This is Science Friday. I'm Ira Plato. A swarm of locusts, the size of a city. Well, it may sound biblical, but it's the reality on the ground right now in East Africa, where the pests are devouring the food supply of tens of millions of people, wreaking havoc on crops and pasture lands. Local residents are doing all that they can to keep the swarms at bay,

but the locusts may be here to stay for a while, as experts suggest, their presence may be due to,

you know, climate change. For more on that story and other short subjects in science, we're joined

by Sarah Zang, staff writer for the Atlantic. Welcome back, Sarah. Hi, Ira. Good to talk to you. Locust swarms, the size of cities? Tell us about that. Yeah, it's almost hard to imagine, right? It's really the worst locust swarm in recent memory in East Africa. These swarms, they'll just land in the field of crops in the morning, and by afternoon, they'll just devoured and strip the entire field of all leaves. And so the reason, as you say, that there have been such huge swarms is because of rain. So desert locusts, which is what these swarms are, they lay their eggs in the soil. And starting about a year ago, there have just been several cycles and have just dumped rain all over the region, which helps trigger these eggs to hatch. So you might have several years' worth of eggs hatching. And locusts, they reproduce really quickly. So once they've hatched, they might have a new generation in just three months. And with each generation, the next one can be is 20 times as big as the previous one. So you can imagine in less than a year, you may have

three generations. The number of Nocus has just gone up by like 8,000 times. So over the past year,

they've just been exploding in numbers and migrating across the region. Anything you can do about it?

Well, unfortunately, it's probably going to get a little bit worse before it gets better. You might

be able to spray insecticides, but, you know, it's a huge region, and there just isn't always a civil

infrastructure to cover everything. There's a lot of rain expected from March through May as

well, so there's probably going to be even more in focus of the next few months, and eventually

the rain stop. Hopefully Hopefully it will let up.

Speaking of agricultural pests, farmers in Florida, I understand, are trying to save their

orange crops from citrus greening disease. Tell us about that. Yeah, they're actually

spraying pesticides. Sorry, not pesticides. They're spraying antibiotics that are used in human diseases

on their trees. So this is really an active, if not last resort, really some desperation.

So as you mentioned, there's this disease called citrus greening disease, which over the past

15 years has just really devastated the Florida citrus crop. It dropped something like 70%.

This disease, which is a bacteria that infects trees,

it causes the trees that grow smaller fruits.

And when they do grow them, they also turn green

and kind of fall off the tree before they're really ripe.

And so starting in 2016, and the EPA,

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