March 2012. More problem of Jatropha seedlings, this time from Laos. There apear to be two problems: one is an attack on the stems below soil level and the other is on seeds in storage. The stem damage in this case seems to be different to that of wireworm reported from Vietnam previously (8799). Would it be best to store the seed with neem leaves or kernel powder?
The grubs from Laos look like weevil larvae (there are no functional legs, the head is proportionately large, the abdomen is tapered, and they are small, so they are unlikely to be white grubs – another potential pest in this situation, although they would be enjoying the roots not the collar). The storage pests look very and sadly familiar. They are probably Tribolium castaneum. The following was suggested:
- empty out all the stored seed, leave it in the sun during the day. Segregate and destroy all damaged seed. Sake the seed in a sieve to separate out some of the insects.
- some beetles (and probably moths if there is webbing on the seeds) would be disturbed and will start wandering around. They can be killed as soon as possible – before they hide away and emerge to cause more damage later. (Any infested seed can be given a squirt with an anti-cockroach aerosol spray). Sweep them up and feed them to the chickens, if not sprayed.
- once the infested seed has been removed, repack the seed in clean sealed bags, but remember the seed is only superficially clean. There will be insect eggs on the outside of the seed and insect larvae inside.
- Yes, a generous mixture of neem leaves will do the trick, or
- As you are not dealing with food – camphor or naphthalene chips (moth balls) can be added to each bag (some people become asthmatic when these chemicals are around and others loose their sense of smell), or
- You can mix the seed with fine sand or any kind of inert dust (10 to 20 measures of seed to one of sand/dust), or
- Spray the seed thoroughly with an insecticide or perhaps a dust formulation would be better ( 1-2 g/kg seed) if there are no instructions. A material with fumigant action would be best. BUT if an insecticidal dust is used, be careful whrn the seed is unpacked.
From Cambodia, came the following:
Are the infested seeds old, i.ei more than 12 months? It was suggested that the seeds are harvested when they are fresh, from yellow fruit, then dried to 6-8% moisture. A moisture meter is useful. Put the seeds in the sun for 2 days, but cover overnight. Then store them in a cool room at leass than 160C. The store room should be insect-proof, and the seeds stored in 25 or 50 kg bags, with plastic liners. If the seeds are stored without temperature control then the germination will be less than 80% after 3 months.