Effects of insect net coverage in field vegetables on pests, diseases, natural enemies, and yield

Abstract

With the reduced availability of effective plant protection products, alternative control measures gain importance. Insect net covers are a promising tool in this regard, because they can reduce pest damage on crop by exclusion of pests. However, as under practical conditions, most crop net covers need to be removed several times during a crop cycle to manage weeds and apply fertilizers, a complete exclusion of pests is not always feasible. In addition, net covers also have an impact on natural enemies, on microclimate, and may cause direct crop damage due to their tracking weight. Therefore, effects of net applications have to be assessed accordingly, depending on the specific crops and pests. In the current paper, effects on pests, on yield, and on the occurrence of diseases are assessed in Chinese cabbage, carrot, and leek. Whereas control of Delia radicum, Phyllotreta spp. and thrips was enhanced, aphids and mining flies showed increased population build ups and caused higher damages under net cover once they had been able to invade. Some plant diseases such as Puccinia spp. and Alternaria spp. did increase under the net covers. Pitfall trap catches in carrots and Chinese cabbage were lower in almost all natural enemy groups monitored under net covers as compared to open field plots. Yield was higher with net coverage in case of Chinese cabbage and leek, but not in carrot. Results are discussed and take into account the exclusion of natural enemies and measured changes in microclimate and photosynthetically active radiation.