Demographics and host-kill parameters of Diglyphus horticola Khan against Chromatomyia horticola (Goureau).

The pea leafminer, Chromatomyia horticola (Goureau) (Diptera: Agromyzidae) is a polyphagous and serious pest of peas. In India, this pest is attacked by many parasitoids and among them Diglyphus horticola Khan (Hymenoptera: Eulophidae) is an important one, however, demographics and pest-kill potential of this parasitoid has not been studied so far. This study presents the first report on its demographics and pest-kill potential on C. horticola. The parasitoid showed three modes of host-killing behaviour viz. host-feeding, parasitism and host-stinging. The parasitoid females killed more number of hosts by parasitism than host-feeding or host-stinging. The pre-adult survival, net reproductive rate, intrinsic rate of increase (rm) and finite rate of increase (λ) were higher on the 5-days old host larvae than those reared on the 3-days old larvae. Demographics and pest-kill parameters of D. horticola were also better on 5-days old host larvae than on 3-days old host larvae. Based on the study, D. horticola appeared to be a promising biocontrol agent for the suppression of C. horticola in peas and could be promoted through conservation biological control. Further studies are required to standardize the mass production protocol and release rates to use the parasitoid by augmentation.

Dissipation kinetics of trifloxystrobin and tebuconazole on apple (Malus domestica) and soil--a multi location study from north western Himalayan region.

A new combinational fungicide formulation trifloxystrobin 25%+tebuconazole 50% (Nativo 75WG), introduced as a part of resistance management strategy, was studied for dissipation behaviour on apple fruits. Nativo 75WG was sprayed twice at the rate of 400 g and 800 g a.i. ha(-1) equal to trifloxystrobin application rate of 100 and 200 g a.i. ha(-1) and tebuconazole at application rate of 200 and 400 g a.i. ha(-1) at four different locations in the Northwest Himalayan region of India. The fruit samples collected at 10d interval and soil samples taken at harvest time were analyzed after second spray. The residual concentrations of trifloxystrobin, its acid metabolite CGA 321113 and tebuconazole were measured. Residues of both fungicides were determined by using gas chromatograph, Agilent 6890N having electron capture detector. The mean initial deposits of trifloxystrobin at four locations were found to be in the range of 0.333-0.387 mg kg(-1) and 0.512-0.714 mg kg(-1) at the application rate of 100 and 200 g a.i. ha(-1), and half-life were found between 19.38-24.93 d and 19.84-28.86 d at the respective doses. The Σ-trifloxystrobin and tebuconazole residues were below determination limit in 40 d apple fruits and soil samples. Initial deposits of trifloxystrobin and tebuconazole were below their Codex MRLs at the respective single doses. The half life value of the tebuconazole deposits ranged between 19.38-25.99 d and 19.84-28.86 d at the respective single and double dose. The study thus suggests 1d pre harvest interval for safe consumption of apple fruit after the application of Nativo 75 WG at single dose.