Silverleaf whitefly, Bemisia argentifolii
Bandedwing whitefly, Trialeurodes abutilonea
Silverleaf whitefly (SLWF) and bandedwing whitefly (BWWF) are the two most common whitefly species that infest Texas cotton.
Both whitefly species are similar in appearance and basic biology. The adults of both species resemble tiny white moths with yellowish bodies, about 1/16 to 1/10 of an inch long. Their wings fold roof-like over their abdomens. The SLWF (Fig. 71) has solid white wings, and the BWWF has grayish-brown colored bands across its wings.
The nymphs are flat, scale-like insects, usually about 1/30 of an inch long (Fig. 72). The immatures feed with sucking mouthparts on the underside of leaves. Damage ranges from stunted growth and reduced plant vigor during the early season to reduced plant vigor, honeydew deposited on open cotton lint (sticky cotton), and prema-
ture defoliation during the mid and late season. Like aphid honeydew, whitefly honeydew is a food source for black sooty molds that can stain lint and reduce fiber quality. Heavy whitefly infestations can severely reduce cotton yield.
To sample for whiteflies:
- Examine the underside of at least 30 key leaves (leaves located at the fifth node down from the terminal) and note how many leaves are infested with at least three
- Use a hand lens to examine a quarter-sized area on the underside of the leaf between the main middle vein and one of the main lateral
- Note how many hand-lens views contain at least one large whitefly nymph (third and fourth instars).
Chemical Control and Action Thresholds
|Insecticide option||Silverleaf whitefly|
|Adulticide||When ≥40% of the 5th node leaves are infested with 3 or more adults|
|Insect growth regulator (IGR)||When ≥40% of the 5th node leaves are
infested with 3 or more adults and nymphs are present
|When ≥40% of quarter- sized disks* contain at least one large nymph|
|Cotton Stage||Bandedwing whitefly|
|Before open bolls||50 whitefly nymphs per 5th node leaf|
|After open bolls||25 whitefly nymphs per 5th node leaf|
|*Quarter-sized area taken between the main middle vein and one of the main lateral veins from a 5th node leaf|