Nitrogen fertiliser input alters the prey consumption rate of a widespread aphid predator, Harmonia axyridis

Seven spot ladybird beetle, (Coccinella septempunctata) is a widely distributed natural enemy of soft-bodied insect pests especially aphids worldwide. Both the adult and larvae of this coccinellid beetle are voracious feeders and serve as a commercially available biological control agent around the globe. Different techniques are adopted to enhance the mass rearing and storage of this natural enemy by taking advantage of its natural ability to withstand under extremely low temperatures and entering diapause under unfavorable low temperature conditions. The key objective of this study was to develop a cost effective technique for enhancing the storage life and predatory potential of the larvae of C. septempunctata through cold storage in conjunction with the use of nuclear techniques, gamma radiations. Results showed that the host eating potential of larvae was enhanced as the cold storage duration was increased. Gamma irradiation further enhanced the feeding potential of larvae that were kept under cold storage. Different irradiation doses also affected the development time of C. septempuntata larvae significantly. Without cold storage, the lower radiation doses (10 and 25 GY) prolonged the developmental time as compared to un-irradiated larvae. Furthermore, the higher dose of radiation (50GY) increased the developmental time after removal from cold storage. This study first time paves the way to use radiation in conjunction with cold storage as an effective technique in implementation of different biological control approaches as a part of any IPM programs

In order to investigate the impact of recycling agricultural wastes as feed for mealworm (Tenebrio molitor), we evaluated the replacing effect by the different level of tangerine shell, Chinese cabbage, king oyster mushroom (Pleurotus eryngii) and Enoki mushroom (Flammulina velutipes) substrates on wheat bran feed. Larval survival rate, larval weight, developmental period of larva, pupation rate and pupal weight were evaluated. In tangerine shell and Chinese cabbage replacement group, no replacing effects found. In all groups replacing by spent King oyster mushroom (Pleurotus eryngii) substrate, survival rate of larva was similar to that of control group but larvae weighed less than control group significantly. Developmental period of larva increases in the group of King oyster mushroom substrate replacement. Larval and pupal weight in Enoki mushroom (Flammulina velutipes) substrate by the level of 40 and 50%, replacement effect showed best results in successive breeding considering pupation rate. It is concluded that replacing 40 and 50% of Enoki mushroom (Flammulina velutipes) substrate is appropriate to substituted diet of Tenebrio molitor larvae.

Effects of elevated atmospheric carbon dioxide on insect–plant interactions

Spodoptera litura (Fabricius, 1775) is a serious polyphagous pest causes serious damage to various crops like tobacco, cotton, cabbage etc. in Asia and other Indian subcontinents. Depletion in host plants may lead to adverse effect on the alternate host plants. During survey, observed S. litura larvae were feeding on Cassia tora, in this study third instar larvae of S. litura larvae were reared on the common and most preferred hosts like castor and tobacco. Larval, prepupal and pupal weight were compared with and other two common hosts. Percent pupation and adult emergence rate were also recorded. Among three hosts, insects which fed on Cassia tora have higher larval weight (0.825 mg) and also observed longer larval period compared to other two hosts. No differences were observed in prepupal, pupal (male and female) weight. Percent pupation was higher in S. litura, which were fed on castor and tobacco i.e., 100 % and 96.67 % respectively, and on C. tora recorded lowest per cent pupation (20 %). Adult emergence rate was found to be non-significant on castor and tobacco fed larvae but the lowest adult emergence was recorded on cassia about 18 %. Feeding of newly hatched instars of S. litura confirms that, it uses C. tora as an alternate host during off-season survival and complete its life cycle. Longer larval duration on C. tora may prone larvae to expose more to the external environment, results in less pupation rate.

