Pepper IPM: Aphids and Viruses

There are several viruses transmitted to peppers by aphids. Cucumber mosaic virus (CMV) is the most important in the northeast, while tobacco etch (TEV), alfalfa mosaic virus (AMV) and potato virus Y (PVY) are less common or destructive.[ppripm6]

In recent years, crop damage to peppers due to CMV has been relatively rare in Connecticut, although it has been more common in Vermont and Quebec. If pepper fields are infected while the plants are still young (June or July) CMV may substantially reduce yields. With early infection, older leaves or fruit may exhibit yellowish, ring-spots. Younger leaves may appear mottled light and dark-green and plants may be stunted. Pepper plants infected with AMV are easily distinguished by their bright, white or yellow, calico patterned leaves. TEV and PVY are more difficult to distinguish, producing dark-green mosaic bands along the leaf veins.

Reservoir hosts for these viruses include many common weeds and crops such as: nightshade, horse nettle and other solanaceous plants, pigweed, ragweed, pokeweed, beans, cucumbers, pumpkins, legumes and many ornamentals. CMV has the widest host range of any aphid-vectored virus. Green peach or melon aphids or both are capable of transmitting these diseases to peppers.

All the viruses mentioned are non persistent, meaning that aphids can only spread the disease for about 2-60 minutes after feeding on an infected host. The further the crop is from the disease reservoir, the more likely the virus will be deactivated when the aphid feeds on your peppers. Controlling weeds within and along the edges of pepper fields and isolating peppers by planting alongside corn, small grains and other grasses helps reduce early season infection. Aphids often infest fields from the direction of the prevailing winds or from other host crops (like stone fruit for GPA). Barrier crops along the south and west borders and between woodlines or peach orchards are the most critical. Just 50 feet of buffer crop helps reduce the chances of early-season virus infection substantially, however, a barrier of 150 feet or more is preferable.

Reflective aluminum-coated mulch delays aphid colonization and has been shown to reduce virus incidence and within-field transmission. Aluminum mulch is mostly utilized in southern states where warmer climates compensate for the soil-cooling effect they produce.

Many commercial varieties are available with TEV, PVY or tobacco mosaic virus (mechanically transmitted) resistance. Better still are the varieties with a combination of virus and bacterial leaf spot resistance, since the latter is a much more common and destructive disease in New England. Several varieties with tolerance or resistance to one or more strains of CMV are currently under development.

Utilizing insecticides to control colonizing aphid populations is not an effective or recommended means of combating non persistent viruses. These viruses can be transmitted in a matter of seconds once an infected aphid lands on a pepper leaf and beings probing or testing for a suitable feeding site. Transmission can occur during this probing process before the insect actually being feeding and ingesting toxins. The presence of an insecticide may increase this probing activity and cause colonizing winged aphids to move between plants more frequently, increasing virus spread. Even after feeding begins, most insecticides do not act immediately, and provide only partial control of GPA or MA at best. Finally, the routine use of broad-spectrum insecticides in a preventive manner, early in the season, will kill beneficial arthropods that contain aphid populations and eventually leads to resistant aphid populations.

Jude Boucher, Vegetable Crops IPM Program Coordinator, University of Connecticut Cooperative Extension System

This information was developed for conditions in the Northeast. Use in other geographical areas may be inappropriate.

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