Chloridea virescens, commonly known as the tobacco budworm, is a moth of the family Noctuidae found throughout the eastern and southwestern United States along with parts of Central America and South America.
It is a major pest of field crops including tobacco (as its common name suggests) and cotton. However, it is able to thrive on a wide variety of host plants ranging from fruits, vegetables, flowers, and weeds. Control of this pest has proven to be particularly difficult due to a variety of factors, but widespread insecticide and pesticide resistance have proven particularly concerning.
Chloridea virescens was formerly a member of the genus Heliothis, but was moved to the reinstated genus Chloridea as a result of genetic and morphological research published in 2013.
Description
Adult C. virescens are brownish in color with a light green tinge. The front wings have three dark bands, each associated with a whitish or cream border. Hindwings are whitish with a dark band at the distal margin. Fully grown adults measure between 28 and 35 mm (1.1 to 1.4 inches) in wingspan. Females are generally darker in color than males.
Life cycle
The tobacco budworm goes through 4 life stages: egg, larval, pupal, and adult. The life cycle generally occurs during the warmer months of late spring to early fall, depending on the region that the budworm is found. During this time, Chloridea virescens can undergo around 4 to 5 generations depending on the region. For larval, pupal, and adult stages, warmer temperatures encourage faster maturation but also faster senescence, while colder climates allow the budworm to mature at a slower rate. Chloridea virescens moths emerge between March and May in the southern United States.
Egg
Females generally produce 300 to 500 eggs in the wild but have been seen to produce 1000 to 1500 eggs on an artificial diet consisting of primarily water, wheat germ, casein, and sucrose at cool temperatures in an Arizona study. Eggs are deposited on the blossoms, fruit, or terminal growths of host plants. They are initially whitish or yellowish and turn grey as they age. With a radius of 0.5 to 0.6 millimeters, eggs are generally spherical with a flattened base where they are attached to the plant. There are 18 to 25 ridges that radiate from the top of the egg. Tobacco budworm eggs are almost indistinguishable from the eggs of the corn earworm. In tobacco budworm eggs, primary ribs terminate before they reach the cells surrounding micropyle, a small pore opening at the top of the egg. On the other hand, corn earworm ridges extend to the rosette.
Larvae
Chloridea virescens larvae usually have 5 to 6 instars or moultings, but there have been instances where 7 instars are necessary to reach the pupal stage. Head width of the larvae starts from 0.26 mm and grows to 2.87 mm by the last instar. Larval length ranges from 1.4 mm in the first instar and grows to 36 mm by the fifth instar. Larvae are a yellow or yellowish green upon hatching, with a yellowish brown head capsule. During later instars, larvae have variable colors ranging from greenish to pinkish, or even a dark red or maroon with a broad brown head capsule. Whitish dorsal and ventral bands run down the length of its body, along with a broad lateral band that is generally brown in color. Larvae also have black thorn-like microspines. Starting from the third or fourth instar, cannibalistic behavior can be observed. Similar to the eggs, early instar C. virescens larvae are difficult to distinguish from corn earworm larvae, with minor differences such as missing or differing lengths of microspines.
Pupae
Pupation, or the process of transforming from an immature stage to an adult, occurs in the soil. Pupae start off a shiny reddish-brown that progresses to a dark brown color. The size of a pupa averages 18.2 mm to 4.7 mm in width. The budworm overwinters in the pupal stage, and diapause or dormancy can be initiated by either short days or low temperatures.
Temperature dependence
Development time and lifespan show a negative correlation with temperature. Higher temperatures result in shorter development times in studies conducted on Chloridea virescens raised in a temperature controlled laboratory environment.