Jesusa Crisostomo Legaspi

PREY PREFERENCE BY DELPHASTUS CATALINAE (COLEOPTERA: COCCINELLIDAE) ON BEMISIA ARGENTIFOLII (HOMOPTERA: ALEYRODIDAE): EFFECTS OF PLANT SPECIES AND PREY STAGES

Abstract Plant species and insect stages were studied for their effects on feeding by predator Delphastus catalinae (Horn) (Coleoptera: Coccinellidae) on the silverleaf whitefly (Bemisia argentifolii Bellows and Perring) (Homoptera: Aleyrodidae). To study the influence of plant species, immature whitefly prey were presented simultaneously to starved predator adults on leaf cuttings of five different plant species: cotton (Gossypium hirsutum L.), tomato (Lycopersicon esculentum Miller), hibiscus (Hibiscus rosa-sinensis L.), cowpea (Vigna unguiculata [L.], Walpers ssp. unguiculata), and collard (Brassica oleracea var. acephala DC). Percentage predation over 24 h was significantly highest on cotton, followed in rank order by collards, cowpea, tomato, and hibiscus. Different predation rates may have been caused by differential response to volatile secondary compounds released by the leaf cuttings. Host stage preference was studied by presenting individual adult predators with equal numbers of prey (200 per replicate) in three aggregate life stages: eggs, small nymphs (1st to 3rd instars) and large nymphs (4th instar to pupae). Adults consumed significantly higher numbers of eggs in a 24-h predation period compared with small or large nymphs. These findings suggest that among the plant species tested, Delphastus catalinae may be most effective on early-season cotton or immediately after whitefly infestation when eggs are predominant.

Survival and Predation of Delphastus catalinae (Coleoptera: Coccinellidae), a Predator of Whiteflies (Homoptera: Aleyrodidae), After Exposure to a Range of Constant Temperatures

Abstract Delphastus catalinae (Horn) is a predator of whiteflies that has shown promise as a tool in pest management strategies. Exposure to short-term temperature extremes can affect the survival of predators in a greenhouse or field environment. The B-biotype sweetpotato whitefly, Bemisia tabaci (Gennadius), survives the winters of mild climates (where temperatures are commonly above 0°C), but it is not known if D. catalinae can survive such winters. The influence of constant temperature on the survival of D. catalinae was determined in the laboratory using eggs and nymphs of the B-biotype B. tabaci. Over 90% of the adult beetles exposed to temperature regimens of 5, 10, 15, 20, 25, 30, and 35°C for 24 h survived when confined with hosts. The lower and upper thresholds for survival over that duration were around 0 and 40°C, respectively; ∼1% of the insects survived temperatures beyond these extremes. Survival of D. catalinae pupae was similar to that of adults. Adult D. catalinae survived up to 5.8 mo when confined on a plant infested with whitefly eggs and nymphs and held at 25°C; 50% of the cohort survived for 3.4 mo. Those held in a similar test at 35°C lived up to 0.6 mo. The number of immature whiteflies consumed during 24 h by adult D. catalinae generally increased with temperatures of 14–30°C. This study provides information on temperatures that may affect the survival of D. catalinae during commercial shipment and after release for biological control in the field or greenhouse, and it may help in the understanding of their ability to survive mild winters.

Life table analysis for Cactoblastis cactorum immatures and female adults under five constant temperatures : Implications for pest management

