2011 Lygus Bug Management Trial in Blackeyes Kearney Research and Extension Center, Parlier, CA C.A. Frate 1, S.C. Mueller and P.B.

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1 2011 Bug Management Trial in Blackeyes Kearney Research and Extension Center, Parlier, CA C.A. Frate 1, S.C. Mueller and P.B. Goodell Introduction bugs are the primary insect pest of blackeye cowpeas (Vigna unguiculata) in the central and southern San Joaquin Valley. currently registered have either been registered for a very long time (dimethoate, Lannate, Orthene) or are pyrethroids. The efficacy of the older materials is sometimes questioned and there is the additional concern that they may be taken off the market in the near future. Pyrethroids can be effective but lygus bug tolerance to them has been documented. With other crops in the area using pyrethriods for lygus bug control, the general level of background resistance may be high enough to make applications less effective than expected when pyrethroids are used by blackeye growers. Newer materials need to be evaluated. Effective control of lygus bugs in blackeyes is difficult. feeding on flower buds, flowers, and early developing seeds in young pods can abort pod and seed development, resulting in reduced yield. Feeding on slightly older pods can result in blemishes where the insect s stylet penetrated the seed. The blemishes are often referred to as lygus stings. As the level of lygus damage increases on seed, beans are downgraded in quality. Each downgrade means a lower price for the farmer. Many growers produce a double flush, which means a first set of flowers blooms and mature beans develop, followed by a second flush of flowers about 10 days later with subsequent pod development. Each period of bloom and developing pods may stretch over a 2-3 week period of time when the crop is susceptible to lygus damage so residual control is highly desirable in lygus insecticides. Developed prior to 1980 s, the treatment threshold for lygus in blackeyes is 0.5 lygus per sweep during bloom and small pod and 1 lygus per sweep during later pod development. Besides the long time during the season where lygus control is desired, the thick crop canopy hinders coverage when insecticide applications are made. After lay-by, a good blackeye crop on 30-inch beds is practically impossible to walk through due to intertwined vines that cross furrows and connect plants across beds. This dense canopy makes it difficult to get good coverage when applications are made. Practically all commercial applications for lygus are by air. Methods In 2011 a trial was conducted at the U.C. Kearney Research and Extension Center in Parlier, CA, to evaluate several insecticides for lygus control in blackeyes. Plots were 12 rows wide by 50 ft long with 5 replications of 10 treatments in a randomized complete block design. Rows 3 & 4 and 10 & 11 were used on an alternating basis to sample for lygus. Rows 6 and 7 were harvested for yield data. CB 46 seed was planted to moisture on June 1 on 30-inch beds. Before emergence, an unseasonable storm dumped about 1.5 inches of rain on the trial between June 4-6. Part of the fifth replication was flooded but in the rest of the trials plants emerged without problems. 1 C.A. Frate, U.C. Cooperative Extension Farm Advisor, Tulare County, 4437 S. Laspina St, Tulare, CA 93274; cafrate@ucdavis.edu; S.C. Mueller, U.C. Cooperative Extension Farm Advisor, Fresno County; and P.B. Goodell, IPM Advisor, UCCE Statewide IPM Program, Kearney Research and Extension Center; IN: University of California Dry Bean Research 2011 Progress Report published by the California Dry Bean Advisory Board, 531-D North Alta Avenue, Dinuba CA 93618

2 To assess lygus populations, 20 sweeps per plot were taken in either the 3 rd and 4 th row or the 10 th and 11 th row. Samples from sweeps were frozen to kill insects to make counting easier. Sweeping started on July 7, five weeks after planting. populations were slow to develop. By July 25 plants were flowering and to the point where it was soon going to be impossible to walk through the plots. Because treatments were applied by hand, plots were sprayed on July 26, even though lygus populations were below the threshold in all but 2 of the 50 plots. Treatments, listed in Table 1, were applied on July 26, 2011, using a backpack sprayer with TXVS10 hollow cone nozzles at 41 psi with a volume of 15 gpa. Dimethoate is an old standard that has been used on blackeyes for lygus and aphid control for over 30 years. Hero and Warrior II are pyrethroid materials. Rimon is an insect growth regulator that disrupts the normal growth and development of immature insects. Beleaf, Belay, and sulfoxaflor are not registered on blackeyes. The adjuvant Penetrator was added to all of the treatments except for dimethoate. It was probably not the best additive to use with insecticides. Chlorotic spots were noticed on exposed leaves in the Rimon+Warror II plots and small necrotic spots were observed on some sulfoxaflor treated leaves. Penetrator may have contributed to the phytotoxic symptoms. In neither case did damage appear to affect plant growth or production. At the time of treatment, plants were in bloom and small pods were evident. Due to a miscommunication on formulation, Warrior II was applied at twice the label rate. The overall average of all plots for total lygus (adults + nymphs) prior to treatment was 7.4 per 20 sweeps (0.4 lygus/sweep). A second insecticide was to be applied later to one of the Hero treatments but plant growth made it impossible to walk through plots. The result was two identical treatments of Hero. Table 1.Treatments for 2011 lygus bug trial in blackeyes, UC Kearney REC, Parlier, CA Formulation Rate Product per Acre 0.25% v/v Dimethoate 2.67 lb ai/gal 1.5 pt no Warrior II lb ai/gal 3.84 fl oz yes Hero EW 1.14 lb ai/gal 11.2 fl oz yes Hero EW 1.14 lb ai/gal 11.2 fl oz yes Beleaf lb ai/gal 2.8 oz yes Steward lb ai/gal 11.3 fl oz yes Rimon 0.83 EC lb ai/gal 12 fl oz Warrior II 2 yes 2.08 lb ai/gal 3.84 fl oz Belay lbs ai/gal 4.5 fl oz yes Sulfoxaflor (Closer) 1 2 lb ai/gal 2.85 fl oz yes UTC ** ** no 1 Not registered for use on blackeye beans in California 2 Warrior II applied at two times the label rate

