Single Insecticide Application Research Articles

Exploiting asynchronous host-parasitoid emergence distributions to optimise insecticide applications and protect beneficial insects– a case study using the citrus gall wasp Bruchophagus fellis (Hymenoptera: Eurytomidae)

The citrus gall wasp (CGW), Bruchophagus fellis (Girault) (Hymenoptera: Eurytomidae), is a serious pest of citrus in southern Australia. Severe infestations can result in yield loss and a reduction in fruit size. Several parasitoid species attack CGW, with Megastigmus brevivalvus (Girault) (Hymenoptera: Torymidae) (MBV) being the dominant species. Both CGW and MBV are univoltine and adult wasps emerge from galls in the spring. Median emergence of MBV lags behind that of CGW by 2–3 weeks. We modelled the effect of spray timing for foliar-applied, non-systemic insecticides on the relative exposures of CGW and MBV based on their emergence distributions and estimated the optimal spray timing that maximises the control of CGW while minimising the impact on MBV. Three temporal emergence distribution scenarios for the two species and 28 periods of residual insecticide activity were considered in the investigation. The results showed that the optimal spray timing was always before the peak emergence of CGW. Depending on the residual activity of the insecticide, the optimal spray date pre-dated the peak emergence of CGW by 1–24 days, with longer lead times for insecticides with longer residual activity. By contrast, the optimal spray date varied little across the different emergence scenarios, suggesting that the results apply over a wide range of locations and seasons. A single insecticide application at the optimal timing may not guarantee satisfactory control of CGW. When the residual activity of the insecticide is short, multiple applications with a combined residual activity of 16 days are needed to ensure insecticide contact with ≥90% of all CGW that emerge in a season.

Alterations in Ferrisia gilli (Hemiptera: Pseudococcidae) phenology in California pistachios and potential impacts on controls.

The mealybug, Ferrisia gilli Gullan, attacks important crops such as almonds, grapes, and pistachios in California. In pistachios, F. gilli has 3 generations per year, and a single insecticide application timed to the presence of first instars of the first or second generation provided sufficient control. This strategy has, recently, become less effective, and here we tested the possible explanation that F. gilli life stages are smeared, with different life stages present concurrently, reducing the efficacy of a single pesticide application. We monitored F. gilli populations and their natural enemies in central California pistachio orchards from 2021 through 2022. We found the first generation of F. gilli was synchronous, but occurred 3 wk earlier than previously reported. Subsequent generations were smeared. Increased yearly temperatures are a likely explanation for the changes observed in phenology. Almost all natural enemies found were lacewings (n > 10,000). Parasitoids were recovered from pistachios in 2021 (n = 4) and 2022 (n = 164), most were hyperparasitoids. Based on these studies, recommendations are made to monitor F. gilli in early May rather than late May to better target insecticide applications for the first instars.

Economic Damage Levels of the Green Shield Bug (Palomena prasina, Hemiptera: Pentatomidae) in Türkiye Hazelnut Orchards

The green shield bug (GSB) (Palomena prasina, Hemiptera: Pentatomidae) is one of the most important pests of hazelnut in Turkish hazelnut orchards. This harmful insect causes serious yield and quality losses by feeding directly on fruits every year. Their feeding on hazelnut fruits may result in nut abortion (empty nuts) in early season and cause shriveled and corked kernels in kernel expansion period. Insect pest management must be decided by depending on insect population level in field according to integrated pest management concept. Economic injury level (EIL) and economic threshold (ET) are the main essential points that must be considered in decision for insect pest control. Thus, it can be possible to protect the natural environment from unnecessary pesticide applications and the growers from high production costs. Therefore, determining of economic decision levels for controlling pests is critical. This is especially important for hazelnuts, which are grown on hundreds of thousands of hectares of land in Türkiye, and for the GSB, a serious pest that requires a couple of chemical applications per year. The economic decision levels vary mainly due to insect species and their damage potential, crop value in the market and control costs which can change over years and countries. This study aimed to calculate the EIL and ET values for GSB control action in hazelnut orchards in Türkiye using new economic market data. Based on previous research, the authors calculated the yield loss caused by one individual of GSB in this study. Direct yield loss, as well as quality and quantity losses from damaged kernels, were calculated separately and then totaled. The data, including crop value and control costs necessary for calculation was updated from free market sources. In the calculation of EIL/ET, the most common formula (EIL= C/ VxbxK) was used. As a result, the economic threshold for a single insecticide application was determined to be3.8 insect/da (=0.1 ha) for K=1 value and 4.76 insect/da for K=0.8 value, for single insecticide application. When ET values were converted in traditional Turkish approach that is special for hazelnut orchards; ET values for K=1 and K=0.8 were 0.76 insect/ 10 “hazelnut “ocak” (traditional growing of hazelnut plants together) and 0.95 insect/ 10 “ocak” respectively. If 2 applications per year for GSB were considered, ET values were doubled up and calculated to be 7.6 and 9.47 insect/da for K=1 and K=0.8 value respectively, and thusly 1.52 and 1.9 insect/ 10 “ocak” for Türkiye. For practical reasons, the ET value for GSB was recommended as 10 insect/da and 2 insects/10 “ocak”, for Türkiye, with consideration of 2 chemical applications and K= 0.8.

