Efficacy of Helicoverpa Armigera Nucleopolyhedrovirus on Soybean for Control of Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae) in Arkansas Agriculture

Helicoverpa armigera nucleopolyhedrovirus (HearNPV) is a naturally occurring virus commercially produced for control of Heliothines, including Helicoverpa zea. One drawback with using this virus for control has been the slower time to mortality compared with synthetic insecticides. However, a new formulation (Heligen®) has anecdotally been thought to result in quicker mortality than previously observed. The objective of this study was to evaluate percent defoliation, the efficacy of HearNPV on mortality for each H. zea larval instar, and the potential for control of a second infestation. Fourteen days after the first infestation, all plants were re-infested with a second instar larva to simulate a second infestation. Helicoverpa armigera nucleopolyhedrovirus was effective at killing 1st–3rd instars, resulting in 99% mortality over 4–6 days. However, 4th and 5th instar mortality only reached 35%. Second infestation larvae died between 3.4 and 3.8 days, significantly faster than the 1st infestation of 2nd instars, which had a mean time to mortality of 4.9 days. An increase in mortality rate is probably due to increasing viral concentrations after viral replication within the first hosts. Final defoliation percentages were significantly smaller in the treated plants versus the untreated plants. Only 3rd and 4th instar larvae caused percent defoliation to exceed the current Arkansas action threshold of 40%. Helicoverpa armigera nucleopolyhedrovirus in the Heligen formulation can control 1st–3rd instars within 4–6 days, while keeping defoliation below the action threshold of 40%.

Dynamic Analysis of a Phytoplankton-Fish Model with the Impulsive Feedback Control Depending on the Fish Density and Its Changing Rate

This paper proposes a comprehensive fishing strategy that takes into consideration the population density of fish and its current growth rate, which provides new ideas for fishing strategies. Firstly, we establish a phytoplankton-fish model with the impulsive feedback control depending on the density and rate of change of the fish. Secondly, the complex phase and impulse sets of this model are divided into three cases, then the Poincar´e map for the model is defined, and analyzed the properties of Poincar´e map. In addition, the sufficient and necessary conditions for the global asymptotic stability of the order-1 periodic solution and existence condition of order- k ( k ≥ 2) periodic solution are discussed. The action threshold depends on the density and rate of change of the fish, which is reasonable than earlier studies. The analysis method proposed in this paper also plays an important role in the analysis of impulse models with complex phase sets or impulse sets.

Evaluation of fungicide efficacy on sunflower rust (Puccinia helianthi) on oilseed and confection sunflower

Sunflower rust, caused by Puccinia helianthi, is an economically and globally important disease of sunflower. Two types of sunflowers are produced in the US Northern Great Plains; the oilseed type and the confection type. Although approximately 80% of the acreage in this region is planted as the oilseed type sunflower, fungicide efficacy and timing studies have been conducted primarily on the more rust-susceptible confection type. A total of ten sunflower rust efficacy field experiments were conducted on oilseed type and confectionary type hybrid trials from 2016-2018. Eleven fungicides from three FRAC groups were evaluated for efficacy and protection of yield. Severity differences among fungicide treatments were identified in both confection and oilseed type sunflower trials. A combined analysis of all confection field trials (five) indicated that rust severity was lower in all fungicide treatments as compared to the non-treated control. Despite rust severity levels below the fungicide action threshold for confection sunflower, seven of the eleven fungicide treatments had yield higher than the non-treated control. In oilseed trials, rust severity was lower in all fungicide treatments as compared to the non-treated control, similar to the findings of the confection type. Rust severity was too low to detect yield differences in oilseed trials. Additional work is needed to elucidate yield-loss potential on oilseed type sunflower and refine the fungicide action threshold on confection type sunflower.

Pengaruh pengelolaan agroekosistem terhadap kelimpahan kutu loncat jeruk Diaphorina citri Kuwayama (Hemiptera: Liviidae)

Asian citrus psyllid (ACP) Diaphorina citri Kuwayama is a serious problem in citrus because it transmits huanglongbing (HLB) disease. Agricultural practices without paying attention to the agroecosystem complexity often cause the agroecosystem more suitable for insect pests proliferation and less friendly to natural enemies. The research aims to study the effectiveness of agroecosystem management compared to conventional farming in the ACP control. The effects of both treatments on the diversity and abundance of ACP’s natural enemies as well as the incidence and severity of HLB were also studied. Agroecosystem management consists of preventive and responsive actions. Preventive action was carried out through a polyculture system, planting refugia and legume cover crop, providing beetle banks, applying lime, applying organic and inorganic fertilizers, citrus pruning intensively, maintaining drainage ditches, and mechanical weed control. Responsive action is short-term control when the abundance of ACP reaches the action threshold. Responsive action was carried out through biological or chemical control. Meanwhile, conventional farming is a series of conventional farming and pest control techniques commonly applied by farmers. Each treatment was applied in three orchards of Siam Orange cv. Pontianak Citrus nobilis Lour var. microcarpa Hassk. The results showed that agroecosystem management was more effective in controlling the ACP population so that its abundance was lower and less fluctuated than conventional farming. ACP’s natural enemies in agroecosystem management were also more diverse than conventional farming. The abundance of ACP’s natural enemies and the incidence and severity of HLB in the two treatments were not significantly different.

