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Pollen beetle (Meligethes aeneus F.) (PB) is one of the most serious pest in rapeseed cultivations in Poland and in other European countries. The pest is known because of its high metabolic potency towards various toxins. Constant and strong selective pressure of different insecticides used to control this pest, has resulted in resistance of PB to many active substances. In connection with this situation, constant monitoring of pollen beetle susceptibility level to all recommended active substances of insecticides is necessary. The objective of the study was to determine the effectiveness of active substances, most often used in Western Poland for PB control. Resistance of pollen beetle to some pyrethroid active substances and organophosphorous insecticide — phosalone and high susceptibility to chlorpyrifos-ethyl was found. Resistance of pollen beetle requires constant insecticide susceptibility level monitoring and using IRM strategy.
Following the limitations regarding the use of the neonicotinoids: clothianidin, thiamethoxam and imidacloprid there are no currently available insecticide seed dressings for oilseed rape in Poland. For maize here is only one seed dressing containing methiocarb available with a very narrow registered scope of use. The impact of limitations on protection possibilities of other major Polish agricultural crops is either negligible or non-existent. In consequence a group of economically important insect pests of maize [dungbeetles (Melolonthidae); click beetles (Elateridae); noctuid moths (Agrotinae)] and oilseed rape [leaf miners (Agromyzidae), turnip sawfly (Athalia colibri Christ.), cabbage weevils (Curculionidae), cabbage root fly (Hylemyia brassicae Bche.), diamond-back moth (Plutella maculipennis Curt.)] is left without any legal possibility of chemical control. For the other important pests of the early growth stage of oilseed rape development, there are only pyrethroids available together with one product containing chloropiryfos that can be applied once per vegetation season. Since both maize and oilseed rape are grown in Poland on the area of approximately 1 million ha (each crop), this situation raises concerns about production possibilities as well as development of pest resistance.
The cotton leafhopper (Amrasca biguttula biguttula Ishida) is considered to be an alarming insect pest causing both quantitative and qualitative loss in cotton. In situ bioassay studies were done and the role of detoxifying enzymes in conferring resistance to neonicotinoid groups of insecticides in low (MUD), medium (DVG), high (HVR) and very high (GLB) pesticide usage areas of Karnataka were determined. Bioassay studies showed that imidacloprid, thiamethoxam, acetamiprid, thiacloprid and clothianidin registered varying levels of resistance for all the locations studied. The resistance ratio was high in imidacloprid (3.35, 8.57, 9.15 and 12.27 fold respectively) and the lowest in dinoferuran (1.86, 5.13, 6.71 and 9.88 fold respectively). Furthermore, the enzyme activity ratio (glutathione-S-transferase) was relatively greater, and corresponded to the higher LC50 values of neonicotinoids for very high, high, medium and low pesticide usage areas. Our study suggested that the higher activity of the detoxifying enzyme in the resistance population of cotton leafhopper apparently has a significant role in endowing resistance to neonicotinoid groups of insecticides. However, this study recommends using neonicotinoids in cotton growing areas with caution.
The strawberry root weevil (Otiorhynchus ovatus L.) is an important pest on strawberry plantations in Poland. Neonicotinoid insecticides: thiametoxam as Actara 25 WG, thiacloprid as Calypso 480 SC, and acetamiprid as Mospilan 20 SP gave good control of the strawberry root weevil on strawberry plantations. The obtained results were better or similar to those obtained with chloropiryfos, diazinon and feni- trothion. Also fipronil (phenopyrazole group) showed very high efficacy in the con­trol of strawberry root weevil.
Responses (knock-down and mortality) of large pine weevil (Hylobius abietis L.) beetles to insecticides of different mechanism of action such as neonicotinoids (clotianidin, acetamiprid) acting on nicotinic receptors of acetylcholine (ACh), pyrethroids (deltamethrin, α-cypermethrin) blocking sodium channels in nerve cell membranes, organophosphates (chlorpiryfos) and carbamates (carbosulfan) both inhibiting acetylcholinesterase (AChE) activity and fenylpirazoles (fipronil) interfering with γ-butyric acid (GABA) receptors were studied. Taking into account speed of insect decay the order of examined groups of substances may be established as follows: first place is occupied by insecticides interferring with GABA receptors, second place by insecticides blocking AChE activity, and third place in parallel insecticides blocking sodium channels and those acting on nicotinic receptors of ACh.
Efforts have been made during the past three decades to develop insecticides with selective properties that act specifically on biochemical sites present in a particular insect group, but whose properties differ from those present in mammals. This approach has led to the discovery of compounds that affect the hormonal regulation of molting and developmental processes in insects such as ecdysone agonists, juvenile hormone (JH) mimics and chitin synthesis inhibitors. The search for potent acylureas has led to the development of novaluron (Rimon) developed by Makhteshim Chemical Works. The LC-50 value of novaluron on 3rd-instar Spodoptera littoralis fed on treated leaves is approximately 0.1 mg a.i./liter. This value resembles that of chlorfluazuron and is tenfold lower than that of teflubenzuron. Novaluron affects nymphs of Bemisia tabaci more than chlorfluazuron and teflubenzuron. Artificial rain, at a rate of 40 mm/h applied 5 and 24 h after treatment in a cotton field had no appreciable effect on the potency of novaluron on both S. littoralis larvae and B. tabaci nymphs. Hence, novaluron can be used in tropical areas and during rainy seasons. In general, benzoylphenyl ureas had no direct effect on parasitoids and phytoseiids and are considered mildly affect other natural enemies. Novaluron has no cross-resistance with conventional insecticides, the JH mimics pyriproxyfen and neonicotinoids. As such, it is considered an important compound in pest management programs.
Pollen beetle (Meligethes aeneus F.) and cabbage seed weevil (Ceutorhynchus assimilis Payk.) occur very often at the same time in winter and spring oilseed rape in Polish climatic conditions. The aim of the study was to determine the susceptibility of pollen beetle and cabbage shoot weevil to the same, selected active substances of insecticides from the group of pyrethroids, organophosphates and neonicotinoids recommended in Poland. The studies were conducted with the use of contact-stomach method, which involves tested beetles exposition to treated leaves and inflorescences of host plants. The results indicated high or very high pollen beetle resistance to pyrethroid active substances (the exception was tau-fluwaliant to which the pest showed susceptibility or weak resistance) and some level of cabbage seed weevil resistance to neonicotinoids. The results clearly indicate that the protection of oilseed rape in Poland requires continuous monitoring of resistance level of both pests and regular update of control programs for both species.
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