Factors Influencing Insecticide Efficacy against Armored and Soft Scales

Scale insects (Hemiptera: Coccoidea) are among the most economically important pests of ornamental plants. Soft scales (Coccidae) are phloem-feeding insects that produce large amounts of honeydew. By contrast, armored scales (Diaspididae) feed on the contents of plant cells and produce a waxy test that covers their bodies. We studied two species of armored scales [pine needle scale (Chionaspis pinifoliae) and oleander scale (Aspidiotus nerii)] and two species of soft scales [calico scale (Eulecanium cerasorum) and striped pine scale (Toumeyella pini)] to compare efficacy of selected insecticides. In addition, we assessed how the duration of first instar emergence might influence insecticide efficacy. Several reduced-risk insecticides (chlorantraniliprole, pyriproxyfen, spiromesifen, and spirotetramat), horticulture oil, and two broad-spectrum insecticide standards (bifenthrin and dinotefuran) were evaluated. Efficacy of insecticides was consistent within each scale family. Bifenthrin and pyriproxyfen were the only insecticides that killed soft scale insects. By contrast, all insecticides killed armored scales when the crawler stage was the target of application. Armored and soft scales may differ in susceptibility to pesticides because of likely differences in the chemical composition of their integuments and covers. Finally, we found that the effectiveness of a single application of insecticide declined by >15% when the duration of the crawling juvenile period was increased from 1 to 4 weeks. Increases in duration of a scale crawling period decreased the efficacy of a pesticide application.

Action Thresholds for Managing Megacopta cribraria (Hemiptera: Plataspidae) in Soybean Based on Sweep-Net Sampling.

The kudzu bug, Megacopta cribraria (F.), first discovered in the United States in 2009, has rapidly become a pest of commercial soybean, Glycine max (L.) Merrill, throughout much of the southeast. Because of its recent arrival, management practices and recommendations are not well established. To develop action thresholds, we evaluated insecticide applications targeted at different densities of adults and nymphs determined using the standard 38-cm diameter sweep net sampling method in 12 soybean field trials conducted in Georgia, North Carolina, and South Carolina from 2011 to 2013. Average peak densities of M. cribraria in the untreated controls reached as high as 63.5 ± 11.0 adults per sweep and 34.7 ± 8.0 nymphs per sweep. Insecticide applications triggered at densities of one adult or nymph of M. cribraria per sweep, two adults or nymphs per sweep, and one adult or nymph per sweep, with nymphs present, resulted in no yield reductions in most cases compared with plots that were aggressively protected with multiple insecticide applications. A single insecticide application timed at the R3 or R4 soybean growth stages also resulted in yields that were equivalent to the aggressively protected plots. Typically, treatments (excluding the untreated control) that resulted in fewer applications were more cost-effective. These results suggest that a single insecticide application targeting nymphs was sufficient to prevent soybean yield reduction at the densities of M. cribraria that we observed.

Efficacy of Silk Channel Injections with Insecticides for Management of Lepidoptera Pests of Sweet Corn.

