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Enhancing Diamondback Moth Management with Mating Disruption By SURENDRA K. DARA | UCCE Entomology and Biologicals Advisor Brussels sprouts field in Santa Maria (photo by S.K. Dara.) Brassica crops such as broccoli, brussels sprouts, cabbage, canola, cauliflower, collards, kale, kohlrabi, turnip and mustards are important vegetable or oilseed crops. The value of brassica vegetables, also known as cole crops, is more than $1.2 billion in California, which is the leading producer of these crops. Among various arthropod pests that attack brassica crops, the diamondback moth (DBM), Plutella xylostella (Lepidoptera: Plutellidae), is of significant importance. Thought to be of European origin, now with worldwide distribution, DBM exclusively feeds on cultivated and weedy crucifers. DBM can have up to 12 generations per year, especially under warmer climate. Female moths deposit 150 eggs on average. Four larval instars feed on foliage and growing parts of young plants or bore into heads or flower buds, resulting in skeletonization of leaves, stunting of the plants or failure of head formation in some hosts. Pupation occurs on the lower surface of leaves or in florets. Adult moths are grayish-brown, and when at rest, a light-colored diamond-shaped pattern can be seen on the upper side of the wings. Farmers typically rely on synthetic and biological insecticidal applications for controlling DBM. Multiple species of parasitoids and predatory arthropods also provide some control. Due to a heavy reliance on insecticidal control, DBM resistance to several insecticides is a common problem. Resistance of DBM to Bacillus thuringiensis (Ferré et al., 1991), abamectin (Pu et al., 2009), emamectin benzoate, indoxacarb and spinosad (Zhao et al., 2006), pyrethroids and other insecticides (Leibee and Savage, 1992; Endersby et al., 2011) have been reported from around the world. Excessive use of any kind of pesticide leads to resistance problems (Dara, 2020) to an individual pesticide or multiple pesticides. Integrated pest management (IPM) strategy encourages the use of various control options for maintaining pest control efficacy and reducing the risk of resistance development (Dara, 2019). Regularly monitoring pest populations to make treatment decisions, rotating pesticides with different modes of action, exploring the potential of biocontrol agents, and other non-chemical control approaches such as mating disruption with pheromones are some of the IPM strategies for controlling the DBM. While sex pheromones are effectively used to manage several lepidopteran pests and are proven to be a critical IPM tool, mating disruption is not fully explored for controlling DBM. A study was conducted in Brussels sprouts to evaluate the efficacy of a sprayable pheromone against the DBM and to enhance current IPM strategies. Methodology The study was conducted on a 10-acre Brussels sprouts field in Santa Maria. Cultivar Marte was planted in early July for harvesting in December 2020. A typical diamondback control program includes monitoring DBM populations with the help of sticky traps and lures and applying various combinations of biological and synthetic pesticides at regular intervals. This study evaluated the efficacy of adding CheckMate DBM-F to the grower standard practice of monitoring the DBM populations with traps and lures and applying pesticides. Treatments included 1.) grower standard pesticide program (See Table 1) grower standard pesticide program with two applications of 3.1 fl oz of CheckMate DBM-F on August 9 and September 11. Treatment materials were applied by a tractor-mounted sprayer using a 100 gpa spray volume and necessary buffering agents and surfactants. Each treatment was five acres and divided into four quadrants representing four replications. In the middle of each quadrant, one Suterra Wing Trap was set up with a 30 Progressive Crop Consultant March / April 2021
