Studies on loss of bio-efficacy of two indirect neem application over time (seed and soil) against Bemisia tabaci (Homoptera: Aleyrodidae) under semi-field conditions

In a choice test, loss of bio-efficacy (1–30 days) of neem (seed and soil application) were studied in a naturally ventilated and lighted greenhouse (semi-field conditions) using a commercial neem product (NeemAzal-U 17%) against Bemisia tabaci Gennadius (Hom., Aleyrodidae) on tomatoes. The fresh neem residue had the strongest effects in all parameters (adult colonisation behaviour, eggs deposition, eggs hatch and immature mortality). This effect decreased gradually over the time. The bio-efficacy loss of neem applied through seed treatment was rapid, and tomato plants grown from seed soaked in neem effectively managed B. tabaci only until the 15-day post application. Soil application was a more stable method to prolong the bio-efficacy of neem against B. tabaci under greenhouse conditions. The bio-efficacy of soil neem application were recorded daily for 1–7-day and during this period, the immature mortality, which was 88.20% for the first day reduced to almost half i.e. 45.01%. The results of the experiments are discussed in context of potential use of neem-based pesticides for Integrated Pest Management of sucking insect-pests in open field or in greenhouse conditions.