Reducing Chemical Insecticide Inputs and Costs by Using Biologically-based Insecticides Against Diamondback Moth and Cabbage Looper on Cole Crops in Texas

Tong-Xian Liu, Associate Professor of Entomology
Texas Agricultural Experiment Station and Texas Cooperative Extension
Texas A&M University System
2415 E. Highway 83
Weslaco, TX 78596
956-968-5585
956-968-0641(fax)
tx-liu@tamu.edu

Executive Summary

The cole crops, including cabbage, Chinese cabbage, broccoli, brussels sprouts, cauliflower, kale, collards, and kohlrabi, are extremely economically important to vegetable production in Texas. Diamondback moth, Plutella xylostella (L.), and cabbage looper, Trichoplusia ni (Hübner), are the two most destructive lepidopterous pests of cole crops in the United States, including Texas. I propose to investigate specific sustainable pest control tactics and practices as alternatives to, and to reduce grower reliance on, high-risk conventional chemical insecticides in cole crops by applying biologically-based insecticides in an integrated pest management (IPM) system. Although cabbage will be used as model crop for developing the IPM program, the pest management program will be almost directly applied to other cole crops.

The overall objective is to deliver an IPM system in cole crops that reduces the use of chemical insecticides and is based on biologically-based insecticides.

The specific objectives for this study are to:

determine the effectiveness of two commercial neem (azadirachtin-based) products (Neemix and Ecozin), two Bacillus thuringiensis-based insecticides (Bt-insecticides: Dipel and Crymax), and two low-risked insecticides, spinosad (SpinTor) and indoxacarb (Avaunt);
determine the effectiveness of the best combinations of rotation of Bt-insecticides with the other test insecticides;
determine the effects of these insecticides on parasitoids (Diadegma insulare and Cotesia plutellae) of the two pests; and
deliver the research findings to growers through extension and internet publications and grower field days and meetings. All insecticide application will be based on the current economic threshold of 1 larva per 3 plants (0.3 larvae per plant).

Objectives

The overall objective is to deliver an IPM system in cole crops that reduces the use of chemical insecticides and is based on biologically-based insecticides. The specific objectives are:

To determine the effectiveness of two Bacillus thuringiensis insecticides (Bt-insecticides: Dipel and Crymax), two neem (azadirachtin-based) insecticides (Neemix and Ecozin), and two low risked insecticides (spinosad and indoxacarb) for management of diamondback moth and cabbage looper on cole crops.
To determine the effectiveness of the best rotation combinations of two Bt-insecticides with the other four test insecticides.
To determine the effects of these insecticides on parasitoids of the two insect pests (Diadegma insulare and Cotesia plutellae).
To deliver the research findings to growers through extension and internet publications and grower field days and meetings.

Justification

The cole crops, including cabbage, Chinese cabbage, broccoli, brussels sprouts, cauliflower, kale, collards, and kohlrabi, are very good sources of Vitamins A, B and C, and are rich in potassium, calcium, floate phosphorus, iron, carotenes, and other nutrients and anti-oxidants. Prior to cultivation and use as food, they were used mainly for medicinal purposes. Research is now showing other health benefits from cole crops related to reducing the risk of cancer and heart disease. The crop crops are extremely important to vegetable production in Texas, one of the largest U.S. producers of fresh market cole crops with a yearly value of $30-60 million depending on market prices. Cole crop production represents a >$20,000,000 industry in south Texas alone (Anonymous 2000). Average insecticide costs of $1,056,000 per year are required in south Texas to manage lepidopterous and aphid pests with no guarantee of adequate control due to the current threat of insecticide resistance, especially with the diamondback moth Plutella xylostella (L.), and cabbage looper, Trichoplusia ni (Hübner). After the mid-1980s, diamondback moth rose to key pest status in south Texas coincidental with the increase in use of pyrethroid insecticides to which diamondback moth resistance has been documented (Magaro and Edelson 1990). However, dominance by diamondback moth or cabbage looper on cole crops in south Texas varies greatly among years and seasons, ranging from 50% to as high as 90% by either species (Liu, unpublished data). Normally, the two species are both important, although the population for each of the two pest species may vary based on the season or year (Liu unpublished data). Therefore, any management program should target both species.