The primary Lepidoptera pests of sweet corn (Zea mays L. convar. saccharata) in Georgia are the corn earworm, Helicoverpa zea (Boddie), and the fall armyworm, Spodoptera frugiperda (J. E. Smith). Management of these pests typically requires multiple insecticide applications from first silking until harvest, with commercial growers frequently spraying daily. This level of insecticide use presents problems for small growers, particularly for "pick-your-own" operations. Injection of oil into the corn ear silk channel 5-8 days after silking initiation has been used to suppress damage by these insects. Initial work with this technique in Georgia provided poor results. Subsequently, a series of experiments was conducted to evaluate the efficacy of silk channel injections as an application methodology for insecticides. A single application of synthetic insecticide, at greatly reduced per acre rates compared with common foliar applications, provided excellent control of Lepidoptera insects attacking the ear tip and suppressed damage by sap beetles (Nitidulidae). While this methodology is labor-intensive, it requires a single application of insecticide at reduced rates applied ∼2 wk prior to harvest, compared with potential daily applications at full rates up to the day of harvest with foliar insecticide applications. This methodology is not likely to eliminate the need for foliar applications because of other insect pests which do not enter through the silk channel or are not affected by the specific selective insecticide used in the silk channel injection, but would greatly reduce the number of applications required. This methodology may prove particularly useful for small acreage growers.

Efficacy of insecticides against the Rice Stem-borer, Chilo suppressalis (Walker) (Lepidoptera: Crambidae), and use of sex pheromones to time accurately the yearly application

Larvae of the Rice Stem-borer, Chilo suppressalis (Walker), cause extensive crop losses worldwide. Since pesticide application is the major management tactic in China, judicious timing of a minimal dose of insecticides is important in developing an IPM program for that pest. Pheromone trap captures of male moths were used to time the single insecticide application in two seasons (2010 and 2011). In 2010, six pesticides – deltamethrin, cygon, chlorpyrifos, cartap, fipronil, and esfenvalerate – gave >90% control of stem-borers, and reduced damage to less than 5.0%. In 2011, control exceeding 90% and a damage level of <5.0% and was achieved with 0.35 kg/ha deltamethrin and chlorpyrifos. Cygon, at either 0.30 or 0.35 kg/ha, provided control exceeding 90% and a damage level of <4.0%. With the proviso that the impact of insecticides on biological control agents remains to be investigated, these three insecticides are recommended for use by Chinese rice farmers.

Probability of Cost-Effective Management of Soybean Aphid (Hemiptera: Aphididae) in North America

Soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), is one of the most damaging pests of soybean, Glycine max (L.) Merrill, in the midwestern United States and Canada. We compared three soybean aphid management techniques in three midwestern states (Iowa, Michigan, and Minnesota) for a 3-yr period (2005-2007). Management techniques included an untreated control, an insecticidal seed treatment, an insecticide fungicide tank-mix applied at flowering (i.e., a prophylactic treatment), and an integrated pest management (IPM) treatment (i.e., an insecticide applied based on a weekly scouting and an economic threshold). In 2005 and 2007, multiple locations experienced aphid population levels that exceeded the economic threshold, resulting in the application of the IPM treatment. Regardless of the timing of the application, all insecticide treatments reduced aphid populations compared with the untreated, and all treatments protected yield as compared with the untreated. Treatment efficacy and cost data were combined to compute the probability of a positive economic return. The IPM treatment had the highest probability of cost effectiveness, compared with the prophylactic tank-mix of fungicide and insecticide. The probability of surpassing the gain threshold was highest in the IPM treatment, regardless of the scouting cost assigned to the treatment (ranging from $0.00 to $19.76/ha). Our study further confirms that a single insecticide application can enhance the profitability of soybean production at risk of a soybean aphid outbreak if used within an IPM based system.

Reduced-Risk Management ofRhagoletis cerasiFlies (Host RacePrunus) in Combination with a Preliminary Phenological Model

Seasonal flight activity of Rhagoletis cerasi (L.) (Diptera: Tephritidae) adults was monitored using yellow sticky traps at sweet cherry orchards under different management regimes in Bursa, northwestern Turkey, during 1997–1998. In the reduced-risk backyard orchards, soil ploughing in the fall or spring to destroy the pupae was combined with a single application of an insecticide, while conventionally managed orchards received six to seven insecticide applications for controlling adults. Traps in commercial orchards caught significantly fewer adults than those in reduced-risk backyard orchards. Levels of cherry fruit fly fruit damage were very low (0.1%) in commercial orchards, whereas infestation rates averaged 2.2% in reduced-risk orchards. A preliminary phenology model was developed for optimal timing of insecticide applications based on air temperature summations since 1 February. In the reduced-risk backyard orchards, the first flies were captured between 25 May and 2 June, corresponding to an average degree-day (DD) accumulation of 582.50 ± 10.50 DD at an altitude of 150 m. However, first adult emergence at 1170 m was recorded between 6 and 14 June, averaging 667.50 ± 14.50 DD. Adult emergence exhibited bimodal peaks in a single flight at low altitude but there was a single peak at high altitude sites. Total adult flight period averaged 459 ± 29.50 and 649 ± 25.50 DD at low and high altitude sites, respectively. Our prediction model suggests that the optimum spray-window for a single insecticide application occurs between 577.70 and 639.40 DD at 150 m and between 780.90 and 848.60 DD at 1170 m.

