Dynamics of economic injury levels for cotton pink bollworm (Pectinophora gossypiella Saunders) in relation to control cost, cotton price and control efficacy

Economic injury levels for Bemisia tabaci (Homoptera: Aleyrodidae) in cotton: impact of crop price, control costs, and efficacy of control

Levels of economic insect damage and their effects on crop production are the most often-discussed issue in insect management today. The economic injury level (EIL) concept is the base for decision-making in most integrated pest management (IPM) programs. IPM programs are fundamentally different from control approaches that handle insect problems by focusing on tolerating insect effects. EIL is essential for IPM programs as it indicates which levels of insect populations can be tolerated and which cannot. By increasing our ability to tolerate insects, it is possible to eliminate or reduce the need for management tactics. Scientists can maintain environmental quality through better decisions on the use of those tactics. EILs help maintain environmental quality by reducing unnecessary use of management tactics, especially insecticides. However, including environmental considerations explicitly in the decision-making process could greatly improve the ability of IPM to sustain environmental quality. The EIL components include economic damage, economic thresholds, and the EIL itself. Increased availability of calculated EILs and their related economic thresholds would reduce unnecessary use of management tactics. An environmental EIL evaluates a management tactic based not only on its direct costs and benefits to the user but also on its effects on the environment. There are many factors that can reduce crop yield. One important cause is insects. Insects that cause loss to the fruits are frequently more destructive than those that damage leaves, stems and roots. For example, cotton is infested by Spodoptera littoralis (Boisd.), Pectinophora gossypiella (Saund.), Helicoverpa armigera (Hün.) and Earias insulana (Boisd.) cause the greatest yield losses. The amount of yield loss is dependent upon a number of factors, i.e., plant variety, soil fertility, insect population and skill in handling crop production, etc. Comparatively tolerant varieties, even at the cost of slightly less yield potential, will be more suitable under such conditions.

<i>Bioeconomic models explaining the relationship between spring barley yield and density of</i> Diuraphis noxia <i>(Mordvilko) were determined by conducting caged field infestation experiments at 3 plant growth stages during 1992 and 1993 in northern Idaho. Barley grain weight per plant and number of kernels per plant declined as quadratic functions of aphid density at the two-leaf (ZGS=12) and flag-leaf (ZGS=39 to 41) plant growth stages. No significant yield loss occurred when plants were infested at flowering or medium milk stages. Infestations did not affect grain protein content. Economic injury levels (EILs) expressed as initial</i> D. noxia <i>density and as cumulative aphid-days were computed as functions of pest control costs, barley crop market values, and control efficacy. Given crop value of $2.00 per bushel and insecticide cost of $15 per acre, control is justified only when density exceeds 1.4</i> D. noxia <i>per plant at the beginning of 2-leaf stage spring barley. Expressed as aphid-days, control is warranted only if one expects pest intensity&gt; to exceed 26 aphid-days during the 14 d following the 2-leaf stage. EILs during the flag-leaf stage were derived for specific weather conditions, in particular, given barley valued at $2.00 per bushel and $15 per acre control costs, EILs during warm and dry• seasons are 7.6</i> D. noxia <i>per plant at the beginning of the flag-leaf stage (or 91 aphid-days per plant). Under the same economic conditions during cool and wet seasons, EILs during the flag-leaf stage are 4.2</i> D. noxia <i>per plant (or 63 aphid-days per plant).</i>

Economic damage levels and treatment thresholds for leafminer insects in Solanum tuberosum crops

In experiments to find the yield loss in soyabean due to the leaf miner, Aproaerema modicella (Deventer) and estimate the economic injury level (EIL), plants were infested at 30 and 45 days after sowing (DAS) with a fixed number of laboratory reared second instar larvae. Grain yield was not reduced by one larva per plant at both 30 and 45 DAS, but the yield reduction which ranged from 2.7 to 6.1% was significant with two larvae per plant at both the ages. With an increase in larval population, there was a corresponding decrease in yield to the extent of 40% and 66% with 10 larvae/plant at 30 and 45 DAS respectively. The regression of yield of leaf miner infestation indicated that yield was reduced by 0.463 and 0.716 g per plant for every larva per plant at 30 and 45 DAS respectively. Yield loss was greater in plants infested at 45 DAS than at 30 DAS with all populations tested. The estimated economic injury level for A. modicella is 0.6 larva/plant at 30 DAS, and 0.2 larva/plant at 45 DAS. The suggested economic threshold level in soyabean of 85–90 days duration is 0.5 larva/plant (1 larva/2 plants) at 30 DAS and 0.2 larva/plant (1 larva/5 plants) at 45 DAS.

