What are black thrips?
Black Thrips (Frankliniella occidentalis) are small, fast-moving insects that can be a problem for chilli farmers. They eat flowers and leaves, leaving them with unsightly marks, especially on ripe fruit that have not been harvested yet. You may notice black bugs on your plants or even in your house if you live near a chilli farm! So how do you get rid of black thrips once they appear in your chilli field? Read more below to find out how to handle these pesky pests... The key to keeping your chillies healthy is good early identification.
Life cycle
The adult female lays eggs in spaces between leaves or on leaf edges. In 1-2 weeks, nymphs hatch and are smaller versions of adults. Nymphs go through six instars before they become mature adults. Once mature, females will lay eggs on or between leaves; eggs take 3-5 days to hatch into 1st instar nymphs. Each stage takes about 3-4 days to complete until adulthood, at which point it will mate and begin laying its own eggs on plant material. Adults live 5-14 days and can survive for 20+ days without a blood meal. After mating, males die within 4-7 days, while females may live another 5-10 day without a blood meal.
Signs and symptoms
Adults are about 1/10 to 1/4-inch long and dark gray to brown in color. They are covered with long gray or white scales, giving them a hairy appearance. Adults can be difficult to see, but their presence is indicated by small black spots (called frass) near plant stems that were laid out on their backs
by young larvae feeding there. These larvae have elongated bodies and shiny heads. As they grow they lose these hairs, which are then visible as light-colored specks of material scattered over leaves and stems, which is why these insects are also known as pepper maggots. The adult stage lives only long enough to mate and lay eggs; it has no mouthparts, so cannot eat plants. It typically dies after laying its second batch of eggs within two weeks if left untreated because it does not feed itself during those two weeks. Only one generation occurs per year; development from egg to pupae takes about seven days at 86 degrees F, eight days at 79 degrees F, and ten days at 74 degrees F. Two generations per year can occur when temperatures are higher (often in greenhouses). Damage: Feeding by either adults or larvae causes distortion and curling of leaf edges.
Disease spread
Black Thrips ( Frankliniella species) are an invasive pest that can decimate chilli crops over night. The adult insects fly to your plants and lay eggs, which hatch into crawlers within days. Once they've fully matured, they fly off again in search of another plant – but meanwhile, hundreds more will be hatching from those eggs. Black Thrips don't just damage crops; if left untreated for too long, they can cause physical harm to your plants too.
Prevention and management
The best way to deal with pests and diseases is to prevent them in the first place. Plants growing in healthy soil, that are kept well watered and are correctly pruned will be much less likely to suffer from pest and disease problems. Fungicides may be used as a last resort where nothing else seems to have worked. There are some organic remedies, but they must be used very carefully and often have severe restrictions on their use. Fungicides should only ever be applied according to manufacturers’ instructions. In any case, consult your local professional grower or your trusted agricultural retailer for advice and guidance specific to your situation.
The commonest cause of damage by fruit flies are infected wounds caused by birds, small mammals (such as rodents) or hail damage during growth.
Fungicides to use
There are various pesticides that can be used for controlling pests and pathogens, but for black thrip control, there are three basic options: neem oil, thiamethoxam (Cruiser) and dimethoate. Neem oil is one of the most cost-effective solutions; however, it can only be used before flowering, so it’s not ideal for early crop protection. Thiamethoxam is applied as a seed treatment or sprayed on as a foliar spray.
Organic ways
Diatomaceous earth can be used in conjunction with other organic sprays for a more effective process. A diatomaceous earth pesticide comes in powder form and is readily available at most home and garden stores. The active ingredient within diatomaceous earth that kills thrips is silica, which dissolves inside their bodies, killing them within hours or days. Mixing one teaspoon of diatomaceous earth into one gallon of water works best as a spray mixture to kill thrips on contact.
Measure to take before effect
The first and foremost step is to understand what exactly needs to be done. While it’s always important to have a structured plan in place, there are many cases where improvisation can save a lot of time and resources. That said, an idea about how much control is needed for your crop is essential. A highly infested field might need more than one pesticide application, or even other measures such as mechanical control or biological control if certain soil-dwelling predators are present.
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