Small rodents with a large surface-area-to-volume ratio and a high thermal conductance are likely to experience conditions where they have to expend large amounts of energy in order to maintain a constant body temperature at low ambient temperatures. The survival of small rodents is thus dependent on their ability to reduce heat loss and increase heat production at low ambient temperatures. Two such animals are the social subterranean rodents Cryptomys damarensis (the Damaraland mole-rat) and Cryptomys hottentotus natalensis (the Natal mole-rat). This study examined the energy savings associated with huddling as a behavioural thermoregulatory mechanism to conserve energy in both these species. Individual oxygen consumption (VO 2 ) was measured in groups ranging in size from one to 15 huddling animals for both species at ambient temperatures of 14, 18, 22, 26 and 30 °C. Savings in energy (VO 2 ) were then compared between the two species. Significant differences in VO 2 (p < 0.05) were found within each species, indicating that both Damaraland mole-rats and Natal mole-rats saved more energy in larger as opposed to smaller groups. VO 2 was also different between the two species, with Damaraland mole-rats showing a higher decrease in VO 2 with increasing group size compared to Natal mole-rats. These findings suggest that huddling confers significant energy savings in both species and that the amount of energy saved is related to each species' ecology. More generally, these findings suggest that group living desert-adapted species are likely to be more prone to heat loss at low ambient temperatures than temperate-adapted species, especially at low group sizes. This is presumably offset against the advantages obtained by having a low metabolic rate and avoiding hyperthermia when temperatures are hot.

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In 3 consecutive years, preharvest applications of Bacillus subtilis field sprays integrated with copper oxychloride or benomyl consistently reduced severity of avocado black spot (BS), caused by Pseudocercospora purpurea at Omega, Republic of South Africa. Control was equal to that obtained with copper oxychloride or benomyl-copper oxychloride in the first and third years of spraying at Omega. In the second year, only the integrated treatment controlled BS, while copper oxychloride proved ineffective. The antagonist was applied on its own or integrated with copper oxychloride sprays at two other geographically distinct locations, Westfalia Estate and Waterval. The integrated and biological treatments at these localities were less effective than copper oxychloride sprays in controlling BS disease. Integrated control was more effective than B. subtilis sprays at Westfalia. On continuation of the biological spray program at Waterval for an additional three seasons, control was as effective as copper oxychloride in the last 2 years of spraying. Sooty blotch (SB), caused by an Akaropeltopsis sp., was reduced by the integrated treatment at Omega during the second season and at Westfalia during the first season. Although the two fungicide treatments reduced SB at Omega in the first season, copper oxychloride increased it above that of the control in the third season. Only the copper oxychloride treatment reduced SB at Waterval in the third season, while the B. subtilis treatment increased disease above that of the control in the fourth season.

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