How long do scale insects live?
Written by
Liu Xiaohui
Reviewed by
Prof. Martin Thorne, Ph.D.Knowing the life spans of scale insects is important for effective time control measures. Female scales live, on average, from 2 to 6 months, and during that time, they can lay eggs continuously. Males, on the other hand, only live for days after mating, thereby completing their one purpose in life. Lifespans vary widely by species and environmental conditions that can impact the scale insect infestations.
Sex Differences
- Females: 2-6 months as egg-laying machines
- Males: 2-7 days focused solely on mating
- Some species lack males entirely (parthenogenesis)
Seasonal Variations
- Summer generations complete cycles in 6-8 weeks
- Overwintering females persist 4-6 months
- Cold climates extend dormant phases
Environmental Factors
- Temperature accelerates development above 70°F (21°C)
- Humidity below 40% reduces egg viability
- Host plant health affects longevity
Over their long life spans, female scales become egg-laying machines. For example, each brown soft scale produces 200-500 eggs in 5 months. Cottony cushion scales produce over 1,000 eggs each! The reproductive capacity of scales explains the fast infestations I have seen rapidly explode in greenhouses in just weeks.
Overwintering strategies increase effective lifespan. Many species will become dormant/diapause during cold weather. Female scales, for example, slow their metabolism while residing in crevices of bark. I have even found live scales after winter temperatures of -10°F (-23°C). Winter survival makes management difficult year-round.
Temperature has a significant effect on the development rate. For example, at 68°F (20°C), scales finish a generation in 8 weeks, while at 86°F (30°C), it is completed in 4 weeks. Now, I track growing degree days to predict events in the life cycle of insects in my orchard.
Males of an introduced scale have the shortest but also the most intense life. Depending on the species, they may emerge without wings or have temporary wings that they use only during mating. After mating, they are dead within 48 hours. In some groups, such as mealybugs, males are wingless, and they must crawl to find a female mate.
Regulate timing targets for vulnerable life stages. Use horticultural oil during dormancy to smother overwintering females. Target crawlers with soap sprays during peak emergence periods. I use a combination of methods for overlapping generations to ensure never-ending protection.
Read the full article: Mastering Scale Insect Identification: A Complete Guide
