The most effective means of control is immediate removal of pods from harvested plants, but this is not always possible at a time when other farm activities are at their peak, so one possible option is the use of cheap dryers. (The Guardian)
The most effective means of prevention are protection against contact with the disease-carrying mosquitoes and mosquito control. These include using insect repellents with substances such as DEET (N,N-diethyl-meta-toluamide; also known as N,N'-diethyl-3-methylbenzamide or NNDB), icaridin (also known as picaridin and KBR3023), PMD (p-menthane-3,8-diol, a substance derived from the lemon eucalyptus tree), or IR3535. Wearing bite-proof long sleeves and trousers (pants) also offers protection. (en.wikipedia.org/wiki/Chikungunya)
As a learner of the English language, I instinctively read "means" as if it were plural, but searching on Internet, and - obviously - selecting only reliable sources, I found both singular and plural usages.
Examples above are confusing, at least to me, because I'm not able to understand the reason why in the first case is used is while in the second one is used are.
Can anybody explain when we should use "means" in singular or in plural sense?