Effective Use of Neonicotinoids for Protection of Citrus Seedlings From Invasion by <I>Diaphorina citri</I> (Hemiptera: Psyllidae)

Abstract

The application of insecticides to control Diaphorina citri Kuwayama (Hemiptera: Psyllidae) is a principal component of the current management for citrus greening disease or Huanglongbing. It is recommended that growers apply systemic insecticides such as imidacloprid and thiamethoxam every 2 mo after seedling planting, but this practice renders the seedlings insecticide-free and vulnerable to psyllid infestation in the first 2 mo. We evaluated the risk of vector invasion during this period from field studies of the psyllid in five new king mandarin, Citrus nobilis Loureiro, orchards in the Mekong Delta region of Vietnam. The first psyllids were found after the first 2 wk, and 2 to 60% of the trees were finally infested by psyllids during the 2 mo. The risk of psyllid invasion could be significantly reduced if the insecticide were applied to seedlings before planting. Three systemics, imidacloprid, thiamethoxam, and clothianidin, were examined in both a net house and in the field to assess how quickly they could be effective after application and how long their efficacy could continue. High psyllid mortality >80% was attained in 10 d after application, and this level was maintained for 90 d in the net house and for 60 d in the field. Based on these results, we propose the effective use of neonicotinoids for protection of citrus seedlings against invasive psyllids during the first 2 mo after planting.

Differential Efficacy of Insecticides According to Crop Growth: The Citrus Psyllid on Citrus Plants

“…These two insecticides were compared with three neonicotinoids, imidacloprid, thiamethoxam and clothianidin, since the efficacy of the latter insecticides had been examined and their efficacy was already known (Ichinose et al, 2010a). Hence, using seedlings of king mandarin, residue effect of five insecticides was tested: imidacloprid (0.20 g/tree), thiamethoxam (0.17 g), clothianidin (0.19 g), methidathion (0.40 g) and fenobucarb (0.50 g).…”

“…The mean of the mortality of the psyllid in the control cup at each observation hour on each observation day was calculated and used to correct the psyllid mortality in cups with insecticide-treated leaves at the same observation time on the same day by using the Abbott's correction formula. The detail of the mortality calculation is described in Ichinose et al (2010a).…”

“…Since no direct control of the pathogen has been established yet, the current management of this disease relies on the control of the vector, especially by insecticides (Halbert & Manjunath, 2004;Yang et al, 2006). Many studies have been performed to examine the efficacy of various insecticides on the control of psyllids, revealing that neonicotinoids such as imidacloprid or thiamethoxam are very effective on the psyllid (Hayashikawa et al, 2006;Yasuda et al, 2006;Srinivasan et al, 2008;Gatineau et al, 2010;Ichinose et al, 2010a). These insecticides are characterised by their long-continued residue effect on the pest, up to several months (Yasuda et al, 2007), and their reducible effects on the psyllid population can continue even after the concentration of the insecticides is decreased below the lethal level (Boina et al, 2009).…”

The utility of the farmer field school as a platform for communication and partnership in agricultural research and development in Vietnam

“…The commonly used classification of citrus in the Mekong Delta, which includes the citrus variety "King Orange" as an orange, was used in this survey. However, King orange is botanically closer to mandarin (Ichinose et al, 2010 Mean net profit averaged over citrus species and provinces was 78,620,000 VND/ha.…”

“…It is still not certain how long psyllids have to feed for the pathogen, once it has been multiplied in the psyllid body, to be transferred, but it is estimated that feeding for several hours is sufficient (Ichinose et al, 2010). Nymphs and adults feed on young shoots and adult females lay eggs on the tips of growing shoots and between opening leaves just…”