Page 1 Page 2 Page 3 Page 4 Page 5 Page 6 Page 7 Page 8 Page 9 Page 10 Page 11 Page 12 Page 13 Page 14 Page 15 Page 16 Page 17 Page 18 Page 19 Page 20 Page 21 Page 22 Page 23 Page 24 Page 25 Page 26 Page 27 Page 28 Page 29 Page 30 Page 31 Page 32 Page 33 Page 34 Page 35 Page 36 Page 37 Page 38 Page 39 Page 40 Page 41 Page 4213 IREC Farmers' Newsletter No. 196 — Summer 2016 We conducted commercial-scale trials to test the adequacy of the industry threshold for southern NSW in controlling thrips numbers and damage and compared it with a lower threshold of 1 thrips/plant and an unsprayed control. Thrips control options Western flower thrips are an established pest in many horticultural crops in southern NSW and have developed resistance to a number of pesticide groups. In 2014–15 season we didn’t know if western flower thrips were going to be a significant thrips pest of establishing cotton, so we needed to use an insecticide with western flower thrips activity. Dimethoate and omethoate are two registered/permitted thrips insecticides in cotton but they are relatively ineffective against western flower thrips. As broad spectrum insecticides they have a high negative impact on a broad range of beneficial insects potentially resulting in the flaring of mite and whitefly populations. Sulfoxaflor (Transform™) is newly registered in cotton for aphid control and was known to have good activity against western flower thrips, hence it was used in the 2014–15 season. Fipronil, used in the 2015–16 trials, is another foliar insecticide registered and widely used for thrips in cotton. It is effective against western flower thrips, however it is highly toxic to bees, has moderate toxicity to a broad range of beneficials and can also flare mite or whitefly populations. Trial details Trials were conducted on commercial furrow-irrigated cotton crops at the IREC Field Station at Whitton and Darlington Point during the 2014–15 and 2015–16 seasons. The trials were planted in two rows on 1-metre beds in the first two weeks of October in the first season and mid-October in the second. We used Sircot variety 74BRFD. All seeds were treated with a fungicide seed treatment Dynasty® (azoxystrobin+ metalaxyl-M+ fludioxonil). Some treatments also used seeds that were coated with the insecticide Cruiser® (thiamethoxam). Pesticide treatments 2014–15 season 1.  Industry thrips threshold: sulfoxaflor (Transform) at 10 thrips/plant 2.  Low threshold: sulfoxaflor at 1 thrips/plant + thiomethoxam (Cruiser) seed treatment 3. Control: no pesticide/untreated 2015–16 season Wet weather prevented paddock access resulting in changed treatments Whitton site 1.  Industry thrips threshold: fipronil (Regent®) at 10 thrips/plant (1 spray only) 2.  Low threshold: fipronil (Regent) and thiomethoxam (Cruiser) (1 spray only) 3. Control: no pesticide/untreated Darlington Point site 1.  Industry thrips threshold: fipronil (Regent) at 10 thrips/plant (1 spray) 2.  Industry threshold: fipronil (Regent) at 10 thrips/plant (2 sprays) 3.  Control: thiomethoxam (Cruiser) seed treatment with no foliar sprays Thrips populations at trial locations Onion thrips (Thrips tabaci) was the dominant species making up 80% of all adult thrips monitored from seedling to 17-leaf stage in both seasons (Figure 1). Other thrips species observed were tomato thrips (Frankliniella schultzei), western flower thrips (F. occidentalis), plague thrips (Thrips imaginis) and some predatory thrips species. A healthy cotton seedling (top) compared with a seedling displaying ‘cupping‘ of the leaves (below) — a symptom of thrips damage. Figure 1. Relative proportions of adult thrips species from trial locations in the early stages of the 2014–15 and 2015–16 seasons. n Tomato Thrips n Western Flower Thrips n Plague Thrips n Onion Thrips n Others 2014–15 2015–16