UV-blocking plastic films and nets influence vectors and virus transmission on greenhouse tomatoes in the humid tropics

We studied the effect of UV-blocked greenhouses made from netting and plastics on the movement and pest status of three important pest of tomatoes: whitefly (Bemisia tabaci), thrips (Ceratothripoides claratris), and aphid (Aphis gossypii). Under UV-blocked greenhouses, fewer white-flies, aphids, and thrips entered the greenhouse compared with the ones having more UV intensity. Similarly, significantly fewer alate aphids and adult B. tabaci/leaf were counted in greenhouses with low UV intensity. Although thrips were the most abundant pest, they also were significantly less abundant in greenhouses with lower UV intensity. Consequently, significantly lower levels of leaf infestation were recorded under these greenhouse conditions. During open gates experiments, virus infection levels reached 96-100% under UV nonblocking greenhouses compared with 6-10% infection levels in greenhouses where UV irradiation was blocked. in addition, the appearance of virus symptoms was considerably delayed under greenhouses made from the UV-blocking roof material, although the majority of the plants tested positive for the tospovirus, capsicum chlorosis virus (CaCV; AIT isolate). The results are discussed in context of improved management of sucking insect pests of tomatoes in the humid tropics.