Because the market tolerance for insects in the fresh cole crops and other leafy vegetable is low to near zero, many different types of insecticides have been used to control diamondback moth and cabbage looper in the past decade (Cartwright et al. 1987, Magaro and Edelson 1990, Liu and Sparks 1999), including pyrethroids (i.e. lambda-cyhalothrin), some newer insecticides (i.e. spinosad, indoxacarb, etc.), and Bacillus thuringiensis-based products (Liu 1999, Liu and Sparks 1999). Although extensive and multiple applications of these insecticides can be effective against these pests, they have potential to cause resistance, harm beneficial arthropods, toxic to humans and expensive.

I propose to develop the IPM program in cabbage, but the pest management program will be almost directly applicable to all other cole crops.

Objective 1. To determine the effectiveness of two Bacillus thuringiensis insecticides (Bt-insecticides: Dipel and Crymax), two neem/azadirachtin-based insecticides (Neemix and Ecozin), and two low risked insecticides (spinosad and indoxacarb) for management of diamondback moth and cabbage looper on cabbage.

In my laboratory, the three commercial neem-based insecticides, AgroNeem , Ecozin , and Neemix , have been evaluated for repellency to adults, oviposition deterrent, antifeedant effect to larvae, and toxicity to eggs of diamondback moth (Liang, Chen and Liu 2002, submitted). We have found that when eggs were treated with Agroneem, Ecozin and Neemix, 61.6, 66.2, and 75.2% of diamondback moth eggs developed to neonates, respectively, although the larval hatching rates in the treatment of Neemix were not significantly different from that in water control (81.2%). All larvae of diamondback moth fed on the leaves treated with the three neem-insecticides died on or before day 7 compared with 70-74% larvae surviving to adults in water control. All three neem insecticides exhibited significant antifeedant effect, and diamondback moth larvae on treated leaves quickly stopped feeding and dropped off treated leaves, resulting in no or minimal damage on the treated cabbage leaves. Diamondback moth larvae that fed on neem insecticide treated leaves were 44-58% lighter, 51-55% shorter, and 48-58% thinner than those fed on water treated leaves. Therefore, we think that the neem-based insecticides have potential to be used in the cole crop IPM programs.

In the past few years, we have also conducted numerous laboratory and field experiments with several Bt-insecticides (Liu 1999), spinosad (Liu and Sparks 1999, Liu et al 1999), and indoxacarb (Liu and Sparks 1999, Liu et al. 2002a, b). We found that under field conditions, field-aged leaf residues of indoxacarb (0-, 3-, 5-, 7-, 10-, 14-, 17, and 21 d-old residues) were toxic to diamondback moth and cabbage looper for at least 14 days, and with one application, indoxacarb was able to suppress both species below the economic threshold for 14-21 d. I also found that under field conditions, effectiveness of Dipel and several other Bt-products varied greatly. When pest pressure was high, all formulations were more effective against diamondback moth than to cabbage looper, whereas no differences occurred when pressure was low. Five weekly applications of Bt-products significantly reduced larval populations of both pest species. However, in two of the three field trials, application of Bt-insecticides alone did not reduce the number of larvae below the economic threshold (1 larva/3 plants), and the market value of the plants was significantly reduced.

Objective 2. To determine the effectiveness of the best rotation combinations of the two Bt-insecticides with other four test insecticides.

Cole crops and most leafy vegetables in Texas have a very small profit margin (J. Robinson, Agricultural Economist, Texas A&M University). Therefore, low input is critical for growers. At present, most neem products (Neemix) and some newer insecticides (indoxacarb and spinosad) are expensive. To reduce expenses while effectively managing the pests, I conducted an experiment to rotate Dipel at full rate (1 lb/ac) with half rate of spinosad (SpinTor 2SC, 3 oz/ac, the full rate can be up to 6 oz/ac), and found that 2 applications of each of these two insecticides had the same results as 4 application of spinosad, resulting in an almost 50% reduction in insecticide and application cost.

In the current proposal, I expect a 30-50% reduction in insecticide and application cost by rotating the less expensive Bt-insecticides with the more expensive neem-based insecticides, spinosad, or indoxacarb.

Objective 3. To determine the effects of these insecticides on parasitoids of the two pests (Diadegma insulare and Cotesia plutellae).

