Petri Dish Lid Research Articles

First Record in Syria of Didymella fabae, the Teleomorph of Ascochyta fabae and Causal Organism of Faba Bean Blight.

Ascochyta blight, caused by Ascochyta fabae Speg., is a common and destructive disease of faba bean (Vicia faba L.) in the Middle East, Europe, Canada, New Zealand (4), and Australia. The main sources of inoculum are debris and seeds from which spores are air- and splashborne. The teleomorph of A. fabae has been reported previously only from England (2). The presence of the teleomorph supports the variability reported in the fungus populations from Canada (3) and Poland (1). Stems of faba bean plants, severely infected with A. fabae, were collected in July 1999 from Tel Hadya, Syria. The plants previously had been inoculated with a mixture of isolates of the pathogen, collected from the main faba bean-growing regions in Syria between 1996 and 1998, and kept under shade. The infested stems were used to inoculate the ICARDA Faba Bean Ascochyta Nursery planted on 29 November 1999. During late January 2000, symptoms appeared on the susceptible faba bean genotype. Stem pieces from debris used for inoculations were collected from the field and examined microscopically for the presence of ascomata. The maximum, minimum, and mean temperatures and rainfall at Tel Hadya during December 1999 were 16.5, 5.8, and 8.7°C and 22.4 mm, respectively. There were 16 nights when temperatures dropped below 0°C, and 10 nights when temperatures were between 0 and 5°C. Ascomata of A. fabae ranged from 76 to 209 μm wide (average 158 ± 3.9 μm) and 101 to 285 μm in length (average 178 ± 4.1 μm). Asci were 10 to 15 μm wide (average 14 ± 0.3 μm) and 51 to 96 μm long (average 63 ± 1.1 μm). Ascospores were 5 to 8 μm wide (average 7 ± 0.2 μm) and 15 to 20 μm in length (average 17 ± 0.3 μm). These measurements are comparable to those reported from England. Individual ascomata were dissected from stem tissue and fixed to the lids of petri dishes containing 2% water agar. After 24 h, the petri dishes were examined microscopically to locate ascospores on the surface of the medium. Germinating ascospores and developing colonies were transferred from water agar to faba bean dextrose agar. Colonies characteristic of A. fabae developed on the latter medium within 7 days of incubation at 20 ± 2°C. Pathogenicity tests of developing colonies were carried out on 3-week-old faba bean plants (Giza 4) using a spore suspension (2.5 × 105 spores per ml) of each of the isolates. Both inoculated seedlings and control seedlings inoculated with sterile water were covered with plastic bags for 48 h in a plastic house maintained at 18 ± 2°C. After removal of the plastic bags, seedlings were wetted four times per day by spraying with tap water to runoff. Inoculated plants showed characteristic symptoms of Ascochyta blight 15 days after inoculation. The fungus was reisolated from lesions that developed on leaflets of all inoculated seedlings, but not from any of the control seedlings. This is the first report of the occurrence of A. fabae, the sexual stage of Didymella fabae Jellis & Punithalingam in Syria, and indicates that the fungus could develop population variants. These findings have implications for breeding for resistance to Ascochyta blight.

First Report of Blumeriella jaapii Teleomorph on Wild Cherry in Italy

Leaf spot disease on wild cherry (Prunus avium L.) was frequently observed in plantations for timber production in central Italy. Acervuli and conidia of Phloeosporella (= Cylindrosporium) padi (Lib.) Arx were detected. Since the presence in Italy of its teleomorph, Blumeriella jaapii (Rehm) Arx (1), has never been reported, the life cycle of the pathogen was investigated. In the autumn of 1996, in some diseased leaves in different locations, microconidia were observed in the same acervuli that produced macroconidia. Also, in a plantation near Rome, fallen leaves with dark, stromatic spots were present. Leaf samples were put into plastic net bags and laid onto the ground under the trees, to be observed after overwintering in the field. In March, fully developed apothecia were present on the lower leaf surface, containing asci and ascospores that matched the description of B. jaapii. To verify the capability of the ascospores produced in nature to infect the host, overwintered leaf fragments with mature apothecia were fixed to the underside of the lids of petri dishes, above healthy cherry leaves laid upside down on moistened filter paper. Uninoculated, healthy leaves kept in petri dishes served as control. Dishes were incubated at room light and temperature conditions. The ascospores were readily discharged and dark spots with hypophyllous or amphigenous acervuli of P. padi developed on infected leaves 20 days later. No symptoms were present in the control leaves. In conclusion, B. jaapii can complete its life cycle in wild cherries in Italy. The possibility of spring infection by ascospores should be considered in disease management programs. Reference: (1) S. Kaszonyi. Acta Phytopathol. Acad. Sci. Hung. 1:93, 1966.