3 Plots were swept for insects (20 sweeps per plot) on the day before treatment, 3 days after treatment (D.A.T.) and on August 2, 8 and 16. On the third day after treatment an alfalfa field on the research station, less than 1/8 mile away, was harvested. A strip of alfalfa was left uncut to prevent migration of lygus bugs to the trial. Beneficial insects were also counted prior to treatment and up to 8 days after treatment. On August 24 the center two rows of each plot were cut followed by threshing on September 16 th. Dirt weights were taken and then seed run through a clipper cleaner for clean weights. Beans from each plot were subsampled and 100 seeds/plot were counted for lygus stings. Results and Discussion Counts for lygus were analyzed using analysis of variance (ANOVA) but several times the analyses were significant for non-additivity, which means the data set does not meet one of the assumptions of ANOVA. In these cases, counts were transformed to log10 and analyzed. If significant, means were then separated based on the log10 analysis but those mean separations are shown in the tables with the actual counts rather than with the transformed data. Pre-treatment and counts taken 3 and 7 days after treatment are listed in Table 2 with subsequent counts for 10, 13, and 21 days after treatment in Table 3. Prior to treatment there were no significant differences among the treatments in the numbers of lygus adults, nymphs, or the combined total. Three days after treatment there was no differences among treatments in the number of lygus nymphs. However, there was a significant reduction in the number of lygus bug adults and combined adults plus nymphs compared to the control for all treatments except Beleaf, which is known to have a mode of action that does not immediately kill lygus bugs. Beleaf affects the insect s stylet mouthpart, preventing feeding. In the case of this insecticide, its effectiveness cannot be judged by counting lygus bugs. Based on both nymphs and adults, all treatments except the untreated control were below the threshold level of 0.5 lygus/sweep three days after treatment. Seven days after application, all treatments were above the early season threshold (0.5 lygus/sweep or 10 lygus/20 sweeps) and all but two treatments had exceeded the threshold for developing pods (1 lygus/sweep or 20 lygus/20 sweeps). It is likely that the harvest of a nearby alfalfa field resulted in an influx of lygus into the trial despite the intervening fields and leaving a strip of alfalfa unharvested. In subsequent counts lygus numbers continued to increase with no significant differences among treatments. Beneficial Counts The only beneficial insects that occurred in sufficient numbers to report were big eyed bug adults and minute pirate bug adults (Table 4) but even their numbers were not very high. There were no significant differences in the counts for either of these insects among treatments on any of the sampling dates. The control and the Beleaf treatments were the only ones in which there were more big eyed bug adults 8 days after treatment than prior to treatment.

4 Yield and Quality Results for yield, shown in Table 5, are based on only 4 replications. There were some really low yielding plots in Rep V that were not representative of the rest of the trial. When Rep V was included in the analysis it was significant for non-additivity. Transforming the data to log10 did not help. However, when only reps 1-4 were analyzed there was no problem with non-additivity. On the whole, yields were low which is not surprising considering the level of lygus that developed prior to harvest. Statistically there were no significant differences among treatments; however the untreated control was the lowest in yield except for one of the two Hero treatments. The only category of seed damage in which there were significant differences among the treatments was the category of seeds with no lygus damage. The untreated control had the least amount of undamaged seed or, in other words, the most damaged seed. Treatments of sulfoxaflor, Belay, Warrior II, Rimon + Warrior II, and Steward had significantly more undamaged seed (or fewer damaged seed) than untreated plots. In summary lygus bug trials in blackeyes are difficult because crop growth makes it hard to walk or drive through plots after lay-by, plots need to be large because of the insect s mobility, and dense canopy makes good coverage difficult. In addition, sampling with a sweep net is not easy when plants are full grown and the mobility of the insect reduces the accuracy of sweeping. This trial presumably had an influx of lygus bugs when a nearby alfalfa field was cut a problem growers often face. The newer materials, although they didn t appear to provide any easy answers to the problem of an influx of lygus bugs, appeared to work as least as well as registered materials. Replacements for dimethoate and alternatives to pyrethroid insecticides would be welcome additions to the currently available insecticides available to growers. Acknowledgements: Thank you to the field staff at the UC Kearney Research and Extension Center for their assistance in conducting this trial and to Jacob Rhea and Walter Martinez for their assistance with this trial.

5 Table 2. counts from the 2011 blackeye lygus bug trial, UC Kearney Research and Extension Center, Parlier, CA. 1 Average counts per 20 sweeps/plot 7/25/2011 (Pre-treat) 7/29/ D.A.T 8/2/ D.A.T Adults Nymphs Adults 2,5 Nymphs 2,5 Adults Nymphs 5 Dimethoate bc bc Warrior II cd bc Hero EW cd bc Hero EW cd bc Beleaf ab ab Steward d bc Rimon 0.83 EC d c Warrior II 4 Belay d bc Sulfoxaflor(Closer) bcd bc UTC a a Probability ** 0.13 ** 0.27 ** 0.13 LSD.05 NS NS NS ** NS ** NS ** NS CV (%) Non-additivity NS NS NS 0.03 NS 0.04 NS 0.05 NS Probability for differences with data transformed (log10) Trial was planted with variety CB 46 on June 1, cut on August 24, and threshed on September 16, Counts are based on 5 replications. Values within a column followed by the same letter do not differ at the 5% level of Probability. 2. Not registered for use on blackeye beans in California. 3. The second treatment of Hero was to have another application but due to plant growth the 2nd application was omitted. 4. Warrior II was applied at two times the label rate. 5. The letters denoting significance at P=5% are based on the analysis of the counts transformed to log10. ** Analysis of these counts were significant for non-additivity so numbers were transformed to log10 for analysis of variance.

6 Table 3. counts from the 2011 blackeye lygus bug trial, UC Kearney Research and Extension Center, Parlier, CA. 1 Adults Average Counts per 20 Sweeps 8/5/ D.A.T 8/8/ D.A.T. 8/16/ D.A.T. Nymphs Adults Nymphs Adults 2,5 Nymphs 5 2,5 Dimethoate a Warrior II b Hero EW abc Hero EW c Beleaf abc Steward a Rimon 0.83 EC bc Warrior II 4 Belay ab Sulfoxaflor ab UTC abc Probability ** ** ** LSD.05 NS NS NS 7.67 NS NS ** ** ** CV (%) Nonadditivity NS NS NS NS NS NS Probability for Treatments (data transformed log10) Trial was planted with variety CB 46 on June 1, cut on August 24, and threshed on September 16, Counts are based on 5 replications. Values within a column followed by the same letter do not differ at the 5% level of Probability. 2. Not registered for use on blackeye beans in California. 3. The second treatment of Hero was to have another application but due to plant growth the 2nd application was omitted. 4. Warrior II was applied at two times the label rate. 5. The letters denoting significance at P=5% are based on analysis of counts transformed to log10. ** Analysis of the counts was significant for non-additivity so numbers were transformed to log10 for analysis of variance.

7 Table 4. Counts of beneficial insects, 2011 blackeye lygus bug trial, U.C. Kearney Research and Extension Center, Parlier,CA 1 Number of Beneficial Insects per 20 Sweeps Pre- Treatment July 25 5 Big Eyed Bug Adults 3 D.A.T. July 29 8 D.A.T. Aug 2 5 Minute Pirate Bug Adults Pre- Treatment July 25 3 D.A.T. July 29 8 D.A.T. Aug 2 Dimethoate Warrior II Hero EW Hero EW Beleaf Steward Rimon 0.83 EC Warrior II 4 Belay Sulfoxaflor (Closer) UTC Probability ** 0.12 ** LSD.05 ** NS ** NS NS NS CV (%) Non-additivity Probability for Treatments data transformed (log10) 0.12 still significant for nonadditivity 1. Trial was planted with variety CB 46 on June 1, cut on August 24, and threshed on September 16, Counts are based on 5 replications. Values within a column followed by the same letter do not differ at the 5% level of Probability. 2. Not registered for use on blackeye beans in California. 3. The second treatment of Hero was to have another application but due to plant growth the 2nd application was omitted. 4. Warrior II was applied at two times the label rate. 5. Analysis of these counts were significant for non-additivity so numbers were transformed to log10 for analysis of variance.

8 Table 5. Yield and quality assessment for the 2011 blackeye lygus bug trial, U.C. Kearney Research and Extension Center, Parlier, CA. 1 Yield Results Dirt Weight cwt/a Clean Weight cwt/a # seeds/100 with no lygus damage # seed/100 with 1 sting Quality Results # seed/100 with 0 or 1 stings # seed/100 with 2 stings #seed/100 with 2 or more stings Dimethoate abc Warrior II ab Hero EW abc Hero EW bc Beleaf abc Steward ab Rimon 0.83 EC a Warrior II 4 Belay ab Sulfoxaflor (Closer) a UTC c Probability LSD.05 NS NS 9.98 NS NS NS NS CV (%) Trial was planted with variety CB 46 on June 1, cut on August 24, and threshed on September 16, Yield data is based on the means of 4 replications. Quality data is based on 5 replications. Values within a column followed by the same letter do not differ at the 5% level of Probability. 2. Not registered for use on blackeye beans in California. 3. The second treatment of Hero was to have another applciation but, due to plant growth, the 2nd application was omitted. 4. Warrior II was applied at two times the label rate.