Use Your New Control Options in Pest Control: Focus on Codling Moth and Leafrollers

Use Your New Control Options in Pest Control: Focus on Codling Moth and Leafrollers Jay F. Brunner, Mike Doerr and Keith Granger Washington State University Tree Fruit Research and Extension Center, Wenatchee, WA Today there are several options to consider for control of codling moth (CM) and leafrollers (LR). Following the passage of the Food Quality Protection Act of 1996 the fruit industry was greatly concerned that it would lose access to many frequently used insecticides or that the use of these products would be severely restricted. This has, in fact, occurred over the past 8 years with products like methyl-parathion (Penncap-M), which is no longer available; chlorpyrifos (Lorsban), which has been restricted to use during the prebloom period; and azinphosmethyl (Guthion), which now has restrictions on the amount used per application and per year along with an extended re-entry interval (14 days). Another concern of the fruit industry was that, while they were losing older insecticide products, new products would be very slow to become registered. The fear was that chemical control tools, especially for the most important pests, would decline to a very few. History has shown that the industry s worst fears have not come to fruition. Today we have more insecticides registered for CM and LR control than we did prior to 1996. However, growers and crop consultants are now faced with deciding how best to choose from the available insecticides to achieve control of these pests. Codling moth control tactics. Table 1 shows the products that are registered and useful for managing CM in apple orchards. The organophosphate (OP) insecticides have been used almost exclusively for CM control since the 1960s. These products have provided excellent crop protection at a reasonable cost. When conducting efficacy trials with new insecticides we include an untreated control and an industry standard, usually Guthion, as a comparison. We are therefore able to compare the level of crop protection provided by a new insecticide to a product such as Guthion for which we have years of experience. Fig. 1 summarizes the results of our efficacy evaluations of new insecticides over the last three years, 2002-2004. These data are presented as the percentage that each treatment reduced successful CM entries/fruit relative to an untreated control. For example, Guthion reduced CM entries/fruit (successful entry of a larva into the fruit) an average of 98%. That is, there were 98% fewer CM entries/fruit than observed in the untreated control. CM populations in our test plots are extremely high. We typically record 70% or more injured fruit at harvest in untreated controls with each fruit averaging about 2 entries. Under these conditions we can easily separate the most effective insecticides from those that are ineffective or those that could be acceptable under less pest pressure. From Fig. 1 it is clear that there are new insecticides that have very good efficacy against CM. Warrior, a relatively new pyrethroid, provides fruit protection nearly equal to that of Guthion. Success, or the organic formulation of this product, Entrust, also provides a high degree of fruit protection. Proclaim, a product not yet registered for use on apple, also 1