Bioassay, Effect of Spinosad on Neonate Leafroller Larvae, 1995

Abstract Spinosad DE-105 1.6% was evaluated using a leaf-dip bioassay method for its effect on PLR and OBLR larvae. Treatments were prepared by diluting the appropriate amount of product (see table) in 500 ml water in a glass beaker. A small amount (approximately 2 u.1) of wetting agent, Latron B-1956, was added to each treatment. An untreated control was prepared using water plus the wetting agent only. Untreated apple leaves were collected from Delicious trees at the WSU Tree Fruit Research and Extension Center, Wenatchee. Leaves were dipped, then allowed to dry. Two punches (2.3 cm diameter) were taken from each leaf. Four punches were placed in a Petri dish (Falcon 1006, 50X9 mm). Petri dishes were chosen randomly, and five 1- to 2-d-old leafroller larvae were placed on the leaf disks. The Petri dish lids were put in place, and dishes were stored inside a food storage container and kept at 75°F (±2°F) constant temperature and 16:8 photoperiod. Petri dishes were examined after 7 and 14 d and larval survival recorded. Ten dishes were used for each treatment (50 larvae per treatment).

Bioassay, Effect of Azadirachtin on Neonate Leafroller Larvae, 1995

Abstract Azadirachtin (Neemix 4.5 F, W. R. Grace & Co.-Conn) was evaluated using a leaf-dip bioassay method for its effect on PLR and OBLR larvae. Treatments were prepared by diluting the appropriate amount of product (see table) in 500 ml water in a glass beaker. A small amount (approximately 2 u.1) of wetting agent, Latron B-1956, was added to each treatment. An untreated control was prepared using water plus the wetting agent only. Untreated apple leaves were collected from Delicious trees at the WSU Tree Fruit Research and Extension Center, Wenatchee. Leaves were dipped, then allowed to dry. Two punches (2.3 cm diameter) were taken from each leaf. Four punches were placed in a Petri dish (Falcon 1006, 50X9 mm). Petri dishes were chosen randomly, and five 1 - to 2-d-old leafroller larvae were placed on the leaf disks. The Petri dish lids were put in place, and dishes were stored inside a food storage container and kept at 75°F (±2°F) constant temperature and 16:8 photoperiod. Petri dishes were examined after 7 and 14 d and larval survival recorded. All surviving larvae at 14 d were preserved in alcohol and head capsule widths measured to determine possible sublethal treatment effects. Ten dishes were used for each treatment (50 larvae per treatment).

Turgor pressure and the mechanics of fungal penetration

This article explores the relationship between cellular turgor pressure and mechanisms used by fungi to invade solid substrates. In the oomycete Saprolegnia ferax, the rate of hyphal growth through solid medium decreases as turgor is reduced and the effect is most pronounced at high agar concentrations. This is the first clear evidence that turgor provides the force for invasive hyphal growth. Among pathogenic fungi, the role of turgor in plant infection has been established by experiments on the rice blast fungus Magnaporthe grisea, which can punch through the surface of rice leaves and a variety of synthetic membranes. In common with other walled organisms, fungal growth hinges on an interplay between turgor and the resistance offered by the wall; irrespective of turgor, no cellular expansion or substrate deformation can occur unless the wall yields. Turgor is the only logical source of the necessary force when fungi penetrate plastics, lift the lids of Petri dishes, or burst through asphalt paving. In other cases, fungi use exoenzymes to soften the substrate in advance of the invading cells. This process is particularly significant in plant infection, which involves a combination of physical force and the secretion of cuticle- and wall-degrading enzymes. Key words: hyphae, osmotic stress, Oomycetes, Magnaporthe, Saprolegnia, turgor pressure.

