasitoids, fungal pathogens and vertebrates such as toads and birds.

Best practices for avoiding pests

Pest and natural enemies monitoring

Monitor aphids populations by examining buds and underside of leaves of 10 randomly selected plants and counting the number of aphids present.  Black ants on amaranth usually indicate presence of aphids. Treatment options should be considered when aphids count increases 10-fold between consecutive scouting observations.

Flea beetles   can be monitored by inspection of the same randomly selected plants used to monitor aphids and counting the number of shot holes found on a leaflet.  Treatment options are considered when shot hole counts double between consecutive scouting observations, or a quarter of the leaf surface is damaged.

While monitoring aphids and flea beetles, it is of great essence to scout for natural enemies. Predators such as ladybird beetles, lacewings hoverflies found on spider plants should be counted and compared to the number of pests found. If natural enemies remain unchanged or decline in number while pests are increasing, pest management interventions may be needed. 

Yellow sticky trap can be used to monitor winged insects including aphids and flea beetles.

Environmental friendly pest management options

Traditional

Aphids and flea beetles can be treated by application of wood ash evenly on infested parts of the plant. Also, weed the fields around raised beds to eliminate flea beetle shelters and breeding sites, adding a row cover helps in keeping beetles away, this is because thick mulch interferes with larva feeding activity. Plant that repel flea beetles such as onions and garlic and those that attract flea beetles such as marigolds can be planted to aid in keeping pest away from spider plant crops.

Bio-based

Neem oil has a broad spectrum of action and can reduce caterpillars and cutworms, as well as aphids and all flea beetle life stages. Selective fungal and nematodes pathogens sold commercially can also be used to manage aphids and flea beetle larvae.

 Traps

Sticky cards are glue- based traps, often yellow in colour to attract bug pests, used to monitor and trap a wide range of insect pests that move about easily in a field.  Place sticky cards every 15 to 30 feet throughout raise beds to capture and reduce the number of adult flea beetles.

Insect – proof netting

It creates a barrier that prevents insects from gaining access to crops, often grown inside high tunnels or screen houses. Netting barriers over seedlings and transplants  can be particularly effective against flea beetles.

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