provides excellent protection from entries but (data not shown) allows a high percentage of stings. Stings occur when the CM larva eats through the apple skin but dies soon thereafter. A scar is produced that can downgrade fruit. Rimon, a new insecticide that should be available for use on apple in 2005, provides excellent CM control. And finally, two of the neonicotinyl insecticides, Assail and Calypso, provide very good fruit protection. Clutch, in the same class as Assail and Calypso (neonicotinyl insecticides) has not proven to be a effective against CM. Other insecticides that do not provide a high degree of fruit protection, less than 90% suppression (e.g. Intrepid, oil, Cyd-X, Esteem - Fig. 1), can still be useful as part of a CM control program. These programs will be discussed later. The list of insecticides that are effective against LR is smaller than that for CM. Table 2 lists only one traditional insecticide, Lorsban, that is effective and registered for use, and this product is restricted to the prebloom period. The pyrethroid insecticides are effective against LR but are not usually recommended because they disrupt integrated mite control and result in increased problems with spider mites. The neonicotinyl insecticides are not effective against LR. Success and Bt products (e.g. Dipel 2X, Javelin, MVP) are effective for LR suppression and, in fact, Success has become an industry standard for postbloom control of this pest. All the insect growth regulators are active against LR. Avaunt has shown activity against LR in small plot trials, but evidence from one field population, plus data from other fruit growing regions, indicates that Avaunt has strong cross-resistance to OP insecticides and would therefore likely fail to provide control of most LR populations in Washington. When registered, Proclaim will offer another effective control option for LR. Some insecticides provide control of both CM and LR. These are Intrepid, Esteem, Rimon, and Success. Growers can take advantage of this information when developing management programs for their orchards. The list of products, new and old, that will provide control of CM, LR or both includes 13 insecticides, not counting the pyrethroids. Because of their negative effects on integrated mite control, the use of pyrethroids should be restricted to situations where CM or LR cannot, for whatever reason, be controlled using other means. Knowing how different insecticides work and the life stages they affect is important to understanding how to use them in a management program. Ovicides are products that kill eggs. CM eggs are deposited on the upper surfaces of leaves or on developing fruit. Some CM ovicides (egg killers) work if they are applied over the top of the egg, that is, topically (Fig. 2). Examples of these products are mineral oil, Assail and Calypso. Other ovicides work if they are applied prior to egg deposition, that is, the CM egg is deposited on top of a residue. Esteem works in this way. Intrepid and Rimon are examples of ovicides that work either topically or as a residue. Larvicides are products that kill an insect s larval stage. For CM, the window of opportunity to kill the larva is very short, after it has hatched and as it attempts to enter the fruit. Most CM eggs are deposited on leaves of fruiting clusters or directly on fruit. A 2

CM larva hatching from an egg placed on a leaf has the ability to find a fruit and enter it within a few hours. Traditional insecticides (Guthion, Imidan, Sevin, Warrior, Danitol and Asana) are highly toxic by contact. That is, a CM larva can be killed by just walking across residues of these products. The newer insecticides (Assail, Calypso, Intrepid, Rimon and Proclaim) have very little contact activity. Their main effect comes when the CM larva consumes the insecticide as it attempts to enter the fruit. Some of these products allow more stings (shallow, unsuccessful entries) than traditional insecticides because the CM larva does not die until after it has partially or completely entered the fruit. This weakness is more of a problem in the second CM generation when scars left by stings are more evident. Table 3 gives characteristics of different insecticides or classes of insecticide. The first column is a relative estimate of efficacy against CM. Efficacy is presented as a range of the percentage an insecticide reduced fruit injury (entries plus stings) relative to an untreated control. The relative efficacy is based on a season-long control program using a particular insecticide. Each insecticide has its own unique timing and re-treatment interval based on the targeted life stage and length of residual control. For example, Guthion provides a high level of efficacy with 4 applications per season (2 per generation) while Sevin or Success applied 6 times (3 per generation) does not provide the level of control achieved with Guthion. The third column in this table is an approximate cost per acre of an application. These costs are for the insecticide only and do not include the expense required to make an application. The values presented are suggested retail prices provided by several agricultural chemical distributors. The range of cost reflects different application rates of different insecticides included in the row. Most of the newer insecticides are more expensive than the traditional insecticides those in the first three rows. This makes sense since newer technology costs more than older technology, no matter where you find it. The final column indicates the way different insecticides act on CM. The insecticides in the first three rows all affect CM larvae by contact, that is, walking across a residue of these products kills CM larvae. The other insecticides act either by ingestion (Assail, Calypso, Intrepid, CM virus, and Success) or direct contact with the CM egg (Esteem, Rimon, and mineral oil or Intrepid, which also acts as an ovicide). Spray coverage of the foliage and fruit is much more important with new insecticide technologies because CM larvae must ingest the insecticide while entering the fruit or eggs must come into direct contact with residues. If spray coverage was not optimal with older insecticides they would still provide some control of CM as they crawled across foliage and fruit contacting toxic residues. Sloppy application practices will not work with new insecticides. CM control failures with new insecticides will most likely arise from poor application practices. Based on the information provided in Table 3, it seems that there would be little incentive to use new insecticides for CM control when, in general, they are more expensive, require more applications, and require more precise application practices to achieve control similar to that achieved with OP insecticides. What, then, is the incentive to use new insecticides for CM control? There are, in fact, several that are outlined in Table 4. First, and maybe foremost, is the challenge of cholinesterase testing rules associated with the use of OP and carbamate insecticides. New insecticides either do not act as nerve poisons 3

