Whiteflies in High Tunnels

High tunnel insect management can be challenging, and whiteflies (Figure 1) on tomatoes and other vegetable crops can be one of the more common challenges. While there are several species of whiteflies that we routinely find in high tunnels, silverleaf whitefly can be more difficult to manage than others.

Figure 1. Whiteflies, both adults and nymphs, can be found on the undersides of leaves. (Photo: Ric Bessin, UK)

Figure 1. Whiteflies, both adults and nymphs, can be found on the undersides of leaves. (Photo: Ric Bessin, UK)

Figure 2. Honeydew produced by whiteflies results in sooty mold growth on leaves and fruit. Honeydew can also be a sign to look for active aphids or whiteflies. (Photo: Ric Bessin, UK)

Figure 2. Honeydew produced by whiteflies results in sooty mold growth on leaves and fruit. Honeydew can also be a sign to look for active aphids or whiteflies. (Photo: Ric Bessin, UK)

Whitefly Damage

Whiteflies damage plants in several ways:

  • They remove plant sap, reducing the efficiency of the plant.
  • Honey dew produced by whiteflies covers leaves, reducing photosynthesis and contaminating fruit (Figure 2).
  • The silverleaf whitefly can transmit tomato yellow curl virus.

Management Strategies

Prevention

Prevention is the first and best tactic to manage whiteflies. Before starting a new crop in the high tunnel, be sure the tunnel is free of weeds and other plants.  To eliminate white flies prior to starting a new crop, let the high tunnel freeze out in winter or seal it in summer so it heats up prior. Side wall curtains can be screened to exclude whiteflies moving into the high tunnel.

Biological Control

Whiteflies can also be managed through biological control. Minute stingless wasps target and kill whitefly nymphs. Encarsia formosa is used to manage the greenhouse whitefly and Eretmocerus eremicus (Figure 3) is commonly used to manage silverleaf whitefly. These are most effectively used when whiteflies are present but not at high levels. However, broad spectrum insecticides can interfere with biological control.

Figure 3. Eretmocerous wasp emerging from a dead whitefly pupa. (Photo: Ric Bessin, UK)

Figure 3. Eretmocerous wasp emerging from a dead whitefly pupa. (Photo: Ric Bessin, UK)

Insecticides

Managing whiteflies with insecticides is challenging. The table below lists recommended insecticides available for managing whiteflies in high tunnels and greenhouses. Producers must not only manage whiteflies, but also the potential for development of insecticide resistance and pre-harvest intervals close to or after harvest begins.

Recommended High Tunnel Insecticides for Whiteflies

Insecticide
IRAC group
Target
Maximum usage per crop
Admire Pro 4A Adults and nymphs 6.7 fl oz
Assail 30 SG 4A Adults and nymphs 16 oz
Closer SC 4C Adults and nymphs 17 fl oz
Courier 40 Sc 16 Nymphs 2 applications
Knack 0.86 EC 7C Nymphs 20 fl oz
Requiem 25 EC UN Adults and nymphs 10 applications
Rimon 0.83 EC 15 Nymphs 36 fl oz
Sivanto 1.67 SL 4D Adults and nymphs 28 fl oz
Venom 70 SG 4A Adults and nymphs 6 oz

 

By Ric Bessin, Extension Entomologist

 

Posted in Greenhouses/High Tunnels, Vegetables