Tiny, Plant-Feeding Insects: Scales

Scales are minuscule parasites that latch onto plants and survive by consuming the plant’s sap. They disguise themselves with a protective, shell-like waxy covering, resembling bumps that can easily be mistaken for a disease.

Various Species of Scales

There exist numerous species of scales, each with its own characteristics.

1. Soft Scales: These scales have a protective waxy substance covering their bodies, making them easier to control. They also produce a sticky substance called honeydew.

2. Armoured/Hard Scales: These scales secrete a hard shell over their bodies for protection against predators. They do not produce honeydew, and their hard shells make it challenging to control them using pesticides.

Host Range

Scale insects feed on a wide range of plants. However, certain species specifically target particular host plants. Some common examples of plants attacked by scales include mango, pigeon peas, citrus, and ornamental plants.

Life Cycle

The adult scale lays its eggs beneath its protective covering, providing shelter during development. After 1-3 weeks, the eggs hatch into small-legged insects known as crawlers or nymphs. These crawlers spread across the plant and its foliage in search of a suitable place to settle until they reach maturity. Once the eggs are laid, the adult scale dies.

Identification

Scales exhibit variations in color, shape, and size, with a round shape being common. Depending on the species, they can appear white, black, orange, green, brown, and more. A mature scale typically measures around 3-5mm. They can be found on plant stems, trunks, twigs, foliage, or fruits, depending on the species.

Feeding and Damage

Scales feed by extracting sap from plants using their specialized mouthparts. This feeding process leads to yellowing, wilting of leaves, and stunted growth as the plant’s vitality diminishes. Severe infestations weaken plants, making them susceptible to other pathogens and unable to withstand adverse weather conditions.

Scales secrete a sticky substance known as honeydew while feeding. This honeydew promotes the growth of a black, soot-like mold on plant parts. When found on leaves, it hampers the rate of photosynthesis.

Control Measures

Controlling scales can be challenging due to their protective covering. However, there are several effective methods available.

1. Insecticides

The most reliable method of control is the use of insecticides. The following insecticides have proven effectiveness against scales:

  • EMERALD 200SL: Mix 20ml with 20l of water.
  • LOYALTY 700WDG: Mix 10g with 20l of water.
  • RANGER 480EC: Mix 30ml with 20l of water.

These chemicals possess both contact and systemic properties, making them highly efficient. To prevent scales from developing resistance, it is advisable to alternate the use of these insecticides.

To eliminate sooty mold resulting from the honeydew, spray JAMBO CLEAN at a ratio of 100ml per 20l of water.

For enhanced efficacy, always include INTEGRA at a ratio of 3ml per 20l of water. INTEGRA acts as a spreader, sticker, wetter, and penetrant, improving the effectiveness of the insecticide.

2. Other Methods

In addition to chemical control, the following methods can be employed to manage scales:

  • Use tolerant and resistant cultivars.
  • Practice crop rotation with non-host crops.
  • Maintain field hygiene.
  • Prune infested plant parts.

Conclusion

Scales are tiny parasitic insects that attach themselves to plants and feed on their sap. With their protective waxy covering, they can be mistaken for a plant disease. Identifying the type of scale and employing appropriate control measures, such as insecticides and alternative methods, can help manage infestations and protect plants from damage.

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