At least we’re not irrigating!
With three inches of rain last week we won’t need to irrigate for a while. That’s the good part; now for the bad part: the weeds keep on growing and diseases run rampant now what with the humid clammy weather. You can cultivate all you want; it doesn’t amount to much. The weeds take root wherever you move them to; it’s kind of like transplanting them. Killing weeds is much easier when the sun is shining. They shrivel up and die right before your eyes.
I’m not going to talk about weeds this week, any more than I already have. Instead I’m going to switch to insect pests; aphids in particular. Aphids are known to gardeners and farmers everywhere and are usually kept in check by natural predators. Usually chemical control is only necessitated when the population gets out of control.
By far the most interesting info about them is their life cycle. They begin as eggs laid the previous fall which hatch out as soon as the weather warms, or as soon as the greenhouse gets heated which may be the case. The first generation consists entirely of females which give birth to live young which also starts feedi immediately. As the population increases, winged aphids make up a generation which flies off looking for new feeding grounds. Rapid population explosions are common in the aphid world. They say if all the descendants from a single aphid lived for a summer there would be over 5 billion of them.
As the summer wears on and the food is becoming limited and the temperatures are cooling, a generation consisting of both males and females appear. They mate, lay eggs and die setting the stage for the next season. Aphids will over winter in a greenhouse; opening the sides or otherwise providing cold air circulation will help kill them off.
Aphids pierce the plant stems and leaves and suck the juices out. Because of their high population; a single leaf can have over 100 aphids, the effect of their feeding is both noticeable and devastating As soon as they feed on a leaf it will curl and provide a safe haven for aphids as it is hard to get a pesticide into the curled leaf area. As they move from leaf to leaf and from plant to plant they spread diseases between plants. As there are literally thousands of aphids diseases spread quickly throughout the field.
Control is easier said than done. Because there are many generations per year, they quickly build up resistance to pesticides. When a pesticide is used it kills most of the insects; the ones that aren’t killed have some resistance. Their offspring will typically have some degree of resistance to the pesticide when their born/hatched. Aphids have so many generations per year they can really build up resistance fast. Where Pyganic worked earlier in the season nothing seems to work really well now.
Susie has released lady beetles and lace wings to gain some control. She sprayed last week with Neem oil before the beneficials were released. The Neem oil seemed to work pretty good, but it rains as soon as we spray – best way to get it to rain is to spray.
Until next week, Brian
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