Sampling and development of economic injury levels for Anthonomus rubi Herbst adults

Identifying the competitive ability of corn hybrids and the economic injury level (EIL) caused by Urochloa plantaginea is important for the adoption of integrated management of this weed. This work aims to evaluate the interference and EIL of U. plantaginea infesting corn hybrids. Treatments included the corn hybrids Syngenta Status VIP3, Syngenta SX8394 VIP3, Pioneer P1630H, Pioneer 30F53 YH, and Dow 135021, as well as 12 densities of U. plantaginea for each hybrid. We used a rectangular hyperbolic model to describe the relationship between corn grain productivity loss and the explanatory variables — plant density (PD), dry mass (DM) of the aerial parts, ground cover (GC), and leaf area (LA). EIL was determined using grain productivity, control cost, corn price, and herbicide efficacy. The rectangular hyperbolic model provides a satisfactory estimate of grain productivity loss regarding the interference of U. plantaginea in corn culture. The hybrids Pioneer 30F53 YH and Pioneer P1630H presented better competitiveness and higher EIL. Sowing the hybrids Pioneer P1630H, Pioneer 30F53 YH, and Dow 135021 increased EIL, justifying the adoption of control measures for U. plantaginea at higher densities.

Specifying the relationship between pests and their host plants in terms of damage is one of the basic concepts of integrated pest management (IPM) programmes. The crop loss and economic injury level (EIL) of Tuta absoluta (Lepidoptera: Gelechiidae) were determined on different tomato cultivars using gain threshold (field experiment) and regression (semi‐field experiment) methods. By assessing the crop loss in 2015 and 2016, four out of seven infested tomato cultivars had a significant yield loss in terms of weight of total fruits versus the control under the open‐field conditions. However, the total number of tomato cultivars had no significant difference to control treatment. The semi‐field experiment included six treatments (0, 2, 4, 6, 8 and 10 gravid females/plant) and examined two tomato cultivars. The tomato cages with between 6 and 10 gravid females/plant showed the highest number and weight of damaged fruits. Based on pesticide control costs, the market value of tomato and the control efficacy, we determined the EIL for T. absoluta. In the field experiment, the EIL value for T. absoluta on “Petomech,” “Cal JN3,” “Rio Grande” and “Early Urbana Y” cultivars was 4.15, 4.47, 4.70 and 5.04 larvae per plant, respectively. Based on regression equations, we calculated the EIL values for T. absoluta on “Cal JN3” and “Early Urbana Y” to be 4.75 and 5.44 larvae/plant, respectively. Crop loss assessment and EIL are necessary components of cost‐effective IPM programs and can be effective tools for making decisions about the application of pesticides against T. absoluta.

Leucoptera coffeella (Lepidoptera: Lyonetiidae) is one of the main pests in coffee crops. The economic injury level (EIL) is the lowest density of the pest at which economic damages match the costs of control measures. The economic threshold (ET) is the density of the pest at which control measures must be taken so that this population does not reach the EIL. These are the main indices used for pest control decision-making. Control of L. coffeella is carried out by manual, tractor, airplane or drone applications. This work aimed to determine EILs and ETs for L. coffeella as a function of insecticide application technology in conventional and organic Coffea arabica crops. Data were collected over five years in commercial C. arabica crops on seven 100 ha central pivots. The cost of control in organic crops was 16.98% higher than conventional. The decreasing order of control cost was manual > drone > airplane > tractor application. Coffee plants were tolerant to low densities (up to 15% mined leaves) of the pest that caused losses of up to 6.56%. At high pest densities (54.20% mined leaves), losses were high (85.62%). In organic and conventional crops and with the use of different insecticide application technologies, EIL and ET were similar. The EIL and ET were 14% and 11% of mined leaves, respectively. Therefore, these indices can be incorporated in integrated pest management programs in C. arabica crops. The indices determined as a function of insecticide application technology in organic and conventional coffee are important as they serve producers with different technological levels. Additionally, EILs and ETs can contribute to more sustainable production, as control methods will only be employed when the pest density reaches these indices.

