Perimeter trap cropping and Admire insecticide for managing cucumber beetles in pumpkin.
OVSFRDP Research Project Report - 2001
Principal Investigators: Jim Jasinski & Celeste Welty
Objectives of research:
1. Determine if perimeter trap crop delays cucumber beetle progression into a pumpkin field.
2. Determine the efficacy of Admire applied only to perimeter rows, the entire field, or at different rates on these areas.
3. Determine if insecticide applications based on proposed thresholds can reduce the incidence of bacterial wilt and scarring on harvested fruit.
During the growing season of 2001, research to determine the effects perimeter trap cropping and Admire (Imidacloprid) soil insecticide on pumpkin pest management was carried out at two locations, the OARDC Western Branch in South Charleston and Waterman Field Laboratory in Columbus. Turks Turban was chosen as a trap crop because in prior OSU trials it was shown to be very attractive to cucumber beetles early season.
The Western Branch had 2 blocks of the following three treatments; Trt.1. 8 rows of Howden pumpkin with no soil insecticide surrounded by 2 rows of Turks Turban squash perimeter trap crop treated with Admire 4.1 oz/1000 ft; Trt. 2. 8 rows of Howden pumpkin treated with Admire 1.1 oz/1000 ft surrounded by 2 rows of Turks Turban squash perimeter trap crop treated with Admire 4.1 oz/1000 ft; and Trt. 3. 12 rows of Howden pumpkins treated with Admire 2.75 oz/1000 ft, no trap crop. The Waterman Farm had 1 block of the same three treatments. Each treatment was approximately 0.31 acres in area and separated from other treatments by an 80 ft wide buffer of soybeans. Row spacing was 7.5 ft with a 15 feet spray lane every two rows.
The Western Branch and Waterman Farm plots were direct seeded on June 11th and 14th, respectively. At both locations precision cone seeders were used for planting. Soil insecticide (Admire) was applied in furrow using a CO2 pressurized tank micro-tube delivery system. Seed spacing for pumpkin was every 18 inches, thinned to 3 feet. The trap crop was planted every 12 inches. Early season scouting for cucumber beetles and feeding damage were performed twice weekly while plants were less than 4th leaf stage, thereafter scouting for beetles, plant damage, and fruit damage was performed weekly.
Two fungicide applications of Bravo Weatherstik plus Nova were made at the Waterman Farm on August 15th and September 5th, while at the Western Branch weekly fungicide applications of Bravo Ultrex plus Benlate were alternated with Quadris from July 31st through September 4th. Nova was substituted for Quadris for one application.
Fruit at the Western Branch were harvested September 21st and 24th; those at the Waterman Farm on September 28th. The center 50 feet of row was harvested in each plot for the 8 rows of pumpkins. Data recorded for each fruit included weight and a rating of beetle feeding damage to flesh and handle. Only orange fruit were harvested.
Results:
No significant differences among treatments were observed in plant damage from beetles rated from cotyledon to 4th leaf stage or from 4th leaf stage up to vine tip (Table 1), although there was a trend of more damage in treatment 1 than in treatments 2 and 3. There was a significant difference in the number of beetles per flower (Striped & Spotted cucumber beetles, Northern & Western corn rootworm beetles) between perimeter and interior field sections on 5 of 8 dates, but not between treatments (Table 2). On all dates, beetle density in flowers was higher in perimeter rows than interior rows. No cucumber beetle pre-fruiting thresholds were reached in any block.
Fruit damage ratings were taken once per week for 6 weeks (Table 3). Cucumber beetle fruit thresholds (20% of fruit damaged) were exceeded at the Western Branch on August 21st in treatment 3 and on September 4th in all three treatments, resulting in Adios application. At the Waterman Farm, ADIOS was applied on August 24th after thresholds were exceeded in treatments 1, 2, & 3, and on September 5th after thresholds were exceeded in treatments 1 & 3.
Mean pumpkin yield and number of fruit differed significantly by treatment, but not mean weight per fruit (Table 4). Yield also differed significantly by block, p<0.01. There was no difference in yield between paired rows (3&4 v. 5&6 v. 7&8 v. 9&10, p>0.05) or inner rows (rows 5&6, 7&-8) versus outer rows (rows 3&4, 9&10; p>0.05).