or act in a very different and highly selective manner against the mammalian nervous system and, therefore, are not subject to the same testing required of OP and carbamate insecticides. If growers switched to using new insecticides for CM and LR control there would be no need for a cholinesterase testing program for Washington tree fruits. This alone should be a strong consideration for growers to consider switching to use of these products. The cost, inconvenience, and public perception associated with cholinesterase testing are not good for the fruit industry. Second, farm worker management is easier when using new insecticides. Because of their human safety these products have short worker re-entry intervals (REI) (4-12 hours). The short REIs of these products make scheduling intensive hand labor, such as fruit thinning, hand-tying and summer pruning, much easier. Third, the EPA has classified most of the new insecticides as reduced risk. This means they have very good safety profiles regarding nontarget organisms. In general, these products are low in toxicity to wildlife, fish and other aquatic organisms. The good environmental safety profile carries over to orchard pest management where we are trying to conserve biological control agents. Fourth, most of the new insecticides have a narrow spectrum of activity and thus do not destroy as many natural enemies in orchards. They are therefore better fits for IPM programs that attempt control tools that encourage biological control of pests. The fifth and final reason to consider a transition to new insecticides in orchard pest control programs is uncertainty associated with the future availability of OP and carbamate insecticides (Guthion, Imidan, Sevin, Lorsban). After 2005, the EPA will consider the future use of these products, at least Guthion and Imidan, in orchards. Depending on how evidence on worker safety turns out, their use could remain as it currently is or they could be banned or their use further restricted. Even if the cost of CM and LR control increased slightly due to a switch to new insecticides it seems reasonable that the upside on worker safety, worker management, environmental protection, and stability of pest management would encourage many growers to at least consider some use of these products now. Because there are so many insecticide choices to use for control of CM and LR it is not enough to know how effective how each product is but there needs to be some concept of how to incorporate different products into a sound and rational pest management program. The remainder of our discussion will focus on strategies for using new insecticides to control CM and LR. Though control of other pests needs to be considered, this discussion should help to begin the process of incorporating new insecticides into your overall pest management program. For this discussion, we will use a diagram of the CM life history showing time on both a temporal and degree-day scale with the generational duration of life stages shown as horizontal lines (Fig. 3). A traditional control program looks something like that shown in Fig. 3. It includes a prebloom oil plus Lorsban application that provides control of San 4