Effects of application rate and interval on the efficacy of sprayable pheromone for mating disruption of the oriental fruit mothGrapholita molesta

The efficacy of microencapsulated sprayable pheromone was evaluated at different application rates and intervals for mating disruption of the oriental fruit moth,Grapholita molesta (Busck), in apple orchards during 2002. The following treatments were arranged in a randomized complete block design with three replications: (i) a low rate of pheromone (6.2 g a.i. ha−1) applied at 14-day intervals, (ii) a medium rate of pheromone (12.4 g a.i. ha−1) applied at 28-day intervals, (iii) a high rate of pheromone (24.7 g a.i. ha−1) applied at 28- day intervals, and (iv) a non-pheromone control (insecticides only). The combination of a single insecticide application against first generationG. molesta at petal fall with one pheromone application each for the second, third and fourth generations at 12.4–24.7 g a.i. ha−1 successfully controlled low populations. Pheromone-treated blocks. had significantly lower trap catches than those in the insecticide-treated control blocks. Among pheromone treatments, significantly more moths were caught in the 6.2 g compared with the 12.4 and 24.7 g rates. Fruit damage was <1% at harvest and there were no significant differences among treatments. Low rate frequent applications of sprayable formulation appeared to be effective under low pest pressure but efficacy declined with increasing populations. Further studies are needed to demonstrate the effectiveness of this approach under higher pest pressure.

A new strategy for the chemical control of fig longicorn, Acalolepta vastator (Newman) (Coleoptera: Cerambycidae), infesting grapevines

Abstract Difficulties in controlling the grapevine borer pest fig longicorn, Acalolepta vastator, were experienced. Variable results with azinphos‐methyl, chlorpyrifos and methidathion applied as seasonal sprays at 2‐weekly or monthly intervals, coupled with inconsistent grower spraying practices, provided unreliable control. Pest resurgence resulted in a range of new chemicals and usage strategies being tested to overcome the problem. After extensive trialling an effective strategy for control of A. vastator was developed. This involved a single application of insecticide at dormancy, and after vineyard pruning, at a much higher rate than that normally registered for crop use. Bifenthrin (Talstar 100 EC) at 1000 mL/100 L, fipronil (Regent 200 SC) at 100 mL/100 L and imidacloprid (Confidor 350 SC) at 200 mL/100 L controlled emerging adults and young. This strategy overcomes a number of problems experienced with the previous chemical application method for this pest.

Effects of chlorpyrifos and sulfur on spider mites (Acari: Tetranychidae) and their natural enemies

In many agricultural systems spider mites are believed to be induced pests, only reaching damaging densities after pesticides decimate predator populations. Wine grapes typically receive two types of pesticides, insecticides and fungicides. Chemicals in either class could impact spider mite densities both directly through spider mite mortality, and indirectly by negatively affecting natural enemies. The impact of a broad-spectrum insecticide (chlorpyrifos) and an inorganic fungicide (sulfur) on mites and their natural enemies was monitored in replicate open-field experiments conducted in an abandoned vineyard in Washington State. In both experiments, chemicals were applied within a 2 × 2 factorial design, allowing assessment of both main and interactive effects of the two chemicals. Following typical management practices on wine grapes in Washington State, we made a single insecticide application early in the season, but repeatedly applied sulfur throughout the season. In the absence of sulfur, chlorpyrifos application led to higher spider mite densities. The main effect of chlorpyrifos appeared to be indirect, perhaps mediated through mortality of generalist phytoseiid mites; generalists appeared to be unable to recover following even a single insecticide application, while there was no evidence for harmful effects of chlorpyrifos on specialist phytoseiid mites. Sulfur had direct suppressive effects on both pest and predatory mites, although in the second experiment the suppressive effect of sulfur on spider mites was weaker when chlorpyrifos was also applied. These field experiments suggest that a complex mix of direct and indirect effects of the two chemicals impacted spider mite population dynamics in our system.

