Multiplying in the Garden: Green Peach Aphid
They are tiny, but their power lies in numbers. These insect pests are born pregnant, and can reproduce out of control in a short time. This column is dedicated to a common pest called the green peach aphid, Myzus persicae.
This pest can be found throughout the world, including all areas of the United States, where it is viewed as a seasonal problem due to its ability to transmit plant viruses. Green peach aphid infests vegetables grown in greenhouses and fields. Its ability to prolifically reproduce and travel in clothing and foliage, as well as in air currents allows high levels of survival in areas with inclement weather and to be a constant challenge in semi tropical environments such as South Central Florida.
The life cycle varies considerably, depending on the presence of cold winters. Development can be rapid, often 10 to 12 days for a complete generation, and with over 20 annual generations reported in mild climates. Where suitable host plants cannot persist, the aphid overwinters in the egg stage on various plants. In the spring, soon after the plant breaks dormancy and begins to grow, the eggs hatch and the nymphs feed on flowers, young foliage, and stems. After several generations, winged aphids overwinter in fruiting plants as well as many native, vegetable, ornamental, grassy plants where they deposit nymphs that will develop on summer hosts. All generations except the autumn generation culminating in egg production are parthenogenetic (non-sexual). In Florida, populations cycle continuously on annual plants.
- Eggs: The eggs measure about 0.6 mm long and 0.3 mm wide and are elliptical in shape. Eggs initially are yellow or green, but soon turn black. Mortality in the egg stage sometimes is quite high.
- Nymphs: Nymphs initially are greenish, but soon turn yellowish, greatly resembling viviparous (parthenogenetic, nymph-producing) adults. It has been reported that there are four nymph stages or instars with a duration of approximately two days each. Females give birth to offspring on average at an age of 10.8 days after she is born. The length of reproduction averages 14.8 days. The average length of life is about 23 days without the presence of predators. The daily rate of reproduction averages 1.6 nymphs per female. The maximum number of generations observed annually is around 20 to 21, depending on the year.
- Adults: Up to 8 generations may occur in the spring, but as aphid densities increase winged forms are produced, which then disperse to summer
hosts. Winged green peach aphids seemingly attempt to colonize nearly all plants available. They often deposit a few young and then again take flight. This dispersive nature contributes significantly to their effectiveness as vectors of plant viruses.In autumn, winged male and female aphids are produced which disperse in search of host plants. Timing is important, as foliage on these plants is physiologically optimal as leaves begin to die. Females arrive first and give birth to wingless egg-laying forms (oviparae). Males are attracted to oviparae (egg-producing females) by a pheromone, capable of mating with several females, and eggs are produced. The oviparous female deposits four to 13 eggs, usually in crevices in and near buds of the host plants. The oviparous female is pinkish in color.
This cycle is repeated throughout the period of favorable weather. In Florida, this cycle repeats continuously, though in the northern areas of the state the aphid development rate slows greatly during the winter.
Green peach aphid feeds on hundreds of host plants in over 40 plant families. Plants that readily support aphids through the winter months include beet, Brussels sprout, cabbage, broccoli, kale, potato, and many winter weeds.
- Sampling: Yellow traps, particularly water pan traps, are commonly used for population monitoring.
- Insecticides: Despite the numerous options potentially available, many producers are dependent on insecticides for suppression of green peach aphid abundance. Systemic chemical insecticides such as imidacloprid are applied at planting time. These chemicals can provide long-lasting protection against aphid population buildup during the critical and susceptible early stages of plant growth.
Contact insecticides such as pyrethrin and rotenone will effectively control green peach aphid adults and larvae and are labeled for use in organic farming when adequate surface coverage is achieved.
Excessive and unnecessary use of insecticides should be avoided. Early in the season, aphid infestations are often spotty, and if such plants or areas are treated in a timely manner, great damage can be prevented later in the season. In some cases, use of insecticides for other, more damaging insects sometimes leads to outbreaks of green peach aphid. Inadvertent destruction of beneficial insects is purported to explain this phenomenon.
Continuous scouting is the best prevention. Proper scouting for aphids during the winter months is extremely important. Check the undersides of the leaves and new tender parts of the plant such as growth points and young shoots.
Place a white piece of paper or plastic sheet under the plant canopy (in the case of vegetable plants such as greens) and gently beat the plant foliage with your fingers or a stick. After doing this, verify for the presence of aphids using a magnifying glass if needed.
When using contact pesticides, apply the chemical early morning or late in the evening when there is a significant reduction in honeybee and other beneficial insect activity. If you need help with pest identification, pest management recommendations or other gardening or agricultural troubleshooting, please contact UF/IFAS Extension Hardee County. We are here to help answer these or any other agriculture related questions. Please contact us at 863-773-2164 for further assistance.