Bioassay approaches to assessing behavioral responses of plum curculio adults (Coleoptera: Curculionidae) to host fruit odor

We evaluated several approaches to developing a simple, sensitive, and reliable laboratory bioassay of responses of overwintered adult plum curculios (PCs),Conotrachelus nenuphar (Herbst), to host fruit odor or its attractive components. A high proportion of assayed PCs responded positively to odor of wild plums under no-choice, moving-air conditions in a wind tunnel and under dual-choice, still-air conditions in enclosed Petri dishes. Positive response to controls lacking host odor, however, was much greater in the wind tunnel, arguing in favor of bioassays under dual-choice conditions in still air to provide greater PC discrimination. Response to host odor (from wild plums or hexane extract of wild plums or Liberty apples) in Petri dish bioassay chambers proved greatest: (1) during the scotophase of PCs under total dark or dim red light conditions, (2) when Petri dishes were completely enclosed, (3) when PCs were starved for 24 or 48 hr, and (4) when PCs were tested within seven weeks after apple tree petal fall. Neither the sex of a PC nor the direction in which a PC was obliged to move to find the source of host odor (upward through a port in the Petri dish lid or downward through a port in the base) had a substantial effect on level of response to host odor or discrimination of host odor from a nonodorous control. We conclude that an enclosed Petri dish bioassay chamber of the type described here should be a valuable asset in the process of chemically identifying components of host fruit odor attractive to PCs.

Bioassay, Laboratory Tests Comparing Dipel and Xentari Against Leafroller Larvae, 1993

Abstract B. thuringiensis products were evaluated for their effect on PLR larvae using artificial diet as a treatment substrate. Treatments were prepared by diluting the appropriate amt of B. thuringiensis (see table) in 500 ml water in a glass beaker. A drop of wetting agent, X-77®, was added to each treatment. An untreated control was prepared using water plus the wetting agent. The pinto bean diet was dyed blue to make leafroller larvae more visible during post-treatment examinations. The diet was cut into small cubes of about Vz inch. Ten diet cubes were placed into a treatment solution for about 30 s, during which time it was stirred continuously. The diet cubes were removed by pouring the treatment solution through a wire sieve. Cubes were placed on a wire screen and allowed to dry. One diet cube was placed in a 1-oz plastic portion cup. Cups containing diet cubes were randomly chosen, and five 1- to 2- d-old leafroller larvae were placed on the cube. The cup lids were put in place, and cups were placed inside a food storage container with a moist paper towel to maintain high humidity and kept at 75°F (±2°F) constant temperature and 16:8 photoperiod. Cups were examined after 3, 7 and 14 d and larval survival recorded. Ten cups were used for each treatment (50 larvae per treatment). A leaf-dip bioassay was also used to compare the effect of treatment substrate on product efficacy. Apple leaves were collected from untreated Red Delicious trees at the WSU Tree Fruit Research and Extension Center, Wenatchee. Leaves were dipped into the same concentrations of Dipel used for the bean-diet bioassay, then allowed to dry. Two punches (2.3 cm diameter) were taken from each leaf. Four punches were placed in each petri dish (Falcon 1006, 50 × 9 mm). Petri dishes were chosen randomly, and five 1- to 2-d-old leafroller larvae were placed on the leaf disks. The petri dish lids were put in place, and dishes were placed inside a food storage container with a moist paper towel to maintain high humidity and kept at 75°F (±2°F) constant temperature and 16:8 photoperiod. Petri dishes were examined after 3, 7 and 14 d and larval survival recorded. Ten dishes were used for each treatment (50 larvae per treatment).