ice (Oryza sativa L.) ranks second to wheat in area and production on the global level.Unfortunately, it is attacked by several insect pests.The rice stem borer, Chilo agamemnon Bles. is the most important in Egypt.The current investigation was carried out at the Experimental Farm of Sakha Agricultural Station, Kafr EL-Sheikh Governorate in 2013 and 2014 rice seasons using two cultivars, Giza 178 (high tillering capacity) and Egyptian Jasmine (medium tillering capacity) to establish the correlation between borer infestation as white heads and rice yield losses to determine the economic threshold and injury levels of C.agamemnon infestation in rice fields.Due to the great difficulty to use the technique of artificial infestation by the rice stem borer, the simulated technique (panicle removal) was applied to induce different levels of simulated white heads.The panicles were removed by hand to get gradual levels of stimulated white heads; 0, 2, 4,6, 8, 10, 12, 14 and 16%.Yield components (panicle weight, 1000-grain weight and filled grain %) increased at the higher levels of panicle removal.This could be interpreted in the light of phenomenon compensation.This phenomenon suggests that the nutrients going to removed panicles are translocated to the adjacent ones.Consequently, the panicles adjacent to the removed ones become healthier than normal, and compensate, to a certain extent, the removed ones.The final grain yield was negatively affected, in the current study, by high levels of panicle removal.In Giza 178 rice cultivar (high tillering), the grain yields were 2315, 2295 and 2311, match to 1815, 1755 & 1781 g/ 2 m 2 at 0, 2 & 4% panicle removal, respectively.However, in both cultivars, the lowest grain yields were at 12, 14 1nd 16 % simulated white head (panicle removal).Considering the cost of chemical control against the rice stem borer, and obtained grain yield at different levels of simulated white heads, economic threshold and economic injury levels were estimated.In Giza 178, the economic threshold was determined as 10 and economic injury as 12 % white heads (panicle removal), while the economic threshold level of Egyptian Jasmine cultivar was determined as 8% white heads, and economic injury as 10% white heads.These results are important to the decision makers and rice growers to avoid using insecticides before the rice stem borer infestation reaches the economic threshold.On the other hand, economic threshold level should be assessed under several circumstances, e.g.location, cultivar, cultural practices, prices of insecticides and prices of rice.

The rice stalk stink bug Tibraca limbativentris Stal, 1860 (Hemiptera: Pentatomidae) is an important pest of paddy rice (Oryza sativa L.) in South America. Current records of economic injury levels (EILs) and economic thresholds (ETs) for this insect are scarce. In this study, we determined EILs and ETs through cumulative insect-days of T. limbativentris adults in two phenological stages of paddy rice. Five field trials were established for the 2015/16 and 2016/17 crop season. To evaluate the relationship between insect-day and yield, rice plants were infested at V4 and R2 with adult male-female pairs of T. limbativentris. Mixed linear models were fitted utilizing the year and block as random factors to estimate the damage to plant, irrespective of the interference of environmental factors. The yield loss per insect-day was then used to calculate EILs using current market values and control costs. Rice grain yields were reduced by 5.91 kg/ha for each insect-day/m2 when infested during V4 stage, with EILs ranging from 3.88 to 11.61 insect-days/m2, while infestation during R2 stage resulted in a yield reduction of 3.16 kg/ha, with EILs ranging from 8.05 to 21.72 insect-days/m2. The results indicate that yield losses of paddy rice due to T. limbativentris infestation vary according to plant phenological stages and management should consider control cost and market value of rice. These EILs and ETs based on insect-days may be an efficient strategy for decision-making in the management of T. limbativentris on paddy rice.

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.

Although transgenic cotton producing insecticidal proteins from Bacillus thuringiensis (Bt) is a cornerstone for pink bollworm control in some countries, integrated pest management remains important for bolstering sustainability of Bt cotton and is critical for controlling pink bollworm where Bt cotton is not available or where this pest has evolved resistance to Bt cotton. Here, we used data on moth captures in gossyplure-baited pheromone traps and boll infestations for 163 Bt and 152 non-Bt cotton fields from Arizona to evaluate accuracy of chemical control decisions relying on moth trapping data and capacity of Bt cotton to suppress survival of offspring produced by moths. Assuming an economic injury level of 12% boll infestation, the accuracy of decisions based on moth captures corresponding to economic thresholds of 6%, 8%, and 10% boll infestation increased from 44.7% to 67.1%. The association between moth captures and boll infestation was positive and significant for non-Bt cotton fields but was not significant for Bt cotton fields. Although chemical control decisions based on trapping data were only moderately accurate, pheromone traps could still be valuable for determining when moth populations are high enough to trigger boll sampling to more rigorously evaluate the need for insecticide sprays.

Economic injury level and sequential sampling plan for Liriomyza huidobrensis management in tomato crops

Plutella xylostella (L.) is a microlepidopteran found in all brassica-producing regions of the world. However, no economic injury level (EIL) has been established for this pest in collard greens. Therefore, studies evaluating the EIL of P. xylostella in this crop based on the number of caterpillars per plant can assist pest monitoring and the most effective time for pest control, ensuring profits and the use of pesticides only when required. The present study assessed leaf consumption of caterpillars at different levels of infestation and determinined the EIL for P. xylostella in collard greens. Based on the yield reduction index of collard greens for P. xylostella, EIL was estimated for different scenarios of pest control costs, setting the market value of the bunch of collard greens, and, alternatively, with prices varying and the control cost fixed. In simulated scenarios for 7 d after infestation, the number of caterpillars per plant was always below 1.38, whereas for 10 d, the maximum number was 1.25 caterpillars per plant. When simulating scenarios with different market values for the bunch of collard greens the lower the price of the collard greens bunch, the higher the mean number of caterpillars per plant to compensate the application cost. The mean number of caterpillars per plant ranged from 4.59 to 0.38 in the evaluation for 7 d, and from 4.17 to 0.35 caterpillars per plant for 10 d according to the price of the bunch of collard greens.