Naturalized Dolichogenidea gelechiidivoris Marsh (Hymenoptera: Braconidae) complement the resident parasitoid complex of Tuta absoluta (Meyrick) (Lepidopera:Gelechiidae) in Spain

Our study aimed to assess the contribution of natural parasitism due to Necremnus tutae Ribes & Bernardo (Hymenoptera: Eulophidae) to the biological control of Tuta absoluta (Meyrick) (Lepidopera:Gelechiidae) in commercial plots where an IPM program based on the use of predatory mirid bugs was implemented. During the samplings, the presence of another parasitoid was detected and, therefore, a second part of our study intended to identify this species and to evaluate the importance of its natural populations in the biological control of the pest. Leaflets with T. absoluta galleries were collected during 2017-2020 from commercial tomato plots in the horticultural production area of Catalonia (Northeast Spain), including greenhouses, open fields, and roof covered tunnels that lack side walls. In the laboratory, T. absoluta larvae were classified as ectoparasitized, alive, or dead. Reared parasitoids from ectoparasitized larvae were mostly morphologically identified as Necremnus sp. with parasitism rates that peaked in summer months with values between 9 and 15%. Some of these ectoparasitized larvae also yielded another parasitoid identified as Dolichogenidea gelechiidivoris Marsh (Hymenoptera: Braconidae) by both morphological and molecular-DNA barcoding methods. In 2020, parasitism rates due to D. gelechiidivoris that increased with season up to 22%. Our work reports for the first time in Europe the presence of the neotropical species D. gelechiidivoris adding this biocontrol agent to the resident parasitoid complex of T. absoluta in Spain.

Biological traits of the predatory mirid Macrolophus praeclarus, a candidate biocontrol agent for the Neotropical region

The predatory mirid Macrolophus praeclarus is widely distributed throughout the Americas, and is reported to prey upon several horticultural pest species. However, little is known about its biology, thermal requirements, crop odour preferences, phytophagy, and capability to induce defensive responses in plants. When five temperatures studied (20, 25, 30, 33 and 35°C) were tested and Ephestia kuehniella was used as prey, the developmental time from egg to adult on tomato, was longest at 20°C (56.3 d) and shortest at 33°C (22.7 d). The ability of nymphs to develop to adults decreased as the temperature increased, with the highest number of nymphs reaching the adult stage at 20°C (78.0%) and lowest at 35°C (0%). The lower and upper developmental thresholds were estimated at 11.2° and 35.3°C, respectively. The maximum developmental rate occurred at 31.7°C and the thermal constant was 454.0 ± 8.1 degree days. The highest predation rate of E. kuehniella eggs was obtained at 30°C. In Y-tube olfactory choice tests, M. praeclarus selected tomato, sweet pepper and eggplant odours more frequently than no plant control treatment. Macrolophus praeclarus feeding did not damage tomato plants compared to another zoophytophagous mirid, Nesidiocoris tenuis, which caused necrotic rings. The phytophagy of M. praeclarus induced defensive responses in tomato plants through the upregulation of the jasmonic acid metabolic pathway. The implications of the findings for using M. praeclarus in tomato biological control programmes in the Americas are discussed.

The Amino Acid-Mediated TOR Pathway Regulates Reproductive Potential and Population Growth in Cyrtorhinus lividipennis Reuter (Hemiptera: Miridae)

The predatory mirid bug, Cyrtorhinus lividipennis Reuter, feeds on brown planthopper (BPH) eggs that are deposited on rice and gramineous plants surrounding rice fields. The development and reproduction of C. lividipennis are inhibited by feeding on BPH eggs from gramineous species, and the underlining regulatory mechanism for this phenomenon is unclear. In the present study, HPLC-MS/MS analysis revealed that the concentrations of six amino acids (AAs:Ala, Arg, Ser, Lys, Thr, and Pro) were significantly higher in rice than in five gramineous species. When C. lividipennis fed on gramineous plants with BPH eggs, expression of several genes in the target of rapamycin (TOR) pathway (Rheb, TOR, and S6K) were significantly lower than that in the insects fed on rice plants with BPH eggs. Treatment of C. lividipennis females with rapamycin, dsRheb, dsTOR, or dsS6K caused a decrease in Rheb, TOR, and S6K expression, and these effects were partially rescued by the juvenile hormone (JH) analog, methoprene. Dietary dsTOR treatment significantly influenced a number of physiological parameters and resulted in impaired predatory capacity, fecundity, and population growth. This study indicates that these six AAs play an important role in the mediated-TOR pathway, which in turn regulates vitellogenin (Vg) synthesis, reproduction, and population growth in C. lividipennis.