Jose scale (SJS) and suppression of LR, European red mite (ERM) eggs and overwintering aphid eggs. Success applied at petal fall, near the beginning of the CM egg-laying period, provides additional control of LR; and four OP insecticide treatments, three Guthion applications and one Imidan are used to achieve CM control. This traditional CM/LR control program is a conceptual representation of the norm for the 1980s and early 1990s. In the 1980s Parathion was often used in place of Lorsban, and Bt products were used in place of Success, which had not yet been registered. The number of Guthion or Imidan applications was less than shown, averaging only about 2.5 per season. In the 1990s, Lorsban replaced Parathion in the prebloom program (Parathion registration was cancelled by regulatory action), and Success gradually replaced Bt products in the petal fall period. The number of Guthion or Imidan applications against CM averaged slightly over 3 per season by the mid-1990s. As new insecticides have became available, growers started to substitute one or more products for the Guthion or Imidan treatments. This substitution approach is shown in Fig. 4. Assail or Calypso is substituted for Guthion in the second application (second cover). It is the short REI of Assail and Calypso that makes this substitution appealing. Since this is the time of year when fruit hand-thinning activities are starting use of products with short REIs makes it easier to manage workers who need to be in the orchard during this period. Fig. 4 shows Intrepid as a substitution for Guthion or Imidan in the second CM generation. Intrepid offers reasonable suppression of CM at this time if the first generation control program has been successful. While Intrepid does not provide the same degree of CM control as the products it replaces, it does offer good control of LR, which Guthion or Imidan do not. Mating disruption (MD) as a CM control tactic is included as a control tactic in Fig. 4. It is not necessary to include CM MD as part of a pest management program when introducing the use of new insecticide but its use always provides more robust crop protection. Figure 4 shows the option of using Lorsban, in the prebloom period, or Success at petal fall, for LR control. These products are necessary if LR densities, or a history of problems with this pest, justify their use. Would the cost of the program shown in Fig. 4 be higher than the traditional program? Yes, the short-term cost (considering only the expense of products) would be higher. A rough approximation of cost of the traditional CM/LR control program (Fig. 3) is $185/acre. The approximate cost of the program in Fig. 4, including the LR controls and assuming use of a half rate of MD, is $260/acre. If MD were not used, the cost of the CM/LR control program would decline by $50, to about $210/acre. No organophosphate programs: It is likely that growers will become more and more interested in implementing CM and LR control programs that do not rely on OP insecticides. In Fig. 5, we show a NO-OP program that should work as well as the OPbased program (Fig. 3) or the OP substitution program (Fig. 4). The program eliminates use of Lorsban, relying on oil only in the prebloom period for control of SJS and suppression of ERM and aphids. LR control is achieved in the postbloom period with the application of Rimon or Esteem at petal fall. Both of these products also provide suppression of CM because of their ovicidal activity. Assail or Calypso is used against larvae of the first CM generation. Intrepid, which also provides LR control, is used 5

against the second CM generation. MD is recommended for this kind of program, especially in the first year or two of a transition from an OP-based program. The cost of the program in Fig. 5 is approximately $250/acre, including the expense for a half-rate of pheromone. One potential problem of removing Lorsban from the insect pest control program could be with Campylomma. We know from experience that residues on bark from delayeddormant applications of Lorsban suppress populations of Campylomma. In some orchards this level of suppression has probably been sufficient to eliminate the need for additional controls for this pest. Therefore, the elimination of Lorsban in the prebloom period could increase the probability that additional controls for Campylomma would be needed. Resistance management. An important characteristic of the pest program represented in Fig. 5 is that NO insecticide is used against the same pest in two consecutive generations. Why is this important? Because it represents a sound resistance management approach designed to conserve the efficacy of new insecticides against our key pests. By not using an insecticide in successive generations of a pest, the selection pressure for resistance is reduced. Also note that we do not use Assail in one CM generation and Calypso in the next. These products are in the same class and have the same mode-of-action. If we used Assail in first CM generation and Calypso in the following generation, selection pressure for resistance to the entire class would be exerted against both generations, thus increasing the chances of resistance development. How should you treat insecticides that have activity against multiple pests? The principle to remember is to NOT use a product for control of one pest at one time of year and then against a different pest later in the growing season if the first pest will also be exposed to the product. For example, we use Rimon against CM in the spring as an ovicide treatment (petal fall) we area also controlling LR. We could consider using Rimon again against LR in the summer but this would mean the same product was used against the same pest on two consecutive generations. Instead, we switched to the use of Intrepid in the second CM generation and got the added bonus of LR suppression. The best resistance management tactic is to use an insecticide against a pest as few times as possible. For this reason, the use of MD is a very good resistance management tool because it typically reduces the use of insecticides for CM control. Tank mixing insecticides: A novel NO-OP program approach is shown in Fig. 6. This approach takes advantage of our knowledge of CM biology and insecticide mode-ofaction to combine two products as a tank mix in one application. Oil is used in the prebloom program for control of scale and suppression of mites and aphids, and Success is applied at petal fall for LR control. Oil (1% v/v) is again applied at 200 CM degreedays, or 50 degree-days before expected CM egg hatch. The oil kills many of the eggs deposited up to this point. A tank mix of a larvicide (Assail or Calypso) and an ovicide (Rimon or Intrepid) is applied as a delayed first cover treatment at 350 degree-days, or 100 degree-days later than the normal egg hatch timing (Fig. 6). No other first-generation treatments are used for CM control. The second-generation treatments could be either 6