Abstract The cactus moth, Cactoblastis cactorum (Berg) (Lepidoptera: Pyralidae), was reported in Florida in 1989, and it is expanding its geographical range to threaten Opuntia cactus (Cactaceae) in the southwestern United States, into Mexico, where it is an important economic crop. Laboratory life history studies were conducted at 18, 22, 26, 30, and 34°C to understand cactus moth biology and to develop strategies for control. Duration of immature stages was generally longest at 18°C, declining significantly at 22°C, and shortest at 26, 30, and 34°C. Total immature developmental time from eggs to pupae was ≈180 d at 18°C, 116 at 22°C, and ranged from 65 to 72 d at 26–34°C. Developmental rate for egg-to-pupal stages was estimated using the logistic equation, rate = 0.0165/(1 + (T/20.7093)−5.8823). Percentage survival of immatures was usually lowest at the temperature extremes tested (18 and 34°C), but they did not differ between the sexes. Estimated lower developmental threshold temperature was 13.3°C, resulting in estimated degree-days for development from ≈845 at 18°C to 1,387 at 34°C. In general, pupal weights declined with increasing temperature, and they were always lower in males than in females. Female adult survivorship was longest at 18°C, and shortest at 34°C, with the other treatments clustered between the temperature extremes. The highest reproductive values were found at 30°C, which indicates an approximate optimal temperature. Net reproductive rate (R0), gross reproductive rate (GRR), generation time (T), intrinsic rate of increase (r), finite rate of increase (&lgr;), and doubling time (DT) were 43.68 ♀/♀, 44.02 ♀/♀, 67.14 d, 0.0562 ♀/♀/d, 1.058 ♀/♀/d, and 12.33 d, respectively. An oviposition rate surface describing mean oviposition rate as a function of time and temperature was, eggs = (−11.241 + 0.854T) d exp (−0.020Td). Given the life history characteristics found in this study and other studies, cost-effective pest management strategies against C. cactorum are discussed.

Life History of Podisus maculiventris (Heteroptera: Pentatomidae) Adult Females Under Different Constant Temperatures

Abstract Life table analysis was performed on Podisus maculiventris (Say) adult females at constant temperatures of 16, 26, 30, and 36°C. Survivorship curves were linear type II, with steeper rates of decline at higher temperatures. Longevity at 16°C (47.2 d) was significantly longer than that at 26°C (14.3 d) or 30°C (12 d). Adults under the 36°C survived only 4.9 d and laid no eggs. Percentage of eggs that hatched was relatively constant at ≈ or about 40% at 16, 26, and 30°C. Numbers of egg clutches (ranging from 5.9 to 9.4), eggs per clutch (13.6–14.6), and eggs in the first clutch (9.0–15.1) did not differ significantly at these three temperatures. However, preoviposition period was significantly longer at 16°C (20.3 d) than at 26°C (6.3 d) and 30°C (4.9 d). Number of eggs laid was related to body weight by the equation E = −139.1 + 3.49w, where E is number of eggs laid per female lifetime, and w is the weight of the predator female. Life table analysis of P. maculiventris female adults showed that both net reproductive rate (R0) and gross reproductive rate (GRR) were highest at 26°C, estimated at 47.8 and 156.0 females per female, respectively. However, the shorter generation times at 30°C (T = 42.2 d) resulted in higher values for the intrinsic rate of increase (r = 0.09), the finite rate of increase (λ = 1.09), and doubling time (DT = 7.7 d). Analysis of cumulative egg production suggests that 26°C may be more suitable for maintaining colonies of P. maculiventris because of the sustained levels of egg production over a longer period, compared with the 30°C treatment.

Life Table Analysis for Podisus maculiventris Immatures and Female Adults Under Four Constant Temperatures