In my laboratory, we have also tested the effects of field dosages of several Bt-insecticides, neem-based insecticides, spinosad and indoxacarb through contact, ingestion and persistent exposures to Cotesia plutellae (Kurdjumov), an endolarval parasitoid of diamondback moth under laboratory conditions (Haseeb, Liu and Jones 2002, submitted). We found that emergence of adults of C. plutellae from insecticide-treated pupae was not significantly different from the control treatment. Contact toxicity to C. plutellae adults varied greatly among the insecticides in a paper residue contact bioassay. The three azadirachtin-based insecticides, Agroneem (29 mg a.i.liter-1), Neemix (50 mg a.i.liter-1) and Ecozin (60 mg ai.liter-1) caused 11.1, 16.7 and 5.6% mortality, respectively. Of the four commercial Bt-insecticides (all at 1.2 mg a.i.liter-1), Crymax and Xentari had no effects on the adult parasitoids, whereas Mattch caused 5.6% mortality, and Dipel caused 11.1% mortality, the highest. Indoxacarb (245 mg a.i.liter-1), ?-cyhalothrin (281 mg a.i.liter-1) and spinosad (75 mg a.i.liter-1) caused 100, 88.5 and 50% mortalities, respectively. Low mortalities (0-5.6%) were recorded through ingestion exposure to azadirachtin-based and Bt- insecticides and indoxacarb, compared with 100% mortalities in the treatments of spinosad or ?-cyhalothrin. Compared with the water control, ingestion of azadirachtin-based insecticides significantly reduced parasitism by 50-57%, and ingestion of the four Bt-insecticides reduced parasitism by 8-25%. However, ingestion of these insecticides did not affect longevity of male and female parasitoid adults with one exception; the female longevity was significantly reduced in the indoxacarb treatment. Insecticide residues caused considerable mortality of C. plutellae adults, 39 and 44% mortality caused by 10 d old indoxacarb and ?-cyhalothrin, respectively, and 24% and 0% mortality caused by 7 and 10 d old residues of spinosad, respectively. However, we do not have any information on the effects of these insecticides on Diadegma insulare, one of the most dominant parasitoid of diamondback moth in south Texas (Legaspi, Liu and Sparks 2000). With this information, we will be able to provide growers with more accurate recommendations on which insecticides are effective and are natural enemy friendly.

Objective 4. The ultimate objective of this project is to deliver the research findings to growers and scientists through extension and internet publications and grower field days and meetings.

I intend to use the information generated from this study to develop a long term, profitable and sustainable IPM system that is biologically based, economical, low input, and effective.

Literature Review

Texas is one of the largest producers of fresh market cole crops in the US (Anonymous 2000). Diamondback moth (DBM), Plutella xylostella (L.), and cabbage looper (CL), Trichoplusia ni (Hübner) are two most destructive pests of cole crops and other leafy vegetables. After the mid-1980s, diamondback moth rose to key pest status coincidental with the increase in use of pyrethroid insecticides to which diamondback moth resistance has been documented (Magaro and Edelson 1990, Shelton and Wyman 1992). Normally, the two species are both important, although the population for each of the two pest species may vary based on the season or year (Liu unpublished data). Therefore, any management program on cole crops in Texas should target both species.

Because the market tolerance for insects in the fresh cole crops and other leafy vegetable is low to near zero, many different types of insecticides have been extensively used to control these two major pests in the past decade (Magaro and Edelson 1990, Liu and Sparks 1999), including pyrethroids (i.e. lambda-cyhalothrin), some newer insecticides (i.e. spinosad, indoxacarb, etc.), and Bacillus thuringiensis-based products (Liu 1999, Liu and Sparks 1999). Although extensive and multiple applications of these insecticides can be effective against these pests, they have potential to cause resistance, harm beneficial arthropods, unsafe food and environment, and are expensive. In addition, tolerance of diamondback moth to spinosad has been reported by the local growers, although no data has been documented.

