Differences between the effects of insecticidal seed and foliar treatments on pea leaf weevils (Sitona lineatus L.) in the field pea (Pisum sativum L.)

Abstract

Seidenglanz M., Rotrekl J., Smýkalová I., Poslušná J., Kolařík P. (2010): Differences between the effects of insecticidal seed and foliar treatments on pea leaf weevils (Sitona lineatus L.) in the field pea (Pisum sativum L.). Plant Protect. Sci., 46: 19-27.Tested seed treatments (two doses of thiamethoxam, thiamethoxam + fludioxonil + metalaxyl-M; two doses of clothianidin + beta-cyfluthrin) showed high effects on pea leaf weevils (Sitona lineatus L.) which approved relatively long-lasting and sufficient protection of several bottom nodes of stipules simultaneously. The effects of foliar treatments (chlorpyrifos + cypermethrin; acetamiprid, lambda-cyhalothrin) sometimes were evident only on the node which was determined as the youngest node at the time of spraying. The effects of the compared seed and foliar treatments on the reduction of S. lineauts larvae numbers on roots were not proven as positive. It is possible to conclude that the foliar application had no real effect in this sense at all. However, positive significant effects of thiamethoxam and clothianidin + beta-cyfluthrin on root nodulation in general were recorded. Especially higher doses of the seed treatments increased overall nodulation from 43% till 363%.

Greenhouse Studies of Thiamethoxam Effects on Pea Leaf Weevil,Sitona lineatus

“…per 100 kg of seed (∼ 82 g. of a.i./ha at the recommended seeding rate of 275 kg/ha as per Government of Saskatchewan Agriculture Knowledge, http://www.agriculture.gov.sk.ca/) had the lowest levels of feeding damage to stipules and was similar to the 50 g dose. These results are similar to those reported by Seidenglanz's et al (2010) field study in the Czech Republic, who found no consistent differences in S. lineatus notching to unfolded pea stipules between a low dose (87.5 g of a.i./ha), equivalent to the registered rate in Canada, and a dose that was two-fold higher. The results of the present study also showed that using a lower rate would not result in a reduction of damage that differed from the untreated plants.…”

“…This finding is important because it shows that growers should not need to take control action for early seeded crops when the weevils arrive past the 5 th node. This is the first study to present data on S. lineatus larval mortality in relation to thiamethoxam, which suggests activity of the chemical in the nodules; Seidenglanz et al (2010) also reported an effect on larval mortality but neglected to present the data.…”

“…In the study by Vankosky et al (2011), there was no effect of seed treatment on yield, which may be explained by incomplete control of the weevil or alternatively by lack of strong effects of the weevil on plant yield. In the study by Seidenglanz (2010), yields were not reported, but damaged nodules were not affected by treatments or were higher in the plots with thiamethoxam or another seed-treatment compared to the controls.…”

“…Seidenglanz et al (2010) reported an increase in total nodulation in the range of 43–363% from a number of compounds that included thiamethoxam, imidacloprid, and chothianidin. More modest nodulation increases (30–100%) in relation to thiamethoxam were reported by Vankosky et al (2011).…”

“…In general, foliar insecticides do not seem to provide sufficient control to prevent larval damage to nodules, despite reductions in adult foliage consumption (Seidenglanz et al 2010; Cárcamo and Vankosky 2011). A number of seed-coated or soil-incorporated systemic insecticides have been used with some degree of success.…”