Exploring the differential responses of rhizosphere soil phosphorus contents associated with nitrogen-fixing and non-nitrogen-fixing plants to different soil nitrogen levels in subtropical karst forests can provide valuable insights into the effects of nitrogen-fixing plants on soil nutrient cycling. Such knowledge will serve as a scientific reference for the extensive planting of nitrogen-fixing plants in vegetation restoration efforts in karst regions. Taking karst forests with varying soil nitrogen levels in Jianshui County, Yunnan Province as test objects, we collected soil samples from the rhizosphere of three types of dominant nitrogen-fixing and non-nitrogen-fixing plants with the same age and analyzed the total phosphorus (TP), organic phosphorus (OP), inorganic phosphorus (IP), available phosphorus (AP), and other soil physicochemical properties. Soil microbial biomass and enzyme activities were measured to assess the influence of nitrogen-fixing plants on rhizosphere soil phosphorus contents under different soil nitrogen levels, as well as the main driving factors. Results showed that the contents of TP, OP and AP in the rhizosphere soil of nitrogen-fixing plants significantly increased by 16.0%, 66.5% and 139.5% under a low soil nitrogen level with the available nitrogen of 15.62 mg·kg-1, and significantly increased by 13.5%, 25.7% and 15.7% under higher soil nitrogen level with the available nitrogen of 37.15 mg·kg-1, respectively. There was no significant difference in IP content between nitrogen-fixing and non-nitrogen-fixing plants under the two soil nitrogen levels. Compared with low soil nitrogen level, the contents of TP and IP in the rhizosphere soil of nitrogen-fixing plants under high soil nitrogen level significantly decreased by 21.3% and 31.7%, and those of non-nitrogen-fixing plants significantly decreased by 19.6% and 39.1%. The AP content in the rhizosphere soil of nitrogen-fixing and non-nitrogen-fixing plants significantly increased by 32.8% and 174.8%, respectively, with no notable change in OP content. Under low nitrogen conditions, nitrogen-fixing plants significantly increased microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), microbial biomass phosphorus (MBP), and alkaline phosphatase (ALP) activity in the rhizosphere soil. Under high nitrogen condition, nitrogen-fixing plants significantly increased MBP and ALP activity, but had no significant effect on MBC and MBN. As soil nitrogen level increased, soil MBC, MBN, MBP, and nitrogen cycle-related enzyme activities in the rhizosphere soil of nitrogen-fixing plants decreased significantly, while ALP activity increased. In contrast, in the rhizosphere soil of non-nitrogen-fixing plants, MBN and ALP activity significantly increased, while nitrogen cycle-related enzyme activities significantly decreased. Mantel analysis indicated that under low nitrogen level, rhizosphere soil phosphorus contents were primarily regulated by a combination of soil physicochemical properties, microbial biomass, and enzyme activity, while they were mainly regulated by soil physicochemical properties under high nitrogen level. In conclusion, compared to non-nitrogen-fixing plants, nitrogen-fixing plants in subtropical karst forests can significantly increased soil TP, OP, and AP contents and this effect is largely regulated by soil nitrogen level. Therefore, introducing nitrogen-fixing plants into low-nitrogen subtropical karst areas at the beginning of vegetation restoration may alleviate phosphorus limitation, improve soil nutrient status, and facilitate vegetation restoration in these regions.

Next generation biological control – an introduction

1 Larval survival and development of Dipel‐susceptible and ‐resistant strains of European corn borer, Ostrinia nubilalis (Hübner), were assayed using diets incorporating low doses of a commercial formulation of Bacillus thuringiensis var. kurstaki Berliner (Dipel ES).2 Larval mortality, growth and development, pupation rate and pupal weight were not significantly different between Dipel‐susceptible and ‐resistant strains when larvae were reared on a nontoxic control diet.3 Larval mortality of Dipel‐resistant larvae did not significantly change as Dipel concentration increased at the tested concentrations, whereas mortality of Dipel‐susceptible larvae increased dramatically as Dipel concentration increased.4 Larval development was significantly delayed when larvae were fed diets containing low doses of Dipel.5 Pupation rate and pupal body weight declined as Dipel concentration increased but it decreased faster for the susceptible strain than for the resistant strain.