Neem-based insecticides containing azadirachtin derived from extracts of neem tree (Azadirachta indica A. Juss, Meliaceae) have played important roles in crop protection. Azadirachtin, a very complex tetranortriterpenoids, has been effectively used against >400 species of insects, including many key crop pests, and has proved to be one of the most promising naturally derived products (plant ingredients) for integrated pest management at the present time (Jacobson 1989, Rembold 1989, Schmutterer 1990, Ascher 1993, Sannaveerappanavar and Viraktamath 1997, Isman 1999, Walter 1999). This compound displays an array of effects on insects, acting as a phago- and oviposition deterrent, repellent, antifeedant, growth retardant, molting inhibitor, sterilant, and preventing insect larvae from developing into adults (Schmutterer 1990, Mordue and Blackwell 1993, Schmutterer 1995). In addition to controlling pest insects, many azadirachtin-based insecticides have negligible effects on natural beneficial insects and low environmental impact (Schmutterer 1990, 1995). Because the neem-based insecticides are not toxic to humans and many beneficial arthropods, and the pests are unlikely to become resistant, these insecticides become more sensible materials to use in most pest management programs. Neem-based insecticides have been tested and used for management of diamondback moth and other pest insects on cabbage (Leskovar and Boales 1996, Perera et al. 2000). Field efficacy test of a neem-based insecticide, AlignTM (3% azadirachtin, formerly AgriDyne, Salt Lake City, UT), was tested against lepidopterous pests, mainly Diamondback moth and Trichoplusia ni (H ner), on cabbage in Texas by Leskovar and Boales (1996). They found that Align significantly reduced the densities of Diamondback moth and Cabbage looper on cabbage plants and foliage damage, and significantly increased marketable head weights. However, the effects of these two commercially available neem-based insecticides in the United States have not been determined on Diamondback moth and its parasitoid D. insulare (Haseeb, Liu and Jones 2002).

The current array of commercially available microbial insecticides, including Bacillus thuringiensis Berliner (Bt), have demonstrated their potentials as effective and environmentally safe alternatives to synthetic chemical insecticides for lepidopterous pests (Wilding 1986). Currently, over 20 commercial formulations of the toxins produced by B. thuringiensis play an important role in integrated pest management programs of lepidopterous pests on vegetables and other field crops because of their high toxicity to many lepidopterous pests and low toxicity to non-target organisms including beneficial insects. Bt-insecticides have been used in south Texas for decades. Most reported data indicated that Bt-insecticides reduced populations of Cabbage looper and Diamondback moth, but overall control has not been adequate under high population pressures (Edelson et al. 1993, Liu 1999, Liu and Sparks 1999).

Spinosad (SpinTor), a relatively new product by Dow AgroSciences (Indianapolis, IN), is one of the recently registered alternatives. It contains the active ingredient, spinosad, that is a fermentation by-product based compound derived from a naturally occurring soil actinomyces bacterium, Saccharopolyspora spinosa, and is a mixture of spinosyn A and spinosyn D (Thompson et al. 1997). As reported, spinosad has two unique modes of action, acting primarily on the insect's nervous system at the nicotinic acetylcholine receptor, and exhibiting activity at the GABA receptor (Salgado 1997). Spinosad has relatively broad-spectrum activities, and has been effectively used for control of many species of insect pests in the orders Lepidoptera, Diptera, Coleoptera and Thysanoptera in various crop systems (Sparks et al. 1995, Bret et al. 1997, Peterson et al. 1997, Richardson et al. 1998).

Indoxacarb (S)-methyl 7-chloro-2,5-dihydro-2-[[(methoxy-carbonyl)[4-(trifluoromethoxy) phenyl] amino] carbonyl]-indeno [1,2-e][1,3,4] oxadiazine-4a(3H)-carboxylae), the active ingredient of Avaunt (Du Pont, Wilmington, DE), is a broad-spectrum, highly efficacious new insecticide that has been recently registered for use on vegetables to control lepidopterous pests and selected insect pests with sucking mouthparts (Harder et al. 1996, Anonymous 1998, Wing et al. 1998). Indoxacarb will be designated a reduced-risk product by the Environment Protection Agency (Anonymous 1998). It has been used for controlling cotton, fruit, and vegetable insects in the United States and many countries. I have been working with indoxacarb for many years (Liu and Sparks 1999, Liu et al. 2002 a, b, Harseeb, Liu and Jones 2002).

Approach and Methods

Objective 1. To determine the effectiveness of two neem (azadirachtin-based) insecticides (Neemix and Ecozin), two Bacillus thuringiensis (Bt) insecticides (Dipel and Crymax), and two low risked insecticides (spinosad and indoxacarb) for management of diamondback moth and cabbage looper on cabbage.

