Whitefly Alert

The situation

This spring is shaping up to be a bad season for whitefly and attendant problems pm tomato of TYLCV (virus) and irregular ripening.  Already we are seeing irregular ripening problems in late picked fall tomatoes (Figure 1.  What factors are causing this situation?

  1. Perfect weather for whiteflies (dry and warm)
  2. Poor market causing growers to hold crops that may not be adequately sprayed and overlap with spring crops.

As a result, whiteflies that built up in fall crops are moving to spring crops carrying virus with them.  Irregular ripening is a physiological disorder unrelated to virus but caused by feeding of whitefly nymphs, not adults.  The threshold for irregular ripening is 1 nymph per 2 leaflets.  Nymphs (Figure 2) are best monitored on the underside of the lower (5-7th node) leaves.

What needs to be done? 

  • Kill any old tomato crops a quickly as possible.  Spray first with a tankmix of pyrethroid and malathion to kill whiteflies in the old crop.
  • Treat seedlings with a systemic insecticide in the transplant water.  If on drip, make a second soil application in 30 days using a systemic insecticide of different mode of action (Table 1).
  • Scout crops every week and apply insecticides as needed to maintain control.  Target nymphs once the threat of immigration from old crops has passed (Table 2).

Table 1: Systemic insecticides applied to soil for whitefly control

 

Table 2

 

Figure 1. Irregular ripening of Roma tomatoes

Figure 2, Third and fourth instar whitefly nymphs (Bemisia tabaci) on tomato.

For more information contact:  Phil Stansly, University of Florida/IFAS/SWFREC, 239-658-3427/ 464-7395 pstansly@ufl.edu

Monica Ozores Hampton, University of Florida/IFAS/SWFREC, 239-658-3412305-318-9949, ozores@ufl.edu