Abstract Detailed life tables and reproduction were studied in nymphs and adult females of Podisus maculiventris (Say) (Heteroptera: Pentatomidae) fed larvae of Galleria mellonella L. (Lepidoptera: Pyralidae) at constant temperatures of 18, 22, 26, and 30°C. Development rates were fitted to the equation Y = a + b ln x. The theoretical development threshold was calculated as T0 = exp (−a/b), resulting in T0 = 12.48 and 12.78°C for females and males, respectively. Degree-days for development ranged from 233.92 in males at 18°C to 338.73 in females at 30°C. In all temperature treatments, P. maculiventris immatures consumed a mean of approximately eight prey items. Mean immature body weights were higher at higher temperatures, but females were heavier than males only at the fifth instar. In adult female P. maculiventris, age at first oviposition ranged from 2.7 d at 30°C to 13.4 d at 18°C. Percentage of egg hatch was lowest at 18°C (11%) and highest at 30°C (36.4%). Survivorship curves showed a linear decline with time, the steepest curves at the highest temperatures. Total number of eggs laid per female ranged from 429.4 at 18°C to 755.4 at 26°C. Mean egg numbers were fitted to a surface equation as eggs = (−6.658 + 0.432T) d exp(−0.002Td) where d and T are age (days) and temperature (°C), respectively. Net and gross reproductive rates were highest at 26°C (R0 = 379.126; gross reproductive rate [GRR] = 491.273 ♀/♀) and lowest at 18°C (R0 = 207.873; GRR = 294.972). Generation and doubling times were shortest at 30°C (T = 35.021 and DT = 4.270 d). Intrinsic and finite rates of increase were also highest at 30°C (r = 0.1623; λ = 1.1763). Reproductive parameters were recalculated using numbers of eggs that actually hatched, resulting in lower values, although the effects of temperature did not change. In the context of mass rearing P. maculiventris, 26°C is the optimal temperature tested, but female predators >21 d should be not be used because they may not be capable of laying viable eggs.

Responses of Delphastus catalinae (Coleoptera: Coccinellidae), a Predator of Whiteflies (Hemiptera: Aleyrodidae), to Relative Humidity: Oviposition, Hatch, and Immature Survival

Abstract Delphastus catalinae (Horn) (Coleoptera: Coccinellidae) is a predator of whiteflies. It is tropical in origin. Whiteflies cause problems in agriculture in both humid and arid environments. A study was conducted to determine any effects of relative humidity on oviposition, hatching, and survival of immature D. catalinae. Comparative tests were conducted among relative humidities of 25, 35, 50, and 85% and between 10 and 85% RH. All tests were conducted at 26°C; hence, vapor pressure deficits ranged from 5.04 to 30.25 mb. The study was conducted using the B-biotype sweetpotato whitefly, Bemisia tabaci (Gennadius), as the host insect, which was reared on collard, Brassica oleracea ssp. acephala de Condolle. Egg hatch and survival to the adult stage were reduced at the lower relative humidities. At 85% RH, 99% of the eggs hatched and ≈90% of the beginning cohort survived to the adult stage. Conversely, ≈85% hatched and ≈60% survived to the adult stage at 25% RH, whereas 50% survived to the adult stage at 10% RH. Eggs required more time to develop at 10% RH (5.3 d) compared with 85% RH (4.1 d); a test was not set up to compare the developmental times for the larval and pupal stages. Weights of male and female D. catalinae were significantly reduced with a reduction in humidity. The results also suggest that density of immature D. catalinae, limited food supply, or both may affect survival and size of the ensuing adults. These results help in the understanding of the ecology of D. catalinae, and they indicate that extremes in ambient moisture can have an impact on the population of this predator.

Life table analysis for immatures and female adults of the predatory beetle, Delphastus catalinae, feeding on whiteflies under three constant temperatures

Abstract Immature development and reproductive life history of Delphastus catalinae (Horn) (Coleoptera: Coccinellidae) feeding on Bemisia tabaci biotype B (Gennadius) (Homoptera: Aleyrodidae) (= B. argentifolii Bellows and Perring) immatures was studied at three constant temperatures: 22, 26 and 30 °C. Lower developmental threshold temperatures (T0) were estimated at 9 and 9.9 °C, for males and females, respectively. Female adults weighed slightly more than males (0.587 and 0.505 mg, respectively). As temperature increased from 22 to 30 °C, developmental time from eggs to eclosion of the adult declined from 24 to 15 days. Thermal units required for immature development was ∼300 degree-days. Percentage egg hatch declined at increasing temperatures, but no significant effect of time was found. The intrinsic rate of increase, r, increased from 0.048 to 0.082 and doubling time decreased from 14.44 to 8.45 days as temperature increased from 22 to 26 °C. Mean daily fecundity was modeled as a function of time and temperature to create a 3-dimensional surface. Overall, Delphastus catalinae was found to perform better at 22 and 26 °C while 30 °C was detrimental to immature development and adult reproduction.