This study aimed to evaluate the reproductive and growth performance of recently developed bivoltine silkworm parental breeds and their hybrids to improve silk production and ensure the long-term sustainability of sericulture. Utilizing five thermotolerant pure breeds (B1, B2, B4, B6 and B8) and four popular CSR breeds (CSR2, CSR27, CSR6 and CSR26), six foundation crosses and eight double hybrids were developed and evaluated for ten traits. Results showed that B1 exhibited superior performance in fecundity (524.00), hatching percentage (98.67%), dead eggs (1.33%), pupal weight (1.31 g), pupation rate (96.84%) and cumulative survival index (CSI) (93.84%). The foundation cross B1 × B2 excelled in fecundity (553.67), larval mortality (2.67%), pupal weight (1.53 g), ERR (97.33%) and CSI (93.27%) while FC2 performed better in hatching percentage (97.60%), dead eggs percentage (2.40%), fifth instar larval duration (157.21 h), fifth instar larval weight (35.64 g/10 larvae) and pupation rate (96.33%). Among the double hybrids, (B1 × B2) × (FC1) demonstrated superior performance in fecundity (614.33), larval mortality (1.41%), pupal weight (2.06 g), ERR (98.59%) and CSI (97.24%). FC2 × FC1 excelled in larval duration (141.11 h), fifth instar larval weight (51.96 g/10 larvae) and pupation rate (98.94%). Double hybrids showed significant improvements compared to parental breeds and foundation crosses, indicating potential for field testing and further development. These results indicate the potential of using the newly identified breeds and foundation crosses in silkworm breeding, particularly in developing new double hybrids as an alternative to established CSR breeds and hybrids.

The Seasonal Occurrence of the Two Aphid Species, Myzus persicae and Aphis gossypii, and their Natural Enemies on Vegetable Crops in Chinju, Korea

본 연구는 꿀벌부채명나방의 경제적 사육을 위한 인공사료 개발을 위하여 수행하였다. 가격이 비싼 벌꿀을 대체하여 물엿과 설탕을 이용한 사료별 꿀벌부채명나방의 발육과 발육기간 및 산란수, 성충 수명 등을 조사하였다. 당 종류별 유충의 두폭과 체장은 비슷하였으나 체중은 1/2벌꿀 + 1/2물엿 처리가 255.5 mg으로 가장 무거웠고, 설탕은 144.3 mg으로 가장 가벼웠다. 꿀벌부채명나방 번데기의 체중도 1/2벌꿀+1/2물엿이 196.7 mg으로 가장 무거웠다. 당 종류별 꿀벌부채명나방의 유충 발육기간은 벌꿀이 포함된 사료가 30.9일로 가장 짧았으며 설탕은 36.5일로 가장 길었다. 꿀벌부채명나방의 용화율과 우화율은 79.3% 이상이었다. 모든 사료에서 꿀벌부채명나방의 교미 성충의 수명은 암컷이 <TEX>$6.3{\sim}8.0$</TEX>일이었고, 수컷은 <TEX>$7.9{\sim}11.2$</TEX>일이었다. 사료별 꿀벌부채명나방 암컷 성충의 산란수는 설탕물 첨가 사료에서 1,269개로 가장 많았다. 당 종류별 인공사료 조성에 대한 비용은 밀기울이 쌀겨보다 10배 정도 많았으며, 벌꿀은 물엿과 설탕의 6배와 13배였다. This research was carried out to develop economical artificial diets of the greater wax moth, Galleria mellonella (L.). Diets were mixed with malt or sugar instead of whole honey for cheaper ones. fecundity, developmental period, pupation rate, emergence rate and adult longevity of G. mellonella depending on diet were examined. The head width and length of larvae were not significantly different among diets tested. However, the weight of larva was the heaviest, 255.5 mg, at 1/2 honey + 1/2 malt diet and lightest, 144.3 mg, at sugar diet. The weight of pupa was also the heaviest at 1/2 honey + 1/2 malt representing 196.7 mg. Larval period was the shortest at honey diet as 30.9 days but the longest at sugar diet as 36.5 days. Pupation and emergence rates were over 79.3% at all diets. The longevity of mated females was ranged from 6.3 to 8.0 days and those of mated males ranged from 7.9 to 11.2 days. The highest number of eggs, 1269, was obtained at sugar diet. Artificial diets replaced by rice bran, malt, and sucrose reduced costs compared with wheat bran plus honey diet. The cost of rice bran was only 10% of wheat bran. Honey was much more expensive than malt and sugar, that is 6 and 13 times, respectively.