AMBANG KENDALI PENGGEREK BUAH KAPAS, Helicoverpa armigera, DENGAN MEMPERHITUNGKAN KEBERADAAN PREDATOR PADA KAPAS

ABSTRAK<br />Helicoverpa armigera adalah salah satu hama utama pada kapas,<br />sehingga perlu dikendalikan. Konsep ambang kendali sebagai salah satu<br />komponen dalam PHT telah dikembangkan untuk H. armigera, namun<br />hanya berdasarkan populasi hama dan belum mempertimbangkan<br />keberadaan musuh alami. Penelitian ini bertujuan untuk menguji ambang<br />kendali H. armigera dengan mempertimbangkan keberadaan musuh alami<br />pada skala luas di daerah pengembangan dengan menggunakan lahan<br />petani. Penelitian ini dilakukan pada pertanaman kapas tumpangsari<br />dengan kedelai yang ditanam sesudah padi di Kecamatan Mantup dan<br />Kembangbau, Lamongan, Jawa Timur pada Maret-Oktober 2005. Lahan<br />yang digunakan seluas 15 hektar, di bawah pengelolaan 36 petani.<br />Pengujian ambang kendali H. armigera dilakukan dengan menerapkan dua<br />perlakuan konsep ambang kendali yang merupakan bagian dari PHT<br />kapas, yaitu: (1) AKH: 4 tanaman terinfestasi/25 tanaman contoh; dan (2)<br />AKH+MA: 4 tanaman terinfestasi/25 tanaman contoh; jumlah tanaman<br />yang terinfestasi yang teramati dikurangi 1 jika ditemukan 8 ekor predator<br />dan kelipatannya. Jika populasi pada petak perlakuan mencapai ambang<br />kendali, dilakukan penyemprotan dengan Ekstrak Biji Mimba (EBM).<br />Setiap lahan petani dibagi dua, setiap bagian menerapkan satu perlakuan<br />(n=36). Pengamatan dilakukan pada 25 unit pengamatan per 1,0 ha yang<br />diambil secara W sampling, setiap 7 hari sejak 50 hari setelah tanam (hst)<br />hingga 90 hst. Satu unit pengamatan adalah 1 m 2 . Parameter yang diamati<br />secara periodik adalah populasi H. armigera (telur dan larva); kerusakan<br />buah, hasil kapas berbiji, serta penggunaan saprodi dan tenaga kerja untuk<br />pengendalian hama. Data yang diperoleh dianalisa dengan menggunakan<br />uji t. Hasil penelitian menunjukkan bahwa populasi H. armigera pada<br />kapas + kedelai dapat ditekan oleh musuh alaminya, khususnya kompleks<br />predator yang terdiri atas laba-laba, kumbang kubah dan kepik mirid.<br />Populasi kompleks predator dapat mencapai 40-80 ekor/25 tanaman.<br />Dengan demikian, penerapan ambang kendali H. armigera pada kapas +<br />kedelai dengan memperhitungkan keberadaan predator menyebabkan tidak<br />perlu dilakukannya penyemprotan insektisida sama sekali, sehingga<br />terdapat keuntungan ekonomis, yaitu penghematan biaya saprodi sebesar<br />Rp 259.000 per hektar dan keuntungan ekologis, yaitu tidak tercemarnya<br />lingkungan oleh senyawa toksik.<br />Kata kunci : Kapas, Gossypium hirsutum L., ambang kendali, Helicoverpa<br />armigera, Jawa Timur<br />ABSTRACT<br />Action threshold for Helicoverpa armigera by<br />considering the presence of predators on cotton<br />Helicoverpa armigera on cotton was considered as the main pest,<br />therefore it always be a focus of pest control. Action threshold concept as<br />an IPM component had been developed for H. armigera on cotton;<br />however it has not considered the presence of natural enemies. The<br />objective of this research is to test the action threshold of H. armigera by<br />considering the presence of natural enemies on cotton intercropped with<br />soybean in farmers’ fields. The test involved 15 hectares of farmers’<br />fields (involving 36 farmers) in Lamongan, East Java in March-October<br />2005. The action thresholds for H. armigera tested were: (1) AKH: 4<br />infested plants/25 sample plants; and (2) AKH+MA: 4 infested plants/25<br />sample plants, and the number of infested plants observed was subtracted<br />by 1 when 8 predators, and it’s folded up, were found in the sample plants.<br />Spray of neem seed extract (NSE) was applied when the pest population<br />reached action threshold level. Each farmer field was divided into two<br />parts to accommodate the treatments. The observations were made<br />periodically on 25 units per 1,0 hectare in 7-days interval on 50 – 90 days<br />after planting (dap). The size of observation unit was 1 m 2 . Parameters<br />observed included H. armigera population (egg and larva); damage bolls,<br />seed cotton production and the cost of pest control. Data were analysed by<br />using t-test. The results showed that H. armigera population on cotton<br />intercropped with soybean could be repress by its natural enemies,<br />especially by the complex predator (consisted of spiders, lady bird beetles<br />and predatory mirid bugs) to be always under action threshold level. The<br />application of action threshold by considering the presence of predator in<br />cotton + soybean fields would lead to unsprayed cultivation. Resulted<br />economical benefit by saving of the production cost Rp 259.000 per<br />hectare as well as ecological advantage by avoiding of sprays of toxic<br />materials in the environment.<br />Key words : Cotton, Gossypium hirsutum L., action threshold,<br />Helicoverpa armigera, East Java