There will be two parts: laboratory bioassays and field trials:

1.1 Laboratory Bioassays. All stages of diamondback moth and cabbage looper will be bioassayed with the insecticides. Both diamondback moth and cabbage looper colonies will be established by collecting larvae and pupae from the cabbage field. Additional colonies will be reared with artificial diets (Shelton et al. 1991). Eggs (24 h old), young (first and second instars) and old (third and fourth instars) of both species will be obtained and used as described in Liu (1999), Liu et al. (1999) and Liu et al. (2002a, b). Cabbage plants, about 30-40 cm high with 8-10 leaves, will be placed on a bench in a greenhouse for treatment. To evaluate efficacy over time (1, 2 3, 4 and 5 d), plants will be treated with the field rate for each insecticide. To determine the relative toxicity (LC50 and LC90) of these insecticides, a series of concentrations will be used to produce a range from very high to low percentage mortalities of third instars. Reverse osmosis water will be used as controls in all experiments. The plants will be first sprayed to run-off with the dilutions or water. After air-drying for 1-2 h, the treated plants will be moved to an insectary with a photoperiod of 14:10 (D:L) h at 25°C and 50-55% relative humidity (RH). Cabbage leaves will be removed from plants and leaf disks (10-12 cm in diam) will be cut and placed in a plastic petri dish (2 cm deep x 15 cm diam). Small holes (20-25, 2 mm in diam) are drilled on the petri dish lids for ventilation. Four pieces of paper tissue will be placed at the bottom of the petri dish, and a few drops of water will be added daily for moisture. Ten larvae for each instar will introduced to each petri dish. Dead and live larvae will be checked for 5 days or until all larvae died or successfully developed to the next stage. Treated leaf disks will be replaced every 2 d. For eggs, 30-50 eggs for each species will be collected on each leaf disk. The leaf disks will be sprayed to runoff. After air-dried for 1-2 h, they will be placed in petri dishes, and larval hatching will be monitored daily until all larvae hatch or the eggs died.

1.2. Field Trials. Field trials will be conducted at the Agricultural Research and Extension Center Research Farm, Texas A&M University at Weslaco, and all six insecticides and an untreated control will be included in the trials (Table 1, next page). Cabbage will be established in double-row on 1-m beds and 25-cm apart. Each treatment plot consisted of two rows of cabbage plants (9.14 m long). Plots will be separated with sorghum windbreaks between beds and a 1.5-m alleyway. All treatments will be arranged in a randomized complete block design with four replications. A standard production protocol developed by the Texas Agricultural Research and Extension Center will be followed. Fertilization consisted of 112 kg/ha of N-32 at planting, and the herbicide Prefar 4E, will be used at 14 liter/ha at planting.

All insecticides will be applied using a tractor-mounted sprayer with three ceramic hollow cone nozzles (TX-6 red) per row (one over the plants, one on each side of the row on drops directed into the plant) at 689.5 kPa (7.03 kg/cm2) at a delivery rate of 374 liter/ha with a traveling speed of 4.83 km/h. Spraying will begin when mean numbers of larvae per plant reaches the economic threshold of one larva per three plants (Cartwright et al. 1987), and thereafter, the plants will be sprayed once per week for five or more times depending on the trial.

Larval sampling will be initiated four weeks after planting in each test, and conducted once per week after the first application. The numbers of small and large larvae per plant will be counted a few hours before each application by checking both the upper and lower surfaces of every leaf for 10 randomly selected plants from each plot.

At termination, a damage/quality evaluation will be made on 10 randomly selected plants from each plot based on the following six categories (Greene et al. 1969): 0 - no apparent damage; 1-minor feeding damage on wrapper outer leaves or 1% leaf area eaten; 2 - minor-moderate feeding damage, or 2-5% leaf area eaten; 3 - moderate damage, or 6-10% leaf area eaten, but no head damage; 4 - moderate-heavy damage on wrapper and outer leaves with minor damage on head, or 11-30% leaf area eaten; and 5 - heavy damage on wrapper and head, or >30% leaf area eaten.

Objective 2. To determine the effectiveness of the best combinations of mixtures and rotation of these insecticides for effective, economical control of the pests.

The cabbage variety, field preparation, experimental design, insecticides application and sampling will be the same as those described in the Objective 1.2 for the field trial. However, the treatments will be as shown in Table 1.

Table 1. Treatments

Laboratory Bioassays			Field Trials
DBM (Objective 1)	CL (Objective 1)	Diadegma (Objective 3)	Season 1 (Objective 1)	Season 2 (Objective 2)	Season 3 (Objective 3)
DI	DI	DI	DI	DI-NE*	?**
CR	CR	CR	CR	DI-EC*
NE	NE	NE	NE	DI-SP
EC	EC	EC	EC	DI-IN
SP	SP	SP	SP	CR-NE*
IN	IN	IN	IN	CR-EC*
				CR-SP
				CR-IN

Abbreviations: Diamondback moth (DBM), cabbage looper (CL), Dipel (DI), Crymax (CR), Neemix (NE), Ecozin (EC), Spinosad (SP), Indoxacarb (IN)

* Treatments will be determined based on the data from laboratory bioassays and field trial-season 1.