Intrepid or Rimon, whichever was NOT used in the tank mix application, or if CM densities were low enough and no LR problems were expected a CM virus product could be used. How does the mixing of two insecticides with different modes-of-action work when applied only one time per CM generation? A key element to this program is the use of oil at 200 degree-days. This treatment kills the eggs that had been laid down between the beginning of CM flight (= Biofix) and this point (#1 - Fig. 7). Killing these early eggs delays the beginning of significant egg hatch and makes it possible to delay the tank mix application until 350 degree-days. At 350 degree-days, some CM eggs would be hatching, but the larvicide (Assail or Calypso) would kill the small larvae as they attempted to enter fruit (#2 - Fig. 7). The ovicide (Rimon or Intrepid) kills eggs that the oil missed but had not yet hatched or deposited after the oil treatment (between 200 and 350 degree-days, #3 - Fig. 7). In other words, these products have kick back activity to kill eggs the oil treatment missed. In addition, the ovicide kills eggs laid down after it is applied (#4 - Fig. 7), thus, eggs that would have hatched after the residue of the larvicide ran out (#5 - Fig. 7) are already dead. By delaying the tank mix application until 350 degree-days the residual activity of both the ovicide and larvicide provides control during the most active period of the CM generation and therefore provides protection for the entire generation. This approach could also be repeated in the second generation, but it would be better to switch to softer controls at this time and conserve the new products as much as possible. This approach can work with the different combinations shown in Fig. 7, even using an OP insecticide as a larvicide, but this would defeat the purpose of a NO- OP program. We have several years of experience testing these kinds of tank mix programs (Fig. 7) under extreme CM pressures. Table 5 provides examples of the percent reduction of CM injury achieved by the different tank mix programs. Most of the tank mix programs provided very good suppression of fruit injury, in some cases similar to that of a standard OP-based program (Guthion). A combination of Rimon with either Assail or Calypso proved to be especially effective. This table also shows that even very soft programs that included just Intrepid or combined treatments of CM virus (Cyd-X) and Intrepid can provide good suppression of CM injury. These latter programs combined with CM MD could be expected to provide very good control where pressures were low to moderate. Conclusions: There are several insecticides to choose from when making decisions about control of CM and LR. The best use of these new products comes through a complete understanding of how they affect the life stages of both pests. The efficacy of many of the new insecticides rivals that achieved by the OP insecticides, though in some cases more frequent applications are required. The best approach to using the new insecticides for CM and LR control is to mix them into a comprehensive approach that avoids overuse of any one class of product. This will help to reduce selection for resistance and extend the effective life of new products. Use of new insecticide technologies will in the short term cost more than programs that rely on old insecticide technologies, but substantial benefits (Table 4) can be derived from use of new insecticides such as the following: ease of farm worker management, 7

elimination of the need for cholinesterase testing, conservation of biological control agents, and an overall reduction in negative environmental effects often attributed to pesticide use. While some of these benefits do not accrue directly to the grower, many do. It is a good time for many Washington apple producers to initiate implementation of NO-OP pest control programs on at least some of their apple production. It takes time to learn how best to use new technologies. The information in this article will be available on the Washington State University Tree Fruit Research and Extension Center web site (http://entomology.tfrec.wsu.edu/entohome.html) where it will be updated as new knowledge becomes available. The information will also be available in a form that can be downloaded and printed for those who would like a hard copy to refer to. 8