Bioassay, Test of Cryolite on Leafroller Larvae, 1994

Abstract Kryocide (cryolite) was evaluated using a leaf-dip bioassay method for its effect on PLR and OBLR larvae. Treatments were prepared by diluting the appropriate amt of product (see table) in 500 ml water in a glass beaker. A small amt (about 2 ml) of wetting agent, X-77®, was added to each treatment. An untreated control was prepared using water plus the wetting agent only. Untreated apple leaves were collected from ‘Red Delicious’ trees at the WSU Tree Fruit Research and Extension Center, Wenatchee. Leaves were dipped, then allowed to dry. Two punches (2.3 cm diameter) were taken from each leaf. Four punches were placed in a petri dish (Falcon 1006, 50 × 9 mm). Petri dishes were chosen randomly, and five 1- to 2-d-old leafroller larvae were placed on the leaf disks. The petri dish lid was put in place and dishes were placed inside a food storage container with a moist paper towel to maintain high humidity and kept at 75°F (± 2°F) constant temperature and a photoperiod of 16:8 (L:D) h. Petri dishes were examined after 7 d and larval survival recorded. Five dishes were used for each treatment (50 larvae per treatment).

Bioassay, Bacillus Thuringiensis Applied in Different Amounts of Water, 1993

Abstract Using a leaf-disk bioassay, B. thuringiensis products applied in different amts of water per acre were evaluated for their effect on PLR larvae. B. thuringiensis products were applied to 10-yr-old spur type ‘Red Delicious’ (Oregon Spur II) on seedling roots that had not been sprayed with conventional insecticides while leaves were present. Treatments were applied at their recommended field rates (see table), carried in water of 400, 100 and 50 gal/acre (gpa), using a conventional speed sprayer operating at 200 psi. Each treatment was replicated three times with four trees in each. Leaves were collected from the interior canopy of treated trees at 1, 3 and 7 d after treatment. One punch (2.3 cm diameter) was taken from each of 20 leaves per treatment on each date. Four punches were placed in a petri dish (Falcon 1006, 50 × 9 mm). Petri dishes were chosen randomly, and five 1- to 2-d-old leafroller larvae were placed on the leaf disks. The petri dish lids were put in place, and dishes were placed inside a food storage container with a moist paper towel to maintain high humidity and kept at 75°F (±2°F) constant temperature and 16:8 photoperiod. Petri dishes were examined after 7 d and larval survival recorded. Five dishes were set up in each replicate (75 larvae per treatment).

Bioassay, Effects of Molt Accelerating Compounds (MAC) on Neonate Leafroller Larvae, 1994

Abstract Experimental ecdysone agonists or Molt Accelerating Compounds (MAC), RH-5992 and RH-2485, were evaluated using a leaf-dip bioassay to determine their effect on PLR and OBLR larvae. Concentrations of RH-5992 and RH-2485 were diluted in 500 ml of water plus 2 ml of X-77® wetting agent. An untreated control was prepared using water plus the wetting agent. Untreatedi apple leaves were collected from ‘Red Delicious’ trees at the WSU Tree Fruit Research and Extension Center, Wenatchee. Leaves were dipped, then allowed to dry. Two punches (2.3 cm diameter) were taken from each leaf. Four punches were placed in a petri dish (Falcon 1006, 50 × 9 mm). Petri qishes were chosen randomly, and five 1- to 2-d-old leafroller larvae were placed on the leaf disks. The petri dish lid was put in place and dishes were placed inside a food storage container with a moist paper towel to maintain high humidity and kept at 75°F (±2°F) constant temperature and a photoperiod of 16:8 (L:D) h. Petri dishes were examined after 7 d and larval survival recorded. Ten dishes were used for each treatment (50 larvae per treatment).