EVALUATION OF FOLIAR INSECTICIDES FOR CONTROL OF CORN BORERS IN FIELD CORN, 2004

The objective of the study was to determine the effectiveness of insecticides applied to corn foliage against corn borers. Field corn ‘Pioneer 3345’, a non-BT cultivar, was planted with a John Deere 7100 Maximerge planter at a rate of 2.2 seed per row ft. at the Cotton Branch Experimental Station, Mariana, AR on 16 Apr (early planting) and 1 May (late planting) 2004. Soil type was silt loam and had been planted to cotton in 2003. Plots consisted of one row 45 ft long. Plots were separated by 80 inches. Replications were separated by 5 ft bare ground buffers. The experimental design was RCB with four replications. Applications were timed by splitting corn stalks in adjacent plots and searching for corn borer pupae. A single insecticide application was made on 30 Jun, one week after the first dark pupae were detected. Insecticides were applied with a CO2 propelled backpack sprayer equipped with two Delvan HB10 nozzles. Spray volume was 14.8 gpa at 25 psi. Insecticide effectiveness was assessed as follows. On 24 Aug 10 randomly selected plants were cut at soil level from each plot. Each stalk was split with a band saw and corn borer damage was assessed for each stalk internodes. On each plant, damage to the first 15 internodes beginning at ground level and counting upward, was determined. Any stalk with a single damaged internode was considered infested. Stalks with more than 2 damaged internodes were categorized as having major damage. Ear damage was rated on a 0 to 5 scale, with 5 the most severe. Data were analyzed using ANOVA and means were separated using an F-protected LSD (P ≤ 0.05).

A freshwater food web model for the combined effects of nutrients and insecticide stress and subsequent recovery

A microcosm experiment that addressed the interaction between eutrophication processes and contaminants was analyzed using a food web model. Both direct and indirect effects of nutrient additions and a single insecticide application (chlorpyrifos) on biomass dynamics and recovery of functional groups were modeled. Direct toxicant effects on sensitive arthropods could be predicted reasonably well using concentration-response relationships from the laboratory with representative species. Model predictions showed that nutrient additions alone caused only small effects on toxicant fate and effects probably due to the relatively high dissipation rate of chlorpyrifos. Enhancement of eutrophication effects by the insecticide was relatively small and seemed to be additive. The recovery of some affected functional groups was hampered in the indoor microcosms due to their isolation from outdoor seed populations. Introducing recolonization scenarios in the model simulated dose-dependent recovery. Recolonization increased the recovering rate after exposure to the pesticide. Modeling can extend the use of microcosms as a link between laboratory and field as this allows the prediction of effects and recovery of ecosystems for concentrations that have not been experimentally tested.

EVALUATION OF FOLIAR INSECTICIDES FOR CONTROL OF CORN BORERS IN FIELD CORN, 2002

The objective of the study was to determine the effectiveness of insecticides applied to corn foliage against corn borers. Field corn Terral 2140, a non-BT cultivar, was planted with a John Deere 7100 Maximerge planter at a rate of 2.2 seed/ row ft. at the Cotton Branch Experimental Station, Mariana, AR on 1 May 2002. Soil type was silt loam and had been planted to cotton in 2001. Plots consisted of one row 45 ft long. Plots were separated by 80 inch. Replications were separated by 5 ft bare ground buffers. The experimental design was RCB with four replications. Applications were timed by splitting corn stalks in adjacent plots and searching for corn borer pupae. A single insecticide application was made on 1 Jul 5 days after the first dark pupae were detected. Insecticides were applied with a CO2 propelled backpack sprayer equipped with two Delvan HB10 nozzles. Spray volume was 23 gpa at 30 psi. Insecticide effectiveness was assessed as follows. On 24 Aug 10 randomly selected plants were cut at soil level from each plot. Each stalk was split with a band saw and corn borer damage was assessed for each stalk area between plant nodes. This area was designated internode. On each plant, damage to the first 15 internodes beginning at ground level and counting upward, was determined. The 1 or 2 internodes above first 15 are generally too narrow for corn borer larvae development and were not split. Any stalk with a single damaged internode was considered infested. Stalks with more than three damaged internodes were categorized as having major damage. Plots were harvested 18 Oct with a Massey-Ferguson 8XP plot combine equipped with a single row corn header.

The ecological economics of insecticide use associated with the Maine potato industry, based on a producer survey

Environmental risks and costs associated with insecticide applications in Maine potato farming have been characterized and estimated using an Aroostook producer survey. The results of this study allow for comparison of pest management strategies based on producer concern for various aspects of the environment, including water quality, human health and animal safety. 'Willingness to pay' survey methodology was used to acquire an environmental cost range for insecticide use. Maine potato producers are willing to pay between $1.00 acre -1 (one acre = 0.4047ha) and $26.80acre -1 to avoid or reduce environmental risk associated with a single insecticide application. The Aroostook producer survey indicates that producers with small farms are generally willing to pay more to avoid or reduce environmental risk than producers with large farms. Mean Maine potato farm size has more than tripled over the past 40 years; therefore, concern for environmental quality on Maine potato farms could be decreasing.