Table 1. Mean plant damage ratings from cotyledon through vine tip caused by chewing cucurbit pests
(0 = None, 1 = Light damage, 2 = Heavy damage). Significant only when p<0.05.
|
Date Growth Stage |
6/22 Cotyledon to 1-leaf |
6/26 1-2 leaf |
6/30 2-3 leaf |
7/4 3-4 leaf |
7/9 4 leaf –Vine Tip |
7/13 4 leaf -Vine Tip |
|
Treatment |
Mean rating of plant damage |
|||||
|
Treatment 1 |
0.34 |
0.36 |
0.48 |
0.38 |
0.18 |
0.85 |
|
Treatment 2 |
0.15 |
0.18 |
0.35 |
0.34 |
0.18 |
0.79 |
|
Treatment 3 |
0.17 |
0.31 |
0.38 |
0.20 |
0.11 |
0.72 |
|
Effect |
P values from ANOVA |
|||||
|
Treatment |
0.38 |
0.65 |
0.75 |
0.46 |
0.37 |
0.77 |
|
Location |
0.70 |
0.37 |
0.98 |
0.70 |
0.24 |
0.35 |
|
Treatment x location |
0.13 |
0.88 |
0.68 |
0.43 |
0.94 |
0.16 |
Table 2.Mean beetle density (all 4 species) in flowers on 8 sampling dates, 2001.
|
|
7/23 |
7/30 |
8/7 |
8/14 |
8/21 |
8/27 |
9/4 |
9/11 |
|
|
Treatment |
Mean number of beetles per flower (all species) |
||||||||
|
Trtmt 1 |
7.2 |
4.7 |
4.5 |
2.1 |
3.3 |
6.5 |
6.0 |
2.5 |
|
|
Trtmt 2 |
3.6 |
4.0 |
5.3 |
2.5 |
3.1 |
5.0 |
6.7 |
2.6 |
|
|
Trtmt 3 |
4.7 |
5.5 |
4.9 |
2.6 |
2.3 |
3.9 |
3.9 |
0.7 |
|
|
Effect |
P values from ANOVA |
||||||||
|
Trtmt |
0.27 |
0.43 |
0.76 |
0.59 |
0.82 |
0.46 |
0.26 |
0.08 |
|
|
Location |
0.91 |
0.42 |
0.0002* |
0.0015* |
0.07 |
0.0109* |
0.0018* |
0.0049* |
|
|
Trt x loc |
0.47 |
0.18 |
0.90 |
0.39 |
0.60 |
0.71 |
0.14 |
0.08 |
|
* Indicates significant difference (p<0.05).
Table 3. Beetle damage on fruit on 6 sampling dates, 2001
(0 = None, 1 = Light damage, 2 = Heavy damage). P-values significant below 0.05.
|
|
8/7 |
8/14 |
8/21 |
8/27 |
9/4 |
9/11 |
|
Treatment |
Mean rating of fruit damage |
|||||
|
Trtmt 1 |
0.16 |
0.10 |
0.12 |
0.36 |
0.42 |
0.62 |
|
Trtmt 2 |
0.08 |
0.07 |
0.13 |
0.17 |
0.27 |
0.47 |
|
Trtmt 3 |
0.11 |
0.08 |
0.22 |
0.28 |
0.40 |
0.58 |
|
Effect |
P values from ANOVA |
|||||
|
Trtmt |
0.22 |
0.83 |
0.22 |
0.41 |
0.21 |
0.29 |
|
Location |
0.61 |
0.72 |
0.35 |
0.76 |
0.73 |
0.11 |
|
Trt x loc |
0.92 |
0.12 |
0.12 |
0.42 |
0.29 |
0.13 |
Discussion:
According to Purdue University laboratory research, prevention of striped and spotted cucumber beetle feeding on seedlings prior to the 4th leaf stage has been shown to reduce the transmission of bacterial wilt. Thus, we were looking at trap cropping as a possible way to protect the pumpkin crop during the critical first two weeks after emergence. Treatments 2 and 3 had lower or equal rates of damage than treatment 1, especially through the first two seedling sample periods, showing that a treated trap crop alone (trt 1) is not adequate to control beetles in the main pumpkin crop. However, a trap crop around a pumpkin crop treated with a low rate of Admire (trt 2) is an alternative to the conventional treatment which is no trap crop but with a higher rate of Admire (trt 3). Activity of Admire was noticed through the end of July, mostly associated with relatively smaller sized plants. As for beetles seen on or around the seedling plants, very few were found during scouting through the first 4 sampling dates. This confirms that scouting for beetle damage especially on the underside of the cotyledons is a better estimate of treatment efficacy rather than counts of beetles.