Bioassay, Tests of Dipel and Myd-0837 on Leafroller Larvae, 1993

Abstract The B. thuringiensis insecticide, Dipel, and a related experimental B. thuringiensis, MYD-0837, were evaluated using a leaf-dip bioassay method for their effect on PLR and OBLR larvae. Treatments were prepared by diluting the appropriate amt of product (see table) in 500 ml water in a glass beaker. A small amt (about 2 u.1) of wetting agent, X-77®, was added to each treatment. An untreated control was prepared using water plus the wetting agent only. Untreated apple leaves were collected from ‘Red Delicious’ trees at the WSU Tree Fruit Research and Extension Center, Wenatchee. Leaves were dipped, then allowed to dry. Two punches (2.3 cm diameter) were taken from each leaf. Four punches were placed in each petri dish (Falcon 1006, 50 × 9 mm). Petri dishes were chosen randomly, and five 1- to 2-d-old leafroller larvae were placed on the leaf disks. The petri dish lids were put in place, and dishes were placed inside a food storage container with a moist paper towel to maintain high humidity and kept at 75°F (±2°F) constant temperature and 16:8 photopervod. Petri dishes were examined after 3 and 7 d and larval survival recorded. Five dishes were used for each treatment (50 larvae per treatment).

Bioassay, Laboratory Tests of Bacillus Thuringiensis Products on Leafroller Larvae, 1994

Abstract B. thuringiensis products, including two experimental products from Sandoz Crop Protection (SAN 420 and SAN 415), were evaluated using a leaf-dip bioassay method for their effect on PLR and OBLR larvae. Treatments were prepared by diluting the appropriate amt of product (see table) in 500 ml water in a glass beaker. A small amt (about 2 ml) of wetting agent, X-77®, was added to each treatment. An untreated control was prepared using water plus the wetting agent only. Untreated apple leaves were collected from ‘Red Delicious’ trees at the WSU Tree Fruit Research and Extension Center, Wenatchee. Leaves were dipped, their allowed to dry. Two punches (2.3 cm diameter) were taken from each leaf. Four punches were placed in a petri dish (Falcon 1006, 50 × 9 mm). Petri dishes were chosen randomly, and five 1- to 2-d-old leafroller larvae were placed on the leaf disks. The petri dish lid was put in place, and dishes were placed inside a food storage container and kept at 75°F (±2°F) constant temperature and a photoperiod of 16:8 (L:D) h. Petri dishes were examined after 7 d and larval survival recorded. Ten dishes were used for each treatment (50 larvae per treatment).

Bioassay, Laboratory Tests of Beauveria Bassiana, Bacillus Thuringiensis, and a Feeding Stimulant on Leafroller Larvae, 1994

Abstract Beauveria bassiana (Naturalis-L), two B. thuringiensis products (Dipel and Troy Bt), and a feeding stimulant (Konsume) combined with a B. thuringiensis product were evaluated using a leaf-dip bioassay method for their effect on PLR and OBLR larvae. Treatments were prepared by diluting the appropriate amt of product (see table) in 500 ml water in a glass beaker. The Konsume treatments received a constant 1X rate of Dipel and 4X-0.25X rates of Konsume. A small amt (about 2 ml) of wetting agent, X-77®, was added to each treatment. An untreated control was prepared using water plus the wetting agent only. Untreated apple leaves were collected from ‘Red Delicious’ trees at the WSU Tree Fruit Research and Extension Center, Wenatchee. Leaves were dipped, then allowed to dry. Two punches (2.3 cm diameter) were taken from each leaf. Four punches were placed in a petri dish (Falcon 1006, 50 × 9 mm). Petri dishes were chosen randomly, and five 1- to 2-d-old leafroller larvae were placed on the leaf disks. The petri dish lid was put in place and dishes were placed inside a food storage container and kept at 75°F (± 2°F) constant temperature and a photoperiod of 16:8 (L:D) h. Petri dishes were examined after 7 d and larval survival recorded. Ten dishes were used for each treatment (50 larvae per treatment).

