FACT SHEET
Cotton Stem Moth
Family Gelechiidae
RECOGNITION
Diagnostic features. Usually tan in the U.S. although Russian species can be dark brown to grey so other color morphs may exist in the U.S. as well. Forewings usually possess dark splotches medially along the length of the wing in contrast to the pink bollworm that often has pairs of splotches that may appear to be dark transverse bands, especially in Delta-trap specimens. Antennal scape possesses a pecten of long scales, similar to the pink bollworm. The male genitalia differs from the pink bollworm by having an gnathos with a stronger, u-shaped curve, and by having a pair of hooks, one each external to the valvae. The uncus does not taper to a point, instead appearing bi-lobed at the tip. Two strong bundles of spines point basally from just above the gnathos.
Platyedra subcinerea (Cotton Stem Moth) Photo credit: Sangmi Lee
Platyedra subcinerea Haworth
Platyedra subcinerea (cotton stem moth) male genitalia, dissected and cleared. Photo credit: Mike Dale
ECOLOGY
Life cycle. The cotton stem moth is native to the Old World (Europe, Russia, and the Mediterranean) but has been documented in the United States since the 1950s. Most information on this species refers to native, Old World populations. It is unclear if the American species have adopted different lifestyle strategies.
Feeding habits. The cotton stem moth larvae feed on the flowers and seeds of various plants in the family Malvaceae, of which cotton is a member. It has been documented on Althaea nudiflora, marsh mallow (Althaea officinale), velvet tree mallow (Lavatera arborea), herb tree mallow (Lavatera trimestris), high mallow (Malva sylvestris), and cultivated cotton (Gossypium herbaceum). Its U.S. hosts probably include closely related species, such as Old World tree mallow (Lavatera thuringiacea), hollyhock (Althaea rosea), and cheeseweed (Malva parviflora).
Seasonal emergence. In Europe, the cotton stem moth larvae are actively feeding during June and July. Adults emerge in August and overwinter as adults. However, in California adults have been caught from March to July, indicating they may have a longer season in the U.S. In the Mediterranean, they can have up to 5 generations per year. Given the similarities between western United States and Mediterranean climate, the cotton stem moth may have many generations per year in the U.S. as well.