A risk-based detection survey for the predatory mirid Macrolophus pygmaeus in New Zealand

Macrolophus pygmaeus, a predatory mirid used to manage greenhouse whitefly, was illegally imported into New Zealand, and for a time was reared and sold to commercial tomato growers. We designed and implemented a risk-based detection survey to determine whether M. pygmaeus was still present in New Zealand a decade later. The survey was designed to have an 80% chance of detecting a single low density (0.05 per lineal metre of host plants) population within 1 km of known points of introduction. The survey was implemented between 8 and 15 March 2018. Local habitat constraints meant that the planned sampling had to be modified but this was accounted for in the subsequent analysis. No M. pygmaeus were found in the samples, but 93 specimens from seven other mirid taxa were detected, validating the sample methods. The survey gives 60% confidence that M. pygmaeus was not present at a mean density of 0.05 per lineal metre of habitat. It gives 80% confidence that a population at 0.1 m−1 was not present and 90% confidence that no population exists at >0.18 m−1. Though there are no published data on typical field population densities of M. pygmaeus, for related species the survey would have had high confidence in detecting any medium to high density population present. Therefore, it is likely that M. pygmaeus is no longer present in New Zealand, but if extant within the sampled areas then we have high certainty that it was at low densities compared to other predaceous mirids.

Implications of using two natural enemies of Tuta absoluta (Lepidoptera: Gelechiidae) toward tomato yield enhancement

Tomato leaf miner (TLM), Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is one of the most destructive tomato pests worldwide. We tested quantity and quality of tomato fruits after simultaneous use of two biological control agents, the predatory mirid bug Nesidiocoris tenuis (Reuter) and the egg parasitoid Trichogramma brassicae Bezdenko against TLM. We varied the timing of predator releases (before or after pest establishment) and the number of parasitoids released (ten or 30 females per week per m2). The highest number of fruits per cage, percentage of undamaged fruits, total yield weight, and undamaged yield weight were all obtained with predator-in-first treatments, with or without parasitoid releases. Furthermore, measures of fruit quality were also highest in predator-in-first treatments, including, highest percentage of water, greatest proportional fresh weight of carbohydrates, most lycopene, most β-carotene, most flavonoids, and highest total chlorophyll. Thus, our findings support a predator-in-first augmentation approach for management of TLM.