Bioassay, Laboratory Tests of Bacillus Thvring1Ensis Products on Leafroller Larvae, 1994

Abstract B. thuringiensis products were evaluated using a leaf-dip bioassay method for their effect on PLR and OBLR larvae. Treatments were prepared by diluting the appropriate amt of product (see table) in 500 ml water in a glass beaker. A small amt (about 2 JJLI) of wetting agent, X-77®, was added to each treatment. An untreated control was prepared using water plus the wetting agent only. Untreated apple leaves were collected from ‘Red Delicious’ trees at the WSU Tree Fruit Research and Extension Center, Wenatchee. Leaves were dipped, then allowed to dry. Two punches (2.3 cm diameter) were taken from each leaf. Four punches were placed in a petri dish (Falcon 1006, 50 × 9 mm). Petri dishes were chosen randomly, and five 1- to 2-d-old leafroller larvae were placed on the leaf disks. The petri dish lid was put in place and dishes were placed inside a food storage container with a moist paper towel to maintain high humidity and kept at 75°F (±2°F) constant temperature and a photoperiod of 16:8 (L:D) h. Petri dishes were examined after 7 d and larval survival recorded. Ten dishes were used for each treatment (50 larvae per treatment).

Bioassay, Laboratory Tests of Bacillus Thuringiensis Products on Leafroller Larvae, 1994

Abstract B. thuringiensis products, including an experimental from Mycogen Corp. (MYX300), were evaluated using a leaf-dip bioassay method for their effect on PLR and OBLR larvae. Treatments were prepared by diluting the appropriate amt of product (see table) in 500 ml water in a glass beaker. A small amt (about 2 ml) of wetting agent, X-77®, was added to each treatment. An untreated control was prepared using water plus the wetting agent only. Untreated apple leaves were collected from ‘Red Delicious’ trees at the WSU Tree Fruit Research and Extension Center, Wenatchee. Leaves were dipped, then allowed to dry. Two punches (2.3 cm diameter) were taken from each leaf. Four punches were placed in a petri dish (Falcon 1006, 50 × 9 mm). Petri dishes were chosen randomly, and five 1- to 2-d-old leafroller larvae were placed on the leaf disks. The petri dish lid was put in place, and dishes were placed inside a food storage container with a moist paper towel to maintain high humidity and kept at 75°F (± 2°F) constant temperature and a photoperiod of 16:8 (L:D) h. Petri dishes were examined after 7 d and larval survival recorded. Ten dishes were used for each treatment (50 larvae per treatment).

Bioassay, Tests of B. Thuringiensis Products Against Overwintering and Non-Overwintering Leafroller Larvae, 1993

Abstract Different B. thuringiensis products were evaluated for their effect on PLR larvae from two sources, a non-diapausing laboratory colony and one collected from the field and destined to enter diapause. Egg masses were collected from the field in Sep, and larvae hatching from these were destined to stop development in the second or third instar and produce hibernacula for overwintering. These larvae were used in tests 1-2 d after hatching. The other source of larvae was from a laboratory colony that was reared continuously in a long-d photoperiod of 16:8 (L:D) h. Larvae from this colony would not stop feeding but continue development. Treatments were prepared by diluting the appropriate amt of product (see table) in 500 ml water in a glass beaker. A small amt (about 2 u,l) of wetting agent, X-77*, was added to each treatment. An untreated control was prepared using water plus the wetting agent only. Untreated apple leaves were collected from ‘Red Delicious’ trees at the WSU Tree Fruit Research and Extension Center, Wenatchee. Leaves were dipped, then allowed to dry. Two punches (2.3 cm diameter) were taken from each leaf. Four punches were placed in each petri dish (Falcon 1006, 50 × 9 mm). Petri dishes were chosen randomly, and five 1- to 2-d-old leafroller larvae were placed on the leaf disks. The petri dish lids were put in place, and dishes were placed inside a food storage container with a moist paper towel to maintain high humidity and kept at 75°F (±2°F) constant temperature and 16:8 photoperiod. Petri dishes were examined after 7 and 10 d and larval survival recorded. Five dishes were used for each treatment (25 larvae per treatment per test). Larvae surviving in each test were collected after the last evaluation and stored in alcohol until head capsule widths could be measured. The average head capsule width is an indication of larval age and is thus a measure of sublethal effects of a treatment on larval development. Three tests were conducted using these methods. Rates in the first test were higher than those used in the final two.

