A recent visit to a client has prompted another article on integrated pest management (IPM). This farmer has two vegetable farms separated by a few kilometres. He uses wasps to control leaf miner and Hawaiian web worm on beet.
I told him about the wasps that control diamond back moth (DBM) larvae and showed him a cabbage with a couple of wasp cocoons attached to the leaves. later noticed a few of these on his cabbages and used Di pel (Bacillus thuringiensis) and Bio Cure to keep the DBM at manageable levels while parasitoid numbers built up.
At the time, the farmer experienced a two-month heatwave with almost no rain. He used water that deposited high levels of minerals on the leaf surfaces, rendering the pesticides useless after a short period. The result on his farm where no IPM is used was an outbreak of moth larvae that caused much damage, while on his other farm no spraying was necessary as the parasitoids were doing this job.
He is saving money on crop chemicals and gets better control where chemicals are being used. After a rainy period, the crop chemicals will work again. However, the farmer now faces potential hazards, of which the first is aphids. This time of the year aphids build up in numbers and are a threat for the cool season.
At this stage, a couple of plants are infested with aphids not yet in the winged stage. Use a knapsack and spray Aphox on these plants. Make sure they are well wetted by also directing the nozzle under the cover leaves. This method covers a huge area in one day. If too many plants become infected through an aphid drift, then spray the entire land. Aphox is very effective and also “soft” on parasitic wasps.
Timing is important as aphids are difficult to eliminate when they have penetrated into the developing plants. T he second potential pest is thrips. If the population increases, it will have to be sprayed. They are a bigger problem in hot, dry conditions and it shouldn’t be necessary to spray from now until possibly September. If spraying is necessary, Bio Cur will reduce the population without too much damage to the wasps. Ensure the pressure and droplet size is right to wet the undersides of the leaves as well. product will also control Bagrada insects, which are a sporadic pest. he third pest is bollworm. It is more of a threat in warmer conditions and the odd plant is affected throughout the land.
When bollworms are visible, it is often too late to avoid damage. safest approach is to use pheromone traps to monitor activity and to plan applications of the above products as and when necessary. – Bill Kerr Contact Bill Kerr on (016) 366 0616 or e-mail [email protected]. |fw