Table 4. The average yield, number of fruit, and weight per fruit.
Significant differences occur between column data followed by different letters. Average yield per acre extrapolated from 4,250 ft2 to 43,560 ft2.
|
|
Avg. Yield (KG) |
Avg. Yield (Ton/A) |
# of Fruit |
Wt. / Fruit (KG) |
Admire cost/A |
Treatment 1 |
828 b |
9.3 |
107 b |
7.38 a |
$29 |
|
Treatment 2 |
951ab |
10.7 |
126 ab |
7.41 a |
$50 |
|
Treatment 3 |
1108 a |
12.5 |
141 a |
7.75 a |
$72 |
|
|
p=0.05 |
|
p=0.02 |
p=0.74 |
|
Treatment 1. Howden pumpkins untreated by Admire, surrounded by squash perimeter trap crop treated with Admire 4.1 oz/1000 ft
Treatment 2. Howden pumpkins treated with Admire 1.1 oz/1000 ft, surrounded by squash perimeter trap crop treated with Admire 4.1 oz/1000 ft
Treatment 3. Howden pumpkins treated with Admire 2.75 oz/1000 ft on all rows, no trap crop
As plants grew from seedling to vine tip, we were surprised that there was no statistical difference in the amount of seedling damage between the perimeter and interior sections of the plots. Turks Turban perimeter trap crop did sustain more injury than the Howden trap crop during this time. Once flowers appeared, differences among the three treatments were still not seen but there was a significant effect of location on most dates; there were more beetles in flowers in perimeter rows than in interior rows. Beetle numbers in the perimeter flowers are higher than interior flowers regardless of the different perimeter crops, suggesting the edges of a field are inherently more attractive to beetles than the interior.
Beetle damage done to the flesh and handle of pumpkin fruit was cumulative throughout the season, but not significantly different by treatment or location. We do not expect to see a direct effect of soil systemic insecticides applied at planting and late season fruit quality. At harvest, we expected that there may be a yield difference among treatments due to prevention of bacterial wilt infection during seedling stages when plants are most susceptible. Treatment 3 had significantly more fruit and higher yield than treatment 1. Protection of main crop seedlings early in the season with low rates may be the reason for the statistical difference in yield between the treatments. There are also yield differences observed between blocks, with both Western Branch blocks yielding more than the Waterman Farm block (p<0.001). The difference may be attributable to soil type and moisture conditions, which varied greatly between the two locations.
Conclusion:
Damage caused by cucumber beetle feeding from emergence to vine tip was not statistically significantly different between the three treatments or by location in the plot. Since seedling plants are most susceptible to bacterial wilt at this stage, control of cucumber beetles early is essential to maximizing yields. For most of the flowering season, there were statistically more beetles in perimeter flowers than those in the interior, regardless of perimeter crop plant. This should have been a positive influence on the pumpkin crop, which in comparison had fewer beetles feeding on it. Fruit feeding damage was not significantly affected by the treatments, though treatment 2 consistently had lower damage ratings than the other two treatments. Yield was significantly higher in treatment 3, where the plot had a uniform low application of Admire. Growers who are willing to pay the cost for the 16 oz/A rate (2.75 oz/1000 ft @ 7.5’ row spacing) of Admire would probably not find an advantage of the trap crop. Growers who would like to get by with minimal rates of Admire would probably find the trap crop useful in lessening the pest pressure from the pumpkin crop. Perimeter trap cropping by itself (trt 1) did not appear to be the best pest management strategy for this crop.