One of the multiple threats to protected areas worldwide, invasive plant species have the potential to decrease biodiversity and ecosystem function. We studied changes in infestation by two widespread invasive plant species – Chromolaena odorata and Mikania micrantha – in India’s Manas National Park, a critical conservation site for threatened flora and fauna. Based on field surveys in 2011 and 2019, we found that C. odorata and M. micrantha were present in most of the sampled plots and had newly invaded over 20% of the plots. However, the abundance of M. micrantha decreased in 45% of the plots while C. odorata increased in >50% of the plots. We used a decision tree-based regression with environmental variables as predictors to generate the distribution, abundance and invasion risk maps of the two species. Among environmental variables, road proximity and fire frequency had the strongest influences, respectively, on C. odorata and M. micrantha. Invaded quadrats exhibited lower native-plant diversity than non-invaded quadrats, and C. odorata specifically had a strong negative association with native-plant community structure. These invasive species have increased their range and abundance, and our predicted invasion risk maps indicate the areas where management intervention is urgently needed.

Two conventional greenhouses were modified into a containment facility for the study of foreign noxious weed species that could be dangerous to North American agriculture. The facility was designed for research on the biology, ecology, and weed control technology of foreign noxious weeds, without the escape of propagules. Two growth chambers and a germinator are located within the containment facility for evaluations under controlled environmental conditions. A standard operating procedure is followed to preclude the escape of weed seeds or propagules while minimizing restrictions to research. The facilities are locked and located in a secure fenced area to reduce the probability of accidental or intentional damage. Procedures for emergencies have been designed to facilitate aid without compromising the containment security. Knowledge concerning weeds that have the potential to threaten North American agriculture will be gained from research performed within this facility.

Disentangling the responses of insects to variations in their thermal environment is central to our understanding of the evolution of temperature-dependent performance in these species. Here, we report results of experiments examining the effects of high (upper lethal temperature = ULT) and low (lower lethal temperature = LLT) temperature and exposure time on the survival of larvae and adults of a multivoltine, nocturnal moth species, Pareuchaetes insulata, a biological control agent whose impact on an invasive weed, Chromolaena odorata has been variable in South Africa. The influence of temperature and acclimation on locomotion performance of the moth was also investigated. Temperature and duration of exposure significantly affected survival of both adults and larvae of P. insulata with more extreme temperatures and/or longer durations proving to be more lethal. Third instar larvae and adults are both freeze intolerant and had LT50 of −5.9 and −4.7°C, respectively, after a 2 h exposure. Although cold acclimation was beneficial to the nocturnal larvae, temperatures below 10°C significantly reduce their locomotion activities. The average daily minimum temperatures in the coldest months at three locations in South Africa are over 5°C lower than those of Fort Lauderdale, Florida, USA, where P. insulata was originally collected. Our results suggest that lethal high or low temperatures at short timescales are trivial in explaining the variable performance of P. insulata, but reduced locomotion at sub-lethal temperatures may be an important driver of the population dynamics of the biocontrol agent (especially in winter months) and may consequently explain the low population levels of the moth because of possible reduced feeding by larvae during night-time low temperatures.

The moth Pareuchaetes pseudoinsulata Rego Barros, whose host plant is the invasive alien plant Chromolaena odorata (L.) King and Robinson, was recently discovered in Uson (6° 14′ 30.77″ N, 6° 04′ 41.37″ E), Evbuabogun (6° 15′ 39.33″ N, 5° 38′ 58.29″ E) and Ekae (6° 15′ 34.90″ N, 5° 37′ 19.75″ E) villages in southern Nigeria after its first release as a biological control agent in that country in 1972. The moth seemed to become more abundant as the rainy season progressed. Studies on some aspects of its biology and behaviour were conducted both in the laboratory and in the field. Females laid eggs on the undersides of C. odorata leaves and on the walls of rearing cages. Female pupae were significantly (P < 0.001) larger than the male ones. Also, adult female wingspan was significantly (P < 0.001) longer compared with that of the males. Adults lived for an average of 4.8 ± 0.01 days and they were active at night, when there was good light intensity. Observations on the behaviour and some aspects of the biology and behaviour are discussed.

