In 2013, a new viral disease which severely affected zucchini was identified and characterized in Spain (Almería and Murcia), in both field and greenhouse crops. It was also isolated in cucumber, pumpkin and melon samples showing the following symptoms: intense yellow patchiness, leaf curling and deformation, and strongly pronounced dwarfing and loss of vigor in plants. It was identified as New Delhi Virus (ToLCNDV).
This virus was first described in India in 1995, but is now reported in several countries and on several plant hosts:
Zucchini, Luffa cylindrica, Cucurbita moschata, Cucumber, Tomato, Cucumis melo.
As with TYLCV, ToLCNDV is transmitted by the circulating and persistent whitefly Bemisia tabaci, so this vector can stay viruliferous throughout its lifespan.
Symptoms
Symptoms associated with this virus are most evident on young leaves that curl up, remain small and yellow (internerval yellowing of varying intensity). In older leaves, the interveinal areas turn yellow in a mosaic pattern and curl up…
Plant growth can be severely slowed or even completely blocked.
In zucchini, fruits may acquire a rough skin and longitudinal cracks may appear, resulting in a serious decline in the quantity and quality of the product, causing a significant loss of yields and income for the grower.
Since the virus has different strains, symptoms differ according to the host plant.
Control
For an adequate integrated management of the New Delhi Virus (ToLCNDV) in the greenhouse zucchini crop, we must control the Bemisia tabaci virus vector as follows:
- Selective releases of the predatory mite Amblyseius montdorensis.
- Maximize the isolation measures in the greenhouse structure, especially in the sashes and doors. It is imperative to verify that there are no cracks through which the whitefly can enter. For this, it is crucial to check the enclosures and use anti-insect netting of adequate density to prevent the entry of this pest.
“Our recommended netting for this type of virus is the 20×10 threads/cm2 anti-insect netting. The modern equipment with which it is manufactured ensures a high uniformity of pores, preventing Bemisia to go through it in all its extension.”
Prevention
Cultural measures such as removal of all crop remains and weeds as a first step (whitefly pupae and larvae may remain in these) and before starting the placement of sticky traps.