Toxicities of destruxins against Bemisia tabaci and its natural enemy, Serangium japonicum

Generalist predators are often used in biological control programs, although they can be detrimental for pest control through interference with other natural enemies. Here, we assess the effects of generalist natural enemies on the control of two major pest species in sweet pepper: the green peach aphid Myzus persicae (Sulzer) and the western flower thrips Frankliniella occidentalis (Pergande). In greenhouses, two commonly used specialist natural enemies of aphids, the parasitoid Aphidius colemani Viereck and the predatory midge Aphidoletes aphidimyza (Rondani), were released together with either Neoseiulus cucumeris Oudemans, a predator of thrips and a hyperpredator of A. aphidimyza, or Orius majusculus (Reuter), a predator of thrips and aphids and intraguild predator of both specialist natural enemies. The combined use of O. majusculus, predatory midges and parasitoids clearly enhanced the suppression of aphids and consequently decreased the number of honeydew-contaminated fruits. Although intraguild predation by O. majusculus on predatory midges and parasitoids will have affected control of aphids negatively, this was apparently offset by the consumption of aphids by O. majusculus. In contrast, the hyperpredator N. cucumeris does not prey upon aphids, but seemed to release aphids from control by consuming eggs of the midge. Both N. cucumeris and O. majusculus did not affect rates of aphid parasitism by A. colemani. Thrips were also controlled effectively by O. majusculus. A laboratory experiment showed that adult predatory bugs feed on thrips as well as aphids and have no clear preference. Thus, the presence of thrips probably promoted the establishment of the predatory bugs and thereby the control of aphids. Our study shows that intraguild predation, which is potentially negative for biological control, may be more than compensated by positive effects of generalist predators, such as the control of multiple pests, and the establishment of natural enemies prior to pest invasions. Future work on biological control should focus on the impact of species interactions in communities of herbivorous arthropods and their enemies.

Botanical pesticide is highly recommended for integrated pest management (IPM), due to its merits such as environmental friendliness, safe to non-target organisms, operators, animals, and food consumers. The experiment was conducted to determine the lethal and sub-lethal effects of allyl isothiocyanate (AITC) on eggs, third instar larvae, pupae, and females and males of Bradysia impatiens Johannsen (B. impatiens). Different concentrations of AITC under ambient CO2 by the conical flask sealed fumigation method were used for the experiment. The results showed that there was a significant linear relationship between different concentrations of AITC and the toxicity regression equation of B. impatiens. The sub-lethal concentrations of AITC had significant effects on the larval stage, pupal stage, pupation rate, pupal weight, adult emergence rate, and oviposition. The pupation rate, pupal weight, and adult emergency rate were significantly (p < 0.05) affected by AITC fumigation. The pupation rate was the lowest after fumigation treatment of AITC at LC50 (36.67%), followed by LC25 (41.94%), compared with the CK (81.39%). Female longevity was significantly (p < 0.05) shortened by fumigation at LC25 (1.75 d) and LC50 (1.64 d), compared with that of CK (2.94 d). Male longevity was shorter at LC25 (1.56 d) than at LC50 (1.25 d) and had no significant difference between these two treatments. The fumigation efficiency of AITC was significantly increased under high CO2 condition. Furthermore, detoxification enzyme activities and antioxidant enzyme activities were accumulated under high CO2 condition. The fumigation method in the application of AITC can be useful in areas where B. impatiens is a major concern.

