Mosaic Virus

Mosaic virus is not a single pathogen but a family of related viruses, most notably Cucumber mosaic virus (CMV) and Tobacco mosaic virus (TMV), that infect a wide range of vegetable crops including tomatoes, peppers, cucurbits, beans, and leafy greens. Each virus has distinct transmission routes, which shapes how control measures are prioritized.

CMV is spread primarily by aphids in a non-persistent manner: aphids acquire the virus within seconds during brief feeding probes on infected plants and can transmit it just as quickly to the next host. This biology makes conventional insecticide timing largely futile as a vector control, since transmission occurs before any spray residue can act. Reflective mulches are more practical because they deter winged aphid migrants from landing in the planting area in the first place. Conditions that favor aphid population growth, including warm dry weather and nitrogen-heavy plantings that produce flush tender growth, correspondingly increase mosaic virus pressure.

TMV spreads through mechanical contact: contaminated hands, tools, and tobacco products are the primary vehicles. TMV can persist on surfaces and in dried tobacco for extended periods, making it a significant risk when workers handle tomatoes or peppers after contact with tobacco.

Symptoms appear most visibly on young tissue as mottled light and dark green leaf patterns, distorted new growth, and reduced or misshapen fruit. Infected plants are systemically colonized and do not recover; early roguing limits spread to neighboring plants.

Variety selection is the most cost-effective long-term defense. Most modern hybrid tomatoes carry TMV resistance, typically coded as "T" or "TMV" in catalog listings. Where resistant varieties are available, planting them substantially reduces risk without any additional management inputs.