Bagworms

the earliest sign is leaves that look scraped thin — pale, papery "windows" where the caterpillar has eaten one side of the leaf and left the other skin behind. As feeding goes on you'll see leaves skeletonised (only the veins left, like green lace) and whole fronds or branches turning brown and bare in patches as the stripping spreads.

the give-away is a small hanging bag or case, like a tiny dangling cocoon, stuck to leaves and twigs. Each bag is a caterpillar's home, built of silk plastered with bits of leaf, twig and droppings, so it looks like a scrap of dead plant — anywhere from the size of your fingernail up to your little finger (about 1–5 cm). Watch a feeding bag and you'll see the caterpillar's dark head and front legs poke out of the open top to eat, then pull straight back in when you touch it.

with a dead curled leaf, a bird dropping, or a spider's egg-sac caught in the tree — a live bag is firmly anchored by silk, hangs down, and sways or inches along on its own, and holds a fat caterpillar when you open it (dead leaves don't move). Also don't confuse it with webworms, which spin a loose shared web of silk over a clump of foliage — a bagworm carries its own single tight bag and makes no communal web.

bagworms build up in the warm season once the canopy is full and dense (the mid-to-late part of the season) — that warm, still, shaded inner canopy is exactly where they thrive. Start checking closely as the hot weather sets in, and straight after any neighbouring block has had bags.

across each block so you cover all four corners and the middle, not just the trees by the path. Bagworms spread slowly out from one spot (a single starting "focus"), so a cluster of a few heavily-bagged trees is your early warning — the patch is what you're hunting.

At each stop pick a tree and check a couple of lower, shaded fronds or inner branches — that's where bags hide first. Turn the frond or leaf over and look on the underside and along the twigs, counting the active (living, feeding) bags — the ones that are green, freshly decorated, and have the caterpillar's head poking out — and note any fresh scraped "window" leaves and skeletonised patches.

, OR you can see bare, stripped patches of leaf loss spreading across the canopy. Below that, keep watching. A few old, empty, dry bags with no fresh feeding is a past attack that has moved on — don't treat for that.

when bags are many but still small and actively feeding (heads out, chewing), spray Bt (Bacillus thuringiensis — a natural bacterium that kills caterpillars but is harmless to people, bees and the helpful wasps). Bt only works when the caterpillar eats the sprayed leaf, so cover the feeding foliage well and spray while the larvae are young and out feeding — once they are big and sealed inside thick bags, nothing reaches them.

only for a severe, expanding outbreak that handpicking and Bt cannot hold, use a recommended insecticide, and spot-treat just the affected block, never the whole plantation. Timing still rules — aim at the young feeding larvae; mature larvae sealed in thick bags survive most sprays. Safety: cover your skin, eyes, nose and mouth; spray in the cool of morning or evening with the wind at your back; keep it off food, water, children and bees; respect the pre-harvest interval (the set number of days you must wait between spraying and picking the crop); and wash yourself and your clothes afterwards. To stop the pest building resistance (surviving the poison so it stops working), rotate to a different chemical group each time rather than using the same one over and over — and remember that broad insecticide kills the parasitic wasps, so over-using it makes the next outbreak worse.

if bags keep multiplying and the bare, stripped patches spread tree to tree despite handpicking and Bt, cut off and burn the worst-hit fronds and branches to physically remove the breeding females and slow the creep, and treat the leading edge of the patch rather than chasing every tree. Where a block is already stripped bare and the larvae have matured, spraying won't bring the leaves back — cut your losses on that block, keep those trees well watered and fed so they can re-flush a new canopy, and put your effort into protecting the healthy blocks around it and knocking back the next generation early.