Table 1. Insecticides registered for codling moth control. Traditional insecticides organophosphate and carbamate Guthion, Imidan, Sevin Pyrethroids Danitol, Warrior, Asana Neonicotinyl insecticides Assail, Calypso Biological insecticides Mineral oil, CM viruses, Success (Entrust), Pheromones Insect growth regulators Intrepid, Esteem, Rimon Other insecticides Avaunt, Proclaim* * not yet registered for use on tree fruit crops. Table 2. Insecticides registered for leafroller control. Traditional insecticides organophosphate Lorsban (prebloom only) Pyrethroids Danitol, Warrior, Asana Neonicotinyl insecticides Biological insecticides Success (Entrust), Bt products, Insect growth regulators Intrepid, Esteem, Rimon Other insecticides Proclaim* * not yet registered for use on tree fruit crops. 9

Table 3. Characteristics of different insecticides based on CM control. Insecticide Relative efficacy 1 No. of applications 2 Approximate $/acre/appl. 3 Exposure method Guthion, Imidan 90-99 4 $22-35 Contact Sevin 70-80 6 $10 Contact Warrior, Danitol, Asana 85-95 4-6 $12-21 Contact Intrepid 60-75 6 $30-35 Ingestion Assail, Calpyso 4 85-95 4 $40-45 Ingestion Esteem 4 40-50 4 $35 Contact (egg) Rimon 5 90-95 6 ($35) Contact (egg) CM virus 50-60 6-8 $30 Ingestion Success 75-85 6 $35 Ingestion Mineral oil 50-60 6-8 $5 Contact (egg) 1 Range (%) of suppression of fruit injury (entries and stings) relative to an untreated orchard. 2 The number of applications per year to achieve the level of suppression (relative efficacy). 3 Cost of one application of the insecticide(s). 4 These products cannot be used this many times in a season so the number of applications is just for comparative purposes. 5 Price not yet established. Table 4. Advantages of using new insecticides for CM control. 1. Farm worker safety considerations newer insecticides have a very low toxicity to humans. 2. Farm worker management the re-entry periods for new insecticides is short, 4-12 hours. 3. Environmental protection most new insecticides have beneficial profiles against non-target organisms. 4. Pest management most new insecticides have less negative effects on biological control agents compared to older insecticides. 5. Preparing for the future no organophosphate insecticides. 10

Table 5. Level of CM fruit injury suppression achieved by different mode-of-action tank mix programs compared to a typical sequential application of treatments. Efficacy (percent reduction in fruit injury relative to an untreated Tank mix program control) Oil @ 200 DD; Calypso + Intrepid @ 350 DD 88.3 Oil @ 200 DD; Calypso + Rimon @ 350 DD 99.7 Oil @ 200 DD; Assail + Rimon @ 350 DD 98.6 Oil @ 200 DD; Assail + Intrepid @ 350 DD 95.0 Oil @ 200 DD; Intrepid; Intrepid * 74.7 Oil @ 200 DD; Cyd-X; Intrepid * 60.3 Guthion; Guthion * 98.7 Assail; Assail * 94.1 * program without tank mix modes-of-action. 11

Figure 1. Average percent suppression of CM entries per fruit from tests conducted in 2002-2004. 12

Figure 2. A diagram of how ovicides work: topically, as a residue on to which an egg is laid, or in either way. 13

Figure 3. A traditional CM and LR control program based on use of OP insecticides. 14

Figure 4. A program where OP alternatives are substituted, including mating disruption, for CM control. 15

Figure 5. A possible NO-OP program using insecticides with different modes-of-action to control LR and CM. 16

Figure 6. A NO-OP program for CM/LR control showing a tank mix application of two insecticides with different modes-of-action in the first generation. 17

Figure 7. This diagram shows how oil followed by a delayed tank mix application of an ovicide and larvicide works to control CM. 18