** Based on the results from all previous bioassays and field trials (seasons 1 and 2), only the most promising treatments will be used in this test to determine the effects to natural enemies (parasitoids) under field conditions.

Objective 3. To determine the effects of these insecticides on parasitoids of the two pests (Diadegma insulare). (We have the data for Cotesia plutellae)

A. Laboratory Bioassays

The larvae of Diamondback moth will be obtained as described for Objective 1. Parasitoids (D. insulare) will be collected from the field or obtained from a commercial supplier. They will be reared under similar laboratory conditions as that for rearing of Diamondback moth. All insecticides will be tested for D. insulare. Water will be used as controls. The concentrations will be the determined based on the recommended field rates with a delivery rate of 100 gal/ac.

The following parameters will be obtained through a series of bioassays:

Lethal and sublethal effects of these insecticides against the pupae and adult of D. insulare. In each treatment 10 pupae of D. insulare (2-3 d old) will be attached on double sided tape on a piece of hard paper and will be dipped into the diluted insecticide for 10 s. Five replicates will be established. In the control, pupae will be dipped in tap water. Then the pupae will be placed in petri dishes and adult emergence will be recorded. Lethal effects of contact toxicities of the same doses of 10 products will be conducted in glass petri dishes (1.5 cm in depth and 9 cm in diameter). First, each lid and bottom of a petri dish will be sprayed at the rate of 2 ml with a Potter tower sprayer. The sprayed petri dishes will be maintained in a fume hood for ca. 1 h and then 10 adults (2-3 d old) irrespective of their gender will be release in each petri dish for 24 h. Five replicates will be established. At completion, mortality will be recorded.

Effects of ingestion toxicities to adults and parasitism rates. In this trial, plastic petri dishes (1.5 cm in depth and 9 cm in diameter) will be modified and a hole of 1 cm in diameter on the side will be drilled. Each insecticidal dilution will be mixed with honey separately. The control (tap water) and insecticidal treatments mixed with honey solution will be dispensed to produce 16 tiny drops (20 µl). Two microscopic glass cover slips were placed in each petri dish for wasp feeding. Ten pairs of parasitoid adults (2-3 d old) will be introduced in each petri dish. Three replicates will be established. Mortality will be recorded in 24 h after treatment. The surviving parasitoid adults of each treatment will be combined together and maintained in one petri dish treatment. The next day 20 second instar Diamondback moth larvae will be offered to a single female in acrylic petri dish for ca. 10 h for parasitization. Ten replicates will be established. After the completion of time, the female parasitoids will be removed and the larvae of Diamondback moth will be reared on radish sprouts. Parasitization of the Diamondback moth larvae and number of D. insulare emerged will be recorded and calculated.

Effects of persistent toxicities to adults. Cabbage will be sown in plastic trays (60 x 35 x 6 cm) in a greenhouse. The seedlings will be transplanted in plastic pots (1.5 liter) on 18 September 2001. The cabbage plants will be sprayed with these insecticides. In the control treatment, only water will be sprayed. The plants will be watered as needed. Three leaves (3 replicates) from each treated plant will be removed and a leaf disk of ca. 9 cm in diameter from each leaf will be removed using a scalpel. The leaf disks will be individually placed in the petri dishes. Then five adult parasitoids, irrespective of sex ratio, will be introduced in each petri dish for 24 h. At completion, mortality will be recorded. The tests will be conducted after 1, 3, 5, 7 and 10 d of plant spraying.

Effects of ingestion toxicities to gender longevity of adults. Each diluted pesticide will be mixed with honey (10% w/v). The solution will be dispensed to produce 16 drops (20 µl each) on a microscopic glass cover slide. Two microscopic glass cover slips will be placed in each acrylic petri dish and three pair of parasitoid (24 h old) will be introduced inside through an opening (1 cm in diameter). Five replications will be established. After 24 h, the parasitoids will be removed and maintained in untreated petri dishes where honey water solution will be provided every third day and male and female longevity will be recorded daily up to the death of all insects.

