Variety Payne Ashley Ashley Payne Ashley. SpaCing 25x25 t 25 x 25 ft 35 x 35 t 30 x 30 t 40 tx 40 t with 1 in middle

Transcription

1 Evaluation of Alternate Row Applications of a Short-Residue Insecticide for Control of First Flight Codling Moth in Walnuts Project Leader: R. A. Van Steenwyk. Cooperating Personnel: J. A. Grant,L. C. Hendricks,W. H. Olson and G. S. Sibbett Abstract A study was conducted during the spring of 1991 to determine if application of a shortresidual insecticide (Lorsban)to alternate middles at various applicationtimings could lengthen the residual activity for conttol of first flight codling moth (em) in walnuts. We can conclude from this ttial that: 1) two applications of Lorsban, applied at 112"nut size and 14 days later to every middle were as effective in reducing CM-infested dropped nuts as was one application of Guthion, applied at 112"nut size; 2) one application of Lorsban, applied at 112"nut size to every middle was as effective in reducing CM-infested dropped nuts as was one application of Lorsban applied at 112"nut size to every other middle and applied to the alternate middles 7 or 14 days later; 3) one application oflorsban, regardless of the timing, was not as effective in reducing CM-infested dropped nuts as were two every middle applications of Lorsban or one application of Guthion; 4) all insecticide applications had fewer CM-infested dropped nuts than did the untreated conttol and 5) Guthion may cause population increases of walnut aphids which then require conttol to prevent damage. Procedures The study consisted of 6 treatments: Guthion 50W at 1.5 lbs AI/ac, applied to every middle at 1/2" nut size (a total of 1.5lbs Al/ac used); Lorsban 4E at 2lbs AI/ac, applied to every middle at 1/2" nut size (a total of 2lbs AI/ac used); Lorsban 4E at 2lbs Al/ac, applied to every middle at 112"nut size and approximately 14 days later (a total of 4lbs Al/ac used); Lorsban 4E at 2 lbs AI/ac, applied to every other middle at 1/2" nut size and to the alternate middle approximately 7 days later (a total of 21bs Al/ac used); Lorsban 4E at 2 Ibs AI/ac, applied to every other middle at 112"nut size and to the alternate middle. approximately 14 days later (a total of2lbs Al/ac used); and an untreated conttol. Each of these treatments was replicated one time in each of 5 orchards throughout the state. Each treatment was applied to an area of 2 or more acres. The basic data concerning the orchards and the experiment is shown in Table 1. All materials were applied with air blast sprayers delivering from 100 to 150 gal water/ac, depending on the site. The effectiveness of the treatments was evaluated by counting counting adult CM caught in pheromone traps and first generation CM-infested dropped nuts. One pheromone trap (Trece Pherocon-l C) was placed in the center of each treatment (5 traps/orchard). The traps were monitored weekly from late March-early April through early July. The pheromone caps were changed at the first insecticide application in late April through early May and the pheromone trap bottoms were changed as needed. Six trees in the center of each treatment were monitored weekly for CM-infested dropped nuts (Table 1). Where walnuts aphids became a problem following the use of Guthion (4 of the 5 orchards), aphid populations were monitored by counting all aphids on 10 leaflets/tree from 6 trees in the center of each treatment

2 Results and Discussion The number of CM-infested dropped nuts per 6 trees is shown in Table 2. A total of 927 CM-infested dropped nuts was found in all treatments at the Woodland orchard while only 44 dropped nuts were found at the Gustine orchard. Because of such large differences in the number of dropped nuts among the orchards, the CM-infested dropped nuts in each treatment in each orchard were calculated as a percentage of the total CM-infesteddropped nuts in that orchard (Table 3). The results show that 1) there was no significant difference between Guthion applied to every middle at 112"nut size and Lorsban applied to every middle at 112"nut size and 14 days later, 2) there were no significantdifferences among Lorsban applied to every middle at 112"nut size, Lorsban applied to every other middle at 112"nut size and 7 or 14 days later to alternate middles, 3) Guthion applied to every middle at 112"nut size had significantly fewer dropped nuts than did Lorsban applied to every middle at 112"nut size and Lorsban applied to every other middle at 112"nut size and 7 or 14 days later to alternate middles and 4) all insecticide applicationshad significantlyfewer CM-infested dropped nuts than did the untreated control. The number of CM/trap/day captured in a pheromone trap from the first application at 112" nut size to approximately 3 weeks later is shown in Table 4. We anticipated that the different application timings would have differential CM mortalities, and that the differential monalities would be reflected in pheromone trap catches. However, only the untreated control showed increased moth captures. Differences among the other treatments were not statistically significant (Table 4). The percent of CM captured by treatment was determined from the total moths captured in each orchard (Table 5). Again, only the untreated control had a significantly higher percentage of total moths than did the other treatments, which did not differ significantly. Walnut aphid populations increased following the application of Guthion in 4 of the 5 orchards (Table 6). In 3 of these orchards, walnut aphid populations required control to prevent damage. No aphid outbreaks were observed with any of the application timings of Lorsban. Since the number of samples and interval between samples of walnut aphid varied among the study orchards, the maximum number of aphidslleaflet observed on any sampling date was analyzed for significance. Only the Guthion treatment had significantly more walnut aphids than did the other treatments, which did not differ significantly