Dynamic Analysis of a Plankton-Herbivore State-Dependent Impulsive Model With Action Threshold Depending On The Density and Its Changing Rate

A plankton-herbivore state-dependent impulsive model with nonlinear impulsive functions and action threshold including population density and rate of change is proposed. Since the use of action threshold makes the model have complex phase set and pulse set, we adopt the Poincaré map as a tool to study its complex dynamics. The Poincaré map is defined on the phase set and its properties in different situations are analyzed. Furthermore, the periodic solution of model are discussed, including the existence and stability conditions of the order-1 periodic solution and the existence of the order-k (k ≥ 2) periodic solutions. Compared with the fixed threshold in the existing literature, our results show that the use of action threshold is more practical, which is conducive to the sustainable development of population and makes people obtain more economic benefits. The analysis method used in this paper can study the complex dynamics of the model more comprehensively and deeply.

Exceeding the threshold value for Trioza apicalis Förster 1848 in carrot fields did not cause damage as revealed during monitoring in Germany from 2017–2020

The carrot psyllid Trioza apicalis Förster 1848 is a carrot pest in Europe that can cause serious damages in case of massive occurrence. Damages up to a total loss of yield have been reported from Scandinavian countries but also from Switzerland. The action threshold to control the pest with chemical pesticides is 0.2 T. apicalis per day and trap caught by sticky traps. We investigated the number of T. apicalis with sticky traps on carrot fields of the study regions Lüneburg/Uelzen and Hameln/Bad Pyrmont in Germany, during the period 2017–2020. The number of T. apicalis caught was generally very low in both study regions. On several fields in successive weeks almost no individuals were found in the study region Hameln/Bad Pyrmont. In Lüneburg/Uelzen was at least one field each year where the number of carrot psyllid was clearly higher than in all other fields and exceeded the threshold level. Surprisingly on carrot fields in close proximity to carrot fields from the previous year, the T. apicalis numbers were only slightly increased. Nonetheless, no loss of yield was reported for any of the fields in the four years of the study, although the generally defined threshold has been exceeded on many of the investigated carrot fields.

Intraplant Distribution, Preferred Sites, and Damage Caused by Euschistus heros (Hemiptera: Pentatomidae) on Cotton

This study investigated (a) the intraplant distribution of Euschistus heros (F.) (Hemiptera: Pentatomidae) in cotton, (b) its preference for different structures and areas of the cotton plant, and (c) the damage caused at different levels of infestation. Our results determined that, regardless of the time of day, E. heros adults significantly preferred the middle third of cotton plants in comparison to the upper and lower areas (F = 30.221; df = 2; P = 0.001). The adults were present on all cotton structures, and numbers were significantly higher on bolls and leaves/branches (F = 25.333; df = 5; P = 0.001) than on flower buds and flowers. In greenhouse tests, fiber yield, number of bolls per plant, and number of internal punctures in bolls responded significantly to increasing infestation levels of E. heros adults. Damage and yield reduction was observed at 1.5 to 2.0 adults/plant, indicating that an action threshold of 1 adult per plant should be adopted to avoid economic losses. Sampling during boll development should be by either whole-plant inspection or beat cloth methods between 0600 and 1800 h.

Sustainable management of the vine mealybug in organic vineyards

The vine mealybug (VMB), Planococcus ficus, is a major grapevine pest worldwide, whose chemical control is often unsatisfactory due to its cryptic behavior, insecticide resistance and high fecundity rate. Recently, increasing restrictions have been applied to insecticides used for managing VMB. This review discusses sustainable VMB management strategies in organic viticulture. Pheromone-mediated mating disruption has been proved to be effective in both organic wine and table-grape vineyards. Biocontrol projects carried out through the release of parasitoids and/or predators have often provided inconclusive results, ranging from effective reduction of mealybug infestation to a marginal impact of parasitoids on VMB density. The latter outcome is likely due to constraints affecting the parasitoid activity, such as the disrupting activity of mealybug-tending ants and broad-spectrum insecticides, or untimely release of parasitoids. Ant suppression should be associated with the release of beneficial organisms, as mealybug-tending ants can severely affect the parasitoid activity. Cultural and physical control and the employment of entomopathogens and natural products mitigate the buildup of VMB populations, but they are not widely applied. VMB control in organic viticulture requires the integration of different strategies, as application of single control tools as a stand-alone treatment may not be effective, especially for high pest infestation. Future research to determine the density action threshold below which sustainable methods are effective and calibrate efforts in relation with pest infestation is needed. A multi-disciplinary approach is required to define the most appropriate sustainable control protocols in different environmental conditions and promote a further spread of organic viticulture.

Review of Methods to Monitor House Fly (Musca domestica) Abundance and Activity

The house fly is a ubiquitous pest commonly associated with animal facilities and urban waste. When present in large numbers, house flies can negatively impact humans and animals through nuisance and the transmission of pathogens. Since the development of fly traps and sticky papers to capture flies in the late 1800s, these and other methods have been used as a means to monitor change in house fly density or fly activity over time. Methods include substrate sampling to record density of immature flies, visual observations of adult fly activity, instantaneous counts of landing or resting flies, accumulation of adult flies on/in traps, or accumulation of fly fecal and regurgitation spots deposited by flies onto white cards. These methods do not estimate true house fly density, but rather provide an index of house fly activity that is related to both fly density and the frequency of individual fly behavior (e.g., frequency of flight, landing events) and which is likely more predictive of negative impacts such as nuisance and pathogen transmission. Routine monitoring of house fly activity is a critical component of a house fly management program. Fly activity should be held to a level below a predetermined activity threshold ('action threshold') above which negative impacts are anticipated to occur. This article is a review of methods utilized for monitoring house fly (Diptera: Muscidae) activity.