Data analysis. The percentage adult emergence, mortality, parasitism and persistent toxicities data will be subjected to arcsin transformation before analysis of variance through the general linear model. Means will be separated with Tukey's Studentized Range (HSD) test at p = 0.05 (SAS Institute 2001). The percentage parasitism will be calculated as: % parasitism = number of C. plutellae pupae/(number of D. insulare pupae + number of Diamondback moth pupae) 100.

B. Effects of these insecticides on natural enemies under field conditions.

Based on the bioassay data and the field trial data, the most effective insecticides and the best rotation combination will be used in this field trial. Plants, field experimental design, and insecticide application will be the same as the previous field trials. However, the sampling methods will be different from the previous trials.

Two to three weeks after planting, the cabbage plants will be randomly examined for any diamondback moth and cabbage looper. As soon as the first insect (any stage) is found, a systematic sampling program will begin. Two cabbage plants from each plot will be destructively collected from the base of the plant at ground level. There will be 8 plants for each treatment (4 replications, 2 plants from each). The plants will be placed with plastic bags immediately in the field, and brought back to the laboratory. All developmental stages of the two species will be collected, placed in vials or plastic petri dishes to rear out any parasitoids. As soon as the insect density reaches the economic threshold, insecticides will be applied. The cabbage plants will be sampled weekly until harvest.

The following parameters will be obtained weekly and used in data analysis for all treatments throughout the whole season: numbers of each developmental stage (eggs, young or old larvae and pupae) for each species, numbers of successfully developed to adults, number of each stage parasitized, number of each stage died caused by pathogens, numbers of each parasitoid species, etc. Eventually, effects of these insecticides or rotation of these insecticides will be determined.

Again, cabbage plant damage in all treatments will be determined at harvest as described above.

Objective 4. To deliver the research findings to growers through extension and internet publications and grower field days and meetings.

The research progress will be evaluated each season by holding a field day at the end of the experiment. All interested growers, extension agents, extension specialists, research scientists in the university system, and industries will be invited. Field days will be held at the Texas A&M Research Center in Weslaco to communicate technology to producers and industry participants each season to transfer information, elicit interest and invite input during the mid-year and annual meeting of Texas Vegetable Association. First, they will tour the experimental plots and fields. Secondly, the researchers will give presentations with photos, data in table and figures, and conclusions from the research conducted in the laboratory and fields. Input (suggestions and comments) from all parties will be collected, and incorporated in future research. At the end of the project, the PI, the research scientist and all collaborators will meet to assess the data and the outcome, and prepare refereed journal publications and producer-oriented extension publications for wide distribution.

Impact Assessment

The impact of this research will be assessed in the following:

Efficacies of the biologically-based insecticides. Both laboratory and field data will be assessed from toxicity in the laboratory bioassays and effectiveness for controlling the target insect pests under field conditions.
Effects to natural enemies. Direct and indirect effects of these insecticides to the major parasitoids will be determined based on the data from the laboratory bioassays and field data. The insecticides that have significant or destructive effects on any parasitoids will be eliminated for more field tests, and the model of action and mechanism of these insecticides to natural enemies will be studied in the future.
Insecticide input and cost analysis. Number of applications, amount of insecticide input, prices for insecticides and applications will be analyzed to determine if the study meet the overall objective – to reduce insecticide input and costs. Other related parameters will also be considered, including reducing toxics in the vegetable (as food), and reducing risks to the environment and labors.

Literature Cited

Anonymous. 1998. AvauntTM, insect control agent. Technical Bulletin H-79164, Du Pont, Wilmington, DE.

Anonymous. 2000. Texas Annual Vegetable Summary. Website: http://www.io.com/ ~tass /tvegansm.htm.

Ascher, K .R. S. 1993. Nonconventional insecticidal effects of pesticides available from the neem tree, Azadirachta indica. Arch. Insect Biochem. Physiol. 22, 433-449.

Bret, B. L., L. L. Larson, J. R. Schoonover, T. C. Sparks, and G. D. Thompson. 1997. Biological properties of spinosad. Down to Earth. 52(1): 6-13.

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Timetable

The project will be initiated as soon as the funding is available. The field studies will be started at the beginning of the season, probably the fall of 2003. Cabbage will be used as a model crop for cole crops.

Year 1 (September 2002 to August 2003)

September to December 2002:

Laboratory Bioassays. Conduct toxicity bioassays to determine the best combinations of mixtures of these insecticides for different developmental stages of diamondback moth and cabbage looper on cabbage.