Ability of Delphastus catalinae (Coleoptera: Coccinellidae), a predator of whiteflies (Homoptera: Aleyrodidae), to survive mild winters.

Delphastus catalinae (Horn) (Coleoptera: Coccinellidae) is a predator of whiteflies and is sold by commercial insectaries to help manage Bemisia tabaci (Gennadius). This beetle is tropical in origi...

Does a Polyphagous Predator Prefer Prey Species That Confer Reproductive Advantage?: Case Study of Podisus maculiventris

Abstract The purpose of this study was to determine whether preferred prey of Podisus maculiventris (Say) (Heteroptera: Pentatomidae) adult females also conferred maximal fecundity. We also studied egg development and maturation as a function of predator age, i.e., “ovigeny” as used predominantly in the context of parasitoids. To determine prey preference, adult females were simultaneously offered five pest prey: 1) beet armyworm, Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae); 2) fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae); 3) cabbage looper, Trichoplusia ni (Hübner) (Lepidoptera: Noctuidae); 4) greater wax moth, Galleria mellonella (L.) (Lepidoptera: Pyralidae); and 5) yellow mealworm, Tenebrio molitor (L.) (Coleoptera: Tenebrionidae) (n = 20). In a second experiment, adult P. maculiventris females were provided a single species of prey (for each of the five prey species, n = 10). This experiment was repeated over four durations: 7, 15, 22, and 30 d. After each time trial, egg load dissections were performed, and numbers of mature and immature eggs were recorded. P. maculiventris displayed a preference of beet armyworm, whether measured as numbers attacked or estimated biomass consumed. However, no significant differences were found in cumulative numbers of eggs laid under the different prey treatments, with the exception of the 22-d trial where significantly more eggs were laid when feeding on the cabbage looper. During the 22-d trial, the number of egg clutches and numbers of eggs per clutch were highest when fed cabbage looper and lowest with yellow mealworm. Percentage of egg hatch combined across time trials was highest in cabbage looper (81.7%) and lowest in greater wax moth (63.8%). Egg load dissections revealed that the total number of eggs and numbers of mature eggs declined significantly with predator age. However, numbers of immature eggs increased. The mean number of mature eggs in 7-d-old predators represented only ≈5% of mean cumulative numbers of eggs laid by 30-d-old predators, indicating that P. maculiventris is strongly synovigenic, where egg development and maturation continues during adulthood. The implications of these results are discussed from the context of P. maculiventris as a biological control agent.

Biological and Ecological Consequences of Diolcogaster sp. (Hymenoptera: Braconidae) Parasitizing Agaraea minuta (Lepidoptera: Arctiidae) and the Effects on Two Costus (Costaceae) Plant Species in Brazil

ABSTRACT Costus spicatus (Jacq.) Sw. and Costus spiralis (Jacq.) Roscoe var. spiralis (Costaceae) are economically important plants due to their pharmacological and medicinal properties and ornamental value. These plants are natives from the Brazilian Atlantic Rainforest and are fed upon by Agaraea minuta Schaus, 1892 (Lepidoptera: Arctiidae). This study describes the damage done by A. minuta on C. spicatus and C. spiralis and the biological and ecological aspects of parasitism of A. minuta by Diolcogaster sp. (Hymenoptera: Braconidae). Twenty stems of C. spicatus and C. spiralis with 100 last-instar caterpillars of A. minuta, were collected per plant in each of 2 years. The stem heights (F, P > 0.05), leaf lengths (F, P > 0.05), leaf widths (F, P > 0.05) and the number of leaves per stem (F, P > 0.05) of both plant species; number of pupae obtained from caterpillars of A. minuta (F, P > 0.05), adult emergence of this defoliator (F, P > 0.05) and of Diolcogaster sp. (F, P > 0.05) were similar during the 2 study periods. Agaraea minuta fed on C. spicatus and C. spiralis, and Diolcogaster sp. was shown to be a parasitoid suppressor of populations of this defoliator.