Bioassay, Effects of Combinations of Mvp and Myd-0837 on Leafroller Larvae, 1993

Abstract The B. thuringiensis insecticide, MVP, and a related experimental B. thuringiensis product, MYD-0837, were evaluated alone and in combination using a leaf-dip bioassay method for their effect on PLR and OBLR larvae. Treatments were prepared by diluting the appropriate amt of product (see table) in 500 ml water in a glass beaker. A small amt (about 2 u,l) of wetting agent, X-77®, was added to each treatment. An untreated control was prepared using water plus the wetting agent only. Untreated apple leaves were collected from ‘Red Delicious’ trees at the WSU Tree Fruit Research and Extension Center, Wenatchee. Leaves were dipped, then allowed to dry. Two punches (2.3 cm diameter) were taken from each leaf. Four punches were placed in each petri dish (Falcon 1006, 50 × 9 mm). Petri dishes were chosen randomly, and five 1- to 2-d-old leafroller larvae were placed on the leaf disks. The petri dish lids were put in place, and dishes were placed inside a food storage container with a moist paper towel to maintain high humidity and kept at 75°F (± 2°F)

A technique for maintaining explants in contact with solid medium in petri dishes

The objective of this study was to develop a system to maintain orchardgrass (Dactylis glomerata L.) leaf segments in contact with solid medium in petri dishes during different orientation of the dishes. To ensure contact with the medium, leaf segments were overlaid with 1800 μm Teflon™ mesh. This was secured with a polypropylene ring which fitted between the petri dish lid and the mesh. This procedure did not affect the somatic embryogenesis response. A significant difference (P=0.05) in increased ethylene accumulation from overlaid segments was recorded on day 5.

Rate Response of Bacillus Thumngiensis Against Leafrollers, 1992

Abstract Bt products were evaluated for their effect on PLR larvae using a leaf-disk bioassay. A series of Bt concentrations ranging from 0.5 to 5 times the recommended field rates were tested. Untreated apple leaves were collected from Red Delicious trees at the WSU Tree Fruit Research and Extension Center, Wenatchee. Bt products were diluted in 500 ml of water plus 2 u,l of X-77, a wetting agent added to aid leaf wetting. An untreated control was prepared using water plus the wetting agent only. Leaves were dipped and allowed to dry. Two disks (2.3 cm diameter) were taken from each leaf. Four leaf disks were placed in a petri dish (Falcon 1006, 50x9 mm). Five one- to two-d-old leafroller larvae were placed on the leaf-disks and the petri dish lid was put in place. Ten dishes were used for each Bt product and rate (50 larvae per treatment). Dishes were placed inside a food storage container with a wet paper towel to maintain a high humidity and kept at 75°F (±2°F) constant temperature and 16:8 photoperiod. Dishes were examined after 48 and 96 h to determine larval survival. Data were corrected for untreated mortality using Abbott’s formula.

Field-Aged Residues of Bacillus Thuringiensis Against Leafrollers, 1992

Abstract Different Bt products were evaluated for their effect on PLR larvae using a leaf-disk bioassay. Bt products were applied to Red Delicious apple trees at their recommended field rates as shown in the table using a handgun sprayer at 300 psi to the point of drip, simulating a dilute spray of approximately 400 gallons per acre. Treated apple leaves were collected 1, 3, 5, 7, and 9 d post-treatment. Two punches (2.3 cm diam) were taken from each of 20 leaves per treatment on each date. Four punches were placed in a petri dish (Falcon 1006, 50 x 9 mm). Five one- to two-d-old leafroller larvae were placed on the leaf disks and the petri dish lid was put in place. Ten dishes were used for each Bt product and rate (50 larvae per treatment). Dishes were placed inside a food storage container with a wet paper towel to maintain a high humidity and kept at 75°F (± 2°F) constant temperature and 16:8 photoperiod. Dishes were examined after 96 and 144 h to determine larval survival. Data were collected for untreated mortality using Abbott’s formula.