Forest recovery in abandoned pastures and agricultural fields is often impeded, therefore it is important to understand the factors limiting regeneration. Patterns of seed arrival and regeneration in five abandoned agricultural clearings nested within a seasonally dry tropical forest in India were examined along five transects radiating from the forest edge into the clearings. Wind-dispersed seeds dominated the seed arrival in clearings compared with vertebrate-dispersed seeds: 5563 wind-dispersed seeds and 1094 vertebrate-dispersed seeds of 14 and 13 tree species, respectively, were recorded. Numbers of the former declined steeply with increasing distance from the forest, whereas the latter showed no evident pattern with distance. Seeds of the invasive herb, Chromolaena odorata, were abundant in clearings. Although wind-dispersed seeds greatly outnumbered vertebrate-dispersed seeds, seedlings and saplings of vertebrate-dispersed species were three times more abundant than those of wind-dispersed species, indicating distinct differences in patterns of actual and effective seed dispersal. This points to recruitment limitation, and suggests that seed arrival may not be the principal barrier to regeneration in these clearings. Nonetheless, the clearings are likely to revert to forest over time.

In 14 forest plots (36 m2) all terrestrial plant species were recorded before slashing and burning of the vegetation. During subsequent cultivation with rainfed rice all resprouting plants were registered in permanent plots (72 m2). The fields studied (one per forest) covered all combinations of forest type and soil usually cultivated on local farms. Forest plots (total 409 species) and field plots (358 species) had 226 species in common. Most resprouting plants were woody. Though nine forests in the sample were secondary, 70% of resprouting plants belonged to primary forest species and with three exceptions, these species did not regenerate by seed.

Experiments in one field inlcuded: different intensities of initial burning, weeding (none, once, twice) and length of the rice cultivation period (1, 2, 3 y). Resprouting plants were monitored in permanent plots (108 m2) during 3 y of cultivation and 2 y of fallow. More plants resprouted after a mild initial burning (5.8 plants m−2) than after a burn of normal intensity (1.4 plants m−2). Weeding and prolonged cultivation strongly reduced species diversity but plant densities were less affected because some climbers and trees were apparently stimulated and expanded.

Fields abandoned after one rice harvest had, within six months, a closed forest canopy of pioneer trees emerging from the pre-existing seed bank and from the growth of resprouting trees. Prolonged cultivation (3 y) destroyed the pre-existing seed bank but affected sprouting plants less, these being the only component in the vegetation able to shade out weeds and forbs such as Chromolaena odorata.

A laboratory study of the dietary preferences and duration of food plants in the gut of Zonocerus variegatus was carried out using three plant species, namely Manihot esculenta, Vernonia amygdalina and Chromolaena odorata. Whole or cut up plants were offered to the grasshopper in the experiments. Overall, whole V. amygdalina was the preferred diet of Z. variegatus, while the insect ate cassava pieces better than whole plant. Chromolaena odorata was the least preferred diet of the three. The duration of the food plant within the insects' gut was shortest for V. amygdalina, which was consumed all at once soon after being offered to the insects. The insects consumed cassava in two successive sessions and C. odorata in three. The total time spent eating was similar for V. amydalina and cassava, which were significantly shorter than that spent eating C. odorata. Evidently, V. amygdalina could serve as a good bait plant for Z. variegatus. However, its status as a human food plant precludes its use as a bait followed by chemical control; it may be used with, for example, fungal biocides such as Metarhizium.

Some aspects of the biology of Callosobruchus maculatus (F.) on three varieties of bambara groundnut, Voandzeia subterranea (L.) Thou and a local brown cowpea variety, Vigna unguiculata (L.) Walp were studied under ambient laboratory conditions. Egg hatchability of C. maculatus was above 90% on all the legume varieties. The mean developmental period of C. maculatus ranged from 23.7 days on cowpea to 28.5 days on the Piele kargu variety of groundnut. The percent emergence of C. maculatus ranged from 61.1% on var. Piele kargu to 89.5% on var. Piele balgu. There was a significant difference (P < 0.05) between the damage caused to the brown cowpea and the bambara groundnut varieties. However, there were no significant differences (P > 0.05) in damage among the three groundnut varieties. In experiments to assess the insecticidal potential of three plant materials against C. maculatus, Azadirachta indica (neem) seed powder showed a higher efficacy than both Citrus sinensis peel powder and the powder of Chromolaena odorata leaves. At 1.0 g per 40 g of legume seed, it was twice as effective as Ci. sinensis and Ch. odorata over a period of 40 days.