Prepare seeds, irrigation equipment, all insecticides needed, fertilizers, herbicides and fungicides, etc. to get ready for the spring field experiments.

January to August 2003:

Field trial to determine the efficacies of each of the six insecticides. Plant cabbage in the field with proper experimental design (treatments, replications, windbreaks, etc.). Scouting will be initiated when cabbages are at 2-4-leaf stage. As soon as the larval density reaches the economic threshold, insecticides will be applied as proposed. Diamondback moth and cabbage looper larvae, as well as natural enemies, will be sampled weekly, and all stages will be checked from 10 plants from each plot.

Year 2 (September 2003 to August 2004)

September to December 2003:

Preliminary data will be analyzed for presentation the ESA meeting or the ESA-branch meetings, or other professional meetings.

Assess all laboratory and field data, and modify the experiment if necessary based on the results from the previous experiments.

Laboratory bioassays to determine the effects of these insecticides to the two species of parasitoids, Diadegma insulare, and Cotesia plutellae.

January to August 2004: Objectives 3 and 4.

Laboratory Bioassays. Continue to the laboratory experiments for toxicity bioassays on the effects of these insecticides on the two parasitoid species (different developmental stages).

Field trial to determine the efficacies of rotations of these insecticides and effects on natural enemies. Field experiment design will be the same as in previous season. Similarly, larval densities for both diamondback moth and cabbage looper will be scouted when cabbages are at 2-4-leaf stage. As soon as the larval density reaches the economic threshold, the insecticides will be applied as proposed. All immature stages (eggs, larvae and pupae) of diamondback moth and cabbage looper, as well as natural enemies, will be destructively sampled weekly by cutting the plant at ground level, taken to the laboratory, and all stages will be counted and collected, and all of these immatures will be reared out for determination of efficacies and effects on natural enemies.

The PI and the research scientist will start analyzing data and writing papers (refereed and extension), and giving presentations at professional and extension meetings. The final report will be presented in August 2004.

The PI or the research scientist may be able to present the results at the ESA meeting or the ESA-branch meetings, or other professional meetings.

Major Participants

Tong-Xian Liu, PI, Associate Professor of Entomology – Vegetable IPM (75% research and 25% extension). He has >10 years of experience developing biorational approaches for managing insect pests of vegetables, conducting basic and applied research on the biology, ecology, and behavior of vegetable pests and their natural enemies, insect-plant interactions, plant resistance to insects, insecticide resistance management, biological control, cultural control practices, sampling techniques, and action thresholds; and delivering the newest information to extension agents, consultants, and growers. He has published >70 refereed papers, and several book chapters and >100 non-refereed and extension publications.
Prof. Guolei Feng, Research Scientist, will spend 50% of her time working on this project.
Several technicians in Dr. Liu's Vegetable IPM Laboratory to provide assistance as needed.
Collaborators
Alton N. Sparks, Jr. Professor of Entomology and Extension Specialist, Texas Cooperative Extension Service. He has >15 years of experiences in vegetable pest management in Texas and elsewhere. He will provide his diamondback moth and cabbage looper management expertise, and help us to evaluate and improve our research.
Juan Anciso, Ph.D., IPM Agent of Vegetable and Citrus. Dr. Anciso has >10 years of experience in vegetable IPM in the Lower Rio Grande Valley. He has been directly working with local growers and scientists, and will provide his expertise and connection with the local growers.
Texas Vegetable Association. We will work closely with the Texas Vegetable Association, to ask inputs from its members, and identify participants for large-scale field trials.

Project Budget

Project Period: September 2003 - August 2004

Budget Category	Grant Funding	Other Funding	Total Funding
Personnel	17,038		17,038
Fringe Benefits	6,241		6,241
Travel	1,100		1,100
Equipment
Supplies	1,812		1,812
Contractual
Other (publication)	1,300		1,300
Total direct costs	27,491		27,491
Indirect costs 45.5%	12,509		12,509
Total	40,000		40,000

Budget Narrative

The funding requested will be used to pay 40% salary, medical insurance and fringe benefits of a research scientist.

The supply costs include fertilizer, herbicides, fungicides, drip-lines, seeds, plastic bags, alcohol, rubber bands, pencils, sticks, and others.

The publications fee is used for 1 refereed-paper ($500), and 500 copies of extension publications at $1.60 per copy ($800).