Trécé Pherocon Diamondback Moth Lure. Lures were replaced once a month in early September and early October. Sticky liners of the traps were replaced every week to count the number of moths trapped. Traps were placed on Aug. 1, 12 and 24, Sept. 1, 11, 18 and 27, and Oct 6, and the moth counts were taken from respective traps on Aug. 8 and 20, Sept. 1, 11, 18 and 27, and Oct. 6 and 15. CheckMate DBM-F was applied at 3.1 fl oz/ac on Aug. 9 and Sept. 11. The number of larvae and their feeding damage on a scale of 0 to 4 (where 0=no damage, 1=light damage, 2=moderate damage, 3=high damage, 4=extensive/irrecoverable) were recorded from 25 random plants within each replication on Aug. 30 and Oct. 6 and 18. Data were subjected to analysis of variance using Statistix software and significant means were separated using Tukey’s HSD test. The retail value of various pesticides was also obtained to compare the cost of treatments. When CheckMate DBM-F[(Z)-11-Hexadecenal (3) , (Z)-11-Hexadecen-1-yl Acetate (1)] was applied the first time on Aug. 9, Dibrom 8 Emulsive was replaced with Warrior II, the buffering agent Quest was not used, and the surfactant Dyne-Amic was replaced with Induce (dimethylpolysiloxane) to avoid potential compatibility issues. The impact of this substitution is expected to be negligible within the scope of this study. The retail cost of 3.1 fl oz Check- Mate DBM-F is $45.60. The cost of lures and traps would be about $4 to $8 per acre for a six-month crop like Brussels sprouts. Results and Discussion Traps in replication 4 in both treatments on August 8 and replication 1 in the grower standard were missing, probably knocked down by a tractor. The day before CheckMate DBM-F was first applied, the mean number of adult DMB caught was 227 in the grower standard and 271 in the plots that would receive the pheromone application (Figure 1, see page 32). There was a gradual decline in moth counts during the rest of the observation period in both treatments. However, the decline was 1 2 3 4 5 6 7 8 9 Date Pesticides 29 July Crymax (Bacillus thuringiensis subsp. kurstaki) 1 lb (IRAC 11) Proclaim (emamectin benzoate) 4.8 oz (6) Avaunt (indoxacarb) 3.5 oz (22A) Dibrom 8 Emulsive (naled) 1 pt (1B) 9 August Crymax 1 lb (11) Radiant SC (spinetoram) 7 fl oz (5) Dibrom 8 Emulsive 1 pt (1B) 21 August Crymax 2 lb (11) Proclaim 4.8 oz (6) Avaunt 3.5 oz (22A) Dibrom 8 Emulsive 1 pt (1B) 25 August Crymax 2 lb (11) Radiant SC 7 fl oz (5) Warrior II (lambda-cyhalothrin) 1.8 fl oz (3A) 1 September Crymax 2 lb (11) Dibrom 8 Emulsive 1 pt (1B) 4 September Crymax 2 lb (11) Proclaim 4.8 oz (6) Lannate SP (methomyl) 1 lb (1A) Rimon 0.83EC (novaluron) 10 fl oz (15) 11 September Crymax 2 lb (11) *Exirel (cyantraniliprole) 20 fl oz (28) Lannate SP 1 lb (1A) 24 September Crymax 2 lb (11) Lannate SP 1 lb (1A) *Movento (spirotetramat) 5 fl oz (23) Radiant SC 7 fl oz (5) 2 October Crymax 2 lb (11) Avaunt 3. 5 oz (22A)Lannate SP 1 lb (1A) *Movento 5 fl oz (23) Radiant SC 6 fl oz (5) higher in the plots that received Check- Mate DBM-F. The number of moths per trap were about 19% higher in the pheromone-treated plots compared to Buffering agents & Surfactants Quest (ammonium sulfate, phosphoric acid, and carbamide) buffering agent 1.4 pt Dyne-Amic (methyl esters of C16-C18 fatty acids, polyalkyleneoxide modified polydimethylsiloxane, alkylphenol ethoxylate) organosilicone-based nonionic surfactant Quest 1.2 pt Dyne-Amic 1 pt Quest 1.2 pt Dyne-Amic 1.2 pt Retail cost $129.04 $108.51 $145.63 Dyne-Amic 12 fl oz $93.65 Quest 1 pt Dyne-Amic 12 fl oz $72.64 Dyne-Amic 12 fl oz $138.05 Dyne-Amic 12 fl oz $146.27 Dyne-Amic 12 fl oz $171.52 Dyne-Amic 12 fl oz $192.17 10 15 October Crymax 2 lb (11) Dyne-Amic 12 fl oz $78.45 Proclaim 4.8 oz (6) Total cost $1,275.93 Table 1. Pesticides, buffering agents and surfactants, their active ingredients, rates/ac (along with the IRAC mode of action groups) and retail pricing for those applied in the grower standard diamondback moth control program. *Applied diamondback moth and aphid control the grower standard before the study but were nearly 98% lower by the end of the Continued on Page 32 March / April 2021 www.progressivecrop.com 31
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Page 24 and 25: New Findings on Limb Dieback of Fig
Page 26 and 27: Figure 3. Left, pycnidia protruding
Page 28 and 29: Figure 4. Susceptibility of various
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Page 34 and 35: Diamondback moth larva and adult (p
Page 36 and 37: Vegetable Growers Express Impressio
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Page 41 and 42: References Biofertilizers Market Si
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