Development and reproduction of Crocidolomia pavonana (F.) (Lepidoptera: Pyralidae) on natural and artificial diets. Development and reproduction of Crocidolomia pavonana on natural and artificial diets were studied in the laboratory (25.2 ± 0.9 C; 84.6% ± 6.7% RH; ca. 12 h photophase). The natural diets tested were broccoli, cabbage, chinese cabbage, and cauliflower leaves. The artificial diets used were agar–based general lepidopteran diets mixed with red bean or broccoli leaves, and supplemented with vitamins and microbial inhibitors. Observation of insect development was done since the egg stage. After the eggs hatched, larvae were kept singly in plastic cups and fed with appropriate diets. Fifty larvae were used for each diet. Records were kept with regard to the duration of each larval instar, pupal period, and the pupal weight. The emerging adults were paired, and then the number of dead adults and that of eggs laid were recorded daily. On all the natural diets tested, the larval stage of C. pavonana passed through four instars. The egg incubation, total larval developmental, and pupal period of C. pavonana on chinese cabbage were the shortest compared to those on the other natural diets. The pupal weight, however, was the highest on broccoli, followed by that on chinese cabbage, cabbage, and cauliflower. The female fecundity was also the highest on broccoli (average 258 eggs/female) followed by that on chinese cabbage (212), cauliflower (162), and cabbage (102). Broccoli diet also yielded adults with the longest lifespan although the adult lifespan on broccoli was not significantly different from that on the other natural diets, except that of males on cabbage. C. pavonana failed to develop successfully on six kinds of artificial diets tested. The best artificial diet (broccoli–based diet with microbial inhibitors 20% of the normal amount) only yielded two males and five females with deformed wings, but none of the emerging females produced eggs.

Effects of four host plants, tobacco, Chinese cabbage, cowpea and sweet potato, on larval and pupal development and survival, and longevity and fecundity of adults of Spodoptera litura (F) (Lepidoptera: Noctuidae), were studied under laboratory conditions (26° C, 60–80% RH), as was the utilization of the four host plants and adaptation on tobacco. All of the biological parameters included in the study were affected by the host plants. In a choice test, S. litura females oviposited most on Chinese cabbage, least on tobacco, and intermediate on cowpea and sweet potato. S. litura larvae developed differently on the four host plants, from shortest to longest in the following order: Chinese cabbage, cowpea, sweet potato, and tobacco. Pupal development was shorter on cowpea than on the other three host plants, and males generally developed longer than females. More females than males were found among emerged adults, and male adults lived 1–2 d longer than females. Larvae survived best on cowpea (81.6%), followed by Chinese cabbage (75.5%), then sweet potato (66.1%), and worst on tobacco (49.2%). Pupal survival rates were relatively high (91.4 – 95.9%) in all four host plant treatments, although that on sweet potato was lower than those on the other three host plants. Pupal weights on tobacco and sweet potato were similar, but both were lower than those on Chinese cabbage and cowpea. Generally, male pupae weighed less than female pupae. Numbers of eggs oviposited by female S. litura were highest on sweet potato, followed by those on cowpea, Chinese cabbage, and lowest on tobacco. Relative food consumption rate was highest on sweet potato, followed by that on cowpea, Chinese cabbage, and lowest on tobacco. In contrast, S. litura larvae that fed on tobacco had higher efficiency of conversion of digested food, highest efficiency of conversion of ingested food, and lowest approximate digestibility as compared with larvae that fed on other host plants. The potential causes for S. litura outbreaks on tobacco are discussed.