Control strategies for the lucerne flea, Sminthurus viridis (L.) (Collembola: Sminthuridae), and their effect on other species in irrigated lucerne in the Hunter dairying region of New South Wales

AbstractThe lucerne flea, Sminthurus viridis (L.), was shown to be capable of causing significant yield loss and reductions in percentage lucerne crown cover of stands of irrigated lucerne in the temperate‐type climate of the Hunter dairying region of New South Wales, an area previously considered unsuitable for lucerne flea establishment. Chlorpyrifos was used in tests of three control strategies, each of which effectively reduced lucerne flea numbers. Prophylactic sprays in autumn to prevent females of the second generation after aestivation from ovipositing gave protection for up to 3 months, but did not remove the necessity for later treatments. A single application of insecticide when lucerne flea was starting to cause severe damage was the most effective and economical control strategy but was difficult to time correctly. Some other pest and beneficial species were affected by the lucerne flea control strategies and this may have to be considered in pest management. Strategies for controlling lucerne flea were also capable of reducing numbers of redlegged earth mites, Halotydeus destructor (Tucker).

Efficacy of Insecticides for Control of Thrips on Onions, 1992

Abstract Nine insecticides were tested for control of thrips on onions grown in a Bernow series fine, sandy loam soil at the Wes Watkins Agricultural Research &amp; Extension Center in Lane, OK. Onions were direct seeded into beds spaced 6 ft apart on 12 Sep, 1991 and thinned to 3 inch intervals on 4 Mar, 1992. Plots measuring 4 rows by 12 ft (0.0066 acre) and 10 ft buffers within rows were arranged in a randomized complete block design with 3 replications. A bed planted to wheat and rye bordered each side of all plots to minimize drift. Populations were assessed by counting all thrips larvae and adults on 5 plants/plot on 5, 8 and 12 Jun. A single insecticide application was made on 5 Jun after pretreatment counts with a CO2-powered backpack sprayer equipped with 2 hollow cone TX-18 nozzles/row that delivered 45 gal/acre at 40 psi. Adult thrips collected 4 Jun from untreated plots were determined to be 86% Frankliniella fusca and 14% Frankliniella occidentalis. Data were transformed [log (x + 1)] and analyzed using analysis of variance (ANOVA, SAS 1988) and means were separated using Ryan’s Q test.

Squash Bug Control on Watermelon, 1989

Abstract The efficacy of several insecticides was investigated in a test with small plots of watermelon grown on a clay laom soil at the Oklahoma Agricultural Experiment Station near Stillwater. Plots were established on 18 May by transplanting seedling plants into plastic mulch. Experimental plots were 30 ft long by 10 ft wide, arranged in a randomized complete block design and replicated 4 times. A single insecticide application was made on 11 Aug, using a CO2 powered backpack sprayer delivering 30 gal/acre at 50 psi through 3 TX-18 hollow-cone nozzles Efficacy of treatments was assessed by randomly selecting 4 areas (1 m2) in each plot and counting squash bug nymphs on all plant parts and the mulch surface within each sample quadrant. Counts were made on 12 Aug (1 DAT), 15 Aug (4 DAT), and 18 Aug (7 DAT). Data were subjected to ANOVA and DMRT.

Control on Watermelon, 1988

Abstract The efficacy of several insecticides was investigated in 2 tests with small plots of watermelons grown on a sandy loam soil near Hinton, Okla. Plots in each test were 30 ft long by 6 ft wide, and each treatment was replicated 3 times. A single insecticide application was made on 1 Sep 1988 using a CO2-powered backpack sprayer. The sprayer delivered 28 gal/acre at 60 psi through 2 TX-10 hollow-cone nozzles. Rigo crop oil concentrate was added to the RH-7988 treatments at the rate of 1 qt/acre to improve leaf penetration. Efficacy was assessed by counting aphids (alate and apterous) on 15 leaves randomly selected from each plot. Counts were made on 5 Sep (4 DAT), 8 Sep (7 DAT), and 15 Sep (14 DAT). Henderson's formula was used to calculate percentage of control for each treatment.