3 Table 1. Basic data for orchards and experiment. Cooperator Grant Van Steenwyk Olson Hendricks Sibbett Location Tracy Woodland Chico Gustine Visalia Variety Payne Ashley Ashley Payne Ashley SpaCing 25x25 t 25 x 25 ft 35 x 35 t 30 x 30 t 40 tx 40 t with 1 in middle CM biofix /15 4/4 Spray rate 125gal 100gal 100gal gal 150 gal Application Dates 112" 513 5/2 5/ IV IV \0 7-day 5/ / day 5/17 5/ /13 5/13 CM drop counts 6/3-7/2, 5/28-6/20, 5/31-7/11, 6/4,6/17, /13, weekly weekly weekly twice/wk Aphid counts None 5/21-6/12, 5/31-7/3, 6/4,6/17, /13, weekly weekly twice/wk Plot size 10 rows x 15 ttees, 10 rows x 39 trees, 10 rows x 12 ttees, 13 rows x 12 trees, 10 rows x 27 ttees, all equal size Lorsban plots; Guthion, Lorsban all equal size all equal size 10 rows x 21 trees, every middle at 1/2" Guthion plot; nut and Lorsban every 10rows x 18trees, Control middle at 112"nut and 14days later, 9 rows x 10trees, other 3 treatments

4 Table 2. Total number of dropped codling moth-infested walnuts for six trees in five locations throughout California, 'r No. dropped CM-infested nuts per six trees... Guthion every middle at 1/2" nut Lorsban every middle at 1/2"nut Lorsban every middle at 1/2"nut and 14 days later Lorsban every other middle at 1/2" nut and 7 days later to alternate middles Lorsban every other middle at 112"nut and 14 days later to alternate middles Control Total

5 'Fable 3. Percent of total dropped codling moth-infested walnuts for six trees in five locations throughout California,

6 Table 4. Number of codling moths captured in pheromone traps for approximately three weeks following the first insecticide application for five locations throughout California, N w N Number codling moths/trap/daycaught in pheromone traps Lorsban every other Lorsban middle at middle at every middle 112"nut and 112"nut and Outhion Lorsban at 1/2"nut 7 days later 14 days later every middle every middle and 14 days to alternate to alternate Location Dates Days at 1/2"nut at 1/2" nut later middles middles Control Woodland 5/2-5/ Visalia Gustine Tracy 5/ Chico 5/ Mean* O.5a O.5a 0.8a 0.6a 0.6a 1.2b Means ollowed by the same letter are not significantlydifferent at the 5% level (DMRTj.

7 Table 5. Percent of total codling moths captured in pheromone traps for approximatelythree weeks following the first insecticideapplication for five locations throughoutcalifornia, I\J Percent of total codling moths/trap/day Lorsban Lorsban Lorsban every other middle at every other middle at every middle 1/2" nut and 1/2" nut and Guthion Lorsban at 1/2"nut 7 days later 14days later every middle everymiddle and 14 days to alternate to alternate Location at l/2"nut at 1/2"nut later middles middles Control w Woodland Visalia Gustine Tracy Chico Mean'" 13.6a 13.2a 16.0a 13.0a 14.6a 29.3b Means followed by the same letter are not significantlydifferentat the 5% level (DMRT). Data analyzed using an arcsin transformation.

8 Table 6. Mean number of walnut aphids per leaflet for four locations throughoutcalifornia, Mean number aphidslleaflet Woodland Visalia Treatment 5/21 5/28 6/4 6/12 5/20 5/22 5/28 6/2 6/ /13 Guthion every middle at /2"nut Lorsbanevery middle at /2" nut N w Lorsban every middle at /2"nut and 14 days later Lorsban every other middle at 1/2"nut and 7 days later to alternatemiddles Lorsban every.other middle at 1/2"nut and 14days later to alternatemiddles Control

9 Table 6 continued. N w U1. Mean number aphids/leaflet Gustine Chico Treatment. 6/4 6/17 7/9 5/31 6/6 6/13 6/20 6/27.-m Guthioneverymiddleat /2"nut Lorsbaneverymiddleat /2"nut Lorsbaneverymiddleat /2"nut and 14days later Lorsbaneveryothermiddle at 1/2"nutand7 dayslater to alternatemiddles Lorsbaneveryothermiddle at 1/2"nutand 14dayslater to alternatemiddles Control

10 Table 7. Maximum number of walnut aphids per leaflet for four locations throughout California, Max. no. aphidslleaflet Treatment Woodland Chico Gustine Visalia Mean* Guthion every middle at Ill" nut a Lorsban every middle at Ill" nut O.3b Lorsban every middle at 1/2"nut and OAb 14 days later I\J w 0'1 Lorsban every other middle at 1/2"nut O.2b and 7 days later to alternatemiddles Lorsban every other middle at 1/2"nut O.2b and 14 days later to alternatemiddles Control O.5b Means ollowed by e same letter are not significantlydifferentat the 5% level (DMRT). Data analyzed using an arcsin transformation.