Onion thrips: Thrips tabaci Lindeman This experiment was conducted to identify insecticides that are effective against onion thrips, which have become extremely difficult to control in New York onion fields. Onion seeds were planted on 29 Apr 2005 in a muck field near Sodus, New York. Treatments were arranged in a RCB design with five replications. Each plot was a single 20ft long row flanked by an untreated row; rows were spaced apart by 15 inches. Foliar insecticide treatments (see Table)

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... applied at 100 gpa and 40 psi using a CO 2 -pressurized backpack sprayer equipped with a single flat fan nozzle (Twinjet 8004 VS). All treatments included the non-ionic surfactant Induce at 0.5% v/v. Plots were sprayed on 11 Jul when the density of onion thrips exceeded the threshold of 1 thrips larva/leaf (= 6 thrips/plant). Additional applications were made on 18 and 25 Jul and 1 Aug. Conditions during this experiment were hot and dry and there was no irrigation. Efficacy of treatments was evaluated by recording the number of onion thrips larvae per plant from 15 randomly selected plants per plot. Adults were not recorded because they often move between plots and their presence does not always reflect the efficacy of the treatment. Plots were visually rated for thrips damage using a scale ranging from 0 to 10. A rating of 0 denoted 100% damage by thrips (leaves turned white), whereas a rating of 10 indicated no damage (leaves were green). Number of thrips larvae per plot was recorded four days after each application, while the damage rating was made only on 3 Aug. Data were analyzed using ANOVA, with mean separation by Fisher's protected LSD (P = 0.05). Severe damage by onion thrips became evident during the last week of the experiment. Thus, only results after the last application (1 Aug) will be discussed. Treatments that provided the best protection against onion thrips included Carzol, Agri-Mek and SpinTor. These treatments also reduced thrips densities to sub-action threshold levels, with the exception of SpinTor. Most of the other products provided a mediocre to poor level of onion thrips control, including the only two labeled products in this trial, Warrior and Lannate. Rotating the use of several products ("rotation" treatment) to control thrips was marginally effective. This result was a consequence of using three products that were either poor to mediocre against thrips in our trial, Warrior, Lannate and Assail. Calcium nitrate was the only treatment that failed to reduce both damage and densities of thrips. Results from this experiment will provide support